WSL2-Linux-Kernel/fs/netfs/iterator.c

370 строки
9.6 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/* Iterator helpers.
*
* Copyright (C) 2022 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/uio.h>
#include <linux/scatterlist.h>
#include <linux/netfs.h>
#include "internal.h"
/**
* netfs_extract_user_iter - Extract the pages from a user iterator into a bvec
* @orig: The original iterator
* @orig_len: The amount of iterator to copy
* @new: The iterator to be set up
* @extraction_flags: Flags to qualify the request
*
* Extract the page fragments from the given amount of the source iterator and
* build up a second iterator that refers to all of those bits. This allows
* the original iterator to disposed of.
*
* @extraction_flags can have ITER_ALLOW_P2PDMA set to request peer-to-peer DMA be
* allowed on the pages extracted.
*
* On success, the number of elements in the bvec is returned, the original
* iterator will have been advanced by the amount extracted.
*
* The iov_iter_extract_mode() function should be used to query how cleanup
* should be performed.
*/
ssize_t netfs_extract_user_iter(struct iov_iter *orig, size_t orig_len,
struct iov_iter *new,
iov_iter_extraction_t extraction_flags)
{
struct bio_vec *bv = NULL;
struct page **pages;
unsigned int cur_npages;
unsigned int max_pages;
unsigned int npages = 0;
unsigned int i;
ssize_t ret;
size_t count = orig_len, offset, len;
size_t bv_size, pg_size;
if (WARN_ON_ONCE(!iter_is_ubuf(orig) && !iter_is_iovec(orig)))
return -EIO;
max_pages = iov_iter_npages(orig, INT_MAX);
bv_size = array_size(max_pages, sizeof(*bv));
bv = kvmalloc(bv_size, GFP_KERNEL);
if (!bv)
return -ENOMEM;
/* Put the page list at the end of the bvec list storage. bvec
* elements are larger than page pointers, so as long as we work
* 0->last, we should be fine.
*/
pg_size = array_size(max_pages, sizeof(*pages));
pages = (void *)bv + bv_size - pg_size;
while (count && npages < max_pages) {
ret = iov_iter_extract_pages(orig, &pages, count,
max_pages - npages, extraction_flags,
&offset);
if (ret < 0) {
pr_err("Couldn't get user pages (rc=%zd)\n", ret);
break;
}
if (ret > count) {
pr_err("get_pages rc=%zd more than %zu\n", ret, count);
break;
}
count -= ret;
ret += offset;
cur_npages = DIV_ROUND_UP(ret, PAGE_SIZE);
if (npages + cur_npages > max_pages) {
pr_err("Out of bvec array capacity (%u vs %u)\n",
npages + cur_npages, max_pages);
break;
}
for (i = 0; i < cur_npages; i++) {
len = ret > PAGE_SIZE ? PAGE_SIZE : ret;
bvec_set_page(bv + npages + i, *pages++, len - offset, offset);
ret -= len;
offset = 0;
}
npages += cur_npages;
}
iov_iter_bvec(new, orig->data_source, bv, npages, orig_len - count);
return npages;
}
EXPORT_SYMBOL_GPL(netfs_extract_user_iter);
/*
* 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 netfs_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)
put_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 netfs_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 netfs_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(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 XARRAY-type iterator and add them to
* the scatterlist. The pages are not pinned.
*/
static ssize_t netfs_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;
}
/**
* netfs_extract_iter_to_sg - Extract pages from an iterator and add ot 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- and XARRAY-type are extracted but aren't pinned; PIPE-
* and DISCARD-type are 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 successul, @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 netfs_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 netfs_extract_user_to_sg(iter, maxsize, sgtable, sg_max,
extraction_flags);
case ITER_BVEC:
return netfs_extract_bvec_to_sg(iter, maxsize, sgtable, sg_max,
extraction_flags);
case ITER_KVEC:
return netfs_extract_kvec_to_sg(iter, maxsize, sgtable, sg_max,
extraction_flags);
case ITER_XARRAY:
return netfs_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(netfs_extract_iter_to_sg);