The patch titled
scatterlist: new helper functions
has been added to the -mm tree. Its filename is
scatterlist-new-helper-functions.patch
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Subject: scatterlist: new helper functions
From: Maxim Levitsky <maximlevitsky@xxxxxxxxx>
While developing memstick driver for legacy memsticks I found the need in
few helpers that I think are ok to have in common sg library
The functions that were added:
* sg_nents/sg_total_len - iterate over sg list to figure out its total
len, number of entries. Useful for not keeping that information in side
channels.
* sg_copy/sg_advance - Alow to break sg lists apart into smaller chunks.
sg_copy creates smaller sg list spanning first 'len' bytes, while
sg_advance edits the sg list in such way that it skips over 'len' bytes.
* sg_compare_to_buffer - another function to hide gory details of access
to sg list by CPU. Allows to transparetly compare contents of the sg
list to given linear buffer. If needed later, a function that compares
two sgs can be added.
All of this code is used by my ms_block.c driver.
Signed-off-by: Maxim Levitsky <maximlevitsky@xxxxxxxxx>
Cc: Alex Dubov <oakad@xxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/scatterlist.h | 6 +
lib/scatterlist.c | 137 ++++++++++++++++++++++++++++++++++
2 files changed, 143 insertions(+)
diff -puN include/linux/scatterlist.h~scatterlist-new-helper-functions include/linux/scatterlist.h
--- a/include/linux/scatterlist.h~scatterlist-new-helper-functions
+++ a/include/linux/scatterlist.h
@@ -199,6 +199,11 @@ static inline void *sg_virt(struct scatt
return page_address(sg_page(sg)) + sg->offset;
}
+struct scatterlist *sg_advance(struct scatterlist *sg, int consumed);
+int sg_nents(struct scatterlist *sg);
+int sg_total_len(struct scatterlist *sg);
+int sg_copy(struct scatterlist *sg_from, struct scatterlist *sg_to, int len);
+
struct scatterlist *sg_next(struct scatterlist *);
struct scatterlist *sg_last(struct scatterlist *s, unsigned int);
void sg_init_table(struct scatterlist *, unsigned int);
@@ -217,6 +222,7 @@ size_t sg_copy_from_buffer(struct scatte
void *buf, size_t buflen);
size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
void *buf, size_t buflen);
+bool sg_compare_to_buffer(struct scatterlist *sg, u8 *buffer, size_t len);
/*
* Maximum number of entries that will be allocated in one piece, if
diff -puN lib/scatterlist.c~scatterlist-new-helper-functions lib/scatterlist.c
--- a/lib/scatterlist.c~scatterlist-new-helper-functions
+++ a/lib/scatterlist.c
@@ -39,6 +39,77 @@ struct scatterlist *sg_next(struct scatt
EXPORT_SYMBOL(sg_next);
/**
+ * sg_advance - advance scatterlist by 'consumed' bytes
+ * @sg - the current sg entry
+ * @consumed - how much bytes to advance
+ *
+ */
+struct scatterlist *sg_advance(struct scatterlist *sg, int consumed)
+{
+ while (consumed >= sg->length) {
+ consumed -= sg->length;
+
+ sg = sg_next(sg);
+ if (!sg)
+ break;
+ }
+
+ WARN_ON(!sg && consumed);
+
+ if (!sg)
+ return NULL;
+
+ sg->offset += consumed;
+ sg->length -= consumed;
+
+ if (sg->offset >= PAGE_SIZE) {
+ struct page *page =
+ nth_page(sg_page(sg), sg->offset / PAGE_SIZE);
+ sg_set_page(sg, page, sg->length, sg->offset % PAGE_SIZE);
+ }
+
+ return sg;
+}
+EXPORT_SYMBOL(sg_advance);
+
+/**
+ * sg_nents - calculate number of sg entries in sg list
+ * @sg - the current sg entry
+ *
+ * Allows to calculate dynamicly the lenght of the sg table, based on
+ * assumption that last entry is NULL
+ */
+int sg_nents(struct scatterlist *sg)
+{
+ int nents = 0;
+ while (sg) {
+ nents++;
+ sg = sg_next(sg);
+ }
+
+ return nents;
+}
+EXPORT_SYMBOL(sg_nents);
+
+/**
+ * sg_total_len - calculate total lenght of scatterlist
+ * @sg - the current sg entry
+ *
+ * Dynamicly calculate total number of bytes in a sg list
+ * based on assumption that list ends with a NULL entry
+ */
+int sg_total_len(struct scatterlist *sg)
+{
+ int len = 0;
+ while (sg) {
+ len += sg->length;
+ sg = sg_next(sg);
+ }
+ return len;
+}
+EXPORT_SYMBOL(sg_total_len);
+
+/**
* sg_last - return the last scatterlist entry in a list
* @sgl: First entry in the scatterlist
* @nents: Number of entries in the scatterlist
@@ -110,6 +181,33 @@ void sg_init_one(struct scatterlist *sg,
}
EXPORT_SYMBOL(sg_init_one);
+/**
+ * sg_copy - copies sg entries from sg_from to sg_to, such
+ * as sg_to covers first 'len' bytes from sg_from.
+ */
+int sg_copy(struct scatterlist *sg_from, struct scatterlist *sg_to, int len)
+{
+ while (len > sg_from->length) {
+ len -= sg_from->length;
+
+ sg_set_page(sg_to, sg_page(sg_from),
+ sg_from->length, sg_from->offset);
+
+ sg_to = sg_next(sg_to);
+ sg_from = sg_next(sg_from);
+
+ if (len && (!sg_from || !sg_to))
+ return -ENOMEM;
+ }
+
+ if (len)
+ sg_set_page(sg_to, sg_page(sg_from),
+ len, sg_from->offset);
+ sg_mark_end(sg_to);
+ return 0;
+}
+EXPORT_SYMBOL(sg_copy);
+
/*
* The default behaviour of sg_alloc_table() is to use these kmalloc/kfree
* helpers.
@@ -517,3 +615,42 @@ size_t sg_copy_to_buffer(struct scatterl
return sg_copy_buffer(sgl, nents, buf, buflen, 1);
}
EXPORT_SYMBOL(sg_copy_to_buffer);
+
+
+/**
+ * sg_compare_to_buffer - compare contents of the data pointeted by sg table
+ * to a kernel ram buffer
+ * @sg - the current sg entry
+ * @buffer - linear buffer to compare with
+ * @len - lenght of that buffer
+ */
+bool sg_compare_to_buffer(struct scatterlist *sg, u8 *buffer, size_t len)
+{
+ unsigned long flags;
+ int retval = 0;
+ struct sg_mapping_iter miter;
+
+ if (sg_total_len(sg) < len)
+ return 1;
+
+ local_irq_save(flags);
+ sg_miter_start(&miter, sg, sg_nents(sg),
+ SG_MITER_ATOMIC | SG_MITER_FROM_SG);
+
+ while (sg_miter_next(&miter) && len > 0) {
+
+ int cmplen = min(miter.length, len);
+ if (memcmp(miter.addr, buffer, cmplen)) {
+ retval = 1;
+ break;
+ }
+
+ buffer += cmplen;
+ len -= cmplen;
+ }
+
+ sg_miter_stop(&miter);
+ local_irq_restore(flags);
+ return retval;
+}
+EXPORT_SYMBOL(sg_compare_to_buffer);
_
Patches currently in -mm which might be from maximlevitsky@xxxxxxxxx are
origin.patch
memstick-core-fix-device_register-error-handling.patch
memstick-factor-out-transfer-initiating-functionality-in-mspro_blockc.patch
memstick-factor-out-transfer-initiating-functionality-in-mspro_blockc-fix.patch
memstick-add-support-for-mspro-specific-data-transfer-method.patch
scatterlist-new-helper-functions.patch
scatterlist-new-helper-functions-fix.patch
memstick-add-driver-for-ricoh-r5c592-card-reader.patch
memstick-add-support-for-legacy-memorysticks.patch
memstick-add-alex-dubov-to-maintainers-of-the-memstick-core.patch
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