btrfs: remove ordered extent check and wait during hole punching and zero range
For hole punching and zero range we have this loop that checks if we have ordered extents after locking the file range, and if so unlock the range, wait for ordered extents, and retry until we don't find more ordered extents. This logic was needed in the past because: 1) 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 (commit 9902af79 ("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 (commit e9adabb9 ("btrfs: use shared lock for direct writes within EOF")); 2) We could race with memory mapped writes, because memory mapped writes don't acquire the inode's VFS lock. We don't have that race anymore, as we have a rw semaphore to synchronize memory mapped writes with fallocate (and reflinking too). That change happened with commit 8d9b4a16 ("btrfs: exclude mmap from happening during all fallocate operations"). So stop looking for ordered extents after locking the file range when doing hole punching and zero range operations. Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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