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>

diff --git a/fs/afs/fsclient.c b/fs/afs/fsclient.c
index bf8904a..6f917dd 100644 (file)
--- a/fs/afs/fsclient.c
+++ b/fs/afs/fsclient.c
@@ -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;
                        }
                }

diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 7784a8b..dc2cb48 100644 (file)
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -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 */

diff --git a/fs/afs/write.c b/fs/afs/write.c
index 3ac52f6..ea66890 100644 (file)
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -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");