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new helper: iov_iter_get_pages_alloc()

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same as iov_iter_get_pages(), except that pages array is allocated
(kmalloc if possible, vmalloc if that fails) and left for caller to
free.  Lustre and NFS ->direct_IO() switched to it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2014-03-21 04:58:33 -04:00
parent f67da30c1d
commit 91f79c43d1
4 changed files with 168 additions and 258 deletions
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40
mm/iov_iter.c
View file

@ -1,6 +1,8 @@
#include <linux/export.h>
#include <linux/uio.h>
#include <linux/pagemap.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
struct iov_iter *i)
@ -263,6 +265,44 @@ ssize_t iov_iter_get_pages(struct iov_iter *i,
}
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)
{
size_t offset = i->iov_offset;
const struct iovec *iov = i->iov;
size_t len;
unsigned long addr;
void *p;
int n;
int res;
len = iov->iov_len - offset;
if (len > i->count)
len = i->count;
if (len > maxsize)
len = maxsize;
addr = (unsigned long)iov->iov_base + offset;
len += *start = addr & (PAGE_SIZE - 1);
addr &= ~(PAGE_SIZE - 1);
n = (len + PAGE_SIZE - 1) / PAGE_SIZE;
p = kmalloc(n * sizeof(struct page *), GFP_KERNEL);
if (!p)
p = vmalloc(n * sizeof(struct page *));
if (!p)
return -ENOMEM;
res = get_user_pages_fast(addr, n, (i->type & WRITE) != WRITE, p);
if (unlikely(res < 0)) {
kvfree(p);
return res;
}
*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)
{
size_t offset = i->iov_offset;