dma-debug: change hash_bucket_find from first-fit to best-fit
authorJoerg Roedel <joerg.roedel@amd.com>
Fri, 5 Jun 2009 10:01:35 +0000 (12:01 +0200)
committerIngo Molnar <mingo@elte.hu>
Sun, 7 Jun 2009 08:04:53 +0000 (10:04 +0200)
commit7caf6a49bb17d0377210693af5737563b31aa5ee
tree1a61bc90002bc2e3d1fc5d028e408b35fb765cbd
parentfe2245c905631a3a353504fc04388ce3dfaf9d9e
dma-debug: change hash_bucket_find from first-fit to best-fit

Some device drivers map the same physical address multiple times to a
dma address. Without an IOMMU this results in the same dma address being
put into the dma-debug hash multiple times. With a first-fit match in
hash_bucket_find() this function may return the wrong dma_debug_entry.

This can result in false positive warnings. This patch fixes it by
changing the first-fit behavior of hash_bucket_find() into a best-fit
algorithm.

Reported-by: Torsten Kaiser <just.for.lkml@googlemail.com>
Reported-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Cc: lethal@linux-sh.org
Cc: just.for.lkml@googlemail.com
Cc: hancockrwd@gmail.com
Cc: jens.axboe@oracle.com
Cc: bharrosh@panasas.com
Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: <stable@kernel.org>
LKML-Reference: <20090605104132.GE24836@amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
lib/dma-debug.c