This patch set 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().
Akinobu Mita (3):
lib/scatterlist: introduce sg_pcopy_from_buffer() and
sg_pcopy_to_buffer()
crypto: talitos: use sg_pcopy_to_buffer()
scsi_debug: fix do_device_access() with wrap around range
drivers/crypto/talitos.c | 60 +-----------------------
drivers/scsi/scsi_debug.c | 43 ++++++++++++++---
include/linux/scatterlist.h | 5 ++
lib/scatterlist.c | 109 ++++++++++++++++++++++++++++++++++++--------
4 files changed, 131 insertions(+), 86 deletions(-)
Cc: Tejun Heo <[email protected]>
Cc: Imre Deak <[email protected]>
Cc: Herbert Xu <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: [email protected]
Cc: "James E.J. Bottomley" <[email protected]>
Cc: Douglas Gilbert <[email protected]>
Cc: [email protected]
--
1.8.1.4
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 <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Imre Deak <[email protected]>
Cc: Herbert Xu <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: [email protected]
Cc: "James E.J. Bottomley" <[email protected]>
Cc: Douglas Gilbert <[email protected]>
Cc: [email protected]
---
include/linux/scatterlist.h | 5 ++
lib/scatterlist.c | 109 ++++++++++++++++++++++++++++++++++++--------
2 files changed, 94 insertions(+), 20 deletions(-)
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 5951e3f..f5dee42 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -241,6 +241,11 @@ 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 a1cf8ca..3b40b72 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -453,6 +453,47 @@ 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;
+}
+
+static bool sg_miter_seek(struct sg_mapping_iter *miter, off_t offset)
+{
+ WARN_ON(miter->addr);
+
+ 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
@@ -478,22 +519,9 @@ 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_page_iter_next(&miter->piter))
- return false;
-
- sg = miter->piter.sg;
- pgoffset = miter->piter.sg_pgoffset;
+ if (!sg_miter_get_next_page(miter))
+ return false;
- 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;
@@ -552,14 +580,16 @@ 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;
@@ -573,6 +603,9 @@ static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
sg_miter_start(&miter, sgl, nents, sg_flags);
+ if (!sg_miter_seek(&miter, skip))
+ return false;
+
local_irq_save(flags);
while (sg_miter_next(&miter) && offset < buflen) {
@@ -607,7 +640,7 @@ 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);
@@ -624,6 +657,42 @@ 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);
--
1.8.1.4
do_device_access() is a function that abstracts copying SG list from/to
ramdisk storage (fake_storep).
It must deal with the ranges exceeding actual fake_storep size, because
such ranges are valid if virtual_gb is set greater than zero, and they
should be treated as fake_storep is repeatedly mirrored up to virtual size.
Unfortunately, it can't deal with the range which wraps around the end of
fake_storep. A wrap around range is copied by two sg_copy_{from,to}_buffer()
calls, but sg_copy_{from,to}_buffer() can't copy from/to in the middle of
SG list, therefore the second call can't copy correctly.
This fixes it by using sg_pcopy_{from,to}_buffer() that can copy from/to
the middle of SG list.
Signed-off-by: Akinobu Mita <[email protected]>
Cc: "James E.J. Bottomley" <[email protected]>
Cc: Douglas Gilbert <[email protected]>
Cc: [email protected]
---
drivers/scsi/scsi_debug.c | 43 ++++++++++++++++++++++++++++++++++++-------
1 file changed, 36 insertions(+), 7 deletions(-)
diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index 21239b3..c1efaf8 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -1614,24 +1614,48 @@ static int check_device_access_params(struct sdebug_dev_info *devi,
return 0;
}
+/* Returns number of bytes copied or -1 if error. */
static int do_device_access(struct scsi_cmnd *scmd,
struct sdebug_dev_info *devi,
unsigned long long lba, unsigned int num, int write)
{
int ret;
unsigned long long block, rest = 0;
- int (*func)(struct scsi_cmnd *, unsigned char *, int);
+ struct scsi_data_buffer *sdb;
+ enum dma_data_direction dir;
+ size_t (*func)(struct scatterlist *, unsigned int, void *, size_t,
+ off_t);
+
+ if (write) {
+ sdb = scsi_out(scmd);
+ dir = DMA_TO_DEVICE;
+ func = sg_pcopy_to_buffer;
+ } else {
+ sdb = scsi_in(scmd);
+ dir = DMA_FROM_DEVICE;
+ func = sg_pcopy_from_buffer;
+ }
- func = write ? fetch_to_dev_buffer : fill_from_dev_buffer;
+ if (!sdb->length)
+ return 0;
+ if (!(scsi_bidi_cmnd(scmd) || scmd->sc_data_direction == dir))
+ return -1;
block = do_div(lba, sdebug_store_sectors);
if (block + num > sdebug_store_sectors)
rest = block + num - sdebug_store_sectors;
- ret = func(scmd, fake_storep + (block * scsi_debug_sector_size),
- (num - rest) * scsi_debug_sector_size);
- if (!ret && rest)
- ret = func(scmd, fake_storep, rest * scsi_debug_sector_size);
+ ret = func(sdb->table.sgl, sdb->table.nents,
+ fake_storep + (block * scsi_debug_sector_size),
+ (num - rest) * scsi_debug_sector_size, 0);
+ if (ret != (num - rest) * scsi_debug_sector_size)
+ return ret;
+
+ if (rest) {
+ ret += func(sdb->table.sgl, sdb->table.nents,
+ fake_storep, rest * scsi_debug_sector_size,
+ (num - rest) * scsi_debug_sector_size);
+ }
return ret;
}
@@ -1888,7 +1912,12 @@ static int resp_read(struct scsi_cmnd *SCpnt, unsigned long long lba,
read_lock_irqsave(&atomic_rw, iflags);
ret = do_device_access(SCpnt, devip, lba, num, 0);
read_unlock_irqrestore(&atomic_rw, iflags);
- return ret;
+ if (ret == -1)
+ return DID_ERROR << 16;
+
+ scsi_in(SCpnt)->resid = scsi_bufflen(SCpnt) - ret;
+
+ return 0;
}
static void dump_sector(unsigned char *buf, int len)
--
1.8.1.4
Use sg_pcopy_to_buffer() which is better than the function previously used.
Because it doesn't do kmap/kunmap for skipped pages.
Signed-off-by: Akinobu Mita <[email protected]>
Cc: Herbert Xu <[email protected]>
Cc: Horia Geanta <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: [email protected]
---
drivers/crypto/talitos.c | 60 +-----------------------------------------------
1 file changed, 1 insertion(+), 59 deletions(-)
diff --git a/drivers/crypto/talitos.c b/drivers/crypto/talitos.c
index 5b2b5e6..661dc3e 100644
--- a/drivers/crypto/talitos.c
+++ b/drivers/crypto/talitos.c
@@ -1112,64 +1112,6 @@ static int sg_count(struct scatterlist *sg_list, int nbytes, bool *chained)
return sg_nents;
}
-/**
- * sg_copy_end_to_buffer - Copy end data from SG list to a linear buffer
- * @sgl: The SG list
- * @nents: Number of SG entries
- * @buf: Where to copy to
- * @buflen: The number of bytes to copy
- * @skip: The number of bytes to skip before copying.
- * Note: skip + buflen should equal SG total size.
- *
- * Returns the number of copied bytes.
- *
- **/
-static size_t sg_copy_end_to_buffer(struct scatterlist *sgl, unsigned int nents,
- void *buf, size_t buflen, unsigned int skip)
-{
- unsigned int offset = 0;
- unsigned int boffset = 0;
- struct sg_mapping_iter miter;
- unsigned long flags;
- unsigned int sg_flags = SG_MITER_ATOMIC;
- size_t total_buffer = buflen + skip;
-
- sg_flags |= SG_MITER_FROM_SG;
-
- sg_miter_start(&miter, sgl, nents, sg_flags);
-
- local_irq_save(flags);
-
- while (sg_miter_next(&miter) && offset < total_buffer) {
- unsigned int len;
- unsigned int ignore;
-
- if ((offset + miter.length) > skip) {
- if (offset < skip) {
- /* Copy part of this segment */
- ignore = skip - offset;
- len = miter.length - ignore;
- if (boffset + len > buflen)
- len = buflen - boffset;
- memcpy(buf + boffset, miter.addr + ignore, len);
- } else {
- /* Copy all of this segment (up to buflen) */
- len = miter.length;
- if (boffset + len > buflen)
- len = buflen - boffset;
- memcpy(buf + boffset, miter.addr, len);
- }
- boffset += len;
- }
- offset += miter.length;
- }
-
- sg_miter_stop(&miter);
-
- local_irq_restore(flags);
- return boffset;
-}
-
/*
* allocate and map the extended descriptor
*/
@@ -1800,7 +1742,7 @@ static int ahash_process_req(struct ahash_request *areq, unsigned int nbytes)
if (to_hash_later) {
int nents = sg_count(areq->src, nbytes, &chained);
- sg_copy_end_to_buffer(areq->src, nents,
+ sg_pcopy_to_buffer(areq->src, nents,
req_ctx->bufnext,
to_hash_later,
nbytes - to_hash_later);
--
1.8.1.4
On Thu, 2013-06-06 at 21:52 +0900, Akinobu Mita wrote:
> 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 <[email protected]>
> Cc: Tejun Heo <[email protected]>
> Cc: Imre Deak <[email protected]>
> Cc: Herbert Xu <[email protected]>
> Cc: "David S. Miller" <[email protected]>
> Cc: [email protected]
> Cc: "James E.J. Bottomley" <[email protected]>
> Cc: Douglas Gilbert <[email protected]>
> Cc: [email protected]
> ---
> include/linux/scatterlist.h | 5 ++
> lib/scatterlist.c | 109 ++++++++++++++++++++++++++++++++++++--------
> 2 files changed, 94 insertions(+), 20 deletions(-)
>
> diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
> index 5951e3f..f5dee42 100644
> --- a/include/linux/scatterlist.h
> +++ b/include/linux/scatterlist.h
> @@ -241,6 +241,11 @@ 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 a1cf8ca..3b40b72 100644
> --- a/lib/scatterlist.c
> +++ b/lib/scatterlist.c
> @@ -453,6 +453,47 @@ 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;
> +}
> +
> +static bool sg_miter_seek(struct sg_mapping_iter *miter, off_t offset)
> +{
> + WARN_ON(miter->addr);
> +
> + 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
> @@ -478,22 +519,9 @@ 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_page_iter_next(&miter->piter))
> - return false;
> -
> - sg = miter->piter.sg;
> - pgoffset = miter->piter.sg_pgoffset;
> + if (!sg_miter_get_next_page(miter))
> + return false;
>
> - 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;
>
> @@ -552,14 +580,16 @@ 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;
> @@ -573,6 +603,9 @@ static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
>
> sg_miter_start(&miter, sgl, nents, sg_flags);
>
> + if (!sg_miter_seek(&miter, skip))
> + return false;
Looks ok to me, perhaps adding the seek functionality to the mapping
iterator would make things more generic and the mapping iterator more
resemble the page iterator. So we'd have a new sg_miter_start_offset and
call it here something like:
sg_miter_start_offset(&miter, sgl, nents, sg_flags, skip);
Just my 2 cents,
Imre
> +
> local_irq_save(flags);
>
> while (sg_miter_next(&miter) && offset < buflen) {
> @@ -607,7 +640,7 @@ 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);
>
> @@ -624,6 +657,42 @@ 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);
Hello,
On Thu, Jun 06, 2013 at 09:52:56PM +0900, Akinobu Mita wrote:
> +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;
> +}
It'd be better if separating out this function is a separate patch.
Mixing factoring out something and adding new stuff makes the patch a
bit harder to read.
> +static bool sg_miter_seek(struct sg_mapping_iter *miter, off_t offset)
> +{
> + WARN_ON(miter->addr);
> +
> + 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;
> +}
While I think the above should work at the beginning, what if @miter
is in the middle of iteration and __remaining isn't zero?
Looks good to me otherwise.
Thanks.
--
tejun
2013/6/6 Imre Deak <[email protected]>:
> Looks ok to me, perhaps adding the seek functionality to the mapping
> iterator would make things more generic and the mapping iterator more
> resemble the page iterator. So we'd have a new sg_miter_start_offset and
> call it here something like:
>
> sg_miter_start_offset(&miter, sgl, nents, sg_flags, skip);
I also thought something like this could be a new interface for sg_miter_* API,
but I haven't found any places where it can be used yet. That's why I made
it a local function and didn't create new interface.
But putting good function comment like other sg_miter_* API for new
local function
is harmless and it helps someone who wants interface like this in the future.
So I'll do so in next version.
2013/6/7 Tejun Heo <[email protected]>:
> Hello,
>
> On Thu, Jun 06, 2013 at 09:52:56PM +0900, Akinobu Mita wrote:
>> +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;
>> +}
>
> It'd be better if separating out this function is a separate patch.
> Mixing factoring out something and adding new stuff makes the patch a
> bit harder to read.
OK, sounds good. I'll do so in next version.
But I feel sg_miter_get_next_page() is not very appropriate name, because
it gets the next page only if necessary. If I can find more appropriate name,
I'll rename it.
>> +static bool sg_miter_seek(struct sg_mapping_iter *miter, off_t offset)
>> +{
>> + WARN_ON(miter->addr);
>> +
>> + 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;
>> +}
>
> While I think the above should work at the beginning, what if @miter
> is in the middle of iteration and __remaining isn't zero?
sg_miter_seek() should work as far as it is called just after sg_miter_start(),
or just after sg_miter_stop() in the middle of iteration (Although I only
tested the former case). I omitted a function comment in excuse of the static
function, but I should write something I said above.