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Commit c55f1396 authored by Miao Xie's avatar Miao Xie Committed by Chris Mason
Browse files

Btrfs: fix deadlock when mounting a degraded fs 



The deadlock happened when we mount degraded filesystem, the reproduced
steps are following:
 # mkfs.btrfs -f -m raid1 -d raid1 <dev0> <dev1>
 # echo 1 > /sys/block/`basename <dev0>`/device/delete
 # mount -o degraded <dev1> <mnt>

The reason was that the counter -- bi_remaining was wrong. If the missing
or unwriteable device was the last device in the mapping array, we would
not submit the original bio, so we shouldn't increase bi_remaining of it
in btrfs_end_bio(), or we would skip the final endio handle.

Fix this problem by adding a flag into btrfs bio structure. If we submit
the original bio, we will set the flag, and we increase bi_remaining counter,
or we don't.

Though there is another way to fix it -- decrease bi_remaining counter of the
original bio when we make sure the original bio is not submitted, this method
need add more check and is easy to make mistake.

Signed-off-by: default avatarMiao Xie <miaox@cn.fujitsu.com>
Reviewed-by: default avatarLiu Bo <bo.li.liu@oracle.com>
Signed-off-by: default avatarChris Mason <clm@fb.com>
parent e990f167

fs/btrfs/volumes.c

+6 −1
Original line number Diff line number Diff line
@@ -5415,8 +5415,12 @@ static void btrfs_end_bio(struct bio *bio, int err) 
			set_bit(BIO_UPTODATE, &bio->bi_flags);

			err = 0;

		}

		kfree(bbio);



		if (likely(bbio->flags & BTRFS_BIO_ORIG_BIO_SUBMITTED))

			bio_endio_nodec(bio, err);

		else

			bio_endio(bio, err);

		kfree(bbio);

	} else if (!is_orig_bio) {

		bio_put(bio);

	}
@@ -5671,6 +5675,7 @@ int btrfs_map_bio(struct btrfs_root *root, int rw, struct bio *bio, 
			BUG_ON(!bio); /* -ENOMEM */

		} else {

			bio = first_bio;

			bbio->flags |= BTRFS_BIO_ORIG_BIO_SUBMITTED;

		}



		submit_stripe_bio(root, bbio, bio,

fs/btrfs/volumes.h

+3 −0
Original line number Diff line number Diff line
@@ -190,11 +190,14 @@ struct btrfs_bio_stripe { 
struct btrfs_bio;

typedef void (btrfs_bio_end_io_t) (struct btrfs_bio *bio, int err);



#define BTRFS_BIO_ORIG_BIO_SUBMITTED	0x1



struct btrfs_bio {

	atomic_t stripes_pending;

	struct btrfs_fs_info *fs_info;

	bio_end_io_t *end_io;

	struct bio *orig_bio;

	unsigned long flags;

	void *private;

	atomic_t error;

	int max_errors;