// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2007 Jens Axboe <[email protected]>
*
* Scatterlist handling helpers.
*/
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/scatterlist.h>
#include <linux/highmem.h>
#include <linux/kmemleak.h>
#include <linux/bvec.h>
#include <linux/uio.h>
#include <linux/folio_queue.h>
/**
* sg_next - return the next scatterlist entry in a list
* @sg: The current sg entry
*
* Description:
* Usually the next entry will be @sg@ + 1, but if this sg element is part
* of a chained scatterlist, it could jump to the start of a new
* scatterlist array.
*
**/
struct scatterlist *sg_next(struct scatterlist *sg)
{
if (sg_is_last(sg))
return NULL;
sg++;
if (unlikely(sg_is_chain(sg)))
sg = sg_chain_ptr(sg);
return sg;
}
EXPORT_SYMBOL(sg_next);
/**
* sg_nents - return total count of entries in scatterlist
* @sg: The scatterlist
*
* Description:
* Allows to know how many entries are in sg, taking into account
* chaining as well
*
**/
int sg_nents(struct scatterlist *sg)
{
int nents;
for (nents = 0; sg; sg = sg_next(sg))
nents++;
return nents;
}
EXPORT_SYMBOL(sg_nents);
/**
* sg_nents_for_len - return total count of entries in scatterlist
* needed to satisfy the supplied length
* @sg: The scatterlist
* @len: The total required length
*
* Description:
* Determines the number of entries in sg that are required to meet
* the supplied length, taking into account chaining as well
*
* Returns:
* the number of sg entries needed, negative error on failure
*
**/
int sg_nents_for_len(struct scatterlist *sg, u64 len)
{
int nents;
u64 total;
if (!len)
return 0;
for (nents = 0, total = 0; sg; sg = sg_next(sg)) {
nents++;
total += sg->length;
if (total >= len)
return nents;
}
return -EINVAL;
}
EXPORT_SYMBOL(sg_nents_for_len);
/**
* sg_last - return the last scatterlist entry in a list
* @sgl: First entry in the scatterlist
* @nents: Number of entries in the scatterlist
*
* Description:
* Should only be used casually, it (currently) scans the entire list
* to get the last entry.
*
* Note that the @sgl@ pointer passed in need not be the first one,
* the important bit is that @nents@ denotes the number of entries that
* exist from @sgl@.
*
**/
struct scatterlist *sg_last(struct scatterlist *sgl, unsigned int nents)
{
struct scatterlist *sg, *ret = NULL;
unsigned int i;
for_each_sg(sgl, sg, nents, i)
ret = sg;
BUG_ON(!sg_is_last(ret));
return ret;
}
EXPORT_SYMBOL(sg_last);
/**
* sg_init_table - Initialize SG table
* @sgl: The SG table
* @nents: Number of entries in table
*
* Notes:
* If this is part of a chained sg table, sg_mark_end() should be
* used only on the last table part.
*
**/
void sg_init_table(struct scatterlist *sgl, unsigned int nents)
{
memset(sgl, 0, sizeof(*sgl) * nents);
sg_init_marker(sgl, nents);
}
EXPORT_SYMBOL(sg_init_table);
/**
* sg_init_one - Initialize a single entry sg list
* @sg: SG entry
* @buf: Virtual address for IO
* @buflen: IO length
*
**/
void sg_init_one(struct scatterlist *sg, const void *buf, unsigned int buflen)
{
sg_init_table(sg, 1);
sg_set_buf(sg, buf, buflen);
}
EXPORT_SYMBOL(sg_init_one);
/*
* The default behaviour of sg_alloc_table() is to use these kmalloc/kfree
* helpers.
*/
static struct scatterlist *sg_kmalloc(unsigned int nents, gfp_t gfp_mask)
{
if (nents == SG_MAX_SINGLE_ALLOC) {
/*
* Kmemleak doesn't track page allocations as they are not
* commonly used (in a raw form) for kernel data structures.
* As we chain together a list of pages and then a normal
* kmalloc (tracked by kmemleak), in order to for that last
* allocation not to become decoupled (and thus a
* false-positive) we need to inform kmemleak of all the
* intermediate allocations.
*/
void *ptr = (void *) __get_free_page(gfp_mask);
kmemleak_alloc(ptr, PAGE_SIZE, 1, gfp_mask);
return ptr;
} else
return kmalloc_array(nents, sizeof(struct scatterlist),
gfp_mask);
}
static void sg_kfree(struct scatterlist *sg, unsigned int nents)
{
if (nents == SG_MAX_SINGLE_ALLOC) {
kmemleak_free(sg);
free_page((unsigned long) sg);
} else
kfree(sg);
}
/**
* __sg_free_table - Free a previously mapped sg table
* @table: The sg table header to use
* @max_ents: The maximum number of entries per single scatterlist
* @nents_first_chunk: Number of entries int the (preallocated) first
* scatterlist chunk, 0 means no such preallocated first chunk
* @free_fn: Free function
* @num_ents: Number of entries in the table
*
* Description:
* Free an sg table previously allocated and setup with
* __sg_alloc_table(). The @max_ents value must be identical to
* that previously used with __sg_alloc_table().
*
**/
void __sg_free_table(struct sg_table *table, unsigned int max_ents,
unsigned int nents_first_chunk, sg_free_fn *free_fn,
unsigned int num_ents)
{
struct scatterlist *sgl, *next;
unsigned curr_max_ents = nents_first_chunk ?: max_ents;
if (unlikely(!table->sgl))
return;
sgl = table->sgl;
while (num_ents) {
unsigned int alloc_size = num_ents;
unsigned int sg_size;
/*
* If we have more than max_ents segments left,
* then assign 'next' to the sg table after the current one.
* sg_size is then one less than alloc size, since the last
* element is the chain pointer.
*/
if (alloc_size > curr_max_ents) {
next = sg_chain_ptr(&sgl[curr_max_ents - 1]);
alloc_size = curr_max_ents;
sg_size = alloc_size - 1;
} else {
sg_size = alloc_size;
next = NULL;
}
num_ents -= sg_size;
if (nents_first_chunk)
nents_first_chunk = 0;
else
free_fn(sgl, alloc_size);
sgl = next;
curr_max_ents = max_ents;
}
table->sgl = NULL;
}
EXPORT_SYMBOL(__sg_free_table);
/**
* sg_free_append_table - Free a previously allocated append sg table.
* @table: The mapped sg append table header
*
**/
void sg_free_append_table(struct sg_append_table *table)
{
__sg_free_table(&table->sgt, SG_MAX_SINGLE_ALLOC, 0, sg_kfree,
table->total_nents);
}
EXPORT_SYMBOL(sg_free_append_table);
/**
* sg_free_table - Free a previously allocated sg table
* @table: The mapped sg table header
*
**/
void sg_free_table(struct sg_table *table)
{
__sg_free_table(table, SG_MAX_SINGLE_ALLOC, 0, sg_kfree,
table->orig_nents);
}
EXPORT_SYMBOL(sg_free_table);
/**
* __sg_alloc_table - Allocate and initialize an sg table with given allocator
* @table: The sg table header to use
* @nents: Number of entries in sg list
* @max_ents: The maximum number of entries the allocator returns per call
* @first_chunk: first SGL if preallocated (may be %NULL)
* @nents_first_chunk: Number of entries in the (preallocated) first
* scatterlist chunk, 0 means no such preallocated chunk provided by user
* @gfp_mask: GFP allocation mask
* @alloc_fn: Allocator to use
*
* Description:
* This function returns a @table @nents long. The allocator is
* defined to return scatterlist chunks of maximum size @max_ents.
* Thus if @nents is bigger than @max_ents, the scatterlists will be
* chained in units of @max_ents.
*
* Notes:
* If this function returns non-0 (eg failure), the caller must call
* __sg_free_table() to cleanup any leftover allocations.
*
**/
int __sg_alloc_table(struct sg_table *table, unsigned int nents,
unsigned int max_ents, struct scatterlist *first_chunk,
unsigned int nents_first_chunk, gfp_t gfp_mask,
sg_alloc_fn *alloc_fn)
{
struct scatterlist *sg, *prv;
unsigned int left;
unsigned curr_max_ents = nents_first_chunk ?: max_ents;
unsigned prv_max_ents;
memset(table, 0, sizeof(*table));
if (nents == 0)
return -EINVAL;
#ifdef CONFIG_ARCH_NO_SG_CHAIN
if (WARN_ON_ONCE(nents > max_ents))
return -EINVAL;
#endif
left = nents;
prv = NULL;
do {
unsigned int sg_size, alloc_size = left;
if (alloc_size > curr_max_ents) {
alloc_size = curr_max_ents;
sg_size = alloc_size - 1;
} else
sg_size = alloc_size;
left -= sg_size;
if (first_chunk) {
sg = first_chunk;
first_chunk = NULL;
} else {
sg = alloc_fn(alloc_size, gfp_mask);
}
if (unlikely(!sg)) {
/*
* Adjust entry count to reflect that the last
* entry of the previous table won't be used for
* linkage. Without this, sg_kfree() may get
* confused.
*/
if (prv)
table->nents = ++table->orig_nents;
return -ENOMEM;
}
sg_init_table(sg, alloc_size);
table->nents = table->orig_nents += sg_size;
/*
* If this is the first mapping, assign the sg table header.
* If this is not the first mapping, chain previous part.
*/
if (prv)
sg_chain(prv, prv_max_ents, sg);
else
table->sgl = sg;
/*
* If no more entries after this one, mark the end
*/
if (!left)
sg_mark_end(&sg[sg_size - 1]);
prv = sg;
prv_max_ents = curr_max_ents;
curr_max_ents = max_ents;
} while (left);
return 0;
}
EXPORT_SYMBOL(__sg_alloc_table);
/**
* sg_alloc_table - Allocate and initialize an sg table
* @table: The sg table header to use
* @nents: Number of entries in sg list
* @gfp_mask: GFP allocation mask
*
* Description:
* Allocate and initialize an sg table. If @nents@ is larger than
* SG_MAX_SINGLE_ALLOC a chained sg table will be setup.
*
**/
int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask)
{
int ret;
ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC,
NULL, 0, gfp_mask, sg_kmalloc);
if (unlikely(ret))
sg_free_table(table);
return ret;
}
EXPORT_SYMBOL(sg_alloc_table);
static struct scatterlist *get_next_sg(struct sg_append_table *table,
struct scatterlist *cur,
unsigned long needed_sges,
gfp_t gfp_mask)
{
struct scatterlist *new_sg, *next_sg;
unsigned int alloc_size;
if (cur) {
next_sg = sg_next(cur);
/* Check if last entry should be keeped for chainning */
if (!sg_is_last(next_sg) || needed_sges == 1)
return next_sg;
}
alloc_size = min_t(unsigned long, needed_sges, SG_MAX_SINGLE_ALLOC);
new_sg = sg_kmalloc(alloc_size, gfp_mask);
if (!new_sg)
return ERR_PTR(-ENOMEM);
sg_init_table(new_sg, alloc_size);
if (cur) {
table->total_nents += alloc_size - 1;
__sg_chain(next_sg, new_sg);
} else {
table->sgt.sgl = new_sg;
table->total_nents = alloc_size;
}
return new_sg;
}
static bool pages_are_mergeable(struct page *a, struct page *b)
{
if (page_to_pfn(a) != page_to_pfn(b) + 1)
return false;
if (!zone_device_pages_have_same_pgmap(a, b))
return false;
return true;
}
/**
* sg_alloc_append_table_from_pages - Allocate and initialize an append sg
* table from an array of pages
* @sgt_append: The sg append table to use
* @pages: Pointer to an array of page pointers
* @n_pages: Number of pages in the pages array
* @offset: Offset from start of the first page to the start of a buffer
* @size: Number of valid bytes in the buffer (after offset)
* @max_segment: Maximum size of a scatterlist element in bytes
* @left_pages: Left pages caller have to set after this call
* @gfp_mask: GFP allocation mask
*
* Description:
* In the first call it allocate and initialize an sg table from a list of
* pages, else reuse the scatterlist from sgt_append. Contiguous ranges of
* the pages are squashed into a single scatterlist entry up to the maximum
* size specified in @max_segment. A user may provide an offset at a start
* and a size of valid data in a buffer specified by the page array. The
* returned sg table is released by sg_free_append_table
*
* Returns:
* 0 on success, negative error on failure
*
* Notes:
* If this function returns non-0 (eg failure), the caller must call
* sg_free_append_table() to cleanup any leftover allocations.
*
* In the fist call, sgt_append must by initialized.
*/
int sg_alloc_append_table_from_pages(struct sg_append_table *sgt_append,
struct page **pages, unsigned int n_pages, unsigned int offset,
unsigned long size, unsigned int max_segment,
unsigned int left_pages, gfp_t gfp_mask)
{
unsigned int chunks, cur_page, seg_len, i, prv_len = 0;
unsigned int added_nents = 0;
struct scatterlist *s = sgt_append->prv;
struct page *last_pg;
/*
* The algorithm below requires max_segment to be aligned to PAGE_SIZE
* otherwise it can overshoot.
*/
max_segment = ALIGN_DOWN(max_segment, PAGE_SIZE);
if (WARN_ON(max_segment < PAGE_SIZE))
return -EINVAL;
if (IS_ENABLED(CONFIG_ARCH_NO_SG_CHAIN) && sgt_append->prv)
return -EOPNOTSUPP;
if (sgt_append->prv) {
unsigned long next_pfn = (page_to_phys(sg_page(sgt_append->prv)) +
sgt_append->prv->offset + sgt_append->prv->length) / PAGE_SIZE;
if (WARN_ON(offset))
return -EINVAL;
/* Merge contiguous pages into the last SG */
prv_len = sgt_append->prv->length;
if (page_to_pfn(pages[0]) == next_pfn) {
last_pg = pfn_to_page(next_pfn - 1);
while (n_pages && pages_are_mergeable(pages[0], last_pg)) {
if (sgt_append->prv->length + PAGE_SIZE > max_segment)
break;
sgt_append->prv->length += PAGE_SIZE;
last_pg = pages[0];
pages++;
n_pages--;
}
if (!n_pages)
goto out;
}
}
/* compute number of contiguous chunks */
chunks = 1;
seg_len = 0;
for (i = 1; i < n_pages; i++) {
seg_len += PAGE_SIZE;
if (seg_len >= max_segment ||
!pages_are_mergeable(pages[i], pages[i - 1])) {
chunks++;
seg_len = 0;
}
}
/* merging chunks and putting them into the scatterlist */
cur_page = 0;
for (i = 0; i < chunks; i++) {
unsigned int j, chunk_size;
/* look for the end of the current chunk */
seg_len = 0;
for (j = cur_page + 1; j < n_pages; j++) {
seg_len += PAGE_SIZE;
if (seg_len >= max_segment ||
!pages_are_mergeable(pages[j], pages[j - 1]))
break;
}
/* Pass how many chunks might be left */
s = get_next_sg(sgt_append, s, chunks - i + left_pages,
gfp_mask);
if (IS_ERR(s)) {
/*
* Adjust entry length to be as before function was
* called.
*/
if (sgt_append->prv)
sgt_append->prv->length = prv_len;
return PTR_ERR(s);
}
chunk_size = ((j - cur_page) << PAGE_SHIFT) - offset;
sg_set_page(s, pages[cur_page],
min_t(unsigned long, size, chunk_size), offset);
added_nents++;
size -= chunk_size;
offset = 0;
cur_page = j;
}
sgt_append->sgt.nents += added_nents;
sgt_append->sgt.orig_nents = sgt_append->sgt.nents;
sgt_append->prv = s;
out:
if (!left_pages)
sg_mark_end(s);
return 0;
}
EXPORT_SYMBOL(sg_alloc_append_table_from_pages);
/**
* sg_alloc_table_from_pages_segment - Allocate and initialize an sg table from
* an array of pages and given maximum
* segment.
* @sgt: The sg table header to use
* @pages: Pointer to an array of page pointers
* @n_pages: Number of pages in the pages array
* @offset: Offset from start of the first page to the start of a buffer
* @size: Number of valid bytes in the buffer (after offset)
* @max_segment: Maximum size of a scatterlist element in bytes
* @gfp_mask: GFP allocation mask
*
* Description:
* Allocate and initialize an sg table from a list of pages. Contiguous
* ranges of the pages are squashed into a single scatterlist node up to the
* maximum size specified in @max_segment. A user may provide an offset at a
* start and a size of valid data in a buffer specified by the page array.
*
* The returned sg table is released by sg_free_table.
*
* Returns:
* 0 on success, negative error on failure
*/
int sg_alloc_table_from_pages_segment(struct sg_table *sgt, struct page **pages,
unsigned int n_pages, unsigned int offset,
unsigned long size, unsigned int max_segment,
gfp_t gfp_mask)
{
struct sg_append_table append = {};
int err;
err = sg_alloc_append_table_from_pages(&append, pages, n_pages, offset,
size, max_segment, 0, gfp_mask);
if (err) {
sg_free_append_table(&append);
return err;
}
memcpy(sgt, &append.sgt, sizeof(*sgt));
WARN_ON(append.total_nents != sgt->orig_nents);
return 0;
}
EXPORT_SYMBOL(sg_alloc_table_from_pages_segment);
#ifdef CONFIG_SGL_ALLOC
/**
* sgl_alloc_order - allocate a scatterlist and its pages
* @length: Length in bytes of the scatterlist. Must be at least one
* @order: Second argument for alloc_pages()
* @chainable: Whether or not to allocate an extra element in the scatterlist
* for scatterlist chaining purposes
* @gfp: Memory allocation flags
* @nent_p: [out] Number of entries in the scatterlist that have pages
*
* Returns: A pointer to an initialized scatterlist or %NULL upon failure.
*/
struct scatterlist *sgl_alloc_order(unsigned long long length,
unsigned int order, bool chainable,
gfp_t gfp, unsigned int *nent_p)
{
struct scatterlist *sgl, *sg;
struct page *page;
unsigned int nent, nalloc;
u32 elem_len;
nent = round_up(length, PAGE_SIZE << order) >> (PAGE_SHIFT + order);
/* Check for integer overflow */
if (length > (nent << (PAGE_SHIFT + order)))
return NULL;
nalloc = nent;
if (chainable) {
/* Check for integer overflow */
if (nalloc + 1 < nalloc)
return NULL;
nalloc++;
}
sgl = kmalloc_array(nalloc, sizeof(struct scatterlist),
gfp & ~GFP_DMA);
if (!sgl)
return NULL;
sg_init_table(sgl, nalloc);
sg = sgl;
while (length) {
elem_len = min_t(u64, length, PAGE_SIZE << order);
page = alloc_pages(gfp, order);
if (!page) {
sgl_free_order(sgl, order);
return NULL;
}
sg_set_page(sg, page, elem_len, 0);
length -= elem_len;
sg = sg_next(sg);
}
WARN_ONCE(length, "length = %lld\n", length);
if (nent_p)
*nent_p = nent;
return sgl;
}
EXPORT_SYMBOL(sgl_alloc_order);
/**
* sgl_alloc - allocate a scatterlist and its pages
* @length: Length in bytes of the scatterlist
* @gfp: Memory allocation flags
* @nent_p: [out] Number of entries in the scatterlist
*
* Returns: A pointer to an initialized scatterlist or %NULL upon failure.
*/
struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp,
unsigned int *nent_p)
{
return sgl_alloc_order(length, 0, false, gfp, nent_p);
}
EXPORT_SYMBOL(sgl_alloc);
/**
* sgl_free_n_order - free a scatterlist and its pages
* @sgl: Scatterlist with one or more elements
* @nents: Maximum number of elements to free
* @order: Second argument for __free_pages()
*
* Notes:
* - If several scatterlists have been chained and each chain element is
* freed separately then it's essential to set nents correctly to avoid that a
* page would get freed twice.
* - All pages in a chained scatterlist can be freed at once by setting @nents
* to a high number.
*/
void sgl_free_n_order(struct scatterlist *sgl, int nents, int order)
{
struct scatterlist *sg;
struct page *page;
int i;
for_each_sg(sgl, sg, nents, i) {
if (!sg)
break;
page = sg_page(sg);
if (page)
__free_pages(page, order);
}
kfree(sgl);
}
EXPORT_SYMBOL(sgl_free_n_order);
/**
* sgl_free_order - free a scatterlist and its pages
* @sgl: Scatterlist with one or more elements
* @order: Second argument for __free_pages()
*/
void sgl_free_order(struct scatterlist *sgl, int order)
{
sgl_free_n_order(sgl, INT_MAX, order);
}
EXPORT_SYMBOL(sgl_free_order);
/**
* sgl_free - free a scatterlist and its pages
* @sgl: Scatterlist with one or more elements
*/
void sgl_free(struct scatterlist *sgl)
{
sgl_free_order(sgl, 0);
}
EXPORT_SYMBOL(sgl_free);
#endif /* CONFIG_SGL_ALLOC */
void __sg_page_iter_start(struct sg_page_iter *piter,
struct scatterlist *sglist, unsigned int nents,
unsigned long pgoffset)
{
piter->__pg_advance = 0;
piter->__nents = nents;
piter->sg = sglist;
piter->sg_pgoffset = pgoffset;
}
EXPORT_SYMBOL(__sg_page_iter_start);
static int sg_page_count(struct scatterlist *sg)
{
return PAGE_ALIGN(sg->offset + sg->length) >> PAGE_SHIFT;
}
bool __sg_page_iter_next(struct sg_page_iter *piter)
{
if (!piter->__nents || !piter->sg)
return false;
piter->sg_pgoffset += piter->__pg_advance;
piter->__pg_advance = 1;
while (piter->sg_pgoffset >= sg_page_count(piter->sg)) {
piter->sg_pgoffset -= sg_page_count(piter->sg);
piter->sg = sg_next(piter->sg);
if (!--piter->__nents || !piter->sg)
return false;
}
return true;
}
EXPORT_SYMBOL(__sg_page_iter_next);
static int sg_dma_page_count(struct scatterlist *sg)
{
return PAGE_ALIGN(sg->offset + sg_dma_len(sg)) >> PAGE_SHIFT;
}
bool __sg_page_iter_dma_next(struct sg_dma_page_iter *dma_iter)
{
struct sg_page_iter *piter = &dma_iter->base;
if (!piter->__nents || !piter->sg)
return false;
piter->sg_pgoffset += piter->__pg_advance;
piter->__pg_advance = 1;
while (piter->sg_pgoffset >= sg_dma_page_count(piter->sg)) {
piter->sg_pgoffset -= sg_dma_page_count(piter->sg);
piter->sg = sg_next(piter->sg);
if (!--piter->__nents || !piter->sg)
return false;
}
return true;
}
EXPORT_SYMBOL(__sg_page_iter_dma_next);
/**
* sg_miter_start - start mapping iteration over a sg list
* @miter: sg mapping iter to be started
* @sgl: sg list to iterate over
* @nents: number of sg entries
* @flags: sg iterator flags
*
* Description:
* Starts mapping iterator @miter.
*
* Context:
* Don't care.
*/
void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
unsigned int nents, unsigned int flags)
{
memset(miter, 0, sizeof(struct sg_mapping_iter));
__sg_page_iter_start(&miter->piter, sgl, nents, 0);
WARN_ON(!(flags & (SG_MITER_TO_SG | SG_MITER_FROM_SG)));
miter->__flags = flags;
}
EXPORT_SYMBOL(sg_miter_start);
static bool sg_miter_get_next_page(struct sg_mapping_iter *miter)
{
if (!miter->__remaining) {
struct scatterlist *sg;
if (!__sg_page_iter_next(&miter->piter))
return false;
sg = miter->piter.sg;
miter->__offset = miter->piter.sg_pgoffset ? 0 : sg->offset;
miter->piter.sg_pgoffset += miter->__offset >> PAGE_SHIFT;
miter->__offset &= PAGE_SIZE - 1;
miter->__remaining = sg->offset + sg->length -
(miter->piter.sg_pgoffset << PAGE_SHIFT) -
miter->__offset;
miter->__remaining = min_t(unsigned long, miter->__remaining,
PAGE_SIZE - miter->__offset);
}
return true;
}
/**
* 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.
*
* Returns:
* true if @miter contains the valid mapping. false if end of sg
* list is reached.
*/
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;
}
EXPORT_SYMBOL(sg_miter_skip);
/**
* sg_miter_next - proceed mapping iterator to the next mapping
* @miter: sg mapping iter to proceed
*
* Description:
* Proceeds @miter to the next mapping. @miter should have been started
* using sg_miter_start(). On successful return, @miter->page,
* @miter->addr and @miter->length point to the current mapping.
*
* Context:
* May sleep if !SG_MITER_ATOMIC.
*
* Returns:
* true if @miter contains the next mapping. false if end of sg
* list is reached.
*/
bool sg_miter_next(struct sg_mapping_iter *miter)
{
sg_miter_stop(miter);
/*
* Get to the next page if necessary.
* __remaining, __offset is adjusted by sg_miter_stop
*/
if (!sg_miter_get_next_page(miter))
return false;
miter->page = sg_page_iter_page(&miter->piter);
miter->consumed = miter->length = miter->__remaining;
if (miter->__flags & SG_MITER_ATOMIC)
miter->addr = kmap_atomic(miter->page) + miter->__offset;
else
miter->addr = kmap(miter->page) + miter->__offset;
return true;
}
EXPORT_SYMBOL(sg_miter_next);
/**
* sg_miter_stop - stop mapping iteration
* @miter: sg mapping iter to be stopped
*
* Description:
* Stops mapping iterator @miter. @miter should have been started
* using sg_miter_start(). A stopped iteration can be resumed by
* calling sg_miter_next() on it. This is useful when resources (kmap)
* need to be released during iteration.
*
* Context:
* Don't care otherwise.
*/
void sg_miter_stop(struct sg_mapping_iter *miter)
{
WARN_ON(miter->consumed > miter->length);
/* drop resources from the last iteration */
if (miter->addr) {
miter->__offset += miter->consumed;
miter->__remaining -= miter->consumed;
if (miter->__flags & SG_MITER_TO_SG)
flush_dcache_page(miter->page);
if (miter->__flags & SG_MITER_ATOMIC) {
WARN_ON_ONCE(!pagefault_disabled());
kunmap_atomic(miter->addr);
} else
kunmap(miter->page);
miter->page = NULL;
miter->addr = NULL;
miter->length = 0;
miter->consumed = 0;
}
}
EXPORT_SYMBOL(sg_miter_stop);
/**
* sg_copy_buffer - Copy data between a linear buffer and an SG list
* @sgl: The SG list
* @nents: Number of SG entries
* @buf: Where to copy from
* @buflen: The number of bytes to copy
* @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.
*
**/
size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
size_t buflen, off_t skip, bool to_buffer)
{
unsigned int offset = 0;
struct sg_mapping_iter miter;
unsigned int sg_flags = SG_MITER_ATOMIC;
if (to_buffer)
sg_flags |= SG_MITER_FROM_SG;
else
sg_flags |= SG_MITER_TO_SG;
sg_miter_start(&miter, sgl, nents, sg_flags);
if (!sg_miter_skip(&miter, skip))
return 0;
while ((offset < buflen) && sg_miter_next(&miter)) {
unsigned int len;
len = min(miter.length, buflen - offset);
if (to_buffer)
memcpy(buf + offset, miter.addr, len);
else
memcpy(miter.addr, buf + offset, len);
offset += len;
}
sg_miter_stop(&miter);
return offset;
}
EXPORT_SYMBOL(sg_copy_buffer);
/**
* sg_copy_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
* @buflen: The number of bytes to copy
*
* Returns the number of copied bytes.
*
**/
size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
const void *buf, size_t buflen)
{
return sg_copy_buffer(sgl, nents, (void *)buf, buflen, 0, false);
}
EXPORT_SYMBOL(sg_copy_from_buffer);
/**
* sg_copy_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
* @buflen: The number of bytes to copy
*
* Returns the number of copied bytes.
*
**/
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, 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
* @buflen: The number of bytes to copy
* @skip: Number of bytes to skip before copying
*
* Returns the number of copied bytes.
*
**/
size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
const void *buf, size_t buflen, off_t skip)
{
return sg_copy_buffer(sgl, nents, (void *)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
* @buflen: The number of bytes to copy
* @skip: Number of bytes to skip before copying
*
* 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);
/**
* sg_zero_buffer - Zero-out a part of a SG list
* @sgl: The SG list
* @nents: Number of SG entries
* @buflen: The number of bytes to zero out
* @skip: Number of bytes to skip before zeroing
*
* Returns the number of bytes zeroed.
**/
size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents,
size_t buflen, off_t skip)
{
unsigned int offset = 0;
struct sg_mapping_iter miter;
unsigned int sg_flags = SG_MITER_ATOMIC | SG_MITER_TO_SG;
sg_miter_start(&miter, sgl, nents, sg_flags);
if (!sg_miter_skip(&miter, skip))
return false;
while (offset < buflen && sg_miter_next(&miter)) {
unsigned int len;
len = min(miter.length, buflen - offset);
memset(miter.addr, 0, len);
offset += len;
}
sg_miter_stop(&miter);
return offset;
}
EXPORT_SYMBOL(sg_zero_buffer);
/*
* Extract and pin a list of up to sg_max pages from UBUF- or IOVEC-class
* iterators, and add them to the scatterlist.
*/
static ssize_t extract_user_to_sg(struct iov_iter *iter,
ssize_t maxsize,
struct sg_table *sgtable,
unsigned int sg_max,
iov_iter_extraction_t extraction_flags)
{
struct scatterlist *sg = sgtable->sgl + sgtable->nents;
struct page **pages;
unsigned int npages;
ssize_t ret = 0, res;
size_t len, off;
/* We decant the page list into the tail of the scatterlist */
pages = (void *)sgtable->sgl +
array_size(sg_max, sizeof(struct scatterlist));
pages -= sg_max;
do {
res = iov_iter_extract_pages(iter, &pages, maxsize, sg_max,
extraction_flags, &off);
if (res <= 0)
goto failed;
len = res;
maxsize -= len;
ret += len;
npages = DIV_ROUND_UP(off + len, PAGE_SIZE);
sg_max -= npages;
for (; npages > 0; npages--) {
struct page *page = *pages;
size_t seg = min_t(size_t, PAGE_SIZE - off, len);
*pages++ = NULL;
sg_set_page(sg, page, seg, off);
sgtable->nents++;
sg++;
len -= seg;
off = 0;
}
} while (maxsize > 0 && sg_max > 0);
return ret;
failed:
while (sgtable->nents > sgtable->orig_nents)
unpin_user_page(sg_page(&sgtable->sgl[--sgtable->nents]));
return res;
}
/*
* Extract up to sg_max pages from a BVEC-type iterator and add them to the
* scatterlist. The pages are not pinned.
*/
static ssize_t extract_bvec_to_sg(struct iov_iter *iter,
ssize_t maxsize,
struct sg_table *sgtable,
unsigned int sg_max,
iov_iter_extraction_t extraction_flags)
{
const struct bio_vec *bv = iter->bvec;
struct scatterlist *sg = sgtable->sgl + sgtable->nents;
unsigned long start = iter->iov_offset;
unsigned int i;
ssize_t ret = 0;
for (i = 0; i < iter->nr_segs; i++) {
size_t off, len;
len = bv[i].bv_len;
if (start >= len) {
start -= len;
continue;
}
len = min_t(size_t, maxsize, len - start);
off = bv[i].bv_offset + start;
sg_set_page(sg, bv[i].bv_page, len, off);
sgtable->nents++;
sg++;
sg_max--;
ret += len;
maxsize -= len;
if (maxsize <= 0 || sg_max == 0)
break;
start = 0;
}
if (ret > 0)
iov_iter_advance(iter, ret);
return ret;
}
/*
* Extract up to sg_max pages from a KVEC-type iterator and add them to the
* scatterlist. This can deal with vmalloc'd buffers as well as kmalloc'd or
* static buffers. The pages are not pinned.
*/
static ssize_t extract_kvec_to_sg(struct iov_iter *iter,
ssize_t maxsize,
struct sg_table *sgtable,
unsigned int sg_max,
iov_iter_extraction_t extraction_flags)
{
const struct kvec *kv = iter->kvec;
struct scatterlist *sg = sgtable->sgl + sgtable->nents;
unsigned long start = iter->iov_offset;
unsigned int i;
ssize_t ret = 0;
for (i = 0; i < iter->nr_segs; i++) {
struct page *page;
unsigned long kaddr;
size_t off, len, seg;
len = kv[i].iov_len;
if (start >= len) {
start -= len;
continue;
}
kaddr = (unsigned long)kv[i].iov_base + start;
off = kaddr & ~PAGE_MASK;
len = min_t(size_t, maxsize, len - start);
kaddr &= PAGE_MASK;
maxsize -= len;
ret += len;
do {
seg = min_t(size_t, len, PAGE_SIZE - off);
if (is_vmalloc_or_module_addr((void *)kaddr))
page = vmalloc_to_page((void *)kaddr);
else
page = virt_to_page((void *)kaddr);
sg_set_page(sg, page, len, off);
sgtable->nents++;
sg++;
sg_max--;
len -= seg;
kaddr += PAGE_SIZE;
off = 0;
} while (len > 0 && sg_max > 0);
if (maxsize <= 0 || sg_max == 0)
break;
start = 0;
}
if (ret > 0)
iov_iter_advance(iter, ret);
return ret;
}
/*
* Extract up to sg_max folios from an FOLIOQ-type iterator and add them to
* the scatterlist. The pages are not pinned.
*/
static ssize_t extract_folioq_to_sg(struct iov_iter *iter,
ssize_t maxsize,
struct sg_table *sgtable,
unsigned int sg_max,
iov_iter_extraction_t extraction_flags)
{
const struct folio_queue *folioq = iter->folioq;
struct scatterlist *sg = sgtable->sgl + sgtable->nents;
unsigned int slot = iter->folioq_slot;
ssize_t ret = 0;
size_t offset = iter->iov_offset;
BUG_ON(!folioq);
if (slot >= folioq_nr_slots(folioq)) {
folioq = folioq->next;
if (WARN_ON_ONCE(!folioq))
return 0;
slot = 0;
}
do {
struct folio *folio = folioq_folio(folioq, slot);
size_t fsize = folioq_folio_size(folioq, slot);
if (offset < fsize) {
size_t part = umin(maxsize - ret, fsize - offset);
sg_set_page(sg, folio_page(folio, 0), part, offset);
sgtable->nents++;
sg++;
sg_max--;
offset += part;
ret += part;
}
if (offset >= fsize) {
offset = 0;
slot++;
if (slot >= folioq_nr_slots(folioq)) {
if (!folioq->next) {
WARN_ON_ONCE(ret < iter->count);
break;
}
folioq = folioq->next;
slot = 0;
}
}
} while (sg_max > 0 && ret < maxsize);
iter->folioq = folioq;
iter->folioq_slot = slot;
iter->iov_offset = offset;
iter->count -= ret;
return ret;
}
/*
* Extract up to sg_max folios from an XARRAY-type iterator and add them to
* the scatterlist. The pages are not pinned.
*/
static ssize_t extract_xarray_to_sg(struct iov_iter *iter,
ssize_t maxsize,
struct sg_table *sgtable,
unsigned int sg_max,
iov_iter_extraction_t extraction_flags)
{
struct scatterlist *sg = sgtable->sgl + sgtable->nents;
struct xarray *xa = iter->xarray;
struct folio *folio;
loff_t start = iter->xarray_start + iter->iov_offset;
pgoff_t index = start / PAGE_SIZE;
ssize_t ret = 0;
size_t offset, len;
XA_STATE(xas, xa, index);
rcu_read_lock();
xas_for_each(&xas, folio, ULONG_MAX) {
if (xas_retry(&xas, folio))
continue;
if (WARN_ON(xa_is_value(folio)))
break;
if (WARN_ON(folio_test_hugetlb(folio)))
break;
offset = offset_in_folio(folio, start);
len = min_t(size_t, maxsize, folio_size(folio) - offset);
sg_set_page(sg, folio_page(folio, 0), len, offset);
sgtable->nents++;
sg++;
sg_max--;
maxsize -= len;
ret += len;
if (maxsize <= 0 || sg_max == 0)
break;
}
rcu_read_unlock();
if (ret > 0)
iov_iter_advance(iter, ret);
return ret;
}
/**
* extract_iter_to_sg - Extract pages from an iterator and add to an sglist
* @iter: The iterator to extract from
* @maxsize: The amount of iterator to copy
* @sgtable: The scatterlist table to fill in
* @sg_max: Maximum number of elements in @sgtable that may be filled
* @extraction_flags: Flags to qualify the request
*
* Extract the page fragments from the given amount of the source iterator and
* add them to a scatterlist that refers to all of those bits, to a maximum
* addition of @sg_max elements.
*
* The pages referred to by UBUF- and IOVEC-type iterators are extracted and
* pinned; BVEC-, KVEC-, FOLIOQ- and XARRAY-type are extracted but aren't
* pinned; DISCARD-type is not supported.
*
* No end mark is placed on the scatterlist; that's left to the caller.
*
* @extraction_flags can have ITER_ALLOW_P2PDMA set to request peer-to-peer DMA
* be allowed on the pages extracted.
*
* If successful, @sgtable->nents is updated to include the number of elements
* added and the number of bytes added is returned. @sgtable->orig_nents is
* left unaltered.
*
* The iov_iter_extract_mode() function should be used to query how cleanup
* should be performed.
*/
ssize_t extract_iter_to_sg(struct iov_iter *iter, size_t maxsize,
struct sg_table *sgtable, unsigned int sg_max,
iov_iter_extraction_t extraction_flags)
{
if (maxsize == 0)
return 0;
switch (iov_iter_type(iter)) {
case ITER_UBUF:
case ITER_IOVEC:
return extract_user_to_sg(iter, maxsize, sgtable, sg_max,
extraction_flags);
case ITER_BVEC:
return extract_bvec_to_sg(iter, maxsize, sgtable, sg_max,
extraction_flags);
case ITER_KVEC:
return extract_kvec_to_sg(iter, maxsize, sgtable, sg_max,
extraction_flags);
case ITER_FOLIOQ:
return extract_folioq_to_sg(iter, maxsize, sgtable, sg_max,
extraction_flags);
case ITER_XARRAY:
return extract_xarray_to_sg(iter, maxsize, sgtable, sg_max,
extraction_flags);
default:
pr_err("%s(%u) unsupported\n", __func__, iov_iter_type(iter));
WARN_ON_ONCE(1);
return -EIO;
}
}
EXPORT_SYMBOL_GPL(extract_iter_to_sg);
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