diff options
| -rw-r--r-- | include/linux/scatterlist.h | 5 | ||||
| -rw-r--r-- | lib/scatterlist.c | 88 |
2 files changed, 88 insertions, 5 deletions
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index 26806775b11..adae88f5b0a 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -244,6 +244,11 @@ size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents, size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents, void *buf, size_t buflen); +size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents, + void *buf, size_t buflen, off_t skip); +size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents, + void *buf, size_t buflen, off_t skip); + /* * Maximum number of entries that will be allocated in one piece, if * a list larger than this is required then chaining will be utilized. diff --git a/lib/scatterlist.c b/lib/scatterlist.c index c35b929435f..129a82f707d 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -476,6 +476,43 @@ static bool sg_miter_get_next_page(struct sg_mapping_iter *miter) } /** + * sg_miter_skip - reposition mapping iterator + * @miter: sg mapping iter to be skipped + * @offset: number of bytes to plus the current location + * + * Description: + * Sets the offset of @miter to its current location plus @offset bytes. + * If mapping iterator @miter has been proceeded by sg_miter_next(), this + * stops @miter. + * + * Context: + * Don't care if @miter is stopped, or not proceeded yet. + * Otherwise, preemption disabled if the SG_MITER_ATOMIC is set. + * + * Returns: + * true if @miter contains the valid mapping. false if end of sg + * list is reached. + */ +static bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset) +{ + sg_miter_stop(miter); + + while (offset) { + off_t consumed; + + if (!sg_miter_get_next_page(miter)) + return false; + + consumed = min_t(off_t, offset, miter->__remaining); + miter->__offset += consumed; + miter->__remaining -= consumed; + offset -= consumed; + } + + return true; +} + +/** * sg_miter_next - proceed mapping iterator to the next mapping * @miter: sg mapping iter to proceed * @@ -561,14 +598,16 @@ EXPORT_SYMBOL(sg_miter_stop); * @nents: Number of SG entries * @buf: Where to copy from * @buflen: The number of bytes to copy - * @to_buffer: transfer direction (non zero == from an sg list to a - * buffer, 0 == from a buffer to an sg list + * @skip: Number of bytes to skip before copying + * @to_buffer: transfer direction (true == from an sg list to a + * buffer, false == from a buffer to an sg list * * Returns the number of copied bytes. * **/ static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, - void *buf, size_t buflen, int to_buffer) + void *buf, size_t buflen, off_t skip, + bool to_buffer) { unsigned int offset = 0; struct sg_mapping_iter miter; @@ -582,6 +621,9 @@ static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, sg_miter_start(&miter, sgl, nents, sg_flags); + if (!sg_miter_skip(&miter, skip)) + return false; + local_irq_save(flags); while (sg_miter_next(&miter) && offset < buflen) { @@ -616,7 +658,7 @@ static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents, void *buf, size_t buflen) { - return sg_copy_buffer(sgl, nents, buf, buflen, 0); + return sg_copy_buffer(sgl, nents, buf, buflen, 0, false); } EXPORT_SYMBOL(sg_copy_from_buffer); @@ -633,6 +675,42 @@ EXPORT_SYMBOL(sg_copy_from_buffer); size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents, void *buf, size_t buflen) { - return sg_copy_buffer(sgl, nents, buf, buflen, 1); + return sg_copy_buffer(sgl, nents, buf, buflen, 0, true); } EXPORT_SYMBOL(sg_copy_to_buffer); + +/** + * sg_pcopy_from_buffer - Copy from a linear buffer to an SG list + * @sgl: The SG list + * @nents: Number of SG entries + * @buf: Where to copy from + * @skip: Number of bytes to skip before copying + * @buflen: The number of bytes to copy + * + * Returns the number of copied bytes. + * + **/ +size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents, + void *buf, size_t buflen, off_t skip) +{ + return sg_copy_buffer(sgl, nents, buf, buflen, skip, false); +} +EXPORT_SYMBOL(sg_pcopy_from_buffer); + +/** + * sg_pcopy_to_buffer - Copy from an SG list to a linear buffer + * @sgl: The SG list + * @nents: Number of SG entries + * @buf: Where to copy to + * @skip: Number of bytes to skip before copying + * @buflen: The number of bytes to copy + * + * Returns the number of copied bytes. + * + **/ +size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents, + void *buf, size_t buflen, off_t skip) +{ + return sg_copy_buffer(sgl, nents, buf, buflen, skip, true); +} +EXPORT_SYMBOL(sg_pcopy_to_buffer); |