Commit fc8a168a authored Nov 08, 2018 by Nikolay Borisov Committed by David Sterba Dec 17, 2018

btrfs: Check for missing device before bio submission in btrfs_map_bio



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>

parent ab457246

fs/btrfs/volumes.c

+2 −7

Original line number	Diff line number	Diff line
		@@ -6109,12 +6109,6 @@ 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);
		@@ -6243,7 +6237,8 @@ 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);

Admin message