/*
* xfs_iozero
*
* xfs_iozero clears the specified range of buffer supplied,
* and marks all the affected blocks as valid and modified. If
* an affected block is not allocated, it will be allocated. If
* an affected block is not completely overwritten, and is not
* valid before the operation, it will be read from disk before
* being partially zeroed.
*/
STATIC int
xfs_iozero(
struct inode *ip, /* inode */
loff_t pos, /* offset in file */
size_t count) /* size of data to zero */
{
unsigned bytes;
struct page *page;
struct address_space *mapping;
int status;
mapping = ip->i_mapping;
do {
unsigned long index, offset;
offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
index = pos >> PAGE_CACHE_SHIFT;
bytes = PAGE_CACHE_SIZE - offset;
if (bytes > count)
bytes = count;
status = -ENOMEM;
page = grab_cache_page(mapping, index);
if (!page)
break;
status = mapping->a_ops->prepare_write(NULL, page, offset,
offset + bytes);
if (status)
goto unlock;
memclear_highpage_flush(page, offset, bytes);
status = mapping->a_ops->commit_write(NULL, page, offset,
offset + bytes);
if (!status) {
pos += bytes;
count -= bytes;
}
unlock:
unlock_page(page);
page_cache_release(page);
if (status)
break;
} while (count);
return (-status);
}
static inline void truncate_partial_page(struct page *page, unsigned partial)
{
memclear_highpage_flush(page, partial, PAGE_CACHE_SIZE-partial);
if (PagePrivate(page))
do_invalidatepage(page, partial);
}
