From 831e1ee60216534c54f2e240f9586d6cfe29b1c2 Mon Sep 17 00:00:00 2001 From: Filipe Manana Date: Tue, 15 Mar 2022 15:22:36 +0000 Subject: [PATCH] btrfs: remove useless dio wait call when doing fallocate zero range When starting a fallocate zero range operation, before getting the first extent map for the range, we make a call to inode_dio_wait(). This logic was needed in the past because direct IO writes within the i_size boundary did not take the inode's VFS lock. This was because that lock used to be a mutex, then some years ago it was switched to a rw semaphore (by commit 9902af79c01a8e ("parallel lookups: actual switch to rwsem")), and then btrfs was changed to take the VFS inode's lock in shared mode for writes that don't cross the i_size boundary (done in commit e9adabb9712ef9 ("btrfs: use shared lock for direct writes within EOF")). The lockless direct IO writes could result in a race with the zero range operation, resulting in the later getting a stale extent map for the range. So remove this no longer needed call to inode_dio_wait(), as fallocate takes the inode's VFS lock in exclusive mode and direct IO writes within i_size take that same lock in shared mode. Signed-off-by: Filipe Manana Signed-off-by: David Sterba --- fs/btrfs/file.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index fa7bbca..bd638cb 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -3237,8 +3237,6 @@ static int btrfs_zero_range(struct inode *inode, u64 bytes_to_reserve = 0; bool space_reserved = false; - inode_dio_wait(inode); - em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, alloc_start, alloc_end - alloc_start); if (IS_ERR(em)) { -- 2.7.4