linux/fs/netfs/iterator.c
David Howells 0bcc402555 netfs: Fix netfs_extract_iter_to_sg() for ITER_UBUF/IOVEC
Fix netfs_extract_iter_to_sg() for ITER_UBUF and ITER_IOVEC to set the
size of the page to the part of the page extracted, not the remaining
amount of data in the extracted page array at that point.

This doesn't yet affect anything as cifs, the only current user, only
passes in non-user-backed iterators.

Fixes: 0185846975 ("netfs: Add a function to extract an iterator into a scatterlist")
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Cc: Steve French <sfrench@samba.org>
Cc: Shyam Prasad N <nspmangalore@gmail.com>
Cc: Rohith Surabattula <rohiths.msft@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2023-04-12 09:26:36 -07:00

370 lines
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);