[PATCH 4.7 133/141] dm log writes: fix bug with too large bios

From: Greg Kroah-Hartman
Date: Thu Oct 06 2016 - 04:50:39 EST

4.7-stable review patch. If anyone has any objections, please let me know.


From: Mikulas Patocka <mpatocka@xxxxxxxxxx>

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

Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Reviewed-by: Josef Bacik <jbacik@xxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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

- 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) {
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;