Make sure that highmem pages are not added to symlink page cache
inode_nohighmem() is sufficient to make sure that page_get_link()
won't try to allocate a highmem page. Moreover, it is sufficient
to make sure that page_symlink/__page_symlink won't do the same
thing. However, any filesystem that manually preseeds the symlink's
page cache upon symlink(2) needs to make sure that the page it
inserts there won't be a highmem one.
Fortunately, only nfs and shmem have run afoul of that...
Signed-off-by: Al Viro <[email protected]>
diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting
index 0f88e60..f1b87d8 100644
--- a/Documentation/filesystems/porting
+++ b/Documentation/filesystems/porting
@@ -508,7 +508,11 @@
[mandatory]
any symlink that might use page_follow_link_light/page_put_link() must
have inode_nohighmem(inode) called before anything might start playing with
- its pagecache.
+ its pagecache. No highmem pages should end up in the pagecache of such
+ symlinks. That includes any preseeding that might be done during symlink
+ creation. __page_symlink() will honour the mapping gfp flags, so once
+ you've done inode_nohighmem() it's safe to use, but if you allocate and
+ insert the page manually, make sure to use the right gfp flags.
--
[mandatory]
->follow_link() is replaced with ->get_link(); same API, except that
