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bio_vec-backed iov_iter 

New variant of iov_iter - ITER_BVEC in iter->type, backed with
bio_vec array instead of iovec one.  Primitives taught to deal
with such beasts, __swap_write() switched to using that kind
of iov_iter.

Note that bio_vec is just a <page, offset, length> triple - there's
nothing block-specific about it.  I've left the definition where it
was, but took it from under ifdef CONFIG_BLOCK.

Next target: ->splice_write()...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2014-04-04 23:12:29 -04:00
parent 81055e584f
commit 62a8067a7f
5 changed files with 385 additions and 44 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
fs/fuse/file.c
View File

@ -1288,7 +1288,7 @@ static int fuse_get_user_pages(struct fuse_req *req, struct iov_iter *ii,
size_t nbytes = 0; /* # bytes already packed in req */
/* Special case for kernel I/O: can copy directly into the buffer */
if (ii->type & REQ_KERNEL) {
if (ii->type & ITER_KVEC) {
unsigned long user_addr = fuse_get_user_addr(ii);
size_t frag_size = fuse_get_frag_size(ii, *nbytesp);

4
include/linux/blk_types.h
View File

@ -5,8 +5,6 @@
#ifndef __LINUX_BLK_TYPES_H
#define __LINUX_BLK_TYPES_H
#ifdef CONFIG_BLOCK
#include <linux/types.h>
struct bio_set;
@ -28,6 +26,8 @@ struct bio_vec {
unsigned int bv_offset;
};
#ifdef CONFIG_BLOCK
struct bvec_iter {
sector_t bi_sector; /* device address in 512 byte
sectors */

14
include/linux/uio.h
View File

@ -19,12 +19,21 @@ struct kvec {
size_t iov_len;
};
enum {
ITER_IOVEC = 0,
ITER_KVEC = 2,
ITER_BVEC = 4,
};
struct iov_iter {
int type;
const struct iovec *iov;
unsigned long nr_segs;
size_t iov_offset;
size_t count;
union {
const struct iovec *iov;
const struct bio_vec *bvec;
};
unsigned long nr_segs;
};
/*
@ -54,6 +63,7 @@ static inline struct iovec iov_iter_iovec(const struct iov_iter *iter)
}
#define iov_for_each(iov, iter, start) \
if (!((start).type & ITER_BVEC)) \
for (iter = (start); \
(iter).count && \
((iov = iov_iter_iovec(&(iter))), 1); \

390
mm/iov_iter.c
View File

@ -4,7 +4,7 @@
#include <linux/slab.h>
#include <linux/vmalloc.h>
size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t bytes,
struct iov_iter *i)
{
size_t skip, copy, left, wanted;
@ -84,9 +84,8 @@ done:
i->iov_offset = skip;
return wanted - bytes;
}
EXPORT_SYMBOL(copy_page_to_iter);
size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
static size_t copy_page_from_iter_iovec(struct page *page, size_t offset, size_t bytes,
struct iov_iter *i)
{
size_t skip, copy, left, wanted;
@ -166,7 +165,6 @@ done:
i->iov_offset = skip;
return wanted - bytes;
}
EXPORT_SYMBOL(copy_page_from_iter);
static size_t __iovec_copy_from_user_inatomic(char *vaddr,
const struct iovec *iov, size_t base, size_t bytes)
@ -195,7 +193,7 @@ static size_t __iovec_copy_from_user_inatomic(char *vaddr,
* were successfully copied. If a fault is encountered then return the number of
* bytes which were copied.
*/
size_t iov_iter_copy_from_user_atomic(struct page *page,
static size_t copy_from_user_atomic_iovec(struct page *page,
struct iov_iter *i, unsigned long offset, size_t bytes)
{
char *kaddr;
@ -215,9 +213,8 @@ size_t iov_iter_copy_from_user_atomic(struct page *page,
return copied;
}
EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
void iov_iter_advance(struct iov_iter *i, size_t bytes)
static void advance_iovec(struct iov_iter *i, size_t bytes)
{
BUG_ON(i->count < bytes);
@ -252,7 +249,6 @@ void iov_iter_advance(struct iov_iter *i, size_t bytes)
i->nr_segs = nr_segs;
}
}
EXPORT_SYMBOL(iov_iter_advance);
/*
* Fault in the first iovec of the given iov_iter, to a maximum length
@ -265,26 +261,16 @@ EXPORT_SYMBOL(iov_iter_advance);
*/
int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
{
char __user *buf = i->iov->iov_base + i->iov_offset;
bytes = min(bytes, i->iov->iov_len - i->iov_offset);
return fault_in_pages_readable(buf, bytes);
if (!(i->type & ITER_BVEC)) {
char __user *buf = i->iov->iov_base + i->iov_offset;
bytes = min(bytes, i->iov->iov_len - i->iov_offset);
return fault_in_pages_readable(buf, bytes);
}
return 0;
}
EXPORT_SYMBOL(iov_iter_fault_in_readable);
/*
* Return the count of just the current iov_iter segment.
*/
size_t iov_iter_single_seg_count(const struct iov_iter *i)
{
const struct iovec *iov = i->iov;
if (i->nr_segs == 1)
return i->count;
else
return min(i->count, iov->iov_len - i->iov_offset);
}
EXPORT_SYMBOL(iov_iter_single_seg_count);
unsigned long iov_iter_alignment(const struct iov_iter *i)
static unsigned long alignment_iovec(const struct iov_iter *i)
{
const struct iovec *iov = i->iov;
unsigned long res;
@ -307,7 +293,6 @@ unsigned long iov_iter_alignment(const struct iov_iter *i)
res |= (unsigned long)iov->iov_base | size;
return res;
}
EXPORT_SYMBOL(iov_iter_alignment);
void iov_iter_init(struct iov_iter *i, int direction,
const struct iovec *iov, unsigned long nr_segs,
@ -315,7 +300,7 @@ void iov_iter_init(struct iov_iter *i, int direction,
{
/* It will get better. Eventually... */
if (segment_eq(get_fs(), KERNEL_DS))
direction |= REQ_KERNEL;
direction |= ITER_KVEC;
i->type = direction;
i->iov = iov;
i->nr_segs = nr_segs;
@ -324,7 +309,7 @@ void iov_iter_init(struct iov_iter *i, int direction,
}
EXPORT_SYMBOL(iov_iter_init);
ssize_t iov_iter_get_pages(struct iov_iter *i,
static ssize_t get_pages_iovec(struct iov_iter *i,
struct page **pages, size_t maxsize,
size_t *start)
{
@ -349,9 +334,8 @@ ssize_t iov_iter_get_pages(struct iov_iter *i,
return res;
return (res == n ? len : res * PAGE_SIZE) - *start;
}
EXPORT_SYMBOL(iov_iter_get_pages);
ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
static ssize_t get_pages_alloc_iovec(struct iov_iter *i,
struct page ***pages, size_t maxsize,
size_t *start)
{
@ -387,9 +371,8 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
*pages = p;
return (res == n ? len : res * PAGE_SIZE) - *start;
}
EXPORT_SYMBOL(iov_iter_get_pages_alloc);
int iov_iter_npages(const struct iov_iter *i, int maxpages)
static int iov_iter_npages_iovec(const struct iov_iter *i, int maxpages)
{
size_t offset = i->iov_offset;
size_t size = i->count;
@ -414,4 +397,347 @@ int iov_iter_npages(const struct iov_iter *i, int maxpages)
}
return min(npages, maxpages);
}
static void memcpy_from_page(char *to, struct page *page, size_t offset, size_t len)
{
char *from = kmap_atomic(page);
memcpy(to, from + offset, len);
kunmap_atomic(from);
}
static void memcpy_to_page(struct page *page, size_t offset, char *from, size_t len)
{
char *to = kmap_atomic(page);
memcpy(to + offset, from, len);
kunmap_atomic(to);
}
static size_t copy_page_to_iter_bvec(struct page *page, size_t offset, size_t bytes,
struct iov_iter *i)
{
size_t skip, copy, wanted;
const struct bio_vec *bvec;
void *kaddr, *from;
if (unlikely(bytes > i->count))
bytes = i->count;
if (unlikely(!bytes))
return 0;
wanted = bytes;
bvec = i->bvec;
skip = i->iov_offset;
copy = min_t(size_t, bytes, bvec->bv_len - skip);
kaddr = kmap_atomic(page);
from = kaddr + offset;
memcpy_to_page(bvec->bv_page, skip + bvec->bv_offset, from, copy);
skip += copy;
from += copy;
bytes -= copy;
while (bytes) {
bvec++;
copy = min(bytes, (size_t)bvec->bv_len);
memcpy_to_page(bvec->bv_page, bvec->bv_offset, from, copy);
skip = copy;
from += copy;
bytes -= copy;
}
kunmap_atomic(kaddr);
if (skip == bvec->bv_len) {
bvec++;
skip = 0;
}
i->count -= wanted - bytes;
i->nr_segs -= bvec - i->bvec;
i->bvec = bvec;
i->iov_offset = skip;
return wanted - bytes;
}
static size_t copy_page_from_iter_bvec(struct page *page, size_t offset, size_t bytes,
struct iov_iter *i)
{
size_t skip, copy, wanted;
const struct bio_vec *bvec;
void *kaddr, *to;
if (unlikely(bytes > i->count))
bytes = i->count;
if (unlikely(!bytes))
return 0;
wanted = bytes;
bvec = i->bvec;
skip = i->iov_offset;
kaddr = kmap_atomic(page);
to = kaddr + offset;
copy = min(bytes, bvec->bv_len - skip);
memcpy_from_page(to, bvec->bv_page, bvec->bv_offset + skip, copy);
to += copy;
skip += copy;
bytes -= copy;
while (bytes) {
bvec++;
copy = min(bytes, (size_t)bvec->bv_len);
memcpy_from_page(to, bvec->bv_page, bvec->bv_offset, copy);
skip = copy;
to += copy;
bytes -= copy;
}
kunmap_atomic(kaddr);
if (skip == bvec->bv_len) {
bvec++;
skip = 0;
}
i->count -= wanted;
i->nr_segs -= bvec - i->bvec;
i->bvec = bvec;
i->iov_offset = skip;
return wanted;
}
static size_t copy_from_user_bvec(struct page *page,
struct iov_iter *i, unsigned long offset, size_t bytes)
{
char *kaddr;
size_t left;
const struct bio_vec *bvec;
size_t base = i->iov_offset;
kaddr = kmap_atomic(page);
for (left = bytes, bvec = i->bvec; left; bvec++, base = 0) {
size_t copy = min(left, bvec->bv_len - base);
if (!bvec->bv_len)
continue;
memcpy_from_page(kaddr + offset, bvec->bv_page,
bvec->bv_offset + base, copy);
offset += copy;
left -= copy;
}
kunmap_atomic(kaddr);
return bytes;
}
static void advance_bvec(struct iov_iter *i, size_t bytes)
{
BUG_ON(i->count < bytes);
if (likely(i->nr_segs == 1)) {
i->iov_offset += bytes;
i->count -= bytes;
} else {
const struct bio_vec *bvec = i->bvec;
size_t base = i->iov_offset;
unsigned long nr_segs = i->nr_segs;
/*
* The !iov->iov_len check ensures we skip over unlikely
* zero-length segments (without overruning the iovec).
*/
while (bytes || unlikely(i->count && !bvec->bv_len)) {
int copy;
copy = min(bytes, bvec->bv_len - base);
BUG_ON(!i->count || i->count < copy);
i->count -= copy;
bytes -= copy;
base += copy;
if (bvec->bv_len == base) {
bvec++;
nr_segs--;
base = 0;
}
}
i->bvec = bvec;
i->iov_offset = base;
i->nr_segs = nr_segs;
}
}
static unsigned long alignment_bvec(const struct iov_iter *i)
{
const struct bio_vec *bvec = i->bvec;
unsigned long res;
size_t size = i->count;
size_t n;
if (!size)
return 0;
res = bvec->bv_offset + i->iov_offset;
n = bvec->bv_len - i->iov_offset;
if (n >= size)
return res | size;
size -= n;
res |= n;
while (size > (++bvec)->bv_len) {
res |= bvec->bv_offset | bvec->bv_len;
size -= bvec->bv_len;
}
res |= bvec->bv_offset | size;
return res;
}
static ssize_t get_pages_bvec(struct iov_iter *i,
struct page **pages, size_t maxsize,
size_t *start)
{
const struct bio_vec *bvec = i->bvec;
size_t len = bvec->bv_len - i->iov_offset;
if (len > i->count)
len = i->count;
if (len > maxsize)
len = maxsize;
*start = bvec->bv_offset + i->iov_offset;
get_page(*pages = bvec->bv_page);
return len;
}
static ssize_t get_pages_alloc_bvec(struct iov_iter *i,
struct page ***pages, size_t maxsize,
size_t *start)
{
const struct bio_vec *bvec = i->bvec;
size_t len = bvec->bv_len - i->iov_offset;
if (len > i->count)
len = i->count;
if (len > maxsize)
len = maxsize;
*start = bvec->bv_offset + i->iov_offset;
*pages = kmalloc(sizeof(struct page *), GFP_KERNEL);
if (!*pages)
return -ENOMEM;
get_page(**pages = bvec->bv_page);
return len;
}
static int iov_iter_npages_bvec(const struct iov_iter *i, int maxpages)
{
size_t offset = i->iov_offset;
size_t size = i->count;
const struct bio_vec *bvec = i->bvec;
int npages = 0;
int n;
for (n = 0; size && n < i->nr_segs; n++, bvec++) {
size_t len = bvec->bv_len - offset;
offset = 0;
if (unlikely(!len)) /* empty segment */
continue;
if (len > size)
len = size;
npages++;
if (npages >= maxpages) /* don't bother going further */
return maxpages;
size -= len;
offset = 0;
}
return min(npages, maxpages);
}
size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
struct iov_iter *i)
{
if (i->type & ITER_BVEC)
return copy_page_to_iter_bvec(page, offset, bytes, i);
else
return copy_page_to_iter_iovec(page, offset, bytes, i);
}
EXPORT_SYMBOL(copy_page_to_iter);
size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
struct iov_iter *i)
{
if (i->type & ITER_BVEC)
return copy_page_from_iter_bvec(page, offset, bytes, i);
else
return copy_page_from_iter_iovec(page, offset, bytes, i);
}
EXPORT_SYMBOL(copy_page_from_iter);
size_t iov_iter_copy_from_user_atomic(struct page *page,
struct iov_iter *i, unsigned long offset, size_t bytes)
{
if (i->type & ITER_BVEC)
return copy_from_user_bvec(page, i, offset, bytes);
else
return copy_from_user_atomic_iovec(page, i, offset, bytes);
}
EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
void iov_iter_advance(struct iov_iter *i, size_t size)
{
if (i->type & ITER_BVEC)
advance_bvec(i, size);
else
advance_iovec(i, size);
}
EXPORT_SYMBOL(iov_iter_advance);
/*
* Return the count of just the current iov_iter segment.
*/
size_t iov_iter_single_seg_count(const struct iov_iter *i)
{
if (i->nr_segs == 1)
return i->count;
else if (i->type & ITER_BVEC)
return min(i->count, i->iov->iov_len - i->iov_offset);
else
return min(i->count, i->bvec->bv_len - i->iov_offset);
}
EXPORT_SYMBOL(iov_iter_single_seg_count);
unsigned long iov_iter_alignment(const struct iov_iter *i)
{
if (i->type & ITER_BVEC)
return alignment_bvec(i);
else
return alignment_iovec(i);
}
EXPORT_SYMBOL(iov_iter_alignment);
ssize_t iov_iter_get_pages(struct iov_iter *i,
struct page **pages, size_t maxsize,
size_t *start)
{
if (i->type & ITER_BVEC)
return get_pages_bvec(i, pages, maxsize, start);
else
return get_pages_iovec(i, pages, maxsize, start);
}
EXPORT_SYMBOL(iov_iter_get_pages);
ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
struct page ***pages, size_t maxsize,
size_t *start)
{
if (i->type & ITER_BVEC)
return get_pages_alloc_bvec(i, pages, maxsize, start);
else
return get_pages_alloc_iovec(i, pages, maxsize, start);
}
EXPORT_SYMBOL(iov_iter_get_pages_alloc);
int iov_iter_npages(const struct iov_iter *i, int maxpages)
{
if (i->type & ITER_BVEC)
return iov_iter_npages_bvec(i, maxpages);
else
return iov_iter_npages_iovec(i, maxpages);
}
EXPORT_SYMBOL(iov_iter_npages);

19
mm/page_io.c
View File

@ -259,23 +259,28 @@ int __swap_writepage(struct page *page, struct writeback_control *wbc,
struct kiocb kiocb;
struct file *swap_file = sis->swap_file;
struct address_space *mapping = swap_file->f_mapping;
struct iovec iov = {
.iov_base = kmap(page),
.iov_len = PAGE_SIZE,
struct bio_vec bv = {
.bv_page = page,
.bv_len = PAGE_SIZE,
.bv_offset = 0
};
struct iov_iter from = {
.type = ITER_BVEC | WRITE,
.count = PAGE_SIZE,
.iov_offset = 0,
.nr_segs = 1,
.bvec = &bv
};
struct iov_iter from;
init_sync_kiocb(&kiocb, swap_file);
kiocb.ki_pos = page_file_offset(page);
kiocb.ki_nbytes = PAGE_SIZE;
iov_iter_init(&from, KERNEL_WRITE, &iov, 1, PAGE_SIZE);
set_page_writeback(page);
unlock_page(page);
ret = mapping->a_ops->direct_IO(KERNEL_WRITE,
ret = mapping->a_ops->direct_IO(ITER_BVEC | WRITE,
&kiocb, &from,
kiocb.ki_pos);
kunmap(page);
if (ret == PAGE_SIZE) {
count_vm_event(PSWPOUT);
ret = 0;