[BLOCK] bh: Ensure bh fits within a page

From: Herbert Xu <herbert@gondor.apana.org.au>
To: Andrew Morton <akpm@osdl.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: [BLOCK] bh: Ensure bh fits within a page
Date: Tue, 1 Aug 2006 13:04:43 +1000	[thread overview]
Message-ID: <20060801030443.GA2221@gondor.apana.org.au> (raw)

Hi Andrew:

[BLOCK] bh: Ensure bh fits within a page

There is a bug in jbd with slab debugging enabled where it was submitting
a bh obtained via jbd_rep_kmalloc which crossed a page boundary.  A lot
of time was spent on tracking this down because the symptoms were far off
from where the problem was.

This patch adds a sanity check to submit_bh so we can immediately spot
anyone doing similar things in future.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

While you're at it, could you fix that jbd bug for us :)

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
--

diff --git a/fs/buffer.c b/fs/buffer.c
index 71649ef..b998f08 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2790,6 +2790,7 @@ int submit_bh(int rw, struct buffer_head
 	BUG_ON(!buffer_locked(bh));
 	BUG_ON(!buffer_mapped(bh));
 	BUG_ON(!bh->b_end_io);
+	WARN_ON(bh_offset(bh) + bh->b_size > PAGE_SIZE);
 
 	if (buffer_ordered(bh) && (rw == WRITE))
 		rw = WRITE_BARRIER;
