[PATCH v2 02/15] btrfs: fix error handling when submitting direct I/O bio

[Omar Sandoval <osandov@osandov.com>]

From: Omar Sandoval <osandov@fb.com>

In btrfs_submit_direct_hook(), if a direct I/O write doesn't span a RAID
stripe or chunk, we submit orig_bio without cloning it. In this case, we
don't increment pending_bios. Then, if btrfs_submit_dio_bio() fails, we
decrement pending_bios to -1, and we never complete orig_bio. Fix it by
initializing pending_bios to 1 instead of incrementing later.

Fixing this exposes another bug: we put orig_bio prematurely and then
put it again from end_io. Fix it by not putting orig_bio.

After this change, pending_bios is really more of a reference count, but
I'll leave that cleanup separate to keep the fix small.

Fixes: e65e15355429 ("btrfs: fix panic caused by direct IO")
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
---
 fs/btrfs/inode.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 259239b33370..b628c319a5b6 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -7939,7 +7939,6 @@ static int btrfs_submit_direct_hook(struct btrfs_dio_private *dip)
 
 	/* bio split */
 	ASSERT(geom.len <= INT_MAX);
-	atomic_inc(&dip->pending_bios);
 	do {
 		clone_len = min_t(int, submit_len, geom.len);
 
@@ -7989,7 +7988,8 @@ static int btrfs_submit_direct_hook(struct btrfs_dio_private *dip)
 	if (!status)
 		return 0;
 
-	bio_put(bio);
+	if (bio != orig_bio)
+		bio_put(bio);
 out_err:
 	dip->errors = 1;
 	/*
@@ -8030,7 +8030,7 @@ static void btrfs_submit_direct(struct bio *dio_bio, struct inode *inode,
 	bio->bi_private = dip;
 	dip->orig_bio = bio;
 	dip->dio_bio = dio_bio;
-	atomic_set(&dip->pending_bios, 0);
+	atomic_set(&dip->pending_bios, 1);
 	io_bio = btrfs_io_bio(bio);
 	io_bio->logical = file_offset;
 
-- 
2.26.1