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btrfs: do not start and wait for delalloc on snapshot roots on transaction commit

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We do not need anymore to start writeback for delalloc of roots that are
being snapshotted and wait for it to complete. This was done in commit
609e804d77 ("Btrfs: fix file corruption after snapshotting due to mix
of buffered/DIO writes") to fix a type of file corruption where files in a
snapshot end up having their i_size updated in a non-ordered way, leaving
implicit file holes, when buffered IO writes that increase a file's size
are followed by direct IO writes that also increase the file's size.

This is not needed anymore because we now have a more generic mechanism
to prevent a non-ordered i_size update since commit 9ddc959e80
("btrfs: use the file extent tree infrastructure"), which addresses this
scenario involving snapshots as well.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Filipe Manana 2020-10-27 12:40:06 +00:00 committed by David Sterba
parent 196d59ab9c
commit 88090ad36a
1 changed files with 6 additions and 43 deletions
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49
fs/btrfs/transaction.c
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@ -1956,10 +1956,8 @@ static void btrfs_cleanup_pending_block_groups(struct btrfs_trans_handle *trans)
}
}
static inline int btrfs_start_delalloc_flush(struct btrfs_trans_handle *trans)
static inline int btrfs_start_delalloc_flush(struct btrfs_fs_info *fs_info)
{
struct btrfs_fs_info *fs_info = trans->fs_info;
/*
* We use writeback_inodes_sb here because if we used
* btrfs_start_delalloc_roots we would deadlock with fs freeze.
@ -1969,50 +1967,15 @@ static inline int btrfs_start_delalloc_flush(struct btrfs_trans_handle *trans)
* from already being in a transaction and our join_transaction doesn't
* have to re-take the fs freeze lock.
*/
if (btrfs_test_opt(fs_info, FLUSHONCOMMIT)) {
if (btrfs_test_opt(fs_info, FLUSHONCOMMIT))
writeback_inodes_sb(fs_info->sb, WB_REASON_SYNC);
} else {
struct btrfs_pending_snapshot *pending;
struct list_head *head = &trans->transaction->pending_snapshots;
/*
* Flush dellaloc for any root that is going to be snapshotted.
* This is done to avoid a corrupted version of files, in the
* snapshots, that had both buffered and direct IO writes (even
* if they were done sequentially) due to an unordered update of
* the inode's size on disk.
*/
list_for_each_entry(pending, head, list) {
int ret;
ret = btrfs_start_delalloc_snapshot(pending->root);
if (ret)
return ret;
}
}
return 0;
}
static inline void btrfs_wait_delalloc_flush(struct btrfs_trans_handle *trans)
static inline void btrfs_wait_delalloc_flush(struct btrfs_fs_info *fs_info)
{
struct btrfs_fs_info *fs_info = trans->fs_info;
if (btrfs_test_opt(fs_info, FLUSHONCOMMIT)) {
if (btrfs_test_opt(fs_info, FLUSHONCOMMIT))
btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);
} else {
struct btrfs_pending_snapshot *pending;
struct list_head *head = &trans->transaction->pending_snapshots;
/*
* Wait for any dellaloc that we started previously for the roots
* that are going to be snapshotted. This is to avoid a corrupted
* version of files in the snapshots that had both buffered and
* direct IO writes (even if they were done sequentially).
*/
list_for_each_entry(pending, head, list)
btrfs_wait_ordered_extents(pending->root,
U64_MAX, 0, U64_MAX);
}
}
int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
@ -2150,7 +2113,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
extwriter_counter_dec(cur_trans, trans->type);
ret = btrfs_start_delalloc_flush(trans);
ret = btrfs_start_delalloc_flush(fs_info);
if (ret)
goto cleanup_transaction;
@ -2166,7 +2129,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
if (ret)
goto cleanup_transaction;
btrfs_wait_delalloc_flush(trans);
btrfs_wait_delalloc_flush(fs_info);
/*
* Wait for all ordered extents started by a fast fsync that joined this