From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guenter Roeck Subject: Re: linux-next: Tree for Jan 20 -- Kernel panic - Unable to mount root fs Date: Wed, 21 Jan 2015 13:03:20 -0800 Message-ID: <54C01418.5060204@roeck-us.net> References: <1528536.jyty2pu4Mz@sifl> <20150121004117.GM29656@ZenIV.linux.org.uk> <54BF1292.2080902@roeck-us.net> <20150121033600.GN29656@ZenIV.linux.org.uk> <54BF2496.4000807@roeck-us.net> <20150121043637.GO29656@ZenIV.linux.org.uk> <20150121110539.GA8924@kria> <54BFAA5D.4040108@roeck-us.net> <20150121182905.GQ29656@ZenIV.linux.org.uk> <54BFF8B3.6060802@roeck-us.net> <20150121200626.GR29656@ZenIV.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: Sabrina Dubroca , Paul Moore , Stephen Rothwell , linux-next@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-audit@redhat.com, Richard Guy Briggs To: Al Viro Return-path: Received: from bh-25.webhostbox.net ([208.91.199.152]:47970 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751526AbbAUVD3 (ORCPT ); Wed, 21 Jan 2015 16:03:29 -0500 Received: from mailnull by bh-25.webhostbox.net with sa-checked (Exim 4.82) (envelope-from ) id 1YE2Qy-0004rE-Rl for linux-fsdevel@vger.kernel.org; Wed, 21 Jan 2015 21:03:29 +0000 In-Reply-To: <20150121200626.GR29656@ZenIV.linux.org.uk> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On 01/21/2015 12:06 PM, Al Viro wrote: > On Wed, Jan 21, 2015 at 11:06:27AM -0800, Guenter Roeck wrote: >> On 01/21/2015 10:29 AM, Al Viro wrote: >>> On Wed, Jan 21, 2015 at 05:32:13AM -0800, Guenter Roeck wrote: >>>> Another data point (though I have no idea if it is useful or what it means): >>>> >>>> In the working case, path_init sets nd->flags to 0x50 or 0x51. >>>> In the non-working case (ie for all files with a '/' in the name), >>>> it sets nd->flags to 0x10 or 0x11, even though it is always called >>>> with the LOOKUP_RCU bit set in flags. >>> >>> Umm... Are those path_init() succeeding or failing? Note that path_init() >>> includes "walk everything except for the last component", so your non-working >>> case is "have it walk anything at all". What's failing there? path_init() >>> or handling the remaining component? >>> >> path_init() returns -2. Guess that explains the unexpected flags ;-). >> The failuere is from >> link_path_walk() >> walk_component() > > Which is to say, lookup gave it a negative dentry. OK, let's just make > vfs_mkdir() and walk_component() print what they are doing; on top of > linux-next > > diff --git a/fs/namei.c b/fs/namei.c > index 323957f..8a4e22f 100644 > --- a/fs/namei.c > +++ b/fs/namei.c > @@ -1586,8 +1586,11 @@ static inline int walk_component(struct nameidata *nd, struct path *path, > inode = path->dentry->d_inode; > } > err = -ENOENT; > - if (!inode || d_is_negative(path->dentry)) > + if (!inode || d_is_negative(path->dentry)) { > + printk(KERN_ERR "walk_component[%p,%pd4] -> negative\n", > + path->dentry, path->dentry); > goto out_path_put; > + } > > if (should_follow_link(path->dentry, follow)) { > if (nd->flags & LOOKUP_RCU) { > @@ -3521,6 +3524,7 @@ int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode) > error = dir->i_op->mkdir(dir, dentry, mode); > if (!error) > fsnotify_mkdir(dir, dentry); > + printk(KERN_ERR "mkdir[%p,%pd4] => %d\n", dentry, dentry, error); > return error; > } > EXPORT_SYMBOL(vfs_mkdir); > ok case (putname commented out): user_path_at_empty lookup usr flags 0x0 path_lookupat: calling path_init 'usr' flags=40 path_init: link_path_walk() returned 0 path_lookupat: path_init 'usr' flags=40[50] returned 0 walk_component: lookup_fast() returned 1 walk_component: lookup_slow() returned 0 walk_component: inode= (null), negative=1 do_path_lookup(usr, 0x10) path_lookupat: calling path_init 'usr' flags=50 path_init: link_path_walk() returned 0 path_lookupat: path_init 'usr' flags=50[50] returned 0 mkdir[c74012a0,/usr] => 0 user_path_at_empty lookup usr flags 0x1 path_lookupat: calling path_init 'usr' flags=41 path_init: link_path_walk() returned 0 path_lookupat: path_init 'usr' flags=41[51] returned 0 walk_component: inode=c74004a0, negative=0 user_path_at_empty lookup usr flags 0x1 path_lookupat: calling path_init 'usr' flags=41 path_init: link_path_walk() returned 0 path_lookupat: path_init 'usr' flags=41[51] returned 0 failing case: path_lookupat: calling path_init 'usr' flags=40 path_init: link_path_walk() returned 0 path_lookupat: path_init 'usr' flags=40[50] returned 0 walk_component: lookup_fast() returned 1 walk_component: lookup_slow() returned 0 walk_component: inode= (null), negative=1 do_path_lookup(usr, 0x10) path_lookupat: calling path_init 'usr' flags=50 path_init: link_path_walk() returned 0 path_lookupat: path_init 'usr' flags=50[50] returned 0 mkdir[c74012a0,/kkk] => 0 <==== SIC! user_path_at_empty lookup usr flags 0x1 path_lookupat: calling path_init 'usr' flags=41 path_init: link_path_walk() returned 0 path_lookupat: path_init 'usr' flags=41[51] returned 0 walk_component: lookup_fast() returned 1 walk_component: lookup_slow() returned 0 walk_component: inode= (null), negative=1 user_path_at_empty lookup usr flags 0x1 path_lookupat: calling path_init 'usr' flags=41 path_init: link_path_walk() returned 0 path_lookupat: path_init 'usr' flags=41[51] returned 0 walk_component: lookup_fast() returned 1 walk_component: lookup_slow() returned 0 walk_component: inode= (null), negative=1 Guenter