ext4: fix race between truncate and __ext4_journalled_writepage()

[uclinux-h8/linux.git] / fs / ext4 / inode.c

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 0554b0b..263a46c 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1701,19 +1701,32 @@ static int __ext4_journalled_writepage(struct page *page,
                ext4_walk_page_buffers(handle, page_bufs, 0, len,
                                       NULL, bget_one);
        }
-       /* As soon as we unlock the page, it can go away, but we have
-        * references to buffers so we are safe */
+       /*
+        * We need to release the page lock before we start the
+        * journal, so grab a reference so the page won't disappear
+        * out from under us.
+        */
+       get_page(page);
        unlock_page(page);
 
        handle = ext4_journal_start(inode, EXT4_HT_WRITE_PAGE,
                                    ext4_writepage_trans_blocks(inode));
        if (IS_ERR(handle)) {
                ret = PTR_ERR(handle);
-               goto out;
+               put_page(page);
+               goto out_no_pagelock;
        }
-
        BUG_ON(!ext4_handle_valid(handle));
 
+       lock_page(page);
+       put_page(page);
+       if (page->mapping != mapping) {
+               /* The page got truncated from under us */
+               ext4_journal_stop(handle);
+               ret = 0;
+               goto out;
+       }
+
        if (inline_data) {
                BUFFER_TRACE(inode_bh, "get write access");
                ret = ext4_journal_get_write_access(handle, inode_bh);
@@ -1739,6 +1752,8 @@ static int __ext4_journalled_writepage(struct page *page,
                                       NULL, bput_one);
        ext4_set_inode_state(inode, EXT4_STATE_JDATA);
 out:
+       unlock_page(page);
+out_no_pagelock:
        brelse(inode_bh);
        return ret;
 }