linux/fs/ext4/balloc.c

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/*
* linux/fs/ext4/balloc.c
*
* Copyright (C) 1992, 1993, 1994, 1995
* Remy Card (card@masi.ibp.fr)
* Laboratoire MASI - Institut Blaise Pascal
* Universite Pierre et Marie Curie (Paris VI)
*
* Enhanced block allocation by Stephen Tweedie (sct@redhat.com), 1993
* Big-endian to little-endian byte-swapping/bitmaps by
* David S. Miller (davem@caip.rutgers.edu), 1995
*/
#include <linux/time.h>
#include <linux/capability.h>
#include <linux/fs.h>
#include <linux/jbd2.h>
#include <linux/ext4_fs.h>
#include <linux/ext4_jbd2.h>
#include <linux/quotaops.h>
#include <linux/buffer_head.h>
Ext4: Uninitialized Block Groups In pass1 of e2fsck, every inode table in the fileystem is scanned and checked, regardless of whether it is in use. This is this the most time consuming part of the filesystem check. The unintialized block group feature can greatly reduce e2fsck time by eliminating checking of uninitialized inodes. With this feature, there is a a high water mark of used inodes for each block group. Block and inode bitmaps can be uninitialized on disk via a flag in the group descriptor to avoid reading or scanning them at e2fsck time. A checksum of each group descriptor is used to ensure that corruption in the group descriptor's bit flags does not cause incorrect operation. The feature is enabled through a mkfs option mke2fs /dev/ -O uninit_groups A patch adding support for uninitialized block groups to e2fsprogs tools has been posted to the linux-ext4 mailing list. The patches have been stress tested with fsstress and fsx. In performance tests testing e2fsck time, we have seen that e2fsck time on ext3 grows linearly with the total number of inodes in the filesytem. In ext4 with the uninitialized block groups feature, the e2fsck time is constant, based solely on the number of used inodes rather than the total inode count. Since typical ext4 filesystems only use 1-10% of their inodes, this feature can greatly reduce e2fsck time for users. With performance improvement of 2-20 times, depending on how full the filesystem is. The attached graph shows the major improvements in e2fsck times in filesystems with a large total inode count, but few inodes in use. In each group descriptor if we have EXT4_BG_INODE_UNINIT set in bg_flags: Inode table is not initialized/used in this group. So we can skip the consistency check during fsck. EXT4_BG_BLOCK_UNINIT set in bg_flags: No block in the group is used. So we can skip the block bitmap verification for this group. We also add two new fields to group descriptor as a part of uninitialized group patch. __le16 bg_itable_unused; /* Unused inodes count */ __le16 bg_checksum; /* crc16(sb_uuid+group+desc) */ bg_itable_unused: If we have EXT4_BG_INODE_UNINIT not set in bg_flags then bg_itable_unused will give the offset within the inode table till the inodes are used. This can be used by fsck to skip list of inodes that are marked unused. bg_checksum: Now that we depend on bg_flags and bg_itable_unused to determine the block and inode usage, we need to make sure group descriptor is not corrupt. We add checksum to group descriptor to detect corruption. If the descriptor is found to be corrupt, we mark all the blocks and inodes in the group used. Signed-off-by: Avantika Mathur <mathur@us.ibm.com> Signed-off-by: Andreas Dilger <adilger@clusterfs.com> Signed-off-by: Mingming Cao <cmm@us.ibm.com> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
2007-10-17 00:38:25 +02:00
#include "group.h"
/*
* balloc.c contains the blocks allocation and deallocation routines
*/
/*
* Calculate the block group number and offset, given a block number
*/
void ext4_get_group_no_and_offset(struct super_block *sb, ext4_fsblk_t blocknr,
unsigned long *blockgrpp, ext4_grpblk_t *offsetp)
{
struct ext4_super_block *es = EXT4_SB(sb)->s_es;
ext4_grpblk_t offset;
blocknr = blocknr - le32_to_cpu(es->s_first_data_block);
offset = do_div(blocknr, EXT4_BLOCKS_PER_GROUP(sb));
if (offsetp)
*offsetp = offset;
if (blockgrpp)
*blockgrpp = blocknr;
}
Ext4: Uninitialized Block Groups In pass1 of e2fsck, every inode table in the fileystem is scanned and checked, regardless of whether it is in use. This is this the most time consuming part of the filesystem check. The unintialized block group feature can greatly reduce e2fsck time by eliminating checking of uninitialized inodes. With this feature, there is a a high water mark of used inodes for each block group. Block and inode bitmaps can be uninitialized on disk via a flag in the group descriptor to avoid reading or scanning them at e2fsck time. A checksum of each group descriptor is used to ensure that corruption in the group descriptor's bit flags does not cause incorrect operation. The feature is enabled through a mkfs option mke2fs /dev/ -O uninit_groups A patch adding support for uninitialized block groups to e2fsprogs tools has been posted to the linux-ext4 mailing list. The patches have been stress tested with fsstress and fsx. In performance tests testing e2fsck time, we have seen that e2fsck time on ext3 grows linearly with the total number of inodes in the filesytem. In ext4 with the uninitialized block groups feature, the e2fsck time is constant, based solely on the number of used inodes rather than the total inode count. Since typical ext4 filesystems only use 1-10% of their inodes, this feature can greatly reduce e2fsck time for users. With performance improvement of 2-20 times, depending on how full the filesystem is. The attached graph shows the major improvements in e2fsck times in filesystems with a large total inode count, but few inodes in use. In each group descriptor if we have EXT4_BG_INODE_UNINIT set in bg_flags: Inode table is not initialized/used in this group. So we can skip the consistency check during fsck. EXT4_BG_BLOCK_UNINIT set in bg_flags: No block in the group is used. So we can skip the block bitmap verification for this group. We also add two new fields to group descriptor as a part of uninitialized group patch. __le16 bg_itable_unused; /* Unused inodes count */ __le16 bg_checksum; /* crc16(sb_uuid+group+desc) */ bg_itable_unused: If we have EXT4_BG_INODE_UNINIT not set in bg_flags then bg_itable_unused will give the offset within the inode table till the inodes are used. This can be used by fsck to skip list of inodes that are marked unused. bg_checksum: Now that we depend on bg_flags and bg_itable_unused to determine the block and inode usage, we need to make sure group descriptor is not corrupt. We add checksum to group descriptor to detect corruption. If the descriptor is found to be corrupt, we mark all the blocks and inodes in the group used. Signed-off-by: Avantika Mathur <mathur@us.ibm.com> Signed-off-by: Andreas Dilger <adilger@clusterfs.com> Signed-off-by: Mingming Cao <cmm@us.ibm.com> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
2007-10-17 00:38:25 +02:00
/* Initializes an uninitialized block bitmap if given, and returns the
* number of blocks free in the group. */
unsigned ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh,
int block_group, struct ext4_group_desc *gdp)
{
unsigned long start;
int bit, bit_max;
unsigned free_blocks, group_blocks;
struct ext4_sb_info *sbi = EXT4_SB(sb);
if (bh) {
J_ASSERT_BH(bh, buffer_locked(bh));
/* If checksum is bad mark all blocks used to prevent allocation
* essentially implementing a per-group read-only flag. */
if (!ext4_group_desc_csum_verify(sbi, block_group, gdp)) {
ext4_error(sb, __FUNCTION__,
"Checksum bad for group %u\n", block_group);
gdp->bg_free_blocks_count = 0;
gdp->bg_free_inodes_count = 0;
gdp->bg_itable_unused = 0;
memset(bh->b_data, 0xff, sb->s_blocksize);
return 0;
}
memset(bh->b_data, 0, sb->s_blocksize);
}
/* Check for superblock and gdt backups in this group */
bit_max = ext4_bg_has_super(sb, block_group);
if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG) ||
block_group < le32_to_cpu(sbi->s_es->s_first_meta_bg) *
sbi->s_desc_per_block) {
if (bit_max) {
bit_max += ext4_bg_num_gdb(sb, block_group);
bit_max +=
le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks);
}
} else { /* For META_BG_BLOCK_GROUPS */
int group_rel = (block_group -
le32_to_cpu(sbi->s_es->s_first_meta_bg)) %
EXT4_DESC_PER_BLOCK(sb);
if (group_rel == 0 || group_rel == 1 ||
(group_rel == EXT4_DESC_PER_BLOCK(sb) - 1))
bit_max += 1;
}
if (block_group == sbi->s_groups_count - 1) {
/*
* Even though mke2fs always initialize first and last group
* if some other tool enabled the EXT4_BG_BLOCK_UNINIT we need
* to make sure we calculate the right free blocks
*/
group_blocks = ext4_blocks_count(sbi->s_es) -
le32_to_cpu(sbi->s_es->s_first_data_block) -
(EXT4_BLOCKS_PER_GROUP(sb) * (sbi->s_groups_count -1));
} else {
group_blocks = EXT4_BLOCKS_PER_GROUP(sb);
}
free_blocks = group_blocks - bit_max;
if (bh) {
for (bit = 0; bit < bit_max; bit++)
ext4_set_bit(bit, bh->b_data);
start = block_group * EXT4_BLOCKS_PER_GROUP(sb) +
le32_to_cpu(sbi->s_es->s_first_data_block);
/* Set bits for block and inode bitmaps, and inode table */
ext4_set_bit(ext4_block_bitmap(sb, gdp) - start, bh->b_data);
ext4_set_bit(ext4_inode_bitmap(sb, gdp) - start, bh->b_data);
for (bit = (ext4_inode_table(sb, gdp) - start),
Ext4: Uninitialized Block Groups In pass1 of e2fsck, every inode table in the fileystem is scanned and checked, regardless of whether it is in use. This is this the most time consuming part of the filesystem check. The unintialized block group feature can greatly reduce e2fsck time by eliminating checking of uninitialized inodes. With this feature, there is a a high water mark of used inodes for each block group. Block and inode bitmaps can be uninitialized on disk via a flag in the group descriptor to avoid reading or scanning them at e2fsck time. A checksum of each group descriptor is used to ensure that corruption in the group descriptor's bit flags does not cause incorrect operation. The feature is enabled through a mkfs option mke2fs /dev/ -O uninit_groups A patch adding support for uninitialized block groups to e2fsprogs tools has been posted to the linux-ext4 mailing list. The patches have been stress tested with fsstress and fsx. In performance tests testing e2fsck time, we have seen that e2fsck time on ext3 grows linearly with the total number of inodes in the filesytem. In ext4 with the uninitialized block groups feature, the e2fsck time is constant, based solely on the number of used inodes rather than the total inode count. Since typical ext4 filesystems only use 1-10% of their inodes, this feature can greatly reduce e2fsck time for users. With performance improvement of 2-20 times, depending on how full the filesystem is. The attached graph shows the major improvements in e2fsck times in filesystems with a large total inode count, but few inodes in use. In each group descriptor if we have EXT4_BG_INODE_UNINIT set in bg_flags: Inode table is not initialized/used in this group. So we can skip the consistency check during fsck. EXT4_BG_BLOCK_UNINIT set in bg_flags: No block in the group is used. So we can skip the block bitmap verification for this group. We also add two new fields to group descriptor as a part of uninitialized group patch. __le16 bg_itable_unused; /* Unused inodes count */ __le16 bg_checksum; /* crc16(sb_uuid+group+desc) */ bg_itable_unused: If we have EXT4_BG_INODE_UNINIT not set in bg_flags then bg_itable_unused will give the offset within the inode table till the inodes are used. This can be used by fsck to skip list of inodes that are marked unused. bg_checksum: Now that we depend on bg_flags and bg_itable_unused to determine the block and inode usage, we need to make sure group descriptor is not corrupt. We add checksum to group descriptor to detect corruption. If the descriptor is found to be corrupt, we mark all the blocks and inodes in the group used. Signed-off-by: Avantika Mathur <mathur@us.ibm.com> Signed-off-by: Andreas Dilger <adilger@clusterfs.com> Signed-off-by: Mingming Cao <cmm@us.ibm.com> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
2007-10-17 00:38:25 +02:00
bit_max = bit + sbi->s_itb_per_group; bit < bit_max; bit++)
ext4_set_bit(bit, bh->b_data);
/*
* Also if the number of blocks within the group is
* less than the blocksize * 8 ( which is the size
* of bitmap ), set rest of the block bitmap to 1
*/
mark_bitmap_end(group_blocks, sb->s_blocksize * 8, bh->b_data);
}
return free_blocks - sbi->s_itb_per_group - 2;
}
/*
* The free blocks are managed by bitmaps. A file system contains several
* blocks groups. Each group contains 1 bitmap block for blocks, 1 bitmap
* block for inodes, N blocks for the inode table and data blocks.
*
* The file system contains group descriptors which are located after the
* super block. Each descriptor contains the number of the bitmap block and
* the free blocks count in the block. The descriptors are loaded in memory
* when a file system is mounted (see ext4_fill_super).
*/
#define in_range(b, first, len) ((b) >= (first) && (b) <= (first) + (len) - 1)
/**
* ext4_get_group_desc() -- load group descriptor from disk
* @sb: super block
* @block_group: given block group
* @bh: pointer to the buffer head to store the block
* group descriptor
*/
struct ext4_group_desc * ext4_get_group_desc(struct super_block * sb,
unsigned int block_group,
struct buffer_head ** bh)
{
unsigned long group_desc;
unsigned long offset;
struct ext4_group_desc * desc;
struct ext4_sb_info *sbi = EXT4_SB(sb);
if (block_group >= sbi->s_groups_count) {
ext4_error (sb, "ext4_get_group_desc",
"block_group >= groups_count - "
"block_group = %d, groups_count = %lu",
block_group, sbi->s_groups_count);
return NULL;
}
smp_rmb();
group_desc = block_group >> EXT4_DESC_PER_BLOCK_BITS(sb);
offset = block_group & (EXT4_DESC_PER_BLOCK(sb) - 1);
if (!sbi->s_group_desc[group_desc]) {
ext4_error (sb, "ext4_get_group_desc",
"Group descriptor not loaded - "
"block_group = %d, group_desc = %lu, desc = %lu",
block_group, group_desc, offset);
return NULL;
}
desc = (struct ext4_group_desc *)(
(__u8 *)sbi->s_group_desc[group_desc]->b_data +
offset * EXT4_DESC_SIZE(sb));
if (bh)
*bh = sbi->s_group_desc[group_desc];
return desc;
}
/**
* read_block_bitmap()
* @sb: super block
* @block_group: given block group
*
* Read the bitmap for a given block_group, reading into the specified
* slot in the superblock's bitmap cache.
*
* Return buffer_head on success or NULL in case of failure.
*/
Ext4: Uninitialized Block Groups In pass1 of e2fsck, every inode table in the fileystem is scanned and checked, regardless of whether it is in use. This is this the most time consuming part of the filesystem check. The unintialized block group feature can greatly reduce e2fsck time by eliminating checking of uninitialized inodes. With this feature, there is a a high water mark of used inodes for each block group. Block and inode bitmaps can be uninitialized on disk via a flag in the group descriptor to avoid reading or scanning them at e2fsck time. A checksum of each group descriptor is used to ensure that corruption in the group descriptor's bit flags does not cause incorrect operation. The feature is enabled through a mkfs option mke2fs /dev/ -O uninit_groups A patch adding support for uninitialized block groups to e2fsprogs tools has been posted to the linux-ext4 mailing list. The patches have been stress tested with fsstress and fsx. In performance tests testing e2fsck time, we have seen that e2fsck time on ext3 grows linearly with the total number of inodes in the filesytem. In ext4 with the uninitialized block groups feature, the e2fsck time is constant, based solely on the number of used inodes rather than the total inode count. Since typical ext4 filesystems only use 1-10% of their inodes, this feature can greatly reduce e2fsck time for users. With performance improvement of 2-20 times, depending on how full the filesystem is. The attached graph shows the major improvements in e2fsck times in filesystems with a large total inode count, but few inodes in use. In each group descriptor if we have EXT4_BG_INODE_UNINIT set in bg_flags: Inode table is not initialized/used in this group. So we can skip the consistency check during fsck. EXT4_BG_BLOCK_UNINIT set in bg_flags: No block in the group is used. So we can skip the block bitmap verification for this group. We also add two new fields to group descriptor as a part of uninitialized group patch. __le16 bg_itable_unused; /* Unused inodes count */ __le16 bg_checksum; /* crc16(sb_uuid+group+desc) */ bg_itable_unused: If we have EXT4_BG_INODE_UNINIT not set in bg_flags then bg_itable_unused will give the offset within the inode table till the inodes are used. This can be used by fsck to skip list of inodes that are marked unused. bg_checksum: Now that we depend on bg_flags and bg_itable_unused to determine the block and inode usage, we need to make sure group descriptor is not corrupt. We add checksum to group descriptor to detect corruption. If the descriptor is found to be corrupt, we mark all the blocks and inodes in the group used. Signed-off-by: Avantika Mathur <mathur@us.ibm.com> Signed-off-by: Andreas Dilger <adilger@clusterfs.com> Signed-off-by: Mingming Cao <cmm@us.ibm.com> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
2007-10-17 00:38:25 +02:00
struct buffer_head *
read_block_bitmap(struct super_block *sb, unsigned int block_group)
{
struct ext4_group_desc * desc;
struct buffer_head * bh = NULL;
ext4_fsblk_t bitmap_blk;
Ext4: Uninitialized Block Groups In pass1 of e2fsck, every inode table in the fileystem is scanned and checked, regardless of whether it is in use. This is this the most time consuming part of the filesystem check. The unintialized block group feature can greatly reduce e2fsck time by eliminating checking of uninitialized inodes. With this feature, there is a a high water mark of used inodes for each block group. Block and inode bitmaps can be uninitialized on disk via a flag in the group descriptor to avoid reading or scanning them at e2fsck time. A checksum of each group descriptor is used to ensure that corruption in the group descriptor's bit flags does not cause incorrect operation. The feature is enabled through a mkfs option mke2fs /dev/ -O uninit_groups A patch adding support for uninitialized block groups to e2fsprogs tools has been posted to the linux-ext4 mailing list. The patches have been stress tested with fsstress and fsx. In performance tests testing e2fsck time, we have seen that e2fsck time on ext3 grows linearly with the total number of inodes in the filesytem. In ext4 with the uninitialized block groups feature, the e2fsck time is constant, based solely on the number of used inodes rather than the total inode count. Since typical ext4 filesystems only use 1-10% of their inodes, this feature can greatly reduce e2fsck time for users. With performance improvement of 2-20 times, depending on how full the filesystem is. The attached graph shows the major improvements in e2fsck times in filesystems with a large total inode count, but few inodes in use. In each group descriptor if we have EXT4_BG_INODE_UNINIT set in bg_flags: Inode table is not initialized/used in this group. So we can skip the consistency check during fsck. EXT4_BG_BLOCK_UNINIT set in bg_flags: No block in the group is used. So we can skip the block bitmap verification for this group. We also add two new fields to group descriptor as a part of uninitialized group patch. __le16 bg_itable_unused; /* Unused inodes count */ __le16 bg_checksum; /* crc16(sb_uuid+group+desc) */ bg_itable_unused: If we have EXT4_BG_INODE_UNINIT not set in bg_flags then bg_itable_unused will give the offset within the inode table till the inodes are used. This can be used by fsck to skip list of inodes that are marked unused. bg_checksum: Now that we depend on bg_flags and bg_itable_unused to determine the block and inode usage, we need to make sure group descriptor is not corrupt. We add checksum to group descriptor to detect corruption. If the descriptor is found to be corrupt, we mark all the blocks and inodes in the group used. Signed-off-by: Avantika Mathur <mathur@us.ibm.com> Signed-off-by: Andreas Dilger <adilger@clusterfs.com> Signed-off-by: Mingming Cao <cmm@us.ibm.com> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
2007-10-17 00:38:25 +02:00
desc = ext4_get_group_desc(sb, block_group, NULL);
if (!desc)
return NULL;
bitmap_blk = ext4_block_bitmap(sb, desc);
Ext4: Uninitialized Block Groups In pass1 of e2fsck, every inode table in the fileystem is scanned and checked, regardless of whether it is in use. This is this the most time consuming part of the filesystem check. The unintialized block group feature can greatly reduce e2fsck time by eliminating checking of uninitialized inodes. With this feature, there is a a high water mark of used inodes for each block group. Block and inode bitmaps can be uninitialized on disk via a flag in the group descriptor to avoid reading or scanning them at e2fsck time. A checksum of each group descriptor is used to ensure that corruption in the group descriptor's bit flags does not cause incorrect operation. The feature is enabled through a mkfs option mke2fs /dev/ -O uninit_groups A patch adding support for uninitialized block groups to e2fsprogs tools has been posted to the linux-ext4 mailing list. The patches have been stress tested with fsstress and fsx. In performance tests testing e2fsck time, we have seen that e2fsck time on ext3 grows linearly with the total number of inodes in the filesytem. In ext4 with the uninitialized block groups feature, the e2fsck time is constant, based solely on the number of used inodes rather than the total inode count. Since typical ext4 filesystems only use 1-10% of their inodes, this feature can greatly reduce e2fsck time for users. With performance improvement of 2-20 times, depending on how full the filesystem is. The attached graph shows the major improvements in e2fsck times in filesystems with a large total inode count, but few inodes in use. In each group descriptor if we have EXT4_BG_INODE_UNINIT set in bg_flags: Inode table is not initialized/used in this group. So we can skip the consistency check during fsck. EXT4_BG_BLOCK_UNINIT set in bg_flags: No block in the group is used. So we can skip the block bitmap verification for this group. We also add two new fields to group descriptor as a part of uninitialized group patch. __le16 bg_itable_unused; /* Unused inodes count */ __le16 bg_checksum; /* crc16(sb_uuid+group+desc) */ bg_itable_unused: If we have EXT4_BG_INODE_UNINIT not set in bg_flags then bg_itable_unused will give the offset within the inode table till the inodes are used. This can be used by fsck to skip list of inodes that are marked unused. bg_checksum: Now that we depend on bg_flags and bg_itable_unused to determine the block and inode usage, we need to make sure group descriptor is not corrupt. We add checksum to group descriptor to detect corruption. If the descriptor is found to be corrupt, we mark all the blocks and inodes in the group used. Signed-off-by: Avantika Mathur <mathur@us.ibm.com> Signed-off-by: Andreas Dilger <adilger@clusterfs.com> Signed-off-by: Mingming Cao <cmm@us.ibm.com> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
2007-10-17 00:38:25 +02:00
if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
bh = sb_getblk(sb, bitmap_blk);
if (!buffer_uptodate(bh)) {
lock_buffer(bh);
if (!buffer_uptodate(bh)) {
ext4_init_block_bitmap(sb, bh, block_group,
desc);
set_buffer_uptodate(bh);
}
unlock_buffer(bh);
}
} else {
bh = sb_bread(sb, bitmap_blk);
}
if (!bh)
ext4_error (sb, __FUNCTION__,
"Cannot read block bitmap - "
"block_group = %d, block_bitmap = %llu",
block_group, bitmap_blk);
return bh;
}
/*
* The reservation window structure operations
* --------------------------------------------
* Operations include:
* dump, find, add, remove, is_empty, find_next_reservable_window, etc.
*
* We use a red-black tree to represent per-filesystem reservation
* windows.
*
*/
/**
* __rsv_window_dump() -- Dump the filesystem block allocation reservation map
* @rb_root: root of per-filesystem reservation rb tree
* @verbose: verbose mode
* @fn: function which wishes to dump the reservation map
*
* If verbose is turned on, it will print the whole block reservation
* windows(start, end). Otherwise, it will only print out the "bad" windows,
* those windows that overlap with their immediate neighbors.
*/
#if 1
static void __rsv_window_dump(struct rb_root *root, int verbose,
const char *fn)
{
struct rb_node *n;
struct ext4_reserve_window_node *rsv, *prev;
int bad;
restart:
n = rb_first(root);
bad = 0;
prev = NULL;
printk("Block Allocation Reservation Windows Map (%s):\n", fn);
while (n) {
rsv = rb_entry(n, struct ext4_reserve_window_node, rsv_node);
if (verbose)
printk("reservation window 0x%p "
"start: %llu, end: %llu\n",
rsv, rsv->rsv_start, rsv->rsv_end);
if (rsv->rsv_start && rsv->rsv_start >= rsv->rsv_end) {
printk("Bad reservation %p (start >= end)\n",
rsv);
bad = 1;
}
if (prev && prev->rsv_end >= rsv->rsv_start) {
printk("Bad reservation %p (prev->end >= start)\n",
rsv);
bad = 1;
}
if (bad) {
if (!verbose) {
printk("Restarting reservation walk in verbose mode\n");
verbose = 1;
goto restart;
}
}
n = rb_next(n);
prev = rsv;
}
printk("Window map complete.\n");
if (bad)
BUG();
}
#define rsv_window_dump(root, verbose) \
__rsv_window_dump((root), (verbose), __FUNCTION__)
#else
#define rsv_window_dump(root, verbose) do {} while (0)
#endif
/**
* goal_in_my_reservation()
* @rsv: inode's reservation window
* @grp_goal: given goal block relative to the allocation block group
* @group: the current allocation block group
* @sb: filesystem super block
*
* Test if the given goal block (group relative) is within the file's
* own block reservation window range.
*
* If the reservation window is outside the goal allocation group, return 0;
* grp_goal (given goal block) could be -1, which means no specific
* goal block. In this case, always return 1.
* If the goal block is within the reservation window, return 1;
* otherwise, return 0;
*/
static int
goal_in_my_reservation(struct ext4_reserve_window *rsv, ext4_grpblk_t grp_goal,
unsigned int group, struct super_block * sb)
{
ext4_fsblk_t group_first_block, group_last_block;
group_first_block = ext4_group_first_block_no(sb, group);
group_last_block = group_first_block + (EXT4_BLOCKS_PER_GROUP(sb) - 1);
if ((rsv->_rsv_start > group_last_block) ||
(rsv->_rsv_end < group_first_block))
return 0;
if ((grp_goal >= 0) && ((grp_goal + group_first_block < rsv->_rsv_start)
|| (grp_goal + group_first_block > rsv->_rsv_end)))
return 0;
return 1;
}
/**
* search_reserve_window()
* @rb_root: root of reservation tree
* @goal: target allocation block
*
* Find the reserved window which includes the goal, or the previous one
* if the goal is not in any window.
* Returns NULL if there are no windows or if all windows start after the goal.
*/
static struct ext4_reserve_window_node *
search_reserve_window(struct rb_root *root, ext4_fsblk_t goal)
{
struct rb_node *n = root->rb_node;
struct ext4_reserve_window_node *rsv;
if (!n)
return NULL;
do {
rsv = rb_entry(n, struct ext4_reserve_window_node, rsv_node);
if (goal < rsv->rsv_start)
n = n->rb_left;
else if (goal > rsv->rsv_end)
n = n->rb_right;
else
return rsv;
} while (n);
/*
* We've fallen off the end of the tree: the goal wasn't inside
* any particular node. OK, the previous node must be to one
* side of the interval containing the goal. If it's the RHS,
* we need to back up one.
*/
if (rsv->rsv_start > goal) {
n = rb_prev(&rsv->rsv_node);
rsv = rb_entry(n, struct ext4_reserve_window_node, rsv_node);
}
return rsv;
}
/**
* ext4_rsv_window_add() -- Insert a window to the block reservation rb tree.
* @sb: super block
* @rsv: reservation window to add
*
* Must be called with rsv_lock hold.
*/
void ext4_rsv_window_add(struct super_block *sb,
struct ext4_reserve_window_node *rsv)
{
struct rb_root *root = &EXT4_SB(sb)->s_rsv_window_root;
struct rb_node *node = &rsv->rsv_node;
ext4_fsblk_t start = rsv->rsv_start;
struct rb_node ** p = &root->rb_node;
struct rb_node * parent = NULL;
struct ext4_reserve_window_node *this;
while (*p)
{
parent = *p;
this = rb_entry(parent, struct ext4_reserve_window_node, rsv_node);
if (start < this->rsv_start)
p = &(*p)->rb_left;
else if (start > this->rsv_end)
p = &(*p)->rb_right;
else {
rsv_window_dump(root, 1);
BUG();
}
}
rb_link_node(node, parent, p);
rb_insert_color(node, root);
}
/**
* ext4_rsv_window_remove() -- unlink a window from the reservation rb tree
* @sb: super block
* @rsv: reservation window to remove
*
* Mark the block reservation window as not allocated, and unlink it
* from the filesystem reservation window rb tree. Must be called with
* rsv_lock hold.
*/
static void rsv_window_remove(struct super_block *sb,
struct ext4_reserve_window_node *rsv)
{
rsv->rsv_start = EXT4_RESERVE_WINDOW_NOT_ALLOCATED;
rsv->rsv_end = EXT4_RESERVE_WINDOW_NOT_ALLOCATED;
rsv->rsv_alloc_hit = 0;
rb_erase(&rsv->rsv_node, &EXT4_SB(sb)->s_rsv_window_root);
}
/*
* rsv_is_empty() -- Check if the reservation window is allocated.
* @rsv: given reservation window to check
*
* returns 1 if the end block is EXT4_RESERVE_WINDOW_NOT_ALLOCATED.
*/
static inline int rsv_is_empty(struct ext4_reserve_window *rsv)
{
/* a valid reservation end block could not be 0 */
return rsv->_rsv_end == EXT4_RESERVE_WINDOW_NOT_ALLOCATED;
}
/**
* ext4_init_block_alloc_info()
* @inode: file inode structure
*
* Allocate and initialize the reservation window structure, and
* link the window to the ext4 inode structure at last
*
* The reservation window structure is only dynamically allocated
* and linked to ext4 inode the first time the open file
* needs a new block. So, before every ext4_new_block(s) call, for
* regular files, we should check whether the reservation window
* structure exists or not. In the latter case, this function is called.
* Fail to do so will result in block reservation being turned off for that
* open file.
*
* This function is called from ext4_get_blocks_handle(), also called
* when setting the reservation window size through ioctl before the file
* is open for write (needs block allocation).
*
* Needs truncate_mutex protection prior to call this function.
*/
void ext4_init_block_alloc_info(struct inode *inode)
{
struct ext4_inode_info *ei = EXT4_I(inode);
struct ext4_block_alloc_info *block_i = ei->i_block_alloc_info;
struct super_block *sb = inode->i_sb;
block_i = kmalloc(sizeof(*block_i), GFP_NOFS);
if (block_i) {
struct ext4_reserve_window_node *rsv = &block_i->rsv_window_node;
rsv->rsv_start = EXT4_RESERVE_WINDOW_NOT_ALLOCATED;
rsv->rsv_end = EXT4_RESERVE_WINDOW_NOT_ALLOCATED;
/*
* if filesystem is mounted with NORESERVATION, the goal
* reservation window size is set to zero to indicate
* block reservation is off
*/
if (!test_opt(sb, RESERVATION))
rsv->rsv_goal_size = 0;
else
rsv->rsv_goal_size = EXT4_DEFAULT_RESERVE_BLOCKS;
rsv->rsv_alloc_hit = 0;
block_i->last_alloc_logical_block = 0;
block_i->last_alloc_physical_block = 0;
}
ei->i_block_alloc_info = block_i;
}
/**
* ext4_discard_reservation()
* @inode: inode
*
* Discard(free) block reservation window on last file close, or truncate
* or at last iput().
*
* It is being called in three cases:
* ext4_release_file(): last writer close the file
* ext4_clear_inode(): last iput(), when nobody link to this file.
* ext4_truncate(): when the block indirect map is about to change.
*
*/
void ext4_discard_reservation(struct inode *inode)
{
struct ext4_inode_info *ei = EXT4_I(inode);
struct ext4_block_alloc_info *block_i = ei->i_block_alloc_info;
struct ext4_reserve_window_node *rsv;
spinlock_t *rsv_lock = &EXT4_SB(inode->i_sb)->s_rsv_window_lock;
if (!block_i)
return;
rsv = &block_i->rsv_window_node;
if (!rsv_is_empty(&rsv->rsv_window)) {
spin_lock(rsv_lock);
if (!rsv_is_empty(&rsv->rsv_window))
rsv_window_remove(inode->i_sb, rsv);
spin_unlock(rsv_lock);
}
}
/**
* ext4_free_blocks_sb() -- Free given blocks and update quota
* @handle: handle to this transaction
* @sb: super block
* @block: start physcial block to free
* @count: number of blocks to free
* @pdquot_freed_blocks: pointer to quota
*/
void ext4_free_blocks_sb(handle_t *handle, struct super_block *sb,
ext4_fsblk_t block, unsigned long count,
unsigned long *pdquot_freed_blocks)
{
struct buffer_head *bitmap_bh = NULL;
struct buffer_head *gd_bh;
unsigned long block_group;
ext4_grpblk_t bit;
unsigned long i;
unsigned long overflow;
struct ext4_group_desc * desc;
struct ext4_super_block * es;
struct ext4_sb_info *sbi;
int err = 0, ret;
ext4_grpblk_t group_freed;
*pdquot_freed_blocks = 0;
sbi = EXT4_SB(sb);
es = sbi->s_es;
if (block < le32_to_cpu(es->s_first_data_block) ||
block + count < block ||
block + count > ext4_blocks_count(es)) {
ext4_error (sb, "ext4_free_blocks",
"Freeing blocks not in datazone - "
"block = %llu, count = %lu", block, count);
goto error_return;
}
ext4_debug ("freeing block(s) %llu-%llu\n", block, block + count - 1);
do_more:
overflow = 0;
ext4_get_group_no_and_offset(sb, block, &block_group, &bit);
/*
* Check to see if we are freeing blocks across a group
* boundary.
*/
if (bit + count > EXT4_BLOCKS_PER_GROUP(sb)) {
overflow = bit + count - EXT4_BLOCKS_PER_GROUP(sb);
count -= overflow;
}
brelse(bitmap_bh);
bitmap_bh = read_block_bitmap(sb, block_group);
if (!bitmap_bh)
goto error_return;
desc = ext4_get_group_desc (sb, block_group, &gd_bh);
if (!desc)
goto error_return;
if (in_range(ext4_block_bitmap(sb, desc), block, count) ||
in_range(ext4_inode_bitmap(sb, desc), block, count) ||
in_range(block, ext4_inode_table(sb, desc), sbi->s_itb_per_group) ||
in_range(block + count - 1, ext4_inode_table(sb, desc),
sbi->s_itb_per_group))
ext4_error (sb, "ext4_free_blocks",
"Freeing blocks in system zones - "
"Block = %llu, count = %lu",
block, count);
/*
* We are about to start releasing blocks in the bitmap,
* so we need undo access.
*/
/* @@@ check errors */
BUFFER_TRACE(bitmap_bh, "getting undo access");
err = ext4_journal_get_undo_access(handle, bitmap_bh);
if (err)
goto error_return;
/*
* We are about to modify some metadata. Call the journal APIs
* to unshare ->b_data if a currently-committing transaction is
* using it
*/
BUFFER_TRACE(gd_bh, "get_write_access");
err = ext4_journal_get_write_access(handle, gd_bh);
if (err)
goto error_return;
jbd_lock_bh_state(bitmap_bh);
for (i = 0, group_freed = 0; i < count; i++) {
/*
* An HJ special. This is expensive...
*/
#ifdef CONFIG_JBD2_DEBUG
jbd_unlock_bh_state(bitmap_bh);
{
struct buffer_head *debug_bh;
debug_bh = sb_find_get_block(sb, block + i);
if (debug_bh) {
BUFFER_TRACE(debug_bh, "Deleted!");
if (!bh2jh(bitmap_bh)->b_committed_data)
BUFFER_TRACE(debug_bh,
"No commited data in bitmap");
BUFFER_TRACE2(debug_bh, bitmap_bh, "bitmap");
__brelse(debug_bh);
}
}
jbd_lock_bh_state(bitmap_bh);
#endif
if (need_resched()) {
jbd_unlock_bh_state(bitmap_bh);
cond_resched();
jbd_lock_bh_state(bitmap_bh);
}
/* @@@ This prevents newly-allocated data from being
* freed and then reallocated within the same
* transaction.
*
* Ideally we would want to allow that to happen, but to
* do so requires making jbd2_journal_forget() capable of
* revoking the queued write of a data block, which
* implies blocking on the journal lock. *forget()
* cannot block due to truncate races.
*
* Eventually we can fix this by making jbd2_journal_forget()
* return a status indicating whether or not it was able
* to revoke the buffer. On successful revoke, it is
* safe not to set the allocation bit in the committed
* bitmap, because we know that there is no outstanding
* activity on the buffer any more and so it is safe to
* reallocate it.
*/
BUFFER_TRACE(bitmap_bh, "set in b_committed_data");
J_ASSERT_BH(bitmap_bh,
bh2jh(bitmap_bh)->b_committed_data != NULL);
ext4_set_bit_atomic(sb_bgl_lock(sbi, block_group), bit + i,
bh2jh(bitmap_bh)->b_committed_data);
/*
* We clear the bit in the bitmap after setting the committed
* data bit, because this is the reverse order to that which
* the allocator uses.
*/
BUFFER_TRACE(bitmap_bh, "clear bit");
if (!ext4_clear_bit_atomic(sb_bgl_lock(sbi, block_group),
bit + i, bitmap_bh->b_data)) {
jbd_unlock_bh_state(bitmap_bh);
ext4_error(sb, __FUNCTION__,
"bit already cleared for block %llu",
(ext4_fsblk_t)(block + i));
jbd_lock_bh_state(bitmap_bh);
BUFFER_TRACE(bitmap_bh, "bit already cleared");
} else {
group_freed++;
}
}
jbd_unlock_bh_state(bitmap_bh);
spin_lock(sb_bgl_lock(sbi, block_group));
desc->bg_free_blocks_count =
cpu_to_le16(le16_to_cpu(desc->bg_free_blocks_count) +
group_freed);
Ext4: Uninitialized Block Groups In pass1 of e2fsck, every inode table in the fileystem is scanned and checked, regardless of whether it is in use. This is this the most time consuming part of the filesystem check. The unintialized block group feature can greatly reduce e2fsck time by eliminating checking of uninitialized inodes. With this feature, there is a a high water mark of used inodes for each block group. Block and inode bitmaps can be uninitialized on disk via a flag in the group descriptor to avoid reading or scanning them at e2fsck time. A checksum of each group descriptor is used to ensure that corruption in the group descriptor's bit flags does not cause incorrect operation. The feature is enabled through a mkfs option mke2fs /dev/ -O uninit_groups A patch adding support for uninitialized block groups to e2fsprogs tools has been posted to the linux-ext4 mailing list. The patches have been stress tested with fsstress and fsx. In performance tests testing e2fsck time, we have seen that e2fsck time on ext3 grows linearly with the total number of inodes in the filesytem. In ext4 with the uninitialized block groups feature, the e2fsck time is constant, based solely on the number of used inodes rather than the total inode count. Since typical ext4 filesystems only use 1-10% of their inodes, this feature can greatly reduce e2fsck time for users. With performance improvement of 2-20 times, depending on how full the filesystem is. The attached graph shows the major improvements in e2fsck times in filesystems with a large total inode count, but few inodes in use. In each group descriptor if we have EXT4_BG_INODE_UNINIT set in bg_flags: Inode table is not initialized/used in this group. So we can skip the consistency check during fsck. EXT4_BG_BLOCK_UNINIT set in bg_flags: No block in the group is used. So we can skip the block bitmap verification for this group. We also add two new fields to group descriptor as a part of uninitialized group patch. __le16 bg_itable_unused; /* Unused inodes count */ __le16 bg_checksum; /* crc16(sb_uuid+group+desc) */ bg_itable_unused: If we have EXT4_BG_INODE_UNINIT not set in bg_flags then bg_itable_unused will give the offset within the inode table till the inodes are used. This can be used by fsck to skip list of inodes that are marked unused. bg_checksum: Now that we depend on bg_flags and bg_itable_unused to determine the block and inode usage, we need to make sure group descriptor is not corrupt. We add checksum to group descriptor to detect corruption. If the descriptor is found to be corrupt, we mark all the blocks and inodes in the group used. Signed-off-by: Avantika Mathur <mathur@us.ibm.com> Signed-off-by: Andreas Dilger <adilger@clusterfs.com> Signed-off-by: Mingming Cao <cmm@us.ibm.com> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
2007-10-17 00:38:25 +02:00
desc->bg_checksum = ext4_group_desc_csum(sbi, block_group, desc);
spin_unlock(sb_bgl_lock(sbi, block_group));
percpu_counter_add(&sbi->s_freeblocks_counter, count);
/* We dirtied the bitmap block */
BUFFER_TRACE(bitmap_bh, "dirtied bitmap block");
err = ext4_journal_dirty_metadata(handle, bitmap_bh);
/* And the group descriptor block */
BUFFER_TRACE(gd_bh, "dirtied group descriptor block");
ret = ext4_journal_dirty_metadata(handle, gd_bh);
if (!err) err = ret;
*pdquot_freed_blocks += group_freed;
if (overflow && !err) {
block += count;
count = overflow;
goto do_more;
}
sb->s_dirt = 1;
error_return:
brelse(bitmap_bh);
ext4_std_error(sb, err);
return;
}
/**
* ext4_free_blocks() -- Free given blocks and update quota
* @handle: handle for this transaction
* @inode: inode
* @block: start physical block to free
* @count: number of blocks to count
*/
void ext4_free_blocks(handle_t *handle, struct inode *inode,
ext4_fsblk_t block, unsigned long count)
{
struct super_block * sb;
unsigned long dquot_freed_blocks;
sb = inode->i_sb;
if (!sb) {
printk ("ext4_free_blocks: nonexistent device");
return;
}
ext4_free_blocks_sb(handle, sb, block, count, &dquot_freed_blocks);
if (dquot_freed_blocks)
DQUOT_FREE_BLOCK(inode, dquot_freed_blocks);
return;
}
/**
* ext4_test_allocatable()
* @nr: given allocation block group
* @bh: bufferhead contains the bitmap of the given block group
*
* For ext4 allocations, we must not reuse any blocks which are
* allocated in the bitmap buffer's "last committed data" copy. This
* prevents deletes from freeing up the page for reuse until we have
* committed the delete transaction.
*
* If we didn't do this, then deleting something and reallocating it as
* data would allow the old block to be overwritten before the
* transaction committed (because we force data to disk before commit).
* This would lead to corruption if we crashed between overwriting the
* data and committing the delete.
*
* @@@ We may want to make this allocation behaviour conditional on
* data-writes at some point, and disable it for metadata allocations or
* sync-data inodes.
*/
static int ext4_test_allocatable(ext4_grpblk_t nr, struct buffer_head *bh)
{
int ret;
struct journal_head *jh = bh2jh(bh);
if (ext4_test_bit(nr, bh->b_data))
return 0;
jbd_lock_bh_state(bh);
if (!jh->b_committed_data)
ret = 1;
else
ret = !ext4_test_bit(nr, jh->b_committed_data);
jbd_unlock_bh_state(bh);
return ret;
}
/**
* bitmap_search_next_usable_block()
* @start: the starting block (group relative) of the search
* @bh: bufferhead contains the block group bitmap
* @maxblocks: the ending block (group relative) of the reservation
*
* The bitmap search --- search forward alternately through the actual
* bitmap on disk and the last-committed copy in journal, until we find a
* bit free in both bitmaps.
*/
static ext4_grpblk_t
bitmap_search_next_usable_block(ext4_grpblk_t start, struct buffer_head *bh,
ext4_grpblk_t maxblocks)
{
ext4_grpblk_t next;
struct journal_head *jh = bh2jh(bh);
while (start < maxblocks) {
next = ext4_find_next_zero_bit(bh->b_data, maxblocks, start);
if (next >= maxblocks)
return -1;
if (ext4_test_allocatable(next, bh))
return next;
jbd_lock_bh_state(bh);
if (jh->b_committed_data)
start = ext4_find_next_zero_bit(jh->b_committed_data,
maxblocks, next);
jbd_unlock_bh_state(bh);
}
return -1;
}
/**
* find_next_usable_block()
* @start: the starting block (group relative) to find next
* allocatable block in bitmap.
* @bh: bufferhead contains the block group bitmap
* @maxblocks: the ending block (group relative) for the search
*
* Find an allocatable block in a bitmap. We honor both the bitmap and
* its last-committed copy (if that exists), and perform the "most
* appropriate allocation" algorithm of looking for a free block near
* the initial goal; then for a free byte somewhere in the bitmap; then
* for any free bit in the bitmap.
*/
static ext4_grpblk_t
find_next_usable_block(ext4_grpblk_t start, struct buffer_head *bh,
ext4_grpblk_t maxblocks)
{
ext4_grpblk_t here, next;
char *p, *r;
if (start > 0) {
/*
* The goal was occupied; search forward for a free
* block within the next XX blocks.
*
* end_goal is more or less random, but it has to be
* less than EXT4_BLOCKS_PER_GROUP. Aligning up to the
* next 64-bit boundary is simple..
*/
ext4_grpblk_t end_goal = (start + 63) & ~63;
if (end_goal > maxblocks)
end_goal = maxblocks;
here = ext4_find_next_zero_bit(bh->b_data, end_goal, start);
if (here < end_goal && ext4_test_allocatable(here, bh))
return here;
ext4_debug("Bit not found near goal\n");
}
here = start;
if (here < 0)
here = 0;
p = ((char *)bh->b_data) + (here >> 3);
r = memscan(p, 0, ((maxblocks + 7) >> 3) - (here >> 3));
next = (r - ((char *)bh->b_data)) << 3;
if (next < maxblocks && next >= start && ext4_test_allocatable(next, bh))
return next;
/*
* The bitmap search --- search forward alternately through the actual
* bitmap and the last-committed copy until we find a bit free in
* both
*/
here = bitmap_search_next_usable_block(here, bh, maxblocks);
return here;
}
/**
* claim_block()
* @block: the free block (group relative) to allocate
* @bh: the bufferhead containts the block group bitmap
*
* We think we can allocate this block in this bitmap. Try to set the bit.
* If that succeeds then check that nobody has allocated and then freed the
* block since we saw that is was not marked in b_committed_data. If it _was_
* allocated and freed then clear the bit in the bitmap again and return
* zero (failure).
*/
static inline int
claim_block(spinlock_t *lock, ext4_grpblk_t block, struct buffer_head *bh)
{
struct journal_head *jh = bh2jh(bh);
int ret;
if (ext4_set_bit_atomic(lock, block, bh->b_data))
return 0;
jbd_lock_bh_state(bh);
if (jh->b_committed_data && ext4_test_bit(block,jh->b_committed_data)) {
ext4_clear_bit_atomic(lock, block, bh->b_data);
ret = 0;
} else {
ret = 1;
}
jbd_unlock_bh_state(bh);
return ret;
}
/**
* ext4_try_to_allocate()
* @sb: superblock
* @handle: handle to this transaction
* @group: given allocation block group
* @bitmap_bh: bufferhead holds the block bitmap
* @grp_goal: given target block within the group
* @count: target number of blocks to allocate
* @my_rsv: reservation window
*
* Attempt to allocate blocks within a give range. Set the range of allocation
* first, then find the first free bit(s) from the bitmap (within the range),
* and at last, allocate the blocks by claiming the found free bit as allocated.
*
* To set the range of this allocation:
* if there is a reservation window, only try to allocate block(s) from the
* file's own reservation window;
* Otherwise, the allocation range starts from the give goal block, ends at
* the block group's last block.
*
* If we failed to allocate the desired block then we may end up crossing to a
* new bitmap. In that case we must release write access to the old one via
* ext4_journal_release_buffer(), else we'll run out of credits.
*/
static ext4_grpblk_t
ext4_try_to_allocate(struct super_block *sb, handle_t *handle, int group,
struct buffer_head *bitmap_bh, ext4_grpblk_t grp_goal,
unsigned long *count, struct ext4_reserve_window *my_rsv)
{
ext4_fsblk_t group_first_block;
ext4_grpblk_t start, end;
unsigned long num = 0;
/* we do allocation within the reservation window if we have a window */
if (my_rsv) {
group_first_block = ext4_group_first_block_no(sb, group);
if (my_rsv->_rsv_start >= group_first_block)
start = my_rsv->_rsv_start - group_first_block;
else
/* reservation window cross group boundary */
start = 0;
end = my_rsv->_rsv_end - group_first_block + 1;
if (end > EXT4_BLOCKS_PER_GROUP(sb))
/* reservation window crosses group boundary */
end = EXT4_BLOCKS_PER_GROUP(sb);
if ((start <= grp_goal) && (grp_goal < end))
start = grp_goal;
else
grp_goal = -1;
} else {
if (grp_goal > 0)
start = grp_goal;
else
start = 0;
end = EXT4_BLOCKS_PER_GROUP(sb);
}
BUG_ON(start > EXT4_BLOCKS_PER_GROUP(sb));
repeat:
if (grp_goal < 0 || !ext4_test_allocatable(grp_goal, bitmap_bh)) {
grp_goal = find_next_usable_block(start, bitmap_bh, end);
if (grp_goal < 0)
goto fail_access;
if (!my_rsv) {
int i;
for (i = 0; i < 7 && grp_goal > start &&
ext4_test_allocatable(grp_goal - 1,
bitmap_bh);
i++, grp_goal--)
;
}
}
start = grp_goal;
if (!claim_block(sb_bgl_lock(EXT4_SB(sb), group),
grp_goal, bitmap_bh)) {
/*
* The block was allocated by another thread, or it was
* allocated and then freed by another thread
*/
start++;
grp_goal++;
if (start >= end)
goto fail_access;
goto repeat;
}
num++;
grp_goal++;
while (num < *count && grp_goal < end
&& ext4_test_allocatable(grp_goal, bitmap_bh)
&& claim_block(sb_bgl_lock(EXT4_SB(sb), group),
grp_goal, bitmap_bh)) {
num++;
grp_goal++;
}
*count = num;
return grp_goal - num;
fail_access:
*count = num;
return -1;
}
/**
* find_next_reservable_window():
* find a reservable space within the given range.
* It does not allocate the reservation window for now:
* alloc_new_reservation() will do the work later.
*
* @search_head: the head of the searching list;
* This is not necessarily the list head of the whole filesystem
*
* We have both head and start_block to assist the search
* for the reservable space. The list starts from head,
* but we will shift to the place where start_block is,
* then start from there, when looking for a reservable space.
*
* @size: the target new reservation window size
*
* @group_first_block: the first block we consider to start
* the real search from
*
* @last_block:
* the maximum block number that our goal reservable space
* could start from. This is normally the last block in this
* group. The search will end when we found the start of next
* possible reservable space is out of this boundary.
* This could handle the cross boundary reservation window
* request.
*
* basically we search from the given range, rather than the whole
* reservation double linked list, (start_block, last_block)
* to find a free region that is of my size and has not
* been reserved.
*
*/
static int find_next_reservable_window(
struct ext4_reserve_window_node *search_head,
struct ext4_reserve_window_node *my_rsv,
struct super_block * sb,
ext4_fsblk_t start_block,
ext4_fsblk_t last_block)
{
struct rb_node *next;
struct ext4_reserve_window_node *rsv, *prev;
ext4_fsblk_t cur;
int size = my_rsv->rsv_goal_size;
/* TODO: make the start of the reservation window byte-aligned */
/* cur = *start_block & ~7;*/
cur = start_block;
rsv = search_head;
if (!rsv)
return -1;
while (1) {
if (cur <= rsv->rsv_end)
cur = rsv->rsv_end + 1;
/* TODO?
* in the case we could not find a reservable space
* that is what is expected, during the re-search, we could
* remember what's the largest reservable space we could have
* and return that one.
*
* For now it will fail if we could not find the reservable
* space with expected-size (or more)...
*/
if (cur > last_block)
return -1; /* fail */
prev = rsv;
next = rb_next(&rsv->rsv_node);
rsv = rb_entry(next,struct ext4_reserve_window_node,rsv_node);
/*
* Reached the last reservation, we can just append to the
* previous one.
*/
if (!next)
break;
if (cur + size <= rsv->rsv_start) {
/*
* Found a reserveable space big enough. We could
* have a reservation across the group boundary here
*/
break;
}
}
/*
* we come here either :
* when we reach the end of the whole list,
* and there is empty reservable space after last entry in the list.
* append it to the end of the list.
*
* or we found one reservable space in the middle of the list,
* return the reservation window that we could append to.
* succeed.
*/
if ((prev != my_rsv) && (!rsv_is_empty(&my_rsv->rsv_window)))
rsv_window_remove(sb, my_rsv);
/*
* Let's book the whole avaliable window for now. We will check the
* disk bitmap later and then, if there are free blocks then we adjust
* the window size if it's larger than requested.
* Otherwise, we will remove this node from the tree next time
* call find_next_reservable_window.
*/
my_rsv->rsv_start = cur;
my_rsv->rsv_end = cur + size - 1;
my_rsv->rsv_alloc_hit = 0;
if (prev != my_rsv)
ext4_rsv_window_add(sb, my_rsv);
return 0;
}
/**
* alloc_new_reservation()--allocate a new reservation window
*
* To make a new reservation, we search part of the filesystem
* reservation list (the list that inside the group). We try to
* allocate a new reservation window near the allocation goal,
* or the beginning of the group, if there is no goal.
*
* We first find a reservable space after the goal, then from
* there, we check the bitmap for the first free block after
* it. If there is no free block until the end of group, then the
* whole group is full, we failed. Otherwise, check if the free
* block is inside the expected reservable space, if so, we
* succeed.
* If the first free block is outside the reservable space, then
* start from the first free block, we search for next available
* space, and go on.
*
* on succeed, a new reservation will be found and inserted into the list
* It contains at least one free block, and it does not overlap with other
* reservation windows.
*
* failed: we failed to find a reservation window in this group
*
* @rsv: the reservation
*
* @grp_goal: The goal (group-relative). It is where the search for a
* free reservable space should start from.
* if we have a grp_goal(grp_goal >0 ), then start from there,
* no grp_goal(grp_goal = -1), we start from the first block
* of the group.
*
* @sb: the super block
* @group: the group we are trying to allocate in
* @bitmap_bh: the block group block bitmap
*
*/
static int alloc_new_reservation(struct ext4_reserve_window_node *my_rsv,
ext4_grpblk_t grp_goal, struct super_block *sb,
unsigned int group, struct buffer_head *bitmap_bh)
{
struct ext4_reserve_window_node *search_head;
ext4_fsblk_t group_first_block, group_end_block, start_block;
ext4_grpblk_t first_free_block;
struct rb_root *fs_rsv_root = &EXT4_SB(sb)->s_rsv_window_root;
unsigned long size;
int ret;
spinlock_t *rsv_lock = &EXT4_SB(sb)->s_rsv_window_lock;
group_first_block = ext4_group_first_block_no(sb, group);
group_end_block = group_first_block + (EXT4_BLOCKS_PER_GROUP(sb) - 1);
if (grp_goal < 0)
start_block = group_first_block;
else
start_block = grp_goal + group_first_block;
size = my_rsv->rsv_goal_size;
if (!rsv_is_empty(&my_rsv->rsv_window)) {
/*
* if the old reservation is cross group boundary
* and if the goal is inside the old reservation window,
* we will come here when we just failed to allocate from
* the first part of the window. We still have another part
* that belongs to the next group. In this case, there is no
* point to discard our window and try to allocate a new one
* in this group(which will fail). we should
* keep the reservation window, just simply move on.
*
* Maybe we could shift the start block of the reservation
* window to the first block of next group.
*/
if ((my_rsv->rsv_start <= group_end_block) &&
(my_rsv->rsv_end > group_end_block) &&
(start_block >= my_rsv->rsv_start))
return -1;
if ((my_rsv->rsv_alloc_hit >
(my_rsv->rsv_end - my_rsv->rsv_start + 1) / 2)) {
/*
* if the previously allocation hit ratio is
* greater than 1/2, then we double the size of
* the reservation window the next time,
* otherwise we keep the same size window
*/
size = size * 2;
if (size > EXT4_MAX_RESERVE_BLOCKS)
size = EXT4_MAX_RESERVE_BLOCKS;
my_rsv->rsv_goal_size= size;
}
}
spin_lock(rsv_lock);
/*
* shift the search start to the window near the goal block
*/
search_head = search_reserve_window(fs_rsv_root, start_block);
/*
* find_next_reservable_window() simply finds a reservable window
* inside the given range(start_block, group_end_block).
*
* To make sure the reservation window has a free bit inside it, we
* need to check the bitmap after we found a reservable window.
*/
retry:
ret = find_next_reservable_window(search_head, my_rsv, sb,
start_block, group_end_block);
if (ret == -1) {
if (!rsv_is_empty(&my_rsv->rsv_window))
rsv_window_remove(sb, my_rsv);
spin_unlock(rsv_lock);
return -1;
}
/*
* On success, find_next_reservable_window() returns the
* reservation window where there is a reservable space after it.
* Before we reserve this reservable space, we need
* to make sure there is at least a free block inside this region.
*
* searching the first free bit on the block bitmap and copy of
* last committed bitmap alternatively, until we found a allocatable
* block. Search start from the start block of the reservable space
* we just found.
*/
spin_unlock(rsv_lock);
first_free_block = bitmap_search_next_usable_block(
my_rsv->rsv_start - group_first_block,
bitmap_bh, group_end_block - group_first_block + 1);
if (first_free_block < 0) {
/*
* no free block left on the bitmap, no point
* to reserve the space. return failed.
*/
spin_lock(rsv_lock);
if (!rsv_is_empty(&my_rsv->rsv_window))
rsv_window_remove(sb, my_rsv);
spin_unlock(rsv_lock);
return -1; /* failed */
}
start_block = first_free_block + group_first_block;
/*
* check if the first free block is within the
* free space we just reserved
*/
if (start_block >= my_rsv->rsv_start && start_block <= my_rsv->rsv_end)
return 0; /* success */
/*
* if the first free bit we found is out of the reservable space
* continue search for next reservable space,
* start from where the free block is,
* we also shift the list head to where we stopped last time
*/
search_head = my_rsv;
spin_lock(rsv_lock);
goto retry;
}
/**
* try_to_extend_reservation()
* @my_rsv: given reservation window
* @sb: super block
* @size: the delta to extend
*
* Attempt to expand the reservation window large enough to have
* required number of free blocks
*
* Since ext4_try_to_allocate() will always allocate blocks within
* the reservation window range, if the window size is too small,
* multiple blocks allocation has to stop at the end of the reservation
* window. To make this more efficient, given the total number of
* blocks needed and the current size of the window, we try to
* expand the reservation window size if necessary on a best-effort
* basis before ext4_new_blocks() tries to allocate blocks,
*/
static void try_to_extend_reservation(struct ext4_reserve_window_node *my_rsv,
struct super_block *sb, int size)
{
struct ext4_reserve_window_node *next_rsv;
struct rb_node *next;
spinlock_t *rsv_lock = &EXT4_SB(sb)->s_rsv_window_lock;
if (!spin_trylock(rsv_lock))
return;
next = rb_next(&my_rsv->rsv_node);
if (!next)
my_rsv->rsv_end += size;
else {
next_rsv = rb_entry(next, struct ext4_reserve_window_node, rsv_node);
if ((next_rsv->rsv_start - my_rsv->rsv_end - 1) >= size)
my_rsv->rsv_end += size;
else
my_rsv->rsv_end = next_rsv->rsv_start - 1;
}
spin_unlock(rsv_lock);
}
/**
* ext4_try_to_allocate_with_rsv()
* @sb: superblock
* @handle: handle to this transaction
* @group: given allocation block group
* @bitmap_bh: bufferhead holds the block bitmap
* @grp_goal: given target block within the group
* @count: target number of blocks to allocate
* @my_rsv: reservation window
* @errp: pointer to store the error code
*
* This is the main function used to allocate a new block and its reservation
* window.
*
* Each time when a new block allocation is need, first try to allocate from
* its own reservation. If it does not have a reservation window, instead of
* looking for a free bit on bitmap first, then look up the reservation list to
* see if it is inside somebody else's reservation window, we try to allocate a
* reservation window for it starting from the goal first. Then do the block
* allocation within the reservation window.
*
* This will avoid keeping on searching the reservation list again and
* again when somebody is looking for a free block (without
* reservation), and there are lots of free blocks, but they are all
* being reserved.
*
* We use a red-black tree for the per-filesystem reservation list.
*
*/
static ext4_grpblk_t
ext4_try_to_allocate_with_rsv(struct super_block *sb, handle_t *handle,
unsigned int group, struct buffer_head *bitmap_bh,
ext4_grpblk_t grp_goal,
struct ext4_reserve_window_node * my_rsv,
unsigned long *count, int *errp)
{
ext4_fsblk_t group_first_block, group_last_block;
ext4_grpblk_t ret = 0;
int fatal;
unsigned long num = *count;
*errp = 0;
/*
* Make sure we use undo access for the bitmap, because it is critical
* that we do the frozen_data COW on bitmap buffers in all cases even
* if the buffer is in BJ_Forget state in the committing transaction.
*/
BUFFER_TRACE(bitmap_bh, "get undo access for new block");
fatal = ext4_journal_get_undo_access(handle, bitmap_bh);
if (fatal) {
*errp = fatal;
return -1;
}
/*
* we don't deal with reservation when
* filesystem is mounted without reservation
* or the file is not a regular file
* or last attempt to allocate a block with reservation turned on failed
*/
if (my_rsv == NULL ) {
ret = ext4_try_to_allocate(sb, handle, group, bitmap_bh,
grp_goal, count, NULL);
goto out;
}
/*
* grp_goal is a group relative block number (if there is a goal)
* 0 <= grp_goal < EXT4_BLOCKS_PER_GROUP(sb)
* first block is a filesystem wide block number
* first block is the block number of the first block in this group
*/
group_first_block = ext4_group_first_block_no(sb, group);
group_last_block = group_first_block + (EXT4_BLOCKS_PER_GROUP(sb) - 1);
/*
* Basically we will allocate a new block from inode's reservation
* window.
*
* We need to allocate a new reservation window, if:
* a) inode does not have a reservation window; or
* b) last attempt to allocate a block from existing reservation
* failed; or
* c) we come here with a goal and with a reservation window
*
* We do not need to allocate a new reservation window if we come here
* at the beginning with a goal and the goal is inside the window, or
* we don't have a goal but already have a reservation window.
* then we could go to allocate from the reservation window directly.
*/
while (1) {
if (rsv_is_empty(&my_rsv->rsv_window) || (ret < 0) ||
!goal_in_my_reservation(&my_rsv->rsv_window,
grp_goal, group, sb)) {
if (my_rsv->rsv_goal_size < *count)
my_rsv->rsv_goal_size = *count;
ret = alloc_new_reservation(my_rsv, grp_goal, sb,
group, bitmap_bh);
if (ret < 0)
break; /* failed */
if (!goal_in_my_reservation(&my_rsv->rsv_window,
grp_goal, group, sb))
grp_goal = -1;
} else if (grp_goal >= 0) {
int curr = my_rsv->rsv_end -
(grp_goal + group_first_block) + 1;
if (curr < *count)
try_to_extend_reservation(my_rsv, sb,
*count - curr);
}
if ((my_rsv->rsv_start > group_last_block) ||
(my_rsv->rsv_end < group_first_block)) {
rsv_window_dump(&EXT4_SB(sb)->s_rsv_window_root, 1);
BUG();
}
ret = ext4_try_to_allocate(sb, handle, group, bitmap_bh,
grp_goal, &num, &my_rsv->rsv_window);
if (ret >= 0) {
my_rsv->rsv_alloc_hit += num;
*count = num;
break; /* succeed */
}
num = *count;
}
out:
if (ret >= 0) {
BUFFER_TRACE(bitmap_bh, "journal_dirty_metadata for "
"bitmap block");
fatal = ext4_journal_dirty_metadata(handle, bitmap_bh);
if (fatal) {
*errp = fatal;
return -1;
}
return ret;
}
BUFFER_TRACE(bitmap_bh, "journal_release_buffer");
ext4_journal_release_buffer(handle, bitmap_bh);
return ret;
}
/**
* ext4_has_free_blocks()
* @sbi: in-core super block structure.
*
* Check if filesystem has at least 1 free block available for allocation.
*/
static int ext4_has_free_blocks(struct ext4_sb_info *sbi)
{
ext4_fsblk_t free_blocks, root_blocks;
free_blocks = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
root_blocks = ext4_r_blocks_count(sbi->s_es);
if (free_blocks < root_blocks + 1 && !capable(CAP_SYS_RESOURCE) &&
sbi->s_resuid != current->fsuid &&
(sbi->s_resgid == 0 || !in_group_p (sbi->s_resgid))) {
return 0;
}
return 1;
}
/**
* ext4_should_retry_alloc()
* @sb: super block
* @retries number of attemps has been made
*
* ext4_should_retry_alloc() is called when ENOSPC is returned, and if
* it is profitable to retry the operation, this function will wait
* for the current or commiting transaction to complete, and then
* return TRUE.
*
* if the total number of retries exceed three times, return FALSE.
*/
int ext4_should_retry_alloc(struct super_block *sb, int *retries)
{
if (!ext4_has_free_blocks(EXT4_SB(sb)) || (*retries)++ > 3)
return 0;
jbd_debug(1, "%s: retrying operation after ENOSPC\n", sb->s_id);
return jbd2_journal_force_commit_nested(EXT4_SB(sb)->s_journal);
}
/**
* ext4_new_blocks() -- core block(s) allocation function
* @handle: handle to this transaction
* @inode: file inode
* @goal: given target block(filesystem wide)
* @count: target number of blocks to allocate
* @errp: error code
*
* ext4_new_blocks uses a goal block to assist allocation. It tries to
* allocate block(s) from the block group contains the goal block first. If that
* fails, it will try to allocate block(s) from other block groups without
* any specific goal block.
*
*/
ext4_fsblk_t ext4_new_blocks(handle_t *handle, struct inode *inode,
ext4_fsblk_t goal, unsigned long *count, int *errp)
{
struct buffer_head *bitmap_bh = NULL;
struct buffer_head *gdp_bh;
unsigned long group_no;
int goal_group;
ext4_grpblk_t grp_target_blk; /* blockgroup relative goal block */
ext4_grpblk_t grp_alloc_blk; /* blockgroup-relative allocated block*/
ext4_fsblk_t ret_block; /* filesyetem-wide allocated block */
int bgi; /* blockgroup iteration index */
int fatal = 0, err;
int performed_allocation = 0;
ext4_grpblk_t free_blocks; /* number of free blocks in a group */
struct super_block *sb;
struct ext4_group_desc *gdp;
struct ext4_super_block *es;
struct ext4_sb_info *sbi;
struct ext4_reserve_window_node *my_rsv = NULL;
struct ext4_block_alloc_info *block_i;
unsigned short windowsz = 0;
#ifdef EXT4FS_DEBUG
static int goal_hits, goal_attempts;
#endif
unsigned long ngroups;
unsigned long num = *count;
*errp = -ENOSPC;
sb = inode->i_sb;
if (!sb) {
printk("ext4_new_block: nonexistent device");
return 0;
}
/*
* Check quota for allocation of this block.
*/
if (DQUOT_ALLOC_BLOCK(inode, num)) {
*errp = -EDQUOT;
return 0;
}
sbi = EXT4_SB(sb);
es = EXT4_SB(sb)->s_es;
ext4_debug("goal=%lu.\n", goal);
/*
* Allocate a block from reservation only when
* filesystem is mounted with reservation(default,-o reservation), and
* it's a regular file, and
* the desired window size is greater than 0 (One could use ioctl
* command EXT4_IOC_SETRSVSZ to set the window size to 0 to turn off
* reservation on that particular file)
*/
block_i = EXT4_I(inode)->i_block_alloc_info;
if (block_i && ((windowsz = block_i->rsv_window_node.rsv_goal_size) > 0))
my_rsv = &block_i->rsv_window_node;
if (!ext4_has_free_blocks(sbi)) {
*errp = -ENOSPC;
goto out;
}
/*
* First, test whether the goal block is free.
*/
if (goal < le32_to_cpu(es->s_first_data_block) ||
goal >= ext4_blocks_count(es))
goal = le32_to_cpu(es->s_first_data_block);
ext4_get_group_no_and_offset(sb, goal, &group_no, &grp_target_blk);
goal_group = group_no;
retry_alloc:
gdp = ext4_get_group_desc(sb, group_no, &gdp_bh);
if (!gdp)
goto io_error;
free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
/*
* if there is not enough free blocks to make a new resevation
* turn off reservation for this allocation
*/
if (my_rsv && (free_blocks < windowsz)
&& (rsv_is_empty(&my_rsv->rsv_window)))
my_rsv = NULL;
if (free_blocks > 0) {
bitmap_bh = read_block_bitmap(sb, group_no);
if (!bitmap_bh)
goto io_error;
grp_alloc_blk = ext4_try_to_allocate_with_rsv(sb, handle,
group_no, bitmap_bh, grp_target_blk,
my_rsv, &num, &fatal);
if (fatal)
goto out;
if (grp_alloc_blk >= 0)
goto allocated;
}
ngroups = EXT4_SB(sb)->s_groups_count;
smp_rmb();
/*
* Now search the rest of the groups. We assume that
* i and gdp correctly point to the last group visited.
*/
for (bgi = 0; bgi < ngroups; bgi++) {
group_no++;
if (group_no >= ngroups)
group_no = 0;
gdp = ext4_get_group_desc(sb, group_no, &gdp_bh);
if (!gdp)
goto io_error;
free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
/*
* skip this group if the number of
* free blocks is less than half of the reservation
* window size.
*/
if (free_blocks <= (windowsz/2))
continue;
brelse(bitmap_bh);
bitmap_bh = read_block_bitmap(sb, group_no);
if (!bitmap_bh)
goto io_error;
/*
* try to allocate block(s) from this group, without a goal(-1).
*/
grp_alloc_blk = ext4_try_to_allocate_with_rsv(sb, handle,
group_no, bitmap_bh, -1, my_rsv,
&num, &fatal);
if (fatal)
goto out;
if (grp_alloc_blk >= 0)
goto allocated;
}
/*
* We may end up a bogus ealier ENOSPC error due to
* filesystem is "full" of reservations, but
* there maybe indeed free blocks avaliable on disk
* In this case, we just forget about the reservations
* just do block allocation as without reservations.
*/
if (my_rsv) {
my_rsv = NULL;
windowsz = 0;
group_no = goal_group;
goto retry_alloc;
}
/* No space left on the device */
*errp = -ENOSPC;
goto out;
allocated:
ext4_debug("using block group %d(%d)\n",
group_no, gdp->bg_free_blocks_count);
BUFFER_TRACE(gdp_bh, "get_write_access");
fatal = ext4_journal_get_write_access(handle, gdp_bh);
if (fatal)
goto out;
ret_block = grp_alloc_blk + ext4_group_first_block_no(sb, group_no);
if (in_range(ext4_block_bitmap(sb, gdp), ret_block, num) ||
in_range(ext4_inode_bitmap(sb, gdp), ret_block, num) ||
in_range(ret_block, ext4_inode_table(sb, gdp),
EXT4_SB(sb)->s_itb_per_group) ||
in_range(ret_block + num - 1, ext4_inode_table(sb, gdp),
EXT4_SB(sb)->s_itb_per_group))
ext4_error(sb, "ext4_new_block",
"Allocating block in system zone - "
"blocks from %llu, length %lu",
ret_block, num);
performed_allocation = 1;
#ifdef CONFIG_JBD2_DEBUG
{
struct buffer_head *debug_bh;
/* Record bitmap buffer state in the newly allocated block */
debug_bh = sb_find_get_block(sb, ret_block);
if (debug_bh) {
BUFFER_TRACE(debug_bh, "state when allocated");
BUFFER_TRACE2(debug_bh, bitmap_bh, "bitmap state");
brelse(debug_bh);
}
}
jbd_lock_bh_state(bitmap_bh);
spin_lock(sb_bgl_lock(sbi, group_no));
if (buffer_jbd(bitmap_bh) && bh2jh(bitmap_bh)->b_committed_data) {
int i;
for (i = 0; i < num; i++) {
if (ext4_test_bit(grp_alloc_blk+i,
bh2jh(bitmap_bh)->b_committed_data)) {
printk("%s: block was unexpectedly set in "
"b_committed_data\n", __FUNCTION__);
}
}
}
ext4_debug("found bit %d\n", grp_alloc_blk);
spin_unlock(sb_bgl_lock(sbi, group_no));
jbd_unlock_bh_state(bitmap_bh);
#endif
if (ret_block + num - 1 >= ext4_blocks_count(es)) {
ext4_error(sb, "ext4_new_block",
"block(%llu) >= blocks count(%llu) - "
"block_group = %lu, es == %p ", ret_block,
ext4_blocks_count(es), group_no, es);
goto out;
}
/*
* It is up to the caller to add the new buffer to a journal
* list of some description. We don't know in advance whether
* the caller wants to use it as metadata or data.
*/
ext4_debug("allocating block %lu. Goal hits %d of %d.\n",
ret_block, goal_hits, goal_attempts);
spin_lock(sb_bgl_lock(sbi, group_no));
Ext4: Uninitialized Block Groups In pass1 of e2fsck, every inode table in the fileystem is scanned and checked, regardless of whether it is in use. This is this the most time consuming part of the filesystem check. The unintialized block group feature can greatly reduce e2fsck time by eliminating checking of uninitialized inodes. With this feature, there is a a high water mark of used inodes for each block group. Block and inode bitmaps can be uninitialized on disk via a flag in the group descriptor to avoid reading or scanning them at e2fsck time. A checksum of each group descriptor is used to ensure that corruption in the group descriptor's bit flags does not cause incorrect operation. The feature is enabled through a mkfs option mke2fs /dev/ -O uninit_groups A patch adding support for uninitialized block groups to e2fsprogs tools has been posted to the linux-ext4 mailing list. The patches have been stress tested with fsstress and fsx. In performance tests testing e2fsck time, we have seen that e2fsck time on ext3 grows linearly with the total number of inodes in the filesytem. In ext4 with the uninitialized block groups feature, the e2fsck time is constant, based solely on the number of used inodes rather than the total inode count. Since typical ext4 filesystems only use 1-10% of their inodes, this feature can greatly reduce e2fsck time for users. With performance improvement of 2-20 times, depending on how full the filesystem is. The attached graph shows the major improvements in e2fsck times in filesystems with a large total inode count, but few inodes in use. In each group descriptor if we have EXT4_BG_INODE_UNINIT set in bg_flags: Inode table is not initialized/used in this group. So we can skip the consistency check during fsck. EXT4_BG_BLOCK_UNINIT set in bg_flags: No block in the group is used. So we can skip the block bitmap verification for this group. We also add two new fields to group descriptor as a part of uninitialized group patch. __le16 bg_itable_unused; /* Unused inodes count */ __le16 bg_checksum; /* crc16(sb_uuid+group+desc) */ bg_itable_unused: If we have EXT4_BG_INODE_UNINIT not set in bg_flags then bg_itable_unused will give the offset within the inode table till the inodes are used. This can be used by fsck to skip list of inodes that are marked unused. bg_checksum: Now that we depend on bg_flags and bg_itable_unused to determine the block and inode usage, we need to make sure group descriptor is not corrupt. We add checksum to group descriptor to detect corruption. If the descriptor is found to be corrupt, we mark all the blocks and inodes in the group used. Signed-off-by: Avantika Mathur <mathur@us.ibm.com> Signed-off-by: Andreas Dilger <adilger@clusterfs.com> Signed-off-by: Mingming Cao <cmm@us.ibm.com> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
2007-10-17 00:38:25 +02:00
if (gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT))
gdp->bg_flags &= cpu_to_le16(~EXT4_BG_BLOCK_UNINIT);
gdp->bg_free_blocks_count =
cpu_to_le16(le16_to_cpu(gdp->bg_free_blocks_count)-num);
Ext4: Uninitialized Block Groups In pass1 of e2fsck, every inode table in the fileystem is scanned and checked, regardless of whether it is in use. This is this the most time consuming part of the filesystem check. The unintialized block group feature can greatly reduce e2fsck time by eliminating checking of uninitialized inodes. With this feature, there is a a high water mark of used inodes for each block group. Block and inode bitmaps can be uninitialized on disk via a flag in the group descriptor to avoid reading or scanning them at e2fsck time. A checksum of each group descriptor is used to ensure that corruption in the group descriptor's bit flags does not cause incorrect operation. The feature is enabled through a mkfs option mke2fs /dev/ -O uninit_groups A patch adding support for uninitialized block groups to e2fsprogs tools has been posted to the linux-ext4 mailing list. The patches have been stress tested with fsstress and fsx. In performance tests testing e2fsck time, we have seen that e2fsck time on ext3 grows linearly with the total number of inodes in the filesytem. In ext4 with the uninitialized block groups feature, the e2fsck time is constant, based solely on the number of used inodes rather than the total inode count. Since typical ext4 filesystems only use 1-10% of their inodes, this feature can greatly reduce e2fsck time for users. With performance improvement of 2-20 times, depending on how full the filesystem is. The attached graph shows the major improvements in e2fsck times in filesystems with a large total inode count, but few inodes in use. In each group descriptor if we have EXT4_BG_INODE_UNINIT set in bg_flags: Inode table is not initialized/used in this group. So we can skip the consistency check during fsck. EXT4_BG_BLOCK_UNINIT set in bg_flags: No block in the group is used. So we can skip the block bitmap verification for this group. We also add two new fields to group descriptor as a part of uninitialized group patch. __le16 bg_itable_unused; /* Unused inodes count */ __le16 bg_checksum; /* crc16(sb_uuid+group+desc) */ bg_itable_unused: If we have EXT4_BG_INODE_UNINIT not set in bg_flags then bg_itable_unused will give the offset within the inode table till the inodes are used. This can be used by fsck to skip list of inodes that are marked unused. bg_checksum: Now that we depend on bg_flags and bg_itable_unused to determine the block and inode usage, we need to make sure group descriptor is not corrupt. We add checksum to group descriptor to detect corruption. If the descriptor is found to be corrupt, we mark all the blocks and inodes in the group used. Signed-off-by: Avantika Mathur <mathur@us.ibm.com> Signed-off-by: Andreas Dilger <adilger@clusterfs.com> Signed-off-by: Mingming Cao <cmm@us.ibm.com> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
2007-10-17 00:38:25 +02:00
gdp->bg_checksum = ext4_group_desc_csum(sbi, group_no, gdp);
spin_unlock(sb_bgl_lock(sbi, group_no));
percpu_counter_sub(&sbi->s_freeblocks_counter, num);
BUFFER_TRACE(gdp_bh, "journal_dirty_metadata for group descriptor");
err = ext4_journal_dirty_metadata(handle, gdp_bh);
if (!fatal)
fatal = err;
sb->s_dirt = 1;
if (fatal)
goto out;
*errp = 0;
brelse(bitmap_bh);
DQUOT_FREE_BLOCK(inode, *count-num);
*count = num;
return ret_block;
io_error:
*errp = -EIO;
out:
if (fatal) {
*errp = fatal;
ext4_std_error(sb, fatal);
}
/*
* Undo the block allocation
*/
if (!performed_allocation)
DQUOT_FREE_BLOCK(inode, *count);
brelse(bitmap_bh);
return 0;
}
ext4_fsblk_t ext4_new_block(handle_t *handle, struct inode *inode,
ext4_fsblk_t goal, int *errp)
{
unsigned long count = 1;
return ext4_new_blocks(handle, inode, goal, &count, errp);
}
/**
* ext4_count_free_blocks() -- count filesystem free blocks
* @sb: superblock
*
* Adds up the number of free blocks from each block group.
*/
ext4_fsblk_t ext4_count_free_blocks(struct super_block *sb)
{
ext4_fsblk_t desc_count;
struct ext4_group_desc *gdp;
int i;
unsigned long ngroups = EXT4_SB(sb)->s_groups_count;
#ifdef EXT4FS_DEBUG
struct ext4_super_block *es;
ext4_fsblk_t bitmap_count;
unsigned long x;
struct buffer_head *bitmap_bh = NULL;
es = EXT4_SB(sb)->s_es;
desc_count = 0;
bitmap_count = 0;
gdp = NULL;
smp_rmb();
for (i = 0; i < ngroups; i++) {
gdp = ext4_get_group_desc(sb, i, NULL);
if (!gdp)
continue;
desc_count += le16_to_cpu(gdp->bg_free_blocks_count);
brelse(bitmap_bh);
bitmap_bh = read_block_bitmap(sb, i);
if (bitmap_bh == NULL)
continue;
x = ext4_count_free(bitmap_bh, sb->s_blocksize);
printk("group %d: stored = %d, counted = %lu\n",
i, le16_to_cpu(gdp->bg_free_blocks_count), x);
bitmap_count += x;
}
brelse(bitmap_bh);
printk("ext4_count_free_blocks: stored = %llu"
", computed = %llu, %llu\n",
EXT4_FREE_BLOCKS_COUNT(es),
desc_count, bitmap_count);
return bitmap_count;
#else
desc_count = 0;
smp_rmb();
for (i = 0; i < ngroups; i++) {
gdp = ext4_get_group_desc(sb, i, NULL);
if (!gdp)
continue;
desc_count += le16_to_cpu(gdp->bg_free_blocks_count);
}
return desc_count;
#endif
}
static inline int test_root(int a, int b)
{
int num = b;
while (a > num)
num *= b;
return num == a;
}
static int ext4_group_sparse(int group)
{
if (group <= 1)
return 1;
if (!(group & 1))
return 0;
return (test_root(group, 7) || test_root(group, 5) ||
test_root(group, 3));
}
/**
* ext4_bg_has_super - number of blocks used by the superblock in group
* @sb: superblock for filesystem
* @group: group number to check
*
* Return the number of blocks used by the superblock (primary or backup)
* in this group. Currently this will be only 0 or 1.
*/
int ext4_bg_has_super(struct super_block *sb, int group)
{
if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER) &&
!ext4_group_sparse(group))
return 0;
return 1;
}
static unsigned long ext4_bg_num_gdb_meta(struct super_block *sb, int group)
{
unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);
unsigned long first = metagroup * EXT4_DESC_PER_BLOCK(sb);
unsigned long last = first + EXT4_DESC_PER_BLOCK(sb) - 1;
if (group == first || group == first + 1 || group == last)
return 1;
return 0;
}
static unsigned long ext4_bg_num_gdb_nometa(struct super_block *sb, int group)
{
if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER) &&
!ext4_group_sparse(group))
return 0;
return EXT4_SB(sb)->s_gdb_count;
}
/**
* ext4_bg_num_gdb - number of blocks used by the group table in group
* @sb: superblock for filesystem
* @group: group number to check
*
* Return the number of blocks used by the group descriptor table
* (primary or backup) in this group. In the future there may be a
* different number of descriptor blocks in each group.
*/
unsigned long ext4_bg_num_gdb(struct super_block *sb, int group)
{
unsigned long first_meta_bg =
le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg);
unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);
if (!EXT4_HAS_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG) ||
metagroup < first_meta_bg)
return ext4_bg_num_gdb_nometa(sb,group);
return ext4_bg_num_gdb_meta(sb,group);
}