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lib/scatterlist: factor out sg_miter_get_next_page() from sg_miter_next()

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This patchset introduces sg_pcopy_from_buffer() and sg_pcopy_to_buffer(),
which copy data between a linear buffer and an SG list.

The only difference between sg_pcopy_{from,to}_buffer() and
sg_copy_{from,to}_buffer() is an additional argument that specifies the
number of bytes to skip the SG list before copying.

The main reason for introducing these functions is to fix a problem in
scsi_debug module.  And there is a local function in crypto/talitos
module, which can be replaced by sg_pcopy_to_buffer().

This patch:

sg_miter_get_next_page() is used to proceed page iterator to the next page
if necessary, and will be used to implement the variants of
sg_copy_{from,to}_buffer() later.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: "James E.J. Bottomley" <JBottomley@parallels.com>
Cc: Douglas Gilbert <dgilbert@interlog.com>
Cc: Horia Geanta <horia.geanta@freescale.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Akinobu Mita 2013-07-08 16:01:52 -07:00 committed by Linus Torvalds
parent 0ea8530dcf
commit 1105200480
1 changed files with 24 additions and 15 deletions
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39
lib/scatterlist.c
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@ -453,6 +453,28 @@ void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
}
EXPORT_SYMBOL(sg_miter_start);
static bool sg_miter_get_next_page(struct sg_mapping_iter *miter)
{
if (!miter->__remaining) {
struct scatterlist *sg;
unsigned long pgoffset;
if (!__sg_page_iter_next(&miter->piter))
return false;
sg = miter->piter.sg;
pgoffset = miter->piter.sg_pgoffset;
miter->__offset = pgoffset ? 0 : sg->offset;
miter->__remaining = sg->offset + sg->length -
(pgoffset << PAGE_SHIFT) - miter->__offset;
miter->__remaining = min_t(unsigned long, miter->__remaining,
PAGE_SIZE - miter->__offset);
}
return true;
}
/**
* sg_miter_next - proceed mapping iterator to the next mapping
* @miter: sg mapping iter to proceed
@ -478,22 +500,9 @@ bool sg_miter_next(struct sg_mapping_iter *miter)
* Get to the next page if necessary.
* __remaining, __offset is adjusted by sg_miter_stop
*/
if (!miter->__remaining) {
struct scatterlist *sg;
unsigned long pgoffset;
if (!sg_miter_get_next_page(miter))
return false;
if (!__sg_page_iter_next(&miter->piter))
return false;
sg = miter->piter.sg;
pgoffset = miter->piter.sg_pgoffset;
miter->__offset = pgoffset ? 0 : sg->offset;
miter->__remaining = sg->offset + sg->length -
(pgoffset << PAGE_SHIFT) - miter->__offset;
miter->__remaining = min_t(unsigned long, miter->__remaining,
PAGE_SIZE - miter->__offset);
}
miter->page = sg_page_iter_page(&miter->piter);
miter->consumed = miter->length = miter->__remaining;