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Filipe Manana 6b0a4f603d btrfs: fix race when defragmenting leads to unnecessary IO 
[ Upstream commit 7f458a3873ae94efe1f37c8b96c97e7298769e98 ]

When defragmenting we skip ranges that have holes or inline extents, so that
we don't do unnecessary IO and waste space. We do this check when calling
should_defrag_range() at btrfs_defrag_file(). However we do it without
holding the inode's lock. The reason we do it like this is to avoid
blocking other tasks for too long, that possibly want to operate on other
file ranges, since after the call to should_defrag_range() and before
locking the inode, we trigger a synchronous page cache readahead. However
before we were able to lock the inode, some other task might have punched
a hole in our range, or we may now have an inline extent there, in which
case we should not set the range for defrag anymore since that would cause
unnecessary IO and make us waste space (i.e. allocating extents to contain
zeros for a hole).

So after we locked the inode and the range in the iotree, check again if
we have holes or an inline extent, and if we do, just skip the range.

I hit this while testing my next patch that fixes races when updating an
inode's number of bytes (subject "btrfs: update the number of bytes used
by an inode atomically"), and it depends on this change in order to work
correctly. Alternatively I could rework that other patch to detect holes
and flag their range with the 'new delalloc' bit, but this itself fixes
an efficiency problem due a race that from a functional point of view is
not harmful (it could be triggered with btrfs/062 from fstests).

CC: stable@vger.kernel.org # 5.4+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
 		2021-01-06 14:48:36 +01:00
..
tests btrfs: Correctly handle empty trees in find_first_clear_extent_bit 2020-02-11 04:35:34 -08:00
Kconfig btrfs: Fix build error while LIBCRC32C is module 2019-07-17 17:03:30 +02:00
Makefile btrfs: migrate the block group lookup code 2019-09-09 14:59:04 +02:00
acl.c
…
async-thread.c Btrfs: fix crash during unmount due to race with delayed inode workers 2020-04-17 10:50:15 +02:00
async-thread.h Btrfs: fix crash during unmount due to race with delayed inode workers 2020-04-17 10:50:15 +02:00
backref.c btrfs: fix double free on ulist after backref resolution failure 2020-07-29 10:18:30 +02:00
backref.h
…
block-group.c btrfs: take overcommit into account in inc_block_group_ro 2020-10-17 10:11:21 +02:00
block-group.h btrfs: move struct io_ctl to free-space-cache.h 2019-09-09 14:59:15 +02:00
block-rsv.c btrfs: force chunk allocation if our global rsv is larger than metadata 2020-06-22 09:31:13 +02:00
block-rsv.h btrfs: migrate the global_block_rsv helpers to block-rsv.c 2019-07-02 12:30:55 +02:00
btrfs_inode.h btrfs: remove assumption about csum type form btrfs_print_data_csum_error() 2019-07-01 13:35:02 +02:00
check-integrity.c btrfs: fix possible NULL-pointer dereference in integrity checks 2020-02-24 08:36:53 +01:00
check-integrity.h
…
compression.c btrfs: move cond_wake_up functions out of ctree 2019-09-09 14:59:15 +02:00
compression.h btrfs: compression: replace set_level callbacks by a common helper 2019-09-09 14:59:11 +02:00
ctree.c btrfs: cleanup cow block on error 2020-11-05 11:43:27 +01:00
ctree.h btrfs: fix readahead hang and use-after-free after removing a device 2020-11-05 11:43:27 +01:00
delalloc-space.c Btrfs: fix qgroup double free after failure to reserve metadata for delalloc 2019-10-17 20:13:44 +02:00
delalloc-space.h btrfs: migrate the delalloc space stuff to it's own home 2019-07-04 17:26:17 +02:00
delayed-inode.c btrfs: qgroup: fix wrong qgroup metadata reserve for delayed inode 2020-11-05 11:43:26 +01:00
delayed-inode.h
…
delayed-ref.c Btrfs: fix race between adding and putting tree mod seq elements and nodes 2020-02-11 04:35:34 -08:00
delayed-ref.h btrfs: migrate the delayed refs rsv code 2019-07-04 17:26:17 +02:00
dev-replace.c btrfs: dev-replace: fail mount if we don't have replace item with target device 2020-11-18 19:20:29 +01:00
dev-replace.h
…
dir-item.c
…
disk-io.c btrfs: fix overflow when copying corrupt csums for a message 2020-10-01 13:18:24 +02:00
disk-io.h btrfs: Make reada_tree_block_flagged private 2019-09-09 14:59:11 +02:00
export.c btrfs: export helpers for subvolume name/id resolution 2020-08-26 10:40:49 +02:00
export.h btrfs: export helpers for subvolume name/id resolution 2020-08-26 10:40:49 +02:00
extent-tree.c btrfs: trim: fix underflow in trim length to prevent access beyond device boundary 2020-12-30 11:51:37 +01:00
extent_io.c btrfs: fix potential deadlock in the search ioctl 2020-09-09 19:12:31 +02:00
extent_io.h btrfs: trim: fix underflow in trim length to prevent access beyond device boundary 2020-12-30 11:51:37 +01:00
extent_map.c Btrfs: fix race between using extent maps and merging them 2020-02-19 19:53:00 +01:00
extent_map.h
…
file-item.c btrfs: do not ignore error from btrfs_next_leaf() when inserting checksums 2020-06-22 09:30:55 +02:00
file.c btrfs: allow btrfs_truncate_block() to fallback to nocow for data space reservation 2020-10-14 10:33:00 +02:00
free-space-cache.c btrfs: fix space cache memory leak after transaction abort 2020-09-03 11:27:02 +02:00
free-space-cache.h btrfs: move struct io_ctl to free-space-cache.h 2019-09-09 14:59:15 +02:00
free-space-tree.c btrfs: move basic block_group definitions to their own header 2019-09-09 14:59:03 +02:00
free-space-tree.h btrfs: move basic block_group definitions to their own header 2019-09-09 14:59:03 +02:00
inode-item.c btrfs: Make btrfs_find_name_in_ext_backref return struct btrfs_inode_extref 2019-09-09 14:59:16 +02:00
inode-map.c btrfs: qgroup: Always free PREALLOC META reserve in btrfs_delalloc_release_extents() 2019-10-15 18:50:07 +02:00
inode-map.h
…
inode.c btrfs: allow btrfs_truncate_block() to fallback to nocow for data space reservation 2020-10-14 10:33:00 +02:00
ioctl.c btrfs: fix race when defragmenting leads to unnecessary IO 2021-01-06 14:48:36 +01:00
locking.c btrfs: move cond_wake_up functions out of ctree 2019-09-09 14:59:15 +02:00
locking.h btrfs: Remove unused locking functions 2019-09-09 14:58:59 +02:00
lzo.c btrfs: compression: replace set_level callbacks by a common helper 2019-09-09 14:59:11 +02:00
misc.h btrfs: move math functions to misc.h 2019-09-09 14:59:15 +02:00
ordered-data.c Btrfs: fix btrfs_wait_ordered_range() so that it waits for all ordered extents 2020-02-28 17:22:24 +01:00
ordered-data.h
…
orphan.c
…
print-tree.c btrfs: require only sector size alignment for parent eb bytenr 2020-09-17 13:47:51 +02:00
print-tree.h
…
props.c btrfs: rename the btrfs_calc_*_metadata_size helpers 2019-09-09 14:59:13 +02:00
props.h
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qgroup.c btrfs: fix lockdep splat when reading qgroup config on mount 2020-12-02 08:49:45 +01:00
qgroup.h btrfs: make btrfs_qgroup_check_reserved_leak take btrfs_inode 2020-09-03 11:26:47 +02:00
raid56.c btrfs: get rid of unique workqueue helper functions 2020-01-09 10:20:06 +01:00
raid56.h
…
rcu-string.h
…
reada.c btrfs: fix readahead hang and use-after-free after removing a device 2020-11-05 11:43:27 +01:00
ref-verify.c btrfs: ref-verify: fix memory leak in btrfs_ref_tree_mod 2020-11-18 19:20:28 +01:00
ref-verify.h
…
relocation.c btrfs: fix min reserved size calculation in merge_reloc_root 2020-11-18 19:20:28 +01:00
root-tree.c btrfs: do not delete mismatched root refs 2020-01-23 08:22:40 +01:00
scrub.c btrfs: allocate scrub workqueues outside of locks 2020-09-09 19:12:31 +02:00
send.c btrfs: use kvzalloc() to allocate clone_roots in btrfs_ioctl_send() 2020-11-05 11:43:26 +01:00
send.h
…
space-info.c btrfs: take overcommit into account in inc_block_group_ro 2020-10-17 10:11:21 +02:00
space-info.h btrfs: take overcommit into account in inc_block_group_ro 2020-10-17 10:11:21 +02:00
struct-funcs.c btrfs: tie extent buffer and it's token together 2019-09-09 14:59:16 +02:00
super.c btrfs: reset compression level for lzo on remount 2020-09-03 11:27:02 +02:00
sysfs.c btrfs: sysfs: use NOFS for device creation 2020-08-21 13:05:22 +02:00
sysfs.h btrfs: sysfs: move helper macros to sysfs.c 2019-09-09 14:59:08 +02:00
transaction.c btrfs: add wrapper for transaction abort predicate 2020-08-26 10:40:49 +02:00
transaction.h btrfs: add wrapper for transaction abort predicate 2020-08-26 10:40:49 +02:00
tree-checker.c btrfs: tree-checker: add missing returns after data_ref alignment checks 2020-12-02 08:49:45 +01:00
tree-checker.h
…
tree-defrag.c
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tree-log.c btrfs: reschedule if necessary when logging directory items 2020-11-05 11:43:26 +01:00
tree-log.h
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ulist.c
…
ulist.h
…
uuid-tree.c btrfs: handle ENOENT in btrfs_uuid_tree_iterate 2019-12-31 16:42:05 +01:00
volumes.c btrfs: trim: fix underflow in trim length to prevent access beyond device boundary 2020-12-30 11:51:37 +01:00
volumes.h btrfs: fix readahead hang and use-after-free after removing a device 2020-11-05 11:43:27 +01:00
xattr.c
…
xattr.h
…
zlib.c btrfs: compression: replace set_level callbacks by a common helper 2019-09-09 14:59:11 +02:00
zstd.c btrfs: move cond_wake_up functions out of ctree 2019-09-09 14:59:15 +02:00