Commit d8a1c16d authored by Filipe Manana's avatar Filipe Manana Committed by Yifan Qiao
Browse files

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

mainline inclusion
from mainline-v5.11-rc1
commit 88090ad3
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I94K22

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=88090ad36a64af1eb5b78d26b2ccd07eedae80b5



------------------------------------------------------

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
609e804d ("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 9ddc959e
("btrfs: use the file extent tree infrastructure"), which addresses this
scenario involving snapshots as well.

Reviewed-by: default avatarJosef Bacik <josef@toxicpanda.com>
Signed-off-by: default avatarFilipe Manana <fdmanana@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarYifan Qiao <qiaoyifan4@huawei.com>
parent ebba5515

fs/btrfs/transaction.c

+6 −43
Original line number Diff line number Diff line
@@ -2015,10 +2015,8 @@ 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.
@@ -2028,50 +2026,15 @@ 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)
@@ -2209,7 +2172,7 @@ 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;
@@ -2225,7 +2188,7 @@ 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