On Mon, Mar 22, 2010 at 03:15:10PM +0900, Tetsuo Handa wrote: > Hello. > > I want to know whether security_path_*() users need to use GFP_NOFS or not. > I couldn't understand what "Can call down to low-level FS?" (__GFP_FS) means. > When do we need to use GFP_NOFS rather than GFP_KERNEL? Yes it's a bit tricky to know. We have some support in lockdep for checking this now. That doesn't check page lock yet, and it's generally unsafe to allocate with __GFP_FS with page lock held. > For example, functions which are called by filesystems? > For example, after dentry->d_inode->i_mutex held? page lock, or any lock which can be blocked upon inside a ->writepage call, or icache/dcache/etc shrinking. i_mutex is most likely OK. We already allow it in some core code (buffered write path) although that could _potentially_ be overridden by a filesystem. However we always call ->writepage with page locked from reclaim, so any lock which nests outside page_lock (including i_mutex) must not block in writepage for reclaim. That leaves the shrinker callbacks. I don't think anybody will take i_mutex from shrinkers although I don't know if that's a rule. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
