path: root/mm/bounce.c
diff options
authorVasily Tarasov <>2007-03-27 08:52:47 +0200
committerJens Axboe <>2007-03-27 08:52:47 +0200
commitf772b3d9ca135087a70406d8466e57d1cf29237e (patch)
treeaeb26fbd7af4a522f267cd50e1ad227e54091ea0 /mm/bounce.c
parent703071b5b93d88d5acb0edd5b9dd86c69ad970f2 (diff)
block: blk_max_pfn is somtimes wrong
There is a small problem in handling page bounce. At the moment blk_max_pfn equals max_pfn, which is in fact not maximum possible _number_ of a page frame, but the _amount_ of page frames. For example for the 32bit x86 node with 4Gb RAM, max_pfn = 0x100000, but not 0xFFFF. request_queue structure has a member q->bounce_pfn and queue needs bounce pages for the pages _above_ this limit. This routine is handled by blk_queue_bounce(), where the following check is produced: if (q->bounce_pfn >= blk_max_pfn) return; Assume, that a driver has set q->bounce_pfn to 0xFFFF, but blk_max_pfn equals 0x10000. In such situation the check above fails and for each bio we always fall down for iterating over pages tied to the bio. I want to notice, that for quite a big range of device drivers (ide, md, ...) such problem doesn't happen because they use BLK_BOUNCE_ANY for bounce_pfn. BLK_BOUNCE_ANY is defined as blk_max_pfn << PAGE_SHIFT, and then the check above doesn't fail. But for other drivers, which obtain reuired value from drivers, it fails. For example sata_nv uses ATA_DMA_MASK or dev->dma_mask. I propose to use (max_pfn - 1) for blk_max_pfn. And the same for blk_max_low_pfn. The patch also cleanses some checks related with bounce_pfn. Signed-off-by: Vasily Tarasov <> Signed-off-by: Andrew Morton <> Signed-off-by: Jens Axboe <>
Diffstat (limited to 'mm/bounce.c')
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/bounce.c b/mm/bounce.c
index 643efbe82402..ad401fc57440 100644
--- a/mm/bounce.c
+++ b/mm/bounce.c
@@ -204,7 +204,7 @@ static void __blk_queue_bounce(request_queue_t *q, struct bio **bio_orig,
* is destination page below bounce pfn?
- if (page_to_pfn(page) < q->bounce_pfn)
+ if (page_to_pfn(page) <= q->bounce_pfn)