linux-kernel - [PATCH 4.14 159/190] btrfs: fix error handling when submitting direct I/O bio

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Message-Id: <20200619141641.687665192@linuxfoundation.org>
Date:   Fri, 19 Jun 2020 16:33:24 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Nikolay Borisov <nborisov@...e.com>,
        Josef Bacik <josef@...icpanda.com>,
        Johannes Thumshirn <johannes.thumshirn@....com>,
        Omar Sandoval <osandov@...com>,
        David Sterba <dsterba@...e.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.14 159/190] btrfs: fix error handling when submitting direct I/O bio

From: Omar Sandoval <osandov@...com>

[ Upstream commit 6d3113a193e3385c72240096fe397618ecab6e43 ]

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")
CC: stable@...r.kernel.org # 4.4+
Reviewed-by: Nikolay Borisov <nborisov@...e.com>
Reviewed-by: Josef Bacik <josef@...icpanda.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@....com>
Signed-off-by: Omar Sandoval <osandov@...com>
Signed-off-by: David Sterba <dsterba@...e.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 2a196bb134d9..3e65ac2d4869 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -8707,7 +8707,6 @@ static int btrfs_submit_direct_hook(struct btrfs_dio_private *dip)
 
 	/* bio split */
 	ASSERT(map_length <= INT_MAX);
-	atomic_inc(&dip->pending_bios);
 	do {
 		clone_len = min_t(int, submit_len, map_length);
 
@@ -8758,7 +8757,8 @@ 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;
 	/*
@@ -8798,7 +8798,7 @@ 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;
 
-- 
2.25.1