2.6.30-stable review patch. If anyone has any objections, please let us know. ------------------ From: Joerg Roedel commit 7caf6a49bb17d0377210693af5737563b31aa5ee upstream. 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 Reported-by: FUJITA Tomonori Signed-off-by: Joerg Roedel 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 Cc: Linus Torvalds LKML-Reference: <20090605104132.GE24836@amd.com> Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- lib/dma-debug.c | 43 +++++++++++++++++++++++++++++++++++++++---- 1 file changed, 39 insertions(+), 4 deletions(-) --- a/lib/dma-debug.c +++ b/lib/dma-debug.c @@ -185,15 +185,50 @@ static void put_hash_bucket(struct hash_ static struct dma_debug_entry *hash_bucket_find(struct hash_bucket *bucket, struct dma_debug_entry *ref) { - struct dma_debug_entry *entry; + struct dma_debug_entry *entry, *ret = NULL; + int matches = 0, match_lvl, last_lvl = 0; list_for_each_entry(entry, &bucket->list, list) { - if ((entry->dev_addr == ref->dev_addr) && - (entry->dev == ref->dev)) + if ((entry->dev_addr != ref->dev_addr) || + (entry->dev != ref->dev)) + continue; + + /* + * Some drivers map the same physical address multiple + * times. Without a hardware IOMMU this results in the + * same device addresses being put into the dma-debug + * hash multiple times too. This can result in false + * positives being reported. Therfore we implement a + * best-fit algorithm here which returns the entry from + * the hash which fits best to the reference value + * instead of the first-fit. + */ + matches += 1; + match_lvl = 0; + entry->size == ref->size ? ++match_lvl : match_lvl; + entry->type == ref->type ? ++match_lvl : match_lvl; + entry->direction == ref->direction ? ++match_lvl : match_lvl; + + if (match_lvl == 3) { + /* perfect-fit - return the result */ return entry; + } else if (match_lvl > last_lvl) { + /* + * We found an entry that fits better then the + * previous one + */ + last_lvl = match_lvl; + ret = entry; + } } - return NULL; + /* + * If we have multiple matches but no perfect-fit, just return + * NULL. + */ + ret = (matches == 1) ? ret : NULL; + + return ret; } /* -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/