lkml.org 
[lkml]   [2013]   [Jan]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2 1/1] block: blk-merge: don't merge the pages with non-contiguous descriptors
On 1/17/2013 4:17 PM, Russell King - ARM Linux wrote:
> On Thu, Jan 17, 2013 at 10:37:42AM +0000, Russell King - ARM Linux wrote:
>> On Thu, Jan 17, 2013 at 09:11:20AM +0000, James Bottomley wrote:
>>> I'd actually prefer page = pfn_to_page(page_to_pfn(page) + 1); because
>>> it makes the code look like the hack it is. The preferred form for all
>>> iterators like this should be to iterate over the pfn instead of a
>>> pointer into the page arrays, because that will always work correctly no
>>> matter how many weird and wonderful memory schemes we come up with.
>> So, why don't we update the code to do that then?
> Also, couldn't the addition of the scatterlist offset to the page also
> be buggy too?
>
> So, what about this patch which addresses both additions by keeping our
> iterator as a pfn as you suggest. It also simplifies some of the code
> in the loop too.
>
> Can the original folk with the problem test this patch?

Yes, this patch also fixes the issue. You may add: Tested-by: Subhash
Jadavani <subhashj@codeaurora.org> .

Regards,
Subhash

>
> arch/arm/mm/dma-mapping.c | 18 ++++++++++--------
> 1 files changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index 6b2fb87..076c26d 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -774,25 +774,27 @@ static void dma_cache_maint_page(struct page *page, unsigned long offset,
> size_t size, enum dma_data_direction dir,
> void (*op)(const void *, size_t, int))
> {
> + unsigned long pfn;
> + size_t left = size;
> +
> + pfn = page_to_pfn(page) + offset / PAGE_SIZE;
> + offset %= PAGE_SIZE;
> +
> /*
> * A single sg entry may refer to multiple physically contiguous
> * pages. But we still need to process highmem pages individually.
> * If highmem is not configured then the bulk of this loop gets
> * optimized out.
> */
> - size_t left = size;
> do {
> size_t len = left;
> void *vaddr;
>
> + page = pfn_to_page(pfn);
> +
> if (PageHighMem(page)) {
> - if (len + offset > PAGE_SIZE) {
> - if (offset >= PAGE_SIZE) {
> - page += offset / PAGE_SIZE;
> - offset %= PAGE_SIZE;
> - }
> + if (len + offset > PAGE_SIZE)
> len = PAGE_SIZE - offset;
> - }
> vaddr = kmap_high_get(page);
> if (vaddr) {
> vaddr += offset;
> @@ -809,7 +811,7 @@ static void dma_cache_maint_page(struct page *page, unsigned long offset,
> op(vaddr, len, dir);
> }
> offset = 0;
> - page++;
> + pfn++;
> left -= len;
> } while (left);
> }
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html



\
 
 \ /
  Last update: 2013-01-17 16:21    [W:0.909 / U:0.584 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site