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authorGoldwyn Rodrigues <rgoldwyn@suse.com>2017-07-04 22:33:07 -0500
committerDavid Sterba <dsterba@suse.com>2017-07-10 15:29:44 +0200
commitff0fa73247e442518936baa43c3f037b17f10fa7 (patch)
tree03cb6c5e75f63c117fbadec630830f5624b3ca2b /fs/btrfs/file.c
parentf95a0d6a95b12a79b7492da7ab687ae4cd741124 (diff)
downloadlinux-ff0fa73247e442518936baa43c3f037b17f10fa7.tar.bz2
btrfs: nowait aio: Correct assignment of pos
Assigning pos for usage early messes up in append mode, where the pos is re-assigned in generic_write_checks(). Assign pos later to get the correct position to write from iocb->ki_pos. Since check_can_nocow also uses the value of pos, we shift generic_write_checks() before check_can_nocow(). Checks with IOCB_DIRECT are present in generic_write_checks(), so checking for IOCB_NOWAIT is enough. Also, put locking sequence in the fast path. This fixes a user visible bug, as reported: "apparently breaks several shell related features on my system. In zsh history stopped working, because no new entries are added anymore. I fist noticed the issue when I tried to build mplayer. It uses a shell script to generate a help_mp.h file: [...] Here is a simple testcase: % echo "foo" >> test % echo "foo" >> test % cat test foo % " Fixes: edf064e7c6fe ("btrfs: nowait aio support") CC: Jens Axboe <axboe@kernel.dk> Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de> Link: https://lkml.kernel.org/r/20170704042306.GA274@x4 Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs/file.c')
-rw-r--r--fs/btrfs/file.c26
1 files changed, 14 insertions, 12 deletions
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 59e2dccdf75b..ad53832838b5 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1875,16 +1875,25 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
ssize_t num_written = 0;
bool sync = (file->f_flags & O_DSYNC) || IS_SYNC(file->f_mapping->host);
ssize_t err;
- loff_t pos = iocb->ki_pos;
+ loff_t pos;
size_t count = iov_iter_count(from);
loff_t oldsize;
int clean_page = 0;
- if ((iocb->ki_flags & IOCB_NOWAIT) &&
- (iocb->ki_flags & IOCB_DIRECT)) {
- /* Don't sleep on inode rwsem */
- if (!inode_trylock(inode))
+ if (!inode_trylock(inode)) {
+ if (iocb->ki_flags & IOCB_NOWAIT)
return -EAGAIN;
+ inode_lock(inode);
+ }
+
+ err = generic_write_checks(iocb, from);
+ if (err <= 0) {
+ inode_unlock(inode);
+ return err;
+ }
+
+ pos = iocb->ki_pos;
+ if (iocb->ki_flags & IOCB_NOWAIT) {
/*
* We will allocate space in case nodatacow is not set,
* so bail
@@ -1895,13 +1904,6 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
inode_unlock(inode);
return -EAGAIN;
}
- } else
- inode_lock(inode);
-
- err = generic_write_checks(iocb, from);
- if (err <= 0) {
- inode_unlock(inode);
- return err;
}
current->backing_dev_info = inode_to_bdi(inode);