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Commit 5e7f2337 authored by Anton Blanchard's avatar Anton Blanchard Committed by Al Viro
Browse files

afs: afs_fill_page reads too much, or wrong data 



afs_fill_page should read the page that is about to be written but
the current implementation has a number of issues. If we aren't
extending the file we always read PAGE_CACHE_SIZE at offset 0. If we
are extending the file we try to read the entire file.

Change afs_fill_page to read PAGE_CACHE_SIZE at the right offset,
clamped to i_size.

While here, avoid calling afs_fill_page when we are doing a
PAGE_CACHE_SIZE write.

Signed-off-by: default avatarAnton Blanchard <anton@samba.org>
Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 8aef1884

fs/afs/write.c

+9 −12
Original line number Diff line number Diff line
@@ -84,23 +84,21 @@ void afs_put_writeback(struct afs_writeback *wb) 
 * partly or wholly fill a page that's under preparation for writing

 */

static int afs_fill_page(struct afs_vnode *vnode, struct key *key,

			 loff_t pos, unsigned len, struct page *page)

			 loff_t pos, struct page *page)

{

	loff_t i_size;

	unsigned eof;

	int ret;

	int len;



	_enter(",,%llu,%u", (unsigned long long)pos, len);



	ASSERTCMP(len, <=, PAGE_CACHE_SIZE);

	_enter(",,%llu", (unsigned long long)pos);



	i_size = i_size_read(&vnode->vfs_inode);

	if (pos + len > i_size)

		eof = i_size;

	if (pos + PAGE_CACHE_SIZE > i_size)

		len = i_size - pos;

	else

		eof = PAGE_CACHE_SIZE;

		len = PAGE_CACHE_SIZE;



	ret = afs_vnode_fetch_data(vnode, key, 0, eof, page);

	ret = afs_vnode_fetch_data(vnode, key, pos, len, page);

	if (ret < 0) {

		if (ret == -ENOENT) {

			_debug("got NOENT from server"
@@ -153,9 +151,8 @@ int afs_write_begin(struct file *file, struct address_space *mapping, 
	*pagep = page;

	/* page won't leak in error case: it eventually gets cleaned off LRU */



	if (!PageUptodate(page)) {

		_debug("not up to date");

		ret = afs_fill_page(vnode, key, pos, len, page);

	if (!PageUptodate(page) && len != PAGE_CACHE_SIZE) {

		ret = afs_fill_page(vnode, key, index << PAGE_CACHE_SHIFT, page);

		if (ret < 0) {

			kfree(candidate);

			_leave(" = %d [prep]", ret);