Patch "dm log writes: fix bug with too large bios" has been added to the 4.7-stable tree

This is a note to let you know that I've just added the patch titled

dm log writes: fix bug with too large bios

to the 4.7-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
dm-log-writes-fix-bug-with-too-large-bios.patch
and it can be found in the queue-4.7 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Mikulas Patocka <[email protected]>
Date: Tue, 30 Aug 2016 16:20:55 -0400
Subject: dm log writes: fix bug with too large bios

From: Mikulas Patocka <[email protected]>

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.

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

@@ -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;

Patches currently in stable-queue which might be from [email protected] are

queue-4.7/dm-log-writes-fix-bug-with-too-large-bios.patch