[CIFS] cifs truncate missing a fix for private map COW race
vmtruncate had added the same fix to handle the case of private pages
being Copy on writed while truncate_inode_pages is going on
Signed-off-by: Steve French <sfrench@us.ibm.com>
diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index dd41677..97ccc51 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -1377,8 +1377,17 @@
}
i_size_write(inode, offset);
spin_unlock(&inode->i_lock);
+ /*
+ * unmap_mapping_range is called twice, first simply for efficiency
+ * so that truncate_inode_pages does fewer single-page unmaps. However
+ * after this first call, and before truncate_inode_pages finishes,
+ * it is possible for private pages to be COWed, which remain after
+ * truncate_inode_pages finishes, hence the second unmap_mapping_range
+ * call must be made for correctness.
+ */
unmap_mapping_range(mapping, offset + PAGE_SIZE - 1, 0, 1);
truncate_inode_pages(mapping, offset);
+ unmap_mapping_range(mapping, offset + PAGE_SIZE - 1, 0, 1);
goto out_truncate;
do_expand: