lib/scatterlist: introduce sg_pcopy_from_buffer() and sg_pcopy_to_buffer()
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. Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: "James E.J. Bottomley" <JBottomley@parallels.com> Cc: Douglas Gilbert <dgilbert@interlog.com> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: Horia Geanta <horia.geanta@freescale.com> Cc: Imre Deak <imre.deak@intel.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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1105200480
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df642cea25
2 changed files with 88 additions and 5 deletions
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@ -244,6 +244,11 @@ size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
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size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
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size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
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void *buf, size_t buflen);
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void *buf, size_t buflen);
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size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
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void *buf, size_t buflen, off_t skip);
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size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
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void *buf, size_t buflen, off_t skip);
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/*
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/*
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* Maximum number of entries that will be allocated in one piece, if
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* Maximum number of entries that will be allocated in one piece, if
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* a list larger than this is required then chaining will be utilized.
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* a list larger than this is required then chaining will be utilized.
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@ -475,6 +475,43 @@ static bool sg_miter_get_next_page(struct sg_mapping_iter *miter)
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return true;
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return true;
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}
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}
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/**
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* sg_miter_skip - reposition mapping iterator
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* @miter: sg mapping iter to be skipped
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* @offset: number of bytes to plus the current location
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*
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* Description:
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* Sets the offset of @miter to its current location plus @offset bytes.
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* If mapping iterator @miter has been proceeded by sg_miter_next(), this
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* stops @miter.
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*
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* Context:
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* Don't care if @miter is stopped, or not proceeded yet.
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* Otherwise, preemption disabled if the SG_MITER_ATOMIC is set.
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*
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* Returns:
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* true if @miter contains the valid mapping. false if end of sg
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* list is reached.
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*/
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static bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset)
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{
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sg_miter_stop(miter);
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while (offset) {
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off_t consumed;
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if (!sg_miter_get_next_page(miter))
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return false;
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consumed = min_t(off_t, offset, miter->__remaining);
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miter->__offset += consumed;
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miter->__remaining -= consumed;
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offset -= consumed;
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}
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return true;
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}
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/**
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/**
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* sg_miter_next - proceed mapping iterator to the next mapping
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* sg_miter_next - proceed mapping iterator to the next mapping
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* @miter: sg mapping iter to proceed
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* @miter: sg mapping iter to proceed
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@ -561,14 +598,16 @@ EXPORT_SYMBOL(sg_miter_stop);
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* @nents: Number of SG entries
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* @nents: Number of SG entries
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* @buf: Where to copy from
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* @buf: Where to copy from
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* @buflen: The number of bytes to copy
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* @buflen: The number of bytes to copy
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* @to_buffer: transfer direction (non zero == from an sg list to a
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* @skip: Number of bytes to skip before copying
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* buffer, 0 == from a buffer to an sg list
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* @to_buffer: transfer direction (true == from an sg list to a
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* buffer, false == from a buffer to an sg list
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*
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*
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* Returns the number of copied bytes.
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* Returns the number of copied bytes.
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*
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*
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**/
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**/
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static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
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static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
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void *buf, size_t buflen, int to_buffer)
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void *buf, size_t buflen, off_t skip,
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bool to_buffer)
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{
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{
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unsigned int offset = 0;
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unsigned int offset = 0;
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struct sg_mapping_iter miter;
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struct sg_mapping_iter miter;
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@ -582,6 +621,9 @@ static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
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sg_miter_start(&miter, sgl, nents, sg_flags);
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sg_miter_start(&miter, sgl, nents, sg_flags);
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if (!sg_miter_skip(&miter, skip))
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return false;
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local_irq_save(flags);
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local_irq_save(flags);
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while (sg_miter_next(&miter) && offset < buflen) {
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while (sg_miter_next(&miter) && offset < buflen) {
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@ -616,7 +658,7 @@ static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
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size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
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size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
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void *buf, size_t buflen)
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void *buf, size_t buflen)
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{
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{
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return sg_copy_buffer(sgl, nents, buf, buflen, 0);
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return sg_copy_buffer(sgl, nents, buf, buflen, 0, false);
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}
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}
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EXPORT_SYMBOL(sg_copy_from_buffer);
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EXPORT_SYMBOL(sg_copy_from_buffer);
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@ -633,6 +675,42 @@ EXPORT_SYMBOL(sg_copy_from_buffer);
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size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
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size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
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void *buf, size_t buflen)
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void *buf, size_t buflen)
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{
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{
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return sg_copy_buffer(sgl, nents, buf, buflen, 1);
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return sg_copy_buffer(sgl, nents, buf, buflen, 0, true);
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}
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}
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EXPORT_SYMBOL(sg_copy_to_buffer);
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EXPORT_SYMBOL(sg_copy_to_buffer);
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/**
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* sg_pcopy_from_buffer - Copy from a linear buffer to an SG list
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* @sgl: The SG list
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* @nents: Number of SG entries
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* @buf: Where to copy from
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* @skip: Number of bytes to skip before copying
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* @buflen: The number of bytes to copy
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*
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* Returns the number of copied bytes.
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*
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**/
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size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
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void *buf, size_t buflen, off_t skip)
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{
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return sg_copy_buffer(sgl, nents, buf, buflen, skip, false);
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}
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EXPORT_SYMBOL(sg_pcopy_from_buffer);
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/**
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* sg_pcopy_to_buffer - Copy from an SG list to a linear buffer
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* @sgl: The SG list
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* @nents: Number of SG entries
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* @buf: Where to copy to
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* @skip: Number of bytes to skip before copying
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* @buflen: The number of bytes to copy
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*
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* Returns the number of copied bytes.
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*
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**/
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size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
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void *buf, size_t buflen, off_t skip)
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{
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return sg_copy_buffer(sgl, nents, buf, buflen, skip, true);
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}
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EXPORT_SYMBOL(sg_pcopy_to_buffer);
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