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| author | Vasily Tarasov <vtaras@openvz.org> | 2007-03-27 08:52:47 +0200 |
|---|---|---|
| committer | Jens Axboe <jens.axboe@oracle.com> | 2007-03-27 08:52:47 +0200 |
| commit | f772b3d9ca135087a70406d8466e57d1cf29237e (patch) | |
| tree | aeb26fbd7af4a522f267cd50e1ad227e54091ea0 /mm/bounce.c | |
| parent | Merge master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 (diff) | |
| download | linux-f772b3d9ca135087a70406d8466e57d1cf29237e.tar.xz linux-f772b3d9ca135087a70406d8466e57d1cf29237e.zip | |
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 <vtaras@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'mm/bounce.c')
| -rw-r--r-- | mm/bounce.c | 2 |
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) continue; /* |