Ext4 in user mode linux hang

["Ondřej Kunc" <ondra@czol.eu>]

Hi,

I've recently tested ext4 in user mode linux VM. I compiled linux 
2.6.36(from debian source package). I configured kernel this way ... 
only disabled modules (to work with default debootstraped debian). Then 
I created this script:

#!/bin/bash
DD="dd if=/dev/zero bs=1k"
for i in `seq 1 1000`; do
         A=$(($RANDOM%50000))
         $DD count=$A of=frag_$A
         for i in `seq 1 100`; do
                 A=$(($RANDOM%50000))
                 rm -f frag_$A
         done
done


This script I'had run on mounted ext4 partition (/dev/ubda -> 
/mnt/test). It's purpose is creating fragmented filesystem to test 
e4defrag. But after some time it hungs the whole virtual system. All 
processes which want to write to /mnt/test are still in D state. I 
issued sysrq t via uml_mconsole and in that output I found traces below.

Ondra



flush-98:16   D 0000000041a0d8b3     0   811      2 0x00000000
67c57d80 60276e90 69857980 6002a1ed 69857990 60013597 67c578c0 69856000
        69856000 67c578c0 698579f0 601d3181 69857a10 601d74a0 698579f0 
69856000
        ffffffff00000a57 62e09800 00000000 69ab1480 69856000 69857a58 
69857aa0 6012274e
Call Trace:
69857958:  [<6002a1ed>] dequeue_task+0x39/0x48
69857968:  [<60013597>] _switch_to+0x5e/0xae
69857998:  [<601d3181>] schedule+0x274/0x2ae
698579f8:  [<6012274e>] start_this_handle+0x2f4/0x395
69857a50:  [<60042f42>] autoremove_wake_function+0x0/0x34
69857aa8:  [<6012297c>] jbd2__journal_start+0xb9/0xf7
69857af8:  [<601229c8>] jbd2_journal_start+0xe/0x10
69857b08:  [<6010abe5>] ext4_journal_start_sb+0xe0/0x125
69857b28:  [<600fa802>] ext4_meta_trans_blocks+0x5b/0xaf
69857b68:  [<60100a43>] ext4_da_writepages+0x249/0x479
69857c58:  [<6005b042>] do_writepages+0x1c/0x25
69857c68:  [<600908bc>] writeback_single_inode+0x93/0x1d4
69857c98:  [<60090c4e>] writeback_sb_inodes+0xa1/0xfe
69857cf8:  [<60091364>] writeback_inodes_wb+0xc5/0xe4
69857d00:  [<60042f76>] wake_bit_function+0x0/0x2e
69857d48:  [<600914f2>] wb_writeback+0x16f/0x1de
69857da8:  [<601d3189>] schedule+0x27c/0x2ae
69857df8:  [<60091674>] wb_do_writeback+0x113/0x130
69857e08:  [<601d3400>] schedule_timeout+0x13e/0x15c
69857e78:  [<6009171a>] bdi_writeback_thread+0x89/0x13f
69857eb0:  [<60091691>] bdi_writeback_thread+0x0/0x13f
69857ed0:  [<60091691>] bdi_writeback_thread+0x0/0x13f
69857ee8:  [<60042c99>] kthread+0x91/0x99
69857f48:  [<60021329>] run_kernel_thread+0x41/0x4a
69857f58:  [<60042c08>] kthread+0x0/0x99
69857f98:  [<60021310>] run_kernel_thread+0x28/0x4a
69857fc8:  [<6001350f>] new_thread_handler+0x71/0x9b

jbd2/ubdb-8   D 0000000041a0d8b3     0  4542      2 0x00000000
6838d640 60276e90 68275ca0 6002a1ed 68275cb0 60013597 6838d180 68274000
        68274000 6838d180 68275d10 601d3181 68fd7470 601d74a0 68275d10 
68274000
        00000000 62e09800 69ab1480 1000077f1 68274000 69ab1518 68275e50 
60122d7b
Call Trace:
68275c78:  [<6002a1ed>] dequeue_task+0x39/0x48
68275c88:  [<60013597>] _switch_to+0x5e/0xae
68275cb8:  [<601d3181>] schedule+0x274/0x2ae
68275d18:  [<60122d7b>] jbd2_journal_commit_transaction+0x16c/0xe59
68275d98:  [<600245e3>] switch_threads+0x2d/0x3d
68275de0:  [<60042f42>] autoremove_wake_function+0x0/0x34
68275df8:  [<600222bb>] set_signals+0x1c/0x2e
68275e18:  [<60043094>] finish_wait+0x64/0x6f
68275e58:  [<60126168>] kjournald2+0xb8/0x1bb
68275e90:  [<60042f42>] autoremove_wake_function+0x0/0x34
68275eb0:  [<601260b0>] kjournald2+0x0/0x1bb
68275ed0:  [<601260b0>] kjournald2+0x0/0x1bb
68275ee8:  [<60042c99>] kthread+0x91/0x99
68275f48:  [<60021329>] run_kernel_thread+0x41/0x4a
68275f58:  [<60042c08>] kthread+0x0/0x99
68275f98:  [<60021310>] run_kernel_thread+0x28/0x4a
68275fc8:  [<6001350f>] new_thread_handler+0x71/0x9b

dd            D 0000000041a0d8b3     0  4952   4593 0x00000000
6838c8c0 67c57d80 67c578f8 60284440 69b6d7a8 60013597 6838c400 69b6c000
        69b6c000 6838c400 69b6d808 601d3181 69b6d7c8 6002a34f 69b6d808 
69b6c000
        00001000 6838c400 696c0838 00000001 ffffffffffffffff 00000000 
69b6d868 601d43a2
Call Trace:
69b6d780:  [<60013597>] _switch_to+0x5e/0xae
69b6d7b0:  [<601d3181>] schedule+0x274/0x2ae
69b6d7c0:  [<6002a34f>] wake_up_process+0x10/0x12
69b6d810:  [<601d43a2>] rwsem_down_failed_common+0xb8/0xd8
69b6d838:  [<600222bb>] set_signals+0x1c/0x2e
69b6d870:  [<601d43e9>] rwsem_down_read_failed+0x12/0x14
69b6d880:  [<60027b98>] call_rwsem_down_read_failed+0x14/0x24
69b6d8c8:  [<601d3b97>] down_read+0x11/0x13
69b6d8d8:  [<600fe1cc>] ext4_map_blocks+0x3e/0x18e
69b6d938:  [<600ffe02>] ext4_da_get_block_prep+0x83/0x2bd
69b6d958:  [<60095705>] alloc_buffer_head+0x18/0x6c
69b6d968:  [<60095d31>] alloc_page_buffers+0x75/0xd1
69b6d9d8:  [<60097105>] block_prepare_write+0x177/0x380
69b6d9e8:  [<6005588b>] add_to_page_cache_locked+0xbf/0xe7
69b6da00:  [<600ffd7f>] ext4_da_get_block_prep+0x0/0x2bd
69b6da98:  [<600973f3>] __block_write_begin+0x12/0x14
69b6daa8:  [<600ffa62>] ext4_da_write_begin+0x123/0x1b4
69b6db28:  [<60054ca0>] generic_file_buffered_write+0x124/0x27e
69b6dbc8:  [<6008889e>] file_update_time+0x3b/0xfe
69b6dc18:  [<60056634>] __generic_file_aio_write+0x380/0x3bf
69b6dcd8:  [<600566cb>] generic_file_aio_write+0x58/0xa2
69b6dd18:  [<600f7f07>] ext4_file_write+0x92/0xa3
69b6dd48:  [<60077a27>] do_sync_write+0xd1/0x10e
69b6ddb8:  [<60015daf>] buffer_op+0xab/0xc7
69b6de68:  [<600783fb>] vfs_write+0xb5/0x169
69b6dea8:  [<60078568>] sys_write+0x45/0x6c
69b6dee8:  [<60015ab8>] handle_syscall+0x58/0x70
69b6df08:  [<60024ecb>] userspace+0x2dd/0x38a
69b6dfc8:  [<60013497>] fork_handler+0x62/0x69

bash          D 0000000041a0d8b3     0  5324   5271 0x00000002
67e2c540 60276e90 67dcfbd0 6002a1ed 67dcfbe0 60013597 67e2c080 67dce000
        67dce000 67e2c080 67dcfc40 601d3181 62a31000 601d74a0 67dcfc40 
67dce000
        67dcfc10 62e09800 00000000 69ab1480 67dce000 67dcfca8 67dcfcf0 
6012274e
Call Trace:
67dcfba8:  [<6002a1ed>] dequeue_task+0x39/0x48
67dcfbb8:  [<60013597>] _switch_to+0x5e/0xae
67dcfbe8:  [<601d3181>] schedule+0x274/0x2ae
67dcfc48:  [<6012274e>] start_this_handle+0x2f4/0x395
67dcfca0:  [<60042f42>] autoremove_wake_function+0x0/0x34
67dcfcf8:  [<6012297c>] jbd2__journal_start+0xb9/0xf7
67dcfd48:  [<601229c8>] jbd2_journal_start+0xe/0x10
67dcfd58:  [<6010abe5>] ext4_journal_start_sb+0xe0/0x125
67dcfd60:  [<6008424f>] filldir+0x0/0x11a
67dcfdb8:  [<600fb08a>] ext4_dirty_inode+0x1b/0x48
67dcfdd8:  [<60091027>] __mark_inode_dirty+0x29/0x199
67dcfdf8:  [<60088a63>] touch_atime+0x102/0x125
67dcfe38:  [<6008424f>] filldir+0x0/0x11a
67dcfe48:  [<600844fd>] vfs_readdir+0x7a/0xa1
67dcfe98:  [<6008469d>] sys_getdents+0x90/0x124
67dcfee8:  [<60015ab8>] handle_syscall+0x58/0x70
67dcff08:  [<60024ecb>] userspace+0x2dd/0x38a
67dcffc8:  [<60013497>] fork_handler+0x62/0x69

-- 
Ondřej Kunc

správce serverové farmy
CZOL media interactive s.r.o.
Sídlo: Moulíkova 2238/1, Praha 5, 15000
Kanceláře: Na Moráni 5357, Chomutov, 43001
Telefon: +420 723 137 981
E-mail: ondra@czol.eu
URL: www.czol.eu, www.cz-hosting.com

--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html