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Commit 6ec047a0 authored by Omar Sandoval's avatar Omar Sandoval Committed by Greg Kroah-Hartman
Browse files

btrfs: use correct count in btrfs_file_write_iter() 



[ Upstream commit c09767a8960ca0500fb636bf73686723337debf4 ]

generic_write_checks() may modify iov_iter_count(), so we must get the
count after the call, not before. Using the wrong one has a couple of
consequences:

1. We check a longer range in check_can_nocow() for nowait than we're
   actually writing.
2. We create extra hole extent maps in btrfs_cont_expand(). As far as I
   can tell, this is harmless, but I might be missing something.

These issues are pretty minor, but let's fix it before something more
important trips on it.

Fixes: edf064e7 ("btrfs: nowait aio support")
Reviewed-by: default avatarJosef Bacik <josef@toxicpanda.com>
Signed-off-by: default avatarOmar Sandoval <osandov@fb.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent cbbc34ab

fs/btrfs/file.c

+2 −1
Original line number Diff line number Diff line
@@ -1895,7 +1895,7 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb, 
	bool sync = (file->f_flags & O_DSYNC) || IS_SYNC(file->f_mapping->host);

	ssize_t err;

	loff_t pos;

	size_t count = iov_iter_count(from);

	size_t count;

	loff_t oldsize;

	int clean_page = 0;
@@ -1917,6 +1917,7 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb, 
	}



	pos = iocb->ki_pos;

	count = iov_iter_count(from);

	if (iocb->ki_flags & IOCB_NOWAIT) {

		/*

		 * We will allocate space in case nodatacow is not set,