linux-kernel - Re: Kernel errors with overlay filesystem v22

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Date:	Thu, 29 May 2014 18:29:36 +0100
From:	David Howells <dhowells@...hat.com>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	dhowells@...hat.com, viro@...IV.linux.org.uk,
	torvalds@...ux-foundation.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, hch@...radead.org,
	akpm@...ux-foundation.org, apw@...onical.com, nbd@...nwrt.org,
	neilb@...e.de, jordipujolp@...il.com, ezk@....cs.sunysb.edu,
	sedat.dilek@...il.com, hooanon05@...oo.co.jp, mszeredi@...e.cz
Subject: Re: Kernel errors with overlay filesystem v22


Here's another lockdep report for you.  If you hard link a file, the attached
occurs.

=============================================
[ INFO: possible recursive locking detected ]
3.15.0-rc6-fsdevel+ #367 Tainted: G        W    
---------------------------------------------
ln/2974 is trying to acquire lock:
 (&sb->s_type->i_mutex_key#9/2){+.+.+.}, at: [<ffffffff81137121>] generic_file_splice_write+0x88/0x154

but task is already holding lock:
 (&sb->s_type->i_mutex_key#9/2){+.+.+.}, at: [<ffffffff8111cf8d>] lock_rename+0xd3/0xdc

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&sb->s_type->i_mutex_key#9/2);
  lock(&sb->s_type->i_mutex_key#9/2);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

7 locks held by ln/2974:
 #0:  (sb_writers#15){.+.+.+}, at: [<ffffffff8112bf5b>] mnt_want_write+0x1c/0x40
 #1:  (&sb->s_type->i_mutex_key#17/1){+.+.+.}, at: [<ffffffff8111c928>] kern_path_create+0x76/0x121
 #2:  (&sb->s_type->i_mutex_key#17){+.+.+.}, at: [<ffffffff8111adfd>] vfs_link+0xf3/0x269
 #3:  (sb_writers#8){.+.+.+}, at: [<ffffffff8112bf5b>] mnt_want_write+0x1c/0x40
 #4:  (&type->s_vfs_rename_key){+.+.+.}, at: [<ffffffff8111cef5>] lock_rename+0x3b/0xdc
 #5:  (&sb->s_type->i_mutex_key#9/1){+.+.+.}, at: [<ffffffff8111cf78>] lock_rename+0xbe/0xdc
 #6:  (&sb->s_type->i_mutex_key#9/2){+.+.+.}, at: [<ffffffff8111cf8d>] lock_rename+0xd3/0xdc

stack backtrace:
CPU: 1 PID: 2974 Comm: ln Tainted: G        W     3.15.0-rc6-fsdevel+ #367
Hardware name:                  /DG965RY, BIOS MQ96510J.86A.0816.2006.0716.2308 07/16/2006
 0000000000000000 ffff8800383399c0 ffffffff8148b779 ffffffff81ffa7a0
 ffff880038339a80 ffffffff81074b0e ffff880038339a00 ffff880038339a80
 0000000000000000 0000000000000000 ffff880000000006 ffffffff00000000
Call Trace:
 [<ffffffff8148b779>] dump_stack+0x4d/0x66
 [<ffffffff81074b0e>] __lock_acquire+0x75a/0x1861
 [<ffffffff810762b6>] lock_acquire+0x9c/0x112
 [<ffffffff81137121>] ? generic_file_splice_write+0x88/0x154
 [<ffffffff811fb909>] ? avc_has_perm+0x1d/0x13b
 [<ffffffff8148e5cf>] mutex_lock_nested+0x60/0x2ff
 [<ffffffff81137121>] ? generic_file_splice_write+0x88/0x154
 [<ffffffff81137121>] generic_file_splice_write+0x88/0x154
 [<ffffffff8113777e>] direct_splice_actor+0x31/0x33
 [<ffffffff81137329>] splice_direct_to_actor+0xc6/0x188
 [<ffffffff8113774d>] ? opipe_prep.part.8+0x9e/0x9e
 [<ffffffff8113745e>] do_splice_direct+0x73/0x9b
 [<ffffffff811e3375>] ovl_copy_up_one+0x509/0x586
 [<ffffffff811e3490>] ovl_copy_up+0x9e/0xd3
 [<ffffffff811e2063>] ovl_link+0x1f/0x55
 [<ffffffff8111ae70>] vfs_link+0x166/0x269
 [<ffffffff8111f4fd>] SyS_linkat+0x103/0x21d
 [<ffffffff814924f4>] tracesys+0xdd/0xe2

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