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/*
* linux/mm/filemap.h
*
* Copyright (C) 1994-1999 Linus Torvalds
*/
#ifndef __FILEMAP_H
#define __FILEMAP_H
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/uio.h>
#include <linux/uaccess.h>
size_t
__filemap_copy_from_user_iovec_inatomic(char *vaddr,
const struct iovec *iov,
size_t base,
size_t bytes);
/*
* Copy as much as we can into the page and return the number of bytes which
* were sucessfully copied. If a fault is encountered then clear the page
* out to (offset+bytes) and return the number of bytes which were copied.
*
* NOTE: For this to work reliably we really want copy_from_user_inatomic_nocache
* to *NOT* zero any tail of the buffer that it failed to copy. If it does,
* and if the following non-atomic copy succeeds, then there is a small window
* where the target page contains neither the data before the write, nor the
* data after the write (it contains zero). A read at this time will see
* data that is inconsistent with any ordering of the read and the write.
* (This has been detected in practice).
*/
static inline size_t
filemap_copy_from_user(struct page *page, unsigned long offset,
const char __user *buf, unsigned bytes)
{
char *kaddr;
int left;
kaddr = kmap_atomic(page, KM_USER0);
left = __copy_from_user_inatomic_nocache(kaddr + offset, buf, bytes);
kunmap_atomic(kaddr, KM_USER0);
if (left != 0) {
/* Do it the slow way */
kaddr = kmap(page);
left = __copy_from_user_nocache(kaddr + offset, buf, bytes);
kunmap(page);
}
return bytes - left;
}
/*
* This has the same sideeffects and return value as filemap_copy_from_user().
* The difference is that on a fault we need to memset the remainder of the
* page (out to offset+bytes), to emulate filemap_copy_from_user()'s
* single-segment behaviour.
*/
static inline size_t
filemap_copy_from_user_iovec(struct page *page, unsigned long offset,
const struct iovec *iov, size_t base, size_t bytes)
{
char *kaddr;
size_t copied;
kaddr = kmap_atomic(page, KM_USER0);
copied = __filemap_copy_from_user_iovec_inatomic(kaddr + offset, iov,
base, bytes);
kunmap_atomic(kaddr, KM_USER0);
if (copied != bytes) {
kaddr = kmap(page);
copied = __filemap_copy_from_user_iovec_inatomic(kaddr + offset, iov,
base, bytes);
if (bytes - copied)
memset(kaddr + offset + copied, 0, bytes - copied);
kunmap(page);
}
return copied;
}
static inline void
filemap_set_next_iovec(const struct iovec **iovp, size_t *basep, size_t bytes)
{
const struct iovec *iov = *iovp;
size_t base = *basep;
do {
int copy = min(bytes, iov->iov_len - base);
bytes -= copy;
base += copy;
if (iov->iov_len == base) {
iov++;
base = 0;
}
} while (bytes);
*iovp = iov;
*basep = base;
}
#endif
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