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    SubjectRe: [block:for-3.14/core] kernel BUG at fs/bio.c:1748
    From
    OK, after a bit more staring I believe the correct fix is the following.

    Fengguang, Please try this one?

    Regards,
    Muthu

    ------------
    In btrfs_end_bio(), we increment bi_remaining if is_orig_bio. If not,
    we restore the orig_bio but failed to increment bi_remaining for
    orig_bio, which triggers a BUG_ON later when bio_endio is called. Fix
    is to increment bi_remaining when we restore the orig bio as well.

    Reported-by: fengguang.wu@intel.com
    CC: Kent Overstreet <kmo@daterainc.com>
    CC: Jens Axboe <axboe@kernel.dk>
    CC: Chris Mason <clm@fv
    Signed-off-by: Muthukumar Ratty <muthur@gmail.com>
    ----------------
    fs/btrfs/volumes.c | 4 ++--
    1 files changed, 2 insertions(+), 2 deletions(-)

    diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
    index 37972d5..2011cc0 100644
    --- a/fs/btrfs/volumes.c
    +++ b/fs/btrfs/volumes.c
    @@ -5297,9 +5297,9 @@ static void btrfs_end_bio(struct bio *bio, int err)
    if (!is_orig_bio) {
    bio_put(bio);
    bio = bbio->orig_bio;
    - } else {
    - atomic_inc(&bio->bi_remaining);
    }
    + atomic_inc(&bio->bi_remaining);
    +
    bio->bi_private = bbio->private;
    bio->bi_end_io = bbio->end_io;
    btrfs_io_bio(bio)->mirror_num = bbio->mirror_num;
    --------------------------


    On Mon, Jan 6, 2014 at 2:10 PM, Kent Overstreet <kmo@daterainc.com> wrote:
    > Chris, the patch below seems to be incorrect - with it we get hangs, so
    > bi_remaining (probably) isn't getting decremented when it should be. You sent
    > Jens fixes for btrfs which I somehow lost when I rebased, do you remember how
    > this is supposed to work? Looking at the code I'm not quite sure what's going on
    > here.
    >
    > On Fri, Jan 03, 2014 at 11:51:31AM -0800, Muthu Kumar wrote:
    >> Looks like Kent missed the btrfs endio in the original commit. How
    >> about this patch:
    >>
    >> ---------
    >>
    >> In btrfs_end_bio, call bio_endio_nodec on the restored bio so the
    >> bi_remaining is accounted for correctly.
    >>
    >> Reported-by: fengguang.wu@intel.com
    >> Cc: Kent Overstreet <kmo@daterainc.com>
    >> CC: Jens Axboe <axboe@kernel.dk>
    >> Signed-off-by: Muthukumar Ratty <muthur@gmail.com>
    >> --------
    >>
    >> fs/btrfs/volumes.c | 6 +++++-
    >> 1 files changed, 5 insertions(+), 1 deletions(-)
    >>
    >> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
    >> index f2130de..edfed52 100644
    >> --- a/fs/btrfs/volumes.c
    >> +++ b/fs/btrfs/volumes.c
    >> @@ -5316,7 +5316,11 @@ static void btrfs_end_bio(struct bio *bio, int err)
    >> }
    >> kfree(bbio);
    >>
    >> - bio_endio(bio, err);
    >> + /*
    >> + * Call endio_nodec on the restored bio so the bi_remaining is
    >> + * accounted for correctly
    >> + */
    >> + bio_endio_nodec(bio, err);
    >> } else if (!is_orig_bio) {
    >> bio_put(bio);
    >> }


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