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dm log writes: fix bug with too large bios 

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>
Cc: stable@vger.kernel.org # v4.1+
This commit is contained in:
Mikulas Patocka 2016-08-30 16:20:55 -04:00 committed by Mike Snitzer
parent a5d60783df
commit 7efb367320
1 changed files with 2 additions and 2 deletions
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4
drivers/md/dm-log-writes.c
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@ -260,7 +260,7 @@ static int log_one_block(struct log_writes_c *lc,
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;
@ -282,7 +282,7 @@ static int log_one_block(struct log_writes_c *lc,
if (ret != block->vecs[i].bv_len) {
atomic_inc(&lc->io_blocks);
submit_bio(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;