[lkml]   [2013]   [Jan]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH v2 1/1] block: blk-merge: don't merge the pages with non-contiguous descriptors
On Thu, 2013-01-17 at 11:04 +0000, Russell King - ARM Linux wrote:
> On Thu, Jan 17, 2013 at 11:01:47AM +0000, James Bottomley wrote:
> > On Thu, 2013-01-17 at 10:47 +0000, Russell King - ARM Linux wrote:
> > > Also, couldn't the addition of the scatterlist offset to the page also
> > > be buggy too?
> >
> > No, fortunately, offset must be within the first page from the point of
> > view of block generated sg lists. As long as nothing within arm
> > violates this, it should be a safe assumption ... although the code
> > seems to assume otherwise.
> Are you absolutely sure about that? I believe I have seen cases where
> that has been violated in the past, though it was many years ago.

From the point of view of the block layer, absolutely: the scatterlist
is generated from an array of bio_vecs. Each bio_vec is a page, offset
and length element and obeys the rule that offset must be within the
page and offset + length cannot stray over the page.

From the point of view of other arm stuff, I don't know.


 \ /
  Last update: 2013-01-17 13:01    [W:0.056 / U:3.076 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site