Re: BUG: warning at mm/truncate.c:60/cancel_dirty_page()

[Hugh Dickins <hugh@veritas.com>]

On Sat, 6 Jan 2007, Sami Farin wrote:

> Linux 2.6.19.1 SMP [2] on Pentium D...
> I was running dt-15.14 [2] and I ran
> "cinfo datafile" (it does mincore()).
> Well it went OK but when I ran "strace cinfo datafile"...:
> 04:18:48.062466 mincore(0x37f1f000, 2147266560, 

You rightly noted in a followup that there have been changes to
mincore, but I doubt they have any bearing on this: I think the
BUG just happened at the same time as your mincore.

> ...
> 2007-01-06 04:19:03.788181500 <4>BUG: warning at mm/truncate.c:60/cancel_dirty_page()
> 2007-01-06 04:19:03.788221500 <4> [<c0103cfb>] dump_trace+0x215/0x21a
> 2007-01-06 04:19:03.788223500 <4> [<c0103da3>] show_trace_log_lvl+0x1a/0x30
> 2007-01-06 04:19:03.788224500 <4> [<c0103dcb>] show_trace+0x12/0x14
> 2007-01-06 04:19:03.788225500 <4> [<c0103ec8>] dump_stack+0x19/0x1b
> 2007-01-06 04:19:03.788227500 <4> [<c01546a6>] cancel_dirty_page+0x7e/0x80
> 2007-01-06 04:19:03.788228500 <4> [<c01546c2>] truncate_complete_page+0x1a/0x47
> 2007-01-06 04:19:03.788229500 <4> [<c0154854>] truncate_inode_pages_range+0x114/0x2ae
> 2007-01-06 04:19:03.788245500 <4> [<c0154a08>] truncate_inode_pages+0x1a/0x1c
> 2007-01-06 04:19:03.788247500 <4> [<c0269244>] fs_flushinval_pages+0x40/0x77
> 2007-01-06 04:19:03.788248500 <4> [<c026d48c>] xfs_write+0x8c4/0xb68
> 2007-01-06 04:19:03.788250500 <4> [<c0268b14>] xfs_file_aio_write+0x7e/0x95
> 2007-01-06 04:19:03.788251500 <4> [<c016d66c>] do_sync_write+0xca/0x119
> 2007-01-06 04:19:03.788265500 <4> [<c016d842>] vfs_write+0x187/0x18c
> 2007-01-06 04:19:03.788267500 <4> [<c016d8e8>] sys_write+0x3d/0x64
> 2007-01-06 04:19:03.788268500 <4> [<c0102e73>] syscall_call+0x7/0xb
> 2007-01-06 04:19:03.788269500 <4> [<001cf410>] 0x1cf410
> 2007-01-06 04:19:03.788289500 <4> =======================

So... XFS uses truncate_inode_pages when serving the write system call.
That's very inventive, and now it looks like Linus' cancel_dirty_page
and new warning have caught it out.  VM people expect it to be called
either when freeing an inode no longer in use, or when doing a truncate,
after ensuring that all pages mapped into userspace have been taken out.

> 
> funny that when stracing, mincore does not return?
> 
> $ time cinfo dtfile-2091
> dtfile-2091: 524285 pages, 0 pages cached (0.00%)
> 
> real    0m0.049s
> user    0m0.003s
> sys     0m0.046s
> 
> safari    6941 29.9 10.8 2098768 108788 pts/2  D+   04:20   3:41 strace -vfttT cinfo dtfile-2091
> 
> strace        D C179A000     0  6941   8737  6942          2089 (NOTLB)
>        e7dddd90 00000046 c172e240 c179a000 c1731880 c17c51a0 c17b5be0 c1771c20
>        e9b1f740 00000086 d55dd74c e7dddd6c 00000000 c02666b8 c17fd700 c2c2513c
>        0000fdac b2203610 0000616f c2c25030 c17fd700 e7ddddf8 c17d31f0 e7dddd9c
> Call Trace:
>  [<c04b4568>] io_schedule+0x26/0x30
>  [<c014cdad>] sync_page+0x3d/0x48
>  [<c04b47b1>] __wait_on_bit_lock+0x45/0x67
>  [<c014d556>] __lock_page+0x88/0x95
>  [<c014e5a7>] filemap_nopage+0x1f4/0x386
>  [<c015b24c>] do_no_page+0x82/0x2fa
>  [<c015b8a3>] __handle_mm_fault+0x1fe/0x2eb
>  [<c0159a99>] get_user_pages+0xc7/0x2e5
>  [<c015bb8a>] access_process_vm+0x74/0x116
>  [<c010639e>] arch_ptrace+0x388/0x539
>  [<c012ad7f>] sys_ptrace+0x58/0xb9
>  [<c0102e73>] syscall_call+0x7/0xb
>  [<0081e410>] 0x81e410
>  =======================
> cinfo         t CB7DA040     0  6942   6941                     (NOTLB)
>        e5fcdee8 00000046 ce7d9284 cb7da040 ce7d9284 cb7da078 cb7da040 e5fcdf10
>        cb7da040 13a973f5 000060e3 00000078 00000000 c2c25030 c1805700 d483013c
>        0021fd53 13a97513 000060e3 d4830030 e5fcdf04 00000005 00000000 e5fcdefc
> Call Trace:
>  [<c012e32b>] ptrace_stop+0xf8/0x17f
>  [<c012e41c>] ptrace_notify+0x6a/0x92
>  [<c01066a9>] do_syscall_trace+0xd4/0x1eb
>  [<c0102f66>] syscall_exit_work+0x16/0x1b
>  [<00878410>] 0x878410
>  =======================
> 
> 
> [1]
> includes these
>         8c08540f8755c451d8b96ea14cfe796bc3cd712d [PATCH] clean up __set_page_dirty_nobuffers()
>         55e829af06681e5d731c03ba04febbd1c76ca293 [PATCH] io-accounting: write accounting
>         e08748ce01e02f0ec154b141f392ccb9555333f4 [PATCH] io-accounting: write-cancel accounting
>         fba2591bf4e418b6c3f9f8794c9dd8fe40ae7bd9 VM: Remove "clear_page_dirty()" and "test_clear_page_dirty()" functions
>         3e67c0987d7567ad666641164a153dca9a43b11d [PATCH] truncate: clear page dirtiness before running try_to_free_buffers()
>         5f2a105d5e33a038a717995d2738434f9c25aed2 [PATCH] truncate: dirty memory accounting fix
>         8368e328dfe1c534957051333a87b3210a12743b Clean up and export cancel_dirty_page() to modules
>         7658cc289288b8ae7dd2c2224549a048431222b3 VM: Fix nasty and subtle race in shared mmap'ed page writeback
>         7c3ab7381e79dfc7db14a67c6f4f3285664e1ec2 [PATCH] io-accounting: core statistics
>         cb876f451455b6187a7d69de2c112c45ec4b7f99 Fix up CIFS for "test_clear_page_dirty()" removal
>         7dfb71030f7636a0d65200158113c37764552f93 [PATCH] Add include/linux/freezer.h and move definitions from sched.h
>         46d2277c796f9f4937bfa668c40b2e3f43e93dd0 Clean up and make try_to_free_buffers() not race with dirty 
>         e61c90188b9956edae1105eef361d8981a352fcd [PATCH] optimize o_direct on block devices
>         5fcf7bb73f66cc1c4ad90788b0f367c4d6852b75 [PATCH] read_zero_pagealigned() locking fix
>         ffaa82008f1aad52a6d3979f49d2a76c2928b60f Fix reiserfs after "test_clear_page_dirty()" removal
>         d0e671a932cb9c653b27393cec26aec012a8d97e [PATCH] Fix JFS after clear_page_dirty() removal
>         9280f6822c2d7112b47107251fce307aefb31f35 [PATCH] fuse: remove clear_page_dirty() call
>         921320210bd2ec4f17053d283355b73048ac0e56 [PATCH] Fix XFS after clear_page_dirty() removal

Gosh.  Might be better to reproduce it on 2.6.20-rc3;
but I think we have to hand this over to some XFS people.

Hugh

> 
> [2]
> dt pattern=iot incr=variable records=32768 lbs=65536 bs=65536 of=dtfile log=dtfile.log.direct.random passes=1 procs=2 iotype=random flags=direct
> http://home.comcast.net/~SCSIguy/SCSI_FAQ/RMiller_Tools/ftp/dt/dt-source.tar.gz
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