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afs: afs_fill_page reads too much, or wrong data

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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: Anton Blanchard <anton@samba.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Anton Blanchard 2011-06-13 22:31:12 +01:00 committed by Al Viro
parent 8aef188452
commit 5e7f23373b
1 changed files with 9 additions and 12 deletions
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21
fs/afs/write.c
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@ -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);