9p: saner ->write_end() on failing copy into non-uptodate page

If we had a short copy into an uptodate page, there's no reason
whatsoever to zero anything; OTOH, if that page had _not_ been
uptodate, we must have been trying to overwrite it completely
and got a short copy.  In that case, overwriting the end with
zeroes, marking uptodate and sending to server is just plain
wrong.  Just unlock, keep it non-uptodate and return 0.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/9p/vfs_addr.c b/fs/9p/vfs_addr.c
index 6181ad79e1a543f307ff4245e5159330c8a5fa7c..ff8ece89fb9966a566c867c31393b78624852a08 100644 (file)
--- a/fs/9p/vfs_addr.c
+++ b/fs/9p/vfs_addr.c
@@ -309,18 +309,10 @@ static int v9fs_write_end(struct file *filp, struct address_space *mapping,
 
        p9_debug(P9_DEBUG_VFS, "filp %p, mapping %p\n", filp, mapping);
 
-       if (unlikely(copied < len)) {
-               /*
-                * zero out the rest of the area
-                */
-               unsigned from = pos & (PAGE_SIZE - 1);
-
-               zero_user(page, from + copied, len - copied);
-               flush_dcache_page(page);
+       if (unlikely(copied < len && !PageUptodate(page))) {
+               copied = 0;
+               goto out;
        }
-
-       if (!PageUptodate(page))
-               SetPageUptodate(page);
        /*
         * No need to use i_size_read() here, the i_size
         * cannot change under us because we hold the i_mutex.
@@ -330,6 +322,7 @@ static int v9fs_write_end(struct file *filp, struct address_space *mapping,
                i_size_write(inode, last_pos);
        }
        set_page_dirty(page);
+out:
        unlock_page(page);
        put_page(page);