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    Subject[PATCH 4.14 159/190] btrfs: fix error handling when submitting direct I/O bio
    Date
    From: Omar Sandoval <osandov@fb.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@vger.kernel.org # 4.4+
    Reviewed-by: Nikolay Borisov <nborisov@suse.com>
    Reviewed-by: Josef Bacik <josef@toxicpanda.com>
    Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
    Signed-off-by: Omar Sandoval <osandov@fb.com>
    Signed-off-by: David Sterba <dsterba@suse.com>
    Signed-off-by: Sasha Levin <sashal@kernel.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


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