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From: Dave Chinner <david@fromorbit.com>
To: CAI Qian <caiqian@redhat.com>
Cc: Jan Kara <jack@suse.cz>, Al Viro <viro@ZenIV.linux.org.uk>,
	tj <tj@kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	linux-xfs <linux-xfs@vger.kernel.org>,
	Jens Axboe <axboe@kernel.dk>, Nick Piggin <npiggin@gmail.com>,
	linux-fsdevel@vger.kernel.org, Miklos Szeredi <miklos@szeredi.hu>,
	Dave Jones <davej@codemonkey.org.uk>
Subject: Re: local DoS - systemd hang or timeout (WAS: Re: [RFC][CFT] splice_read reworked)
Date: Mon, 10 Oct 2016 08:51:46 +1100
Message-ID: <20161009215146.GL9806@dastard> (raw)
In-Reply-To: <1720038662.1062048.1475851398433.JavaMail.zimbra@redhat.com>

On Fri, Oct 07, 2016 at 10:43:18AM -0400, CAI Qian wrote:
> Hmm, this round of trinity triggered a different hang.
> 
> [ 2094.487964]  [<ffffffff813e27b7>] call_rwsem_down_write_failed+0x17/0x30
> [ 2094.495450]  [<ffffffff817d1bff>] down_write+0x5f/0x80
> [ 2094.508284]  [<ffffffff8127e301>] chown_common.isra.12+0x131/0x1e0
> [ 2094.553784] 2 locks held by trinity-c0/3126:
> [ 2094.558552]  #0:  (sb_writers#14){.+.+.+}, at: [<ffffffff81284be1>] __sb_start_write+0xd1/0xf0
> [ 2094.568240]  #1:  (&sb->s_type->i_mutex_key#17){++++++}, at: [<ffffffff8127e301>] chown_common.isra.12+0x131/0x1e0

Waiting on i_mutex.

> [ 2094.643597]  [<ffffffff817d24b7>] rwsem_down_read_failed+0x107/0x190
> [ 2094.665119]  [<ffffffff810f8b0b>] down_read_nested+0x5b/0x80
> [ 2094.691133]  [<ffffffff812bdbbd>] vfs_fsync_range+0x3d/0xb0
> [ 2094.721844] 1 lock held by trinity-c1/3127:
> [ 2094.726515]  #0:  (&xfs_nondir_ilock_class){++++..}, at: [<ffffffffa03335fa>] xfs_ilock+0xfa/0x260 [xfs]

Waiting on i_ilock.

> [ 2094.808078]  [<ffffffff817cf4df>] mutex_lock_nested+0x19f/0x450
> [ 2094.820715]  [<ffffffff812a5313>] __fdget_pos+0x43/0x50
> [ 2094.826544]  [<ffffffff81297f53>] SyS_getdents+0x83/0x140
> [ 2094.856682]  #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff812a5313>] __fdget_pos+0x43/0x50

concurrent readdir on the same directory fd, blocked on fd.

> [ 2094.936885]  [<ffffffff817cf4df>] mutex_lock_nested+0x19f/0x450
> [ 2094.956620]  [<ffffffff812a5313>] __fdget_pos+0x43/0x50
> [ 2094.962454]  [<ffffffff81298091>] SyS_getdents64+0x81/0x130
> [ 2094.988204] 1 lock held by trinity-c3/3129:
> [ 2094.992872]  #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff812a5313>] __fdget_pos+0x43/0x50

Same.

> [ 2095.073118]  [<ffffffff817cf4df>] mutex_lock_nested+0x19f/0x450
> [ 2095.091589]  [<ffffffff812811dd>] SyS_lseek+0x1d/0xb0
> [ 2095.097229]  [<ffffffff81003c9c>] do_syscall_64+0x6c/0x1e0
> [ 2095.110547] 1 lock held by trinity-c4/3130:
> [ 2095.115216]  #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff812a5313>] __fdget_pos+0x43/0x50

Concurrent lseek on directory fd, blocked on fd.


> [ 2095.188230]  [<ffffffff817d24b7>] rwsem_down_read_failed+0x107/0x190
> [ 2095.223558]  [<ffffffffa03335fa>] xfs_ilock+0xfa/0x260 [xfs]
> [ 2095.229894]  [<ffffffffa03337d4>] xfs_ilock_attr_map_shared+0x34/0x40 [xfs]
> [ 2095.237682]  [<ffffffffa02ccfaf>] xfs_attr_get+0xdf/0x1b0 [xfs]
> [ 2095.244312]  [<ffffffffa0341bfc>] xfs_xattr_get+0x4c/0x70 [xfs]
> [ 2095.250924]  [<ffffffff812ad269>] generic_getxattr+0x59/0x70
> [ 2095.257244]  [<ffffffff812acf9b>] vfs_getxattr+0x8b/0xb0
> [ 2095.263177]  [<ffffffffa0435bd6>] ovl_xattr_get+0x46/0x60 [overlay]
> [ 2095.270176]  [<ffffffffa04331aa>] ovl_other_xattr_get+0x1a/0x20 [overlay]
> [ 2095.277756]  [<ffffffff812ad269>] generic_getxattr+0x59/0x70
> [ 2095.284079]  [<ffffffff81345e9e>] cap_inode_need_killpriv+0x2e/0x40
> [ 2095.291078]  [<ffffffff81349a33>] security_inode_need_killpriv+0x33/0x50
> [ 2095.298560]  [<ffffffff812a2fb0>] dentry_needs_remove_privs+0x30/0x50
> [ 2095.305743]  [<ffffffff8127ea21>] do_truncate+0x51/0xc0
> [ 2095.311581]  [<ffffffff81284be1>] ? __sb_start_write+0xd1/0xf0
> [ 2095.318094]  [<ffffffff81284be1>] ? __sb_start_write+0xd1/0xf0
> [ 2095.324609]  [<ffffffff8127edde>] do_sys_ftruncate.constprop.15+0xfe/0x160
> [ 2095.332286]  [<ffffffff8127ee7e>] SyS_ftruncate+0xe/0x10
> [ 2095.338225]  [<ffffffff81003c9c>] do_syscall_64+0x6c/0x1e0
> [ 2095.344339]  [<ffffffff817d4a3f>] entry_SYSCALL64_slow_path+0x25/0x25
> [ 2095.351531] 2 locks held by trinity-c5/3131:
> [ 2095.356297]  #0:  (sb_writers#14){.+.+.+}, at: [<ffffffff81284be1>] __sb_start_write+0xd1/0xf0
> [ 2095.365983]  #1:  (&xfs_nondir_ilock_class){++++..}, at: [<ffffffffa03335fa>] xfs_ilock+0xfa/0x260 [xfs]

truncate on overlay, removing xattrs from XFS file, blocked on
i_ilock.

> [ 2095.440372]  [<ffffffff817d2782>] rwsem_down_write_failed+0x242/0x4b0
> [ 2095.474300]  [<ffffffff8127e413>] chmod_common+0x63/0x150
> [ 2095.513452] 2 locks held by trinity-c6/3132:
> [ 2095.518217]  #0:  (sb_writers#14){.+.+.+}, at: [<ffffffff81284be1>] __sb_start_write+0xd1/0xf0
> [ 2095.527895]  #1:  (&sb->s_type->i_mutex_key#17){++++++}, at: [<ffffffff8127e413>] chmod_common+0x63/0x150

chmod, blocked on i_mutex.

> [ 2095.602379]  [<ffffffff817d24b7>] rwsem_down_read_failed+0x107/0x190
> [ 2095.616490]  [<ffffffff813e2788>] call_rwsem_down_read_failed+0x18/0x30
> [ 2095.623877]  [<ffffffff810f8b0b>] down_read_nested+0x5b/0x80
> [ 2095.649889]  [<ffffffff812bdbbd>] vfs_fsync_range+0x3d/0xb0
> [ 2095.680610] 1 lock held by trinity-c7/3133:
> [ 2095.685281]  #0:  (&xfs_nondir_ilock_class){++++..}, at: [<ffffffffa03335fa>] xfs_ilock+0xfa/0x260 [xfs]

fsync on file, blocked on i_ilock.

> [ 2095.759662]  [<ffffffff817d24b7>] rwsem_down_read_failed+0x107/0x190
> [ 2095.807155]  [<ffffffff812bdbbd>] vfs_fsync_range+0x3d/0xb0
> [ 2095.813377]  [<ffffffff812bdc8d>] do_fsync+0x3d/0x70
> [ 2095.818921]  [<ffffffff812bdf63>] SyS_fdatasync+0x13/0x20
> [ 2095.838261] 1 lock held by trinity-c8/3135:
> [ 2095.842930]  #0:  (&xfs_nondir_ilock_class){++++..}, at: [<ffffffffa03335fa>] xfs_ilock+0xfa/0x260 [xfs]

ditto.

> [ 2095.917305]  [<ffffffff817d24b7>] rwsem_down_read_failed+0x107/0x190
> [ 2095.958968]  [<ffffffffa0333790>] xfs_ilock_data_map_shared+0x30/0x40 [xfs]
> [ 2095.966752]  [<ffffffffa03128c6>] __xfs_get_blocks+0x96/0x9d0 [xfs]
> [ 2095.989413]  [<ffffffffa0313214>] xfs_get_blocks+0x14/0x20 [xfs]
> [ 2095.996122]  [<ffffffff812cca44>] do_mpage_readpage+0x474/0x800
> [ 2096.029678]  [<ffffffff812ccf0d>] mpage_readpages+0x13d/0x1b0
> [ 2096.050724]  [<ffffffffa0311f14>] xfs_vm_readpages+0x54/0x170 [xfs]
> [ 2096.057724]  [<ffffffff811f1a1d>] __do_page_cache_readahead+0x2ad/0x370
> [ 2096.079787]  [<ffffffff811f2014>] force_page_cache_readahead+0x94/0xf0
> [ 2096.087077]  [<ffffffff811f2168>] SyS_readahead+0xa8/0xc0
> [ 2096.106427] 1 lock held by trinity-c9/3136:
> [ 2096.111097]  #0:  (&xfs_nondir_ilock_class){++++..}, at: [<ffffffffa03335fa>] xfs_ilock+0xfa/0x260 [xfs]

readhead blocking in i_ilock before reading in extents.

Nothing here indicates a deadlock. Everything is waiting for locks,
but nothing is holding locks in a way that indicates that progress
is not being made. This sort of thing can happen when slow storage
is massively overloaded - sysrq-w is really the only way to get a
better picutre of what is happening here, but so far there's no
concrete evidence of a hang from this output.

Cheers,

Dave.

-- 
Dave Chinner
david@fromorbit.com

  parent reply index

Thread overview: 101+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20160908235521.GL2356@ZenIV.linux.org.uk>
     [not found] ` <20160909015324.GD30056@dastard>
     [not found]   ` <CA+55aFzohsUXj_3BeFNr2t50Wm=G+7toRDEz=Tk7VJqP3n1hXQ@mail.gmail.com>
     [not found]     ` <CA+55aFxrqCng2Qxasc9pyMrKUGFjo==fEaFT1vkH9Lncte3RgQ@mail.gmail.com>
     [not found]       ` <20160909023452.GO2356@ZenIV.linux.org.uk>
     [not found]         ` <CA+55aFwHQMjO4-vtfB9-ytc=o+DRo-HXVGckvXLboUxgpwb7_g@mail.gmail.com>
     [not found]           ` <20160909221945.GQ2356@ZenIV.linux.org.uk>
     [not found]             ` <CA+55aFzTOOB6oEVaaGD0N7Uznk-W9+ULPwzsxS_L_oZqGVSeLA@mail.gmail.com>
     [not found]               ` <20160914031648.GB2356@ZenIV.linux.org.uk>
     [not found]                 ` <20160914133925.2fba4629@roar.ozlabs.ibm.com>
2016-09-18  5:33                   ` xfs_file_splice_read: possible circular locking dependency detected Al Viro
2016-09-19  3:08                     ` Nicholas Piggin
2016-09-19  6:11                       ` Al Viro
2016-09-19  7:26                         ` Nicholas Piggin
     [not found]                 ` <CA+55aFznQaOWoSMNphgGJJWZ=8-odrc0DAUMzfGPQe+_N4UgNA@mail.gmail.com>
     [not found]                   ` <20160914042559.GC2356@ZenIV.linux.org.uk>
     [not found]                     ` <20160917082007.GA6489@ZenIV.linux.org.uk>
     [not found]                       ` <20160917190023.GA8039@ZenIV.linux.org.uk>
2016-09-18 19:31                         ` skb_splice_bits() and large chunks in pipe (was " Al Viro
2016-09-18 20:12                           ` Linus Torvalds
2016-09-18 22:31                             ` Al Viro
2016-09-19  0:18                               ` Linus Torvalds
2016-09-23 19:00                         ` [RFC][CFT] splice_read reworked Al Viro
2016-09-23 19:01                           ` [PATCH 01/11] fix memory leaks in tracing_buffers_splice_read() Al Viro
2016-09-23 19:02                           ` [PATCH 02/11] splice_to_pipe(): don't open-code wakeup_pipe_readers() Al Viro
2016-09-23 19:02                           ` [PATCH 03/11] splice: switch get_iovec_page_array() to iov_iter Al Viro
2016-09-23 19:03                           ` [PATCH 04/11] splice: lift pipe_lock out of splice_to_pipe() Al Viro
2016-09-23 19:45                             ` Linus Torvalds
2016-09-23 20:10                               ` Al Viro
2016-09-23 20:36                                 ` Linus Torvalds
2016-09-24  3:59                                   ` Al Viro
2016-09-24 17:29                                     ` Al Viro
2016-09-27 15:38                                       ` Nicholas Piggin
2016-09-27 15:53                                       ` Chuck Lever
2016-09-24  3:59                                   ` [PATCH 04/12] " Al Viro
2016-09-26 13:35                                     ` Miklos Szeredi
2016-09-27  4:14                                       ` Al Viro
2016-12-17 19:54                                     ` Andreas Schwab
2016-12-18 19:28                                       ` Linus Torvalds
2016-12-18 19:57                                         ` Andreas Schwab
2016-12-18 20:12                                         ` Al Viro
2016-12-18 20:30                                           ` Al Viro
2016-12-18 22:10                                             ` Linus Torvalds
2016-12-18 22:18                                               ` Al Viro
2016-12-18 22:22                                                 ` Linus Torvalds
2016-12-18 22:49                                               ` Andreas Schwab
2016-12-21 18:56                                               ` Andreas Schwab
2016-12-21 19:12                                                 ` Linus Torvalds
2016-09-24  4:00                                   ` [PATCH 06/12] new helper: add_to_pipe() Al Viro
2016-09-26 13:49                                     ` Miklos Szeredi
2016-09-24  4:01                                   ` [PATCH 10/12] new iov_iter flavour: pipe-backed Al Viro
2016-09-29 20:53                                     ` Miklos Szeredi
2016-09-29 22:50                                       ` Al Viro
2016-09-30  7:30                                         ` Miklos Szeredi
2016-10-03  3:34                                           ` [RFC] O_DIRECT vs EFAULT (was Re: [PATCH 10/12] new iov_iter flavour: pipe-backed) Al Viro
2016-10-03 17:07                                             ` Linus Torvalds
2016-10-03 18:54                                               ` Al Viro
2016-09-24  4:01                                   ` [PATCH 11/12] switch generic_file_splice_read() to use of ->read_iter() Al Viro
2016-09-24  4:02                                   ` [PATCH 12/12] switch default_file_splice_read() to use of pipe-backed iov_iter Al Viro
2016-09-23 19:03                           ` [PATCH 05/11] skb_splice_bits(): get rid of callback Al Viro
2016-09-23 19:04                           ` [PATCH 06/11] new helper: add_to_pipe() Al Viro
2016-09-23 19:04                           ` [PATCH 07/11] fuse_dev_splice_read(): switch to add_to_pipe() Al Viro
2016-09-23 19:06                           ` [PATCH 08/11] cifs: don't use memcpy() to copy struct iov_iter Al Viro
2016-09-23 19:08                           ` [PATCH 09/11] fuse_ioctl_copy_user(): don't open-code copy_page_{to,from}_iter() Al Viro
2016-09-26  9:31                             ` Miklos Szeredi
2016-09-23 19:09                           ` [PATCH 10/11] new iov_iter flavour: pipe-backed Al Viro
2016-09-23 19:10                           ` [PATCH 11/11] switch generic_file_splice_read() to use of ->read_iter() Al Viro
2016-09-30 13:32                           ` [RFC][CFT] splice_read reworked CAI Qian
2016-09-30 17:42                             ` CAI Qian
2016-09-30 18:33                               ` CAI Qian
2016-10-03  1:37                                 ` Al Viro
2016-10-03 17:49                                   ` CAI Qian
2016-10-04 17:39                                     ` local DoS - systemd hang or timeout (WAS: Re: [RFC][CFT] splice_read reworked) CAI Qian
2016-10-04 21:42                                       ` tj
2016-10-05 14:09                                         ` CAI Qian
2016-10-05 15:30                                           ` tj
2016-10-05 15:54                                             ` CAI Qian
2016-10-05 18:57                                               ` CAI Qian
2016-10-05 20:05                                                 ` Al Viro
2016-10-06 12:20                                                   ` CAI Qian
2016-10-06 12:25                                                     ` CAI Qian
2016-10-06 16:11                                                       ` CAI Qian
2016-10-06 17:00                                                         ` Linus Torvalds
2016-10-06 18:12                                                           ` CAI Qian
2016-10-07  9:57                                                           ` Dave Chinner
2016-10-07 15:25                                                             ` Linus Torvalds
2016-10-07  7:08                                                       ` Jan Kara
2016-10-07 14:43                                                         ` CAI Qian
2016-10-07 15:27                                                           ` CAI Qian
2016-10-07 18:56                                                             ` CAI Qian
2016-10-09 21:54                                                               ` Dave Chinner
2016-10-10 14:10                                                                 ` CAI Qian
2016-10-10 20:14                                                                   ` CAI Qian
2016-10-10 21:57                                                                   ` Dave Chinner
2016-10-12 19:50                                                                     ` [bisected] " CAI Qian
2016-10-12 20:59                                                                       ` Dave Chinner
2016-10-13 16:25                                                                         ` CAI Qian
2016-10-13 20:49                                                                           ` Dave Chinner
2016-10-13 20:56                                                                             ` CAI Qian
2016-10-09 21:51                                                           ` Dave Chinner [this message]
2016-10-21 15:38                                                         ` [4.9-rc1+] overlayfs lockdep CAI Qian
2016-10-24 12:57                                                           ` Miklos Szeredi
2016-10-07  9:27                                                     ` local DoS - systemd hang or timeout (WAS: Re: [RFC][CFT] splice_read reworked) Dave Chinner
2016-10-03  1:42                               ` [RFC][CFT] splice_read reworked Al Viro
2016-10-03 14:06                                 ` CAI Qian
2016-10-03 15:20                                   ` CAI Qian
2016-10-03 21:12                                     ` Dave Chinner
2016-10-04 13:57                                       ` CAI Qian
2016-10-03 20:32                                   ` CAI Qian
2016-10-03 20:35                                     ` Al Viro
2016-10-04 13:29                                       ` CAI Qian
2016-10-04 14:28                                         ` Al Viro
2016-10-04 16:21                                           ` CAI Qian
2016-10-04 20:12                                             ` Al Viro
2016-10-05 14:30                                               ` CAI Qian
2016-10-05 16:07                                                 ` Al Viro
2016-09-19  0:22 skb_splice_bits() and large chunks in pipe (was Re: xfs_file_splice_read: possible circular locking dependency detected Al Viro
2016-09-20  9:51 ` Herbert Xu

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