diff options
| 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 | |
| parent | 703071b5b93d88d5acb0edd5b9dd86c69ad970f2 (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 <vtaras@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
| -rw-r--r-- | block/ll_rw_blk.c | 6 | ||||
| -rw-r--r-- | mm/bounce.c | 2 |
2 files changed, 4 insertions, 4 deletions
diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c index 38c293b987b7..3de06953ac33 100644 --- a/block/ll_rw_blk.c +++ b/block/ll_rw_blk.c @@ -1221,7 +1221,7 @@ void blk_recount_segments(request_queue_t *q, struct bio *bio) * considered part of another segment, since that might * change with the bounce page. */ - high = page_to_pfn(bv->bv_page) >= q->bounce_pfn; + high = page_to_pfn(bv->bv_page) > q->bounce_pfn; if (high || highprv) goto new_hw_segment; if (cluster) { @@ -3658,8 +3658,8 @@ int __init blk_dev_init(void) open_softirq(BLOCK_SOFTIRQ, blk_done_softirq, NULL); register_hotcpu_notifier(&blk_cpu_notifier); - blk_max_low_pfn = max_low_pfn; - blk_max_pfn = max_pfn; + blk_max_low_pfn = max_low_pfn - 1; + blk_max_pfn = max_pfn - 1; return 0; } 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; /* |