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    Subject[PATCH 4.7 133/141] dm log writes: fix bug with too large bios
    Date
    4.7-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Mikulas Patocka <mpatocka@redhat.com>

    commit 7efb367320f56fc4d549875b6f3a6940018ef2e5 upstream.

    bio_alloc() can allocate a bio with at most BIO_MAX_PAGES (256) vector
    entries. However, the incoming bio may have more vector entries if it
    was allocated by other means. For example, bcache submits bios with
    more than BIO_MAX_PAGES entries. This results in bio_alloc() failure.

    To avoid the failure, change the code so that it allocates bio with at
    most BIO_MAX_PAGES entries. If the incoming bio has more entries,
    bio_add_page() will fail and a new bio will be allocated - the code that
    handles bio_add_page() failure already exists in the dm-log-writes
    target.

    Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
    Reviewed-by: Josef Bacik <jbacik@fb.com>
    Signed-off-by: Mike Snitzer <snitzer@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/md/dm-log-writes.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    --- a/drivers/md/dm-log-writes.c
    +++ b/drivers/md/dm-log-writes.c
    @@ -259,7 +259,7 @@ static int log_one_block(struct log_writ
    sector++;

    atomic_inc(&lc->io_blocks);
    - bio = bio_alloc(GFP_KERNEL, block->vec_cnt);
    + bio = bio_alloc(GFP_KERNEL, min(block->vec_cnt, BIO_MAX_PAGES));
    if (!bio) {
    DMERR("Couldn't alloc log bio");
    goto error;
    @@ -280,7 +280,7 @@ static int log_one_block(struct log_writ
    if (ret != block->vecs[i].bv_len) {
    atomic_inc(&lc->io_blocks);
    submit_bio(WRITE, bio);
    - bio = bio_alloc(GFP_KERNEL, block->vec_cnt - i);
    + bio = bio_alloc(GFP_KERNEL, min(block->vec_cnt - i, BIO_MAX_PAGES));
    if (!bio) {
    DMERR("Couldn't alloc log bio");
    goto error;

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