From 393418676a7602e1d7d3f6e560159c65c8cbd50e Mon Sep 17 00:00:00 2001 From: "Aneesh Kumar K.V" Date: Mon, 5 Jan 2009 21:38:14 -0500 Subject: [PATCH] ext4: Fix the race between read_inode_bitmap() and ext4_new_inode() We need to make sure we update the inode bitmap and clear EXT4_BG_INODE_UNINIT flag with sb_bgl_lock held, since ext4_read_inode_bitmap() looks at EXT4_BG_INODE_UNINIT to decide whether to initialize the inode bitmap each time it is called. (introduced by commit c806e68f.) ext4_read_inode_bitmap does: spin_lock(sb_bgl_lock(EXT4_SB(sb), block_group)); if (desc->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT)) { ext4_init_inode_bitmap(sb, bh, block_group, desc); and ext4_new_inode does if (!ext4_set_bit_atomic(sb_bgl_lock(sbi, group), ino, inode_bitmap_bh->b_data)) ...... ... spin_lock(sb_bgl_lock(sbi, group)); gdp->bg_flags &= cpu_to_le16(~EXT4_BG_INODE_UNINIT); i.e., on allocation we update the bitmap then we take the sb_bgl_lock and clear the EXT4_BG_INODE_UNINIT flag. What can happen is a parallel ext4_read_inode_bitmap can zero out the bitmap in between the above ext4_set_bit_atomic and spin_lock(sb_bg_lock..) The race results in below user visible errors EXT4-fs error (device sdb1): ext4_free_inode: bit already cleared for inode 168449 EXT4-fs warning (device sdb1): ext4_unlink: Deleting nonexistent file ... EXT4-fs warning (device sdb1): ext4_rmdir: empty directory has too many links ... # ls -al /mnt/tmp/f/p369/d3/d6/d39/db2/dee/d10f/d3f/l71 ls: /mnt/tmp/f/p369/d3/d6/d39/db2/dee/d10f/d3f/l71: Stale NFS file handle Signed-off-by: Aneesh Kumar K.V Signed-off-by: "Theodore Ts'o" Cc: stable@kernel.org --- fs/ext4/ialloc.c | 146 ++++++++++++++++++++++++++++------------------- 1 file changed, 86 insertions(+), 60 deletions(-) diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c index b47427a21f1c..d4e544f30be2 100644 --- a/fs/ext4/ialloc.c +++ b/fs/ext4/ialloc.c @@ -572,6 +572,79 @@ static int find_group_other(struct super_block *sb, struct inode *parent, return -1; } +/* + * claim the inode from the inode bitmap. If the group + * is uninit we need to take the groups's sb_bgl_lock + * and clear the uninit flag. The inode bitmap update + * and group desc uninit flag clear should be done + * after holding sb_bgl_lock so that ext4_read_inode_bitmap + * doesn't race with the ext4_claim_inode + */ +static int ext4_claim_inode(struct super_block *sb, + struct buffer_head *inode_bitmap_bh, + unsigned long ino, ext4_group_t group, int mode) +{ + int free = 0, retval = 0, count; + struct ext4_sb_info *sbi = EXT4_SB(sb); + struct ext4_group_desc *gdp = ext4_get_group_desc(sb, group, NULL); + + spin_lock(sb_bgl_lock(sbi, group)); + if (ext4_set_bit(ino, inode_bitmap_bh->b_data)) { + /* not a free inode */ + retval = 1; + goto err_ret; + } + ino++; + if ((group == 0 && ino < EXT4_FIRST_INO(sb)) || + ino > EXT4_INODES_PER_GROUP(sb)) { + spin_unlock(sb_bgl_lock(sbi, group)); + ext4_error(sb, __func__, + "reserved inode or inode > inodes count - " + "block_group = %u, inode=%lu", group, + ino + group * EXT4_INODES_PER_GROUP(sb)); + return 1; + } + /* If we didn't allocate from within the initialized part of the inode + * table then we need to initialize up to this inode. */ + if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) { + + if (gdp->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT)) { + gdp->bg_flags &= cpu_to_le16(~EXT4_BG_INODE_UNINIT); + /* When marking the block group with + * ~EXT4_BG_INODE_UNINIT we don't want to depend + * on the value of bg_itable_unused even though + * mke2fs could have initialized the same for us. + * Instead we calculated the value below + */ + + free = 0; + } else { + free = EXT4_INODES_PER_GROUP(sb) - + ext4_itable_unused_count(sb, gdp); + } + + /* + * Check the relative inode number against the last used + * relative inode number in this group. if it is greater + * we need to update the bg_itable_unused count + * + */ + if (ino > free) + ext4_itable_unused_set(sb, gdp, + (EXT4_INODES_PER_GROUP(sb) - ino)); + } + count = ext4_free_inodes_count(sb, gdp) - 1; + ext4_free_inodes_set(sb, gdp, count); + if (S_ISDIR(mode)) { + count = ext4_used_dirs_count(sb, gdp) + 1; + ext4_used_dirs_set(sb, gdp, count); + } + gdp->bg_checksum = ext4_group_desc_csum(sbi, group, gdp); +err_ret: + spin_unlock(sb_bgl_lock(sbi, group)); + return retval; +} + /* * There are two policies for allocating an inode. If the new inode is * a directory, then a forward search is made for a block group with both @@ -594,7 +667,7 @@ struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, int mode) struct ext4_super_block *es; struct ext4_inode_info *ei; struct ext4_sb_info *sbi; - int ret2, err = 0, count; + int ret2, err = 0; struct inode *ret; ext4_group_t i; int free = 0; @@ -658,8 +731,13 @@ repeat_in_this_group: if (err) goto fail; - if (!ext4_set_bit_atomic(sb_bgl_lock(sbi, group), - ino, inode_bitmap_bh->b_data)) { + BUFFER_TRACE(group_desc_bh, "get_write_access"); + err = ext4_journal_get_write_access(handle, + group_desc_bh); + if (err) + goto fail; + if (!ext4_claim_inode(sb, inode_bitmap_bh, + ino, group, mode)) { /* we won it */ BUFFER_TRACE(inode_bitmap_bh, "call ext4_handle_dirty_metadata"); @@ -668,10 +746,13 @@ repeat_in_this_group: inode_bitmap_bh); if (err) goto fail; + /* zero bit is inode number 1*/ + ino++; goto got; } /* we lost it */ ext4_handle_release_buffer(handle, inode_bitmap_bh); + ext4_handle_release_buffer(handle, group_desc_bh); if (++ino < EXT4_INODES_PER_GROUP(sb)) goto repeat_in_this_group; @@ -691,22 +772,6 @@ repeat_in_this_group: goto out; got: - ino++; - if ((group == 0 && ino < EXT4_FIRST_INO(sb)) || - ino > EXT4_INODES_PER_GROUP(sb)) { - ext4_error(sb, __func__, - "reserved inode or inode > inodes count - " - "block_group = %u, inode=%lu", group, - ino + group * EXT4_INODES_PER_GROUP(sb)); - err = -EIO; - goto fail; - } - - BUFFER_TRACE(group_desc_bh, "get_write_access"); - err = ext4_journal_get_write_access(handle, group_desc_bh); - if (err) - goto fail; - /* We may have to initialize the block bitmap if it isn't already */ if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_GDT_CSUM) && gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) { @@ -743,49 +808,10 @@ got: if (err) goto fail; } - - spin_lock(sb_bgl_lock(sbi, group)); - /* If we didn't allocate from within the initialized part of the inode - * table then we need to initialize up to this inode. */ - if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) { - if (gdp->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT)) { - gdp->bg_flags &= cpu_to_le16(~EXT4_BG_INODE_UNINIT); - - /* When marking the block group with - * ~EXT4_BG_INODE_UNINIT we don't want to depend - * on the value of bg_itable_unused even though - * mke2fs could have initialized the same for us. - * Instead we calculated the value below - */ - - free = 0; - } else { - free = EXT4_INODES_PER_GROUP(sb) - - ext4_itable_unused_count(sb, gdp); - } - - /* - * Check the relative inode number against the last used - * relative inode number in this group. if it is greater - * we need to update the bg_itable_unused count - * - */ - if (ino > free) - ext4_itable_unused_set(sb, gdp, - (EXT4_INODES_PER_GROUP(sb) - ino)); - } - - count = ext4_free_inodes_count(sb, gdp) - 1; - ext4_free_inodes_set(sb, gdp, count); - if (S_ISDIR(mode)) { - count = ext4_used_dirs_count(sb, gdp) + 1; - ext4_used_dirs_set(sb, gdp, count); - } - gdp->bg_checksum = ext4_group_desc_csum(sbi, group, gdp); - spin_unlock(sb_bgl_lock(sbi, group)); BUFFER_TRACE(group_desc_bh, "call ext4_handle_dirty_metadata"); err = ext4_handle_dirty_metadata(handle, NULL, group_desc_bh); - if (err) goto fail; + if (err) + goto fail; percpu_counter_dec(&sbi->s_freeinodes_counter); if (S_ISDIR(mode))