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Richard Weinberger cf6f54e3f1 UBIFS: Kill unneeded locking in ubifs_init_security 
Fixes the following lockdep splat:
[    1.244527] =============================================
[    1.245193] [ INFO: possible recursive locking detected ]
[    1.245193] 4.2.0-rc1+ #37 Not tainted
[    1.245193] ---------------------------------------------
[    1.245193] cp/742 is trying to acquire lock:
[    1.245193]  (&sb->s_type->i_mutex_key#9){+.+.+.}, at: [<ffffffff812b3f69>] ubifs_init_security+0x29/0xb0
[    1.245193]
[    1.245193] but task is already holding lock:
[    1.245193]  (&sb->s_type->i_mutex_key#9){+.+.+.}, at: [<ffffffff81198e7f>] path_openat+0x3af/0x1280
[    1.245193]
[    1.245193] other info that might help us debug this:
[    1.245193]  Possible unsafe locking scenario:
[    1.245193]
[    1.245193]        CPU0
[    1.245193]        ----
[    1.245193]   lock(&sb->s_type->i_mutex_key#9);
[    1.245193]   lock(&sb->s_type->i_mutex_key#9);
[    1.245193]
[    1.245193]  *** DEADLOCK ***
[    1.245193]
[    1.245193]  May be due to missing lock nesting notation
[    1.245193]
[    1.245193] 2 locks held by cp/742:
[    1.245193]  #0:  (sb_writers#5){.+.+.+}, at: [<ffffffff811ad37f>] mnt_want_write+0x1f/0x50
[    1.245193]  #1:  (&sb->s_type->i_mutex_key#9){+.+.+.}, at: [<ffffffff81198e7f>] path_openat+0x3af/0x1280
[    1.245193]
[    1.245193] stack backtrace:
[    1.245193] CPU: 2 PID: 742 Comm: cp Not tainted 4.2.0-rc1+ #37
[    1.245193] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.7.5-0-ge51488c-20140816_022509-build35 04/01/2014
[    1.245193]  ffffffff8252d530 ffff88007b023a38 ffffffff814f6f49 ffffffff810b56c5
[    1.245193]  ffff88007c30cc80 ffff88007b023af8 ffffffff810a150d ffff88007b023a68
[    1.245193]  000000008101302a ffff880000000000 00000008f447e23f ffffffff8252d500
[    1.245193] Call Trace:
[    1.245193]  [<ffffffff814f6f49>] dump_stack+0x4c/0x65
[    1.245193]  [<ffffffff810b56c5>] ? console_unlock+0x1c5/0x510
[    1.245193]  [<ffffffff810a150d>] __lock_acquire+0x1a6d/0x1ea0
[    1.245193]  [<ffffffff8109fa78>] ? __lock_is_held+0x58/0x80
[    1.245193]  [<ffffffff810a1a93>] lock_acquire+0xd3/0x270
[    1.245193]  [<ffffffff812b3f69>] ? ubifs_init_security+0x29/0xb0
[    1.245193]  [<ffffffff814fc83b>] mutex_lock_nested+0x6b/0x3a0
[    1.245193]  [<ffffffff812b3f69>] ? ubifs_init_security+0x29/0xb0
[    1.245193]  [<ffffffff812b3f69>] ? ubifs_init_security+0x29/0xb0
[    1.245193]  [<ffffffff812b3f69>] ubifs_init_security+0x29/0xb0
[    1.245193]  [<ffffffff8128e286>] ubifs_create+0xa6/0x1f0
[    1.245193]  [<ffffffff81198e7f>] ? path_openat+0x3af/0x1280
[    1.245193]  [<ffffffff81195d15>] vfs_create+0x95/0xc0
[    1.245193]  [<ffffffff8119929c>] path_openat+0x7cc/0x1280
[    1.245193]  [<ffffffff8109ffe3>] ? __lock_acquire+0x543/0x1ea0
[    1.245193]  [<ffffffff81088f20>] ? sched_clock_cpu+0x90/0xc0
[    1.245193]  [<ffffffff81088c00>] ? calc_global_load_tick+0x60/0x90
[    1.245193]  [<ffffffff81088f20>] ? sched_clock_cpu+0x90/0xc0
[    1.245193]  [<ffffffff811a9cef>] ? __alloc_fd+0xaf/0x180
[    1.245193]  [<ffffffff8119ac55>] do_filp_open+0x75/0xd0
[    1.245193]  [<ffffffff814ffd86>] ? _raw_spin_unlock+0x26/0x40
[    1.245193]  [<ffffffff811a9cef>] ? __alloc_fd+0xaf/0x180
[    1.245193]  [<ffffffff81189bd9>] do_sys_open+0x129/0x200
[    1.245193]  [<ffffffff81189cc9>] SyS_open+0x19/0x20
[    1.245193]  [<ffffffff81500717>] entry_SYSCALL_64_fastpath+0x12/0x6f

While the lockdep splat is a false positive, becuase path_openat holds i_mutex
of the parent directory and ubifs_init_security() tries to acquire i_mutex
of a new inode, it reveals that taking i_mutex in ubifs_init_security() is
in vain because it is only being called in the inode allocation path
and therefore nobody else can see the inode yet.

Cc: stable@vger.kernel.org # 3.20-
Reported-and-tested-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Reviewed-and-tested-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: dedekind1@gmail.com
2015-09-29 12:45:42 +02:00
..
budget.c UBIFS: extend debug/message capabilities 2015-03-25 11:08:41 +02:00
commit.c UBIFS: extend debug/message capabilities 2015-03-25 11:08:41 +02:00
compress.c UBIFS: extend debug/message capabilities 2015-03-25 11:08:41 +02:00
debug.c UBIFS: extend debug/message capabilities 2015-03-25 11:08:41 +02:00
debug.h UBIFS: print less 2012-08-31 17:32:58 +03:00
dir.c ubifs: switch to simple_follow_link() 2015-05-10 22:18:25 -04:00
file.c ubifs: switch to simple_follow_link() 2015-05-10 22:18:25 -04:00
find.c UBIFS: fix mounting problems after power cuts 2012-10-26 16:26:44 +03:00
gc.c UBIFS: remove unnecessary code in ubifs_garbage_collect 2013-10-22 13:34:27 +01:00
io.c UBIFS: extend debug/message capabilities 2015-03-25 11:08:41 +02:00
ioctl.c UBIFS: extend debug/message capabilities 2015-03-25 11:08:41 +02:00
journal.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-04-26 17:22:07 -07:00
Kconfig UBIFS: remove Kconfig debugging option 2012-05-16 19:53:46 +03:00
key.h UBIFS: mark unused key objects as invalid 2010-08-30 10:19:08 +03:00
log.c UBIFS: extend debug/message capabilities 2015-03-25 11:08:41 +02:00
lprops.c UBIFS: extend debug/message capabilities 2015-03-25 11:08:41 +02:00
lpt_commit.c UBIFS: extend debug/message capabilities 2015-03-25 11:08:41 +02:00
lpt.c UBIFS: extend debug/message capabilities 2015-03-25 11:08:41 +02:00
Makefile UBIFS: remove Kconfig debugging option 2012-05-16 19:53:46 +03:00
master.c UBIFS: extend debug/message capabilities 2015-03-25 11:08:41 +02:00
misc.h Revert "UBIFS: add a log overlap assertion" 2014-07-28 19:15:19 +03:00
orphan.c UBIFS: extend debug/message capabilities 2015-03-25 11:08:41 +02:00
recovery.c UBIFS: extend debug/message capabilities 2015-03-25 11:08:41 +02:00
replay.c UBIFS: extend debug/message capabilities 2015-03-25 11:08:41 +02:00
sb.c UBIFS: extend debug/message capabilities 2015-03-25 11:08:41 +02:00
scan.c UBIFS: extend debug/message capabilities 2015-03-25 11:08:41 +02:00
shrinker.c UBIFS: Remove incorrect assertion in shrink_tnc() 2014-06-02 11:28:24 +03:00
super.c This pull request includes the following UBI/UBIFS changes: 2015-06-25 14:11:34 -07:00
tnc_commit.c UBIFS: extend debug/message capabilities 2015-03-25 11:08:41 +02:00
tnc_misc.c UBIFS: extend debug/message capabilities 2015-03-25 11:08:41 +02:00
tnc.c UBIFS: extend debug/message capabilities 2015-03-25 11:08:41 +02:00
ubifs-media.h UBIFS: add a superblock flag for free space fix-up 2011-05-16 14:12:14 +03:00
ubifs.h UBIFS: extend debug/message capabilities 2015-03-25 11:08:41 +02:00
xattr.c UBIFS: Kill unneeded locking in ubifs_init_security 2015-09-29 12:45:42 +02:00