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afs: Handle a short write to an AFS page 

Handle the situation where afs_write_begin() is told to expect that a
full-page write will be made, but this doesn't happen (EFAULT, CTRL-C,
etc.), and so afs_write_end() sees a partial write took place.  Currently,
no attempt is to deal with the discrepency.

Fix this by loading the gap from the server.

Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: David Howells <dhowells@redhat.com>
This commit is contained in:
David Howells 2017-03-16 16:27:44 +00:00
parent 3448e65217
commit e8e581a88c
3 changed files with 23 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
fs/afs/fsclient.c
View File

@ -393,8 +393,10 @@ static int afs_deliver_fs_fetch_data(struct afs_call *call)
if (req->remain > 0) {
call->offset = 0;
req->index++;
if (req->index >= req->nr_pages)
if (req->index >= req->nr_pages) {
call->unmarshall = 4;
goto begin_discard;
}
goto begin_page;
}
}

2
fs/afs/internal.h
View File

@ -130,7 +130,7 @@ struct afs_call_type {
*/
struct afs_read {
loff_t pos; /* Where to start reading */
loff_t len; /* How much to read */
loff_t len; /* How much we're asking for */
loff_t actual_len; /* How much we're actually getting */
atomic_t usage;
unsigned int remain; /* Amount remaining */

28
fs/afs/write.c
View File

@ -84,10 +84,9 @@ 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, struct page *page)
loff_t pos, unsigned int len, struct page *page)
{
struct afs_read *req;
loff_t i_size;
int ret;
_enter(",,%llu", (unsigned long long)pos);
@ -99,16 +98,11 @@ static int afs_fill_page(struct afs_vnode *vnode, struct key *key,
atomic_set(&req->usage, 1);
req->pos = pos;
req->len = len;
req->nr_pages = 1;
req->pages[0] = page;
get_page(page);
i_size = i_size_read(&vnode->vfs_inode);
if (pos + PAGE_SIZE > i_size)
req->len = i_size - pos;
else
req->len = PAGE_SIZE;
ret = afs_vnode_fetch_data(vnode, key, req);
afs_put_read(req);
if (ret < 0) {
@ -164,7 +158,7 @@ int afs_write_begin(struct file *file, struct address_space *mapping,
/* page won't leak in error case: it eventually gets cleaned off LRU */
if (!PageUptodate(page) && len != PAGE_SIZE) {
ret = afs_fill_page(vnode, key, index << PAGE_SHIFT, page);
ret = afs_fill_page(vnode, key, pos & PAGE_MASK, PAGE_SIZE, page);
if (ret < 0) {
kfree(candidate);
_leave(" = %d [prep]", ret);
@ -258,7 +252,9 @@ int afs_write_end(struct file *file, struct address_space *mapping,
struct page *page, void *fsdata)
{
struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
struct key *key = file->private_data;
loff_t i_size, maybe_i_size;
int ret;
_enter("{%x:%u},{%lx}",
vnode->fid.vid, vnode->fid.vnode, page->index);
@ -274,6 +270,20 @@ int afs_write_end(struct file *file, struct address_space *mapping,
spin_unlock(&vnode->writeback_lock);
}
if (!PageUptodate(page)) {
if (copied < len) {
/* Try and load any missing data from the server. The
* unmarshalling routine will take care of clearing any
* bits that are beyond the EOF.
*/
ret = afs_fill_page(vnode, key, pos + copied,
len - copied, page);
if (ret < 0)
return ret;
}
SetPageUptodate(page);
}
set_page_dirty(page);
if (PageDirty(page))
_debug("dirtied");