Patch "dm crypt: fix error with too large bios" has been added to the 4.4-stable tree

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

dm crypt: fix error with too large bios

to the 4.4-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-crypt-fix-error-with-too-large-bios.patch
and it can be found in the queue-4.4 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 16:38:42 -0400
Subject: dm crypt: fix error with too large bios

From: Mikulas Patocka <[email protected]>

commit 4e870e948fbabf62b78e8410f04c67703e7c816b upstream.

When dm-crypt processes writes, it allocates a new bio in crypt_alloc_buffer(). The bio is allocated from a bio set and it can have at most BIO_MAX_PAGES vector entries, however the incoming bio can be larger (e.g. if it was allocated by bcache). If the incoming bio is larger, bio_alloc_bioset() fails and an error is returned.

To avoid the error, we test for a too large bio in the function crypt_map() and use dm_accept_partial_bio() to split the bio. dm_accept_partial_bio() trims the current bio to the desired size and asks DM core to send another bio with the rest of the data.

---
 drivers/md/dm-crypt.c |    7 +++++++
 1 file changed, 7 insertions(+)

@@ -1920,6 +1920,13 @@ static int crypt_map(struct dm_target *t
 		return DM_MAPIO_REMAPPED;
 	}
 
+	/*
+	 * Check if bio is too large, split as needed.
+	 */
+	if (unlikely(bio->bi_iter.bi_size > (BIO_MAX_PAGES << PAGE_SHIFT)) &&
+	    bio_data_dir(bio) == WRITE)
+		dm_accept_partial_bio(bio, ((BIO_MAX_PAGES << PAGE_SHIFT) >> SECTOR_SHIFT));
+
 	io = dm_per_bio_data(bio, cc->per_bio_data_size);
 	crypt_io_init(io, cc, bio, dm_target_offset(ti, bio->bi_iter.bi_sector));
 	io->ctx.req = (struct ablkcipher_request *)(io + 1);

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

queue-4.4/dm-crypt-fix-error-with-too-large-bios.patch queue-4.4/dm-log-writes-move-io-accounting-earlier-to-fix-error-path.patch