[PATCH AUTOSEL 4.19 071/219] btrfs: Check for missing device before bio submission in btrfs_map_bio

Sasha Levin
2019-11-22T06:27:04Z

From: Nikolay Borisov <nborisov@suse.com>

[ Upstream commit fc8a168aa9ab1680c2bd52bf9db7c994e0f2524f ]

Before btrfs_map_bio submits all stripe bios it does a number of checks
to ensure the device for every stripe is present. However, it doesn't do
a DEV_STATE_MISSING check, instead this is relegated to the lower level
btrfs_schedule_bio (in the async submission case, sync submission
doesn't check DEV_STATE_MISSING at all). Additionally
btrfs_schedule_bios does the duplicate device->bdev check which has
already been performed in btrfs_map_bio.

This patch moves the DEV_STATE_MISSING check in btrfs_map_bio and
removes the duplicate device->bdev check. Doing so ensures that no bio
cloning/submission happens for both async/sync requests in the face of
missing device. This makes the async io submission path slightly shorter
in terms of instruction count. No functional changes.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.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/volumes.c | 9 ++-------
1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index a8297e7489d98..f84c18e86c816 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -6106,12 +6106,6 @@ static noinline void btrfs_schedule_bio(struct btrfs_device *device,
int should_queue = 1;
struct btrfs_pending_bios *pending_bios;

- if (test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state) ||
- !device->bdev) {
- bio_io_error(bio);
- return;
- }
-
/* don't bother with additional async steps for reads, right now */
if (bio_op(bio) == REQ_OP_READ) {
btrfsic_submit_bio(bio);
@@ -6240,7 +6234,8 @@ blk_status_t btrfs_map_bio(struct btrfs_fs_info *fs_info, struct bio *bio,

for (dev_nr = 0; dev_nr < total_devs; dev_nr++) {
dev = bbio->stripes[dev_nr].dev;
- if (!dev || !dev->bdev ||
+ if (!dev || !dev->bdev || test_bit(BTRFS_DEV_STATE_MISSING,
+ &dev->dev_state) ||
(bio_op(first_bio) == REQ_OP_WRITE &&
!test_bit(BTRFS_DEV_STATE_WRITEABLE, &dev->dev_state))) {
bbio_error(bbio, first_bio, logical);
--
2.20.1