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btrfs: remove pointless barrier from btrfs_sync_file()

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The memory barrier (smp_mb()) at btrfs_sync_file() is completely redundant
now that fs_info->last_trans_committed is read using READ_ONCE(), with the
helper btrfs_get_last_trans_committed(), and written using WRITE_ONCE()
with the helper btrfs_set_last_trans_committed().

This barrier was introduced in 2011, by commit a4abeea41a ("Btrfs: kill
trans_mutex"), but even back then it was not correct since the writer side
(in btrfs_commit_transaction()), did not issue a pairing memory barrier
after it updated fs_info->last_trans_committed.

So remove this barrier.

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 2023-10-04 11:38:52 +01:00 committed by David Sterba
parent 0124855ff1
commit 5ca1949b79
1 changed files with 0 additions and 1 deletions
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fs/btrfs/file.c
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@ -1889,7 +1889,6 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
atomic_inc(&root->log_batch);
smp_mb();
if (skip_inode_logging(&ctx)) {
/*
* We've had everything committed since the last time we were