On Thu, 2009-03-19 at 14:54 +0000, hooanon05@xxxxxxxxxxx wrote: > > Hello David and Al, > I have a question about NFSD readdir. > > By the commit 14f7dd632011bb89c035722edd6ea0d90ca6b078 > "[PATCH] Copy XFS readdir hack into nfsd code", nfsd_buffered_filldir() > was introduced and nfs3svc_encode_entry_plus() (the 'func' parameter) is > not called from vfs_readdir(). > > In 2.6.27, when nfs3svc_encode_entry_plus() calls lookup_one_len(), the > i_mutex lock was acquired by vfs_readdir() and it was not a problem. > > After the commit (above), nfsd_readdir/nfsd_buffered_readdir/vfs_readdir > calls nfsd_buffered_filldir(), and nfs3svc_encode_entry_plus() is called > later. > In this sequence, lookup_one_len() is called without i_mutex held. > > Isn't it a problem? Yes, well spotted. It didn't matter when the buffered readdir() was purely internal to XFS, because it didn't matter there that we called ->lookup() without i_mutex set. But now we're exposing arbitrary file systems to it, we need to make sure we follow the locking rules. I _think_ it's sufficient to make the affected callers of lookup_one_len() lock the parent's i_mutex for themselves before calling it. I'll take a closer look... -- David Woodhouse Open Source Technology Centre David.Woodhouse@xxxxxxxxx Intel Corporation -- 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
