LXR linux/mm/filemap.h

   1/*
   2 *      linux/mm/filemap.h
   3 *
   4 * Copyright (C) 1994-1999  Linus Torvalds
   5 */
   6
   7#ifndef __FILEMAP_H
   8#define __FILEMAP_H
   9
  10#include <linux/types.h>
  11#include <linux/fs.h>
  12#include <linux/mm.h>
  13#include <linux/highmem.h>
  14#include <linux/uio.h>
  15#include <linux/uaccess.h>
  16
  17size_t
  18__filemap_copy_from_user_iovec_inatomic(char *vaddr,
  19                                        const struct iovec *iov,
  20                                        size_t base,
  21                                        size_t bytes);
  22
  23/*
  24 * Copy as much as we can into the page and return the number of bytes which
  25 * were sucessfully copied.  If a fault is encountered then clear the page
  26 * out to (offset+bytes) and return the number of bytes which were copied.
  27 *
  28 * NOTE: For this to work reliably we really want copy_from_user_inatomic_nocache
  29 * to *NOT* zero any tail of the buffer that it failed to copy.  If it does,
  30 * and if the following non-atomic copy succeeds, then there is a small window
  31 * where the target page contains neither the data before the write, nor the
  32 * data after the write (it contains zero).  A read at this time will see
  33 * data that is inconsistent with any ordering of the read and the write.
  34 * (This has been detected in practice).
  35 */
  36static inline size_t
  37filemap_copy_from_user(struct page *page, unsigned long offset,
  38                        const char __user *buf, unsigned bytes)
  39{
  40        char *kaddr;
  41        int left;
  42
  43        kaddr = kmap_atomic(page, KM_USER0);
  44        left = __copy_from_user_inatomic_nocache(kaddr + offset, buf, bytes);
  45        kunmap_atomic(kaddr, KM_USER0);
  46
  47        if (left != 0) {
  48                /* Do it the slow way */
  49                kaddr = kmap(page);
  50                left = __copy_from_user_nocache(kaddr + offset, buf, bytes);
  51                kunmap(page);
  52        }
  53        return bytes - left;
  54}
  55
  56/*
  57 * This has the same sideeffects and return value as filemap_copy_from_user().
  58 * The difference is that on a fault we need to memset the remainder of the
  59 * page (out to offset+bytes), to emulate filemap_copy_from_user()'s
  60 * single-segment behaviour.
  61 */
  62static inline size_t
  63filemap_copy_from_user_iovec(struct page *page, unsigned long offset,
  64                        const struct iovec *iov, size_t base, size_t bytes)
  65{
  66        char *kaddr;
  67        size_t copied;
  68
  69        kaddr = kmap_atomic(page, KM_USER0);
  70        copied = __filemap_copy_from_user_iovec_inatomic(kaddr + offset, iov,
  71                                                         base, bytes);
  72        kunmap_atomic(kaddr, KM_USER0);
  73        if (copied != bytes) {
  74                kaddr = kmap(page);
  75                copied = __filemap_copy_from_user_iovec_inatomic(kaddr + offset, iov,
  76                                                                 base, bytes);
  77                if (bytes - copied)
  78                        memset(kaddr + offset + copied, 0, bytes - copied);
  79                kunmap(page);
  80        }
  81        return copied;
  82}
  83
  84static inline void
  85filemap_set_next_iovec(const struct iovec **iovp, size_t *basep, size_t bytes)
  86{
  87        const struct iovec *iov = *iovp;
  88        size_t base = *basep;
  89
  90        do {
  91                int copy = min(bytes, iov->iov_len - base);
  92
  93                bytes -= copy;
  94                base += copy;
  95                if (iov->iov_len == base) {
  96                        iov++;
  97                        base = 0;
  98                }
  99        } while (bytes);
 100        *iovp = iov;
 101        *basep = base;
 102}
 103#endif
 104