From: Omar Sandoval osandov@fb.com
[ 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: edf064e7c6fe ("btrfs: nowait aio support") Reviewed-by: Josef Bacik josef@toxicpanda.com Signed-off-by: Omar Sandoval osandov@fb.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/btrfs/file.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index 78490e544c91e..c2c93fe9d7fd5 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -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,