On Fri, Jun 11, 2010 at 9:12 AM, Shaohua Li <shaohua.li@xxxxxxxxx> wrote: > On Fri, Jun 11, 2010 at 01:41:41AM +0800, Jerome Ibanes wrote: >> List, >> >> I ran into a hang issue (race condition: cpu is high when the server is >> idle, meaning that btrfs is hanging, and IOwait is high as well) running >> 2.6.34 on debian/lenny on a x86_64 server (dual Opteron 275 w/ 16GB ram). >> The btrfs filesystem live on 18x300GB scsi spindles, configured as Raid-0, >> as shown below: >> >> Label: none uuid: bc6442c6-2fe2-4236-a5aa-6b7841234c52 >> Total devices 18 FS bytes used 2.94TB >> devid 5 size 279.39GB used 208.33GB path /dev/cciss/c1d0 >> devid 17 size 279.39GB used 208.34GB path /dev/cciss/c1d8 >> devid 16 size 279.39GB used 209.33GB path /dev/cciss/c1d7 >> devid 4 size 279.39GB used 208.33GB path /dev/cciss/c0d4 >> devid 1 size 279.39GB used 233.72GB path /dev/cciss/c0d1 >> devid 13 size 279.39GB used 208.33GB path /dev/cciss/c1d4 >> devid 8 size 279.39GB used 208.33GB path /dev/cciss/c1d11 >> devid 12 size 279.39GB used 208.33GB path /dev/cciss/c1d3 >> devid 3 size 279.39GB used 208.33GB path /dev/cciss/c0d3 >> devid 9 size 279.39GB used 208.33GB path /dev/cciss/c1d12 >> devid 6 size 279.39GB used 208.33GB path /dev/cciss/c1d1 >> devid 11 size 279.39GB used 208.33GB path /dev/cciss/c1d2 >> devid 14 size 279.39GB used 208.33GB path /dev/cciss/c1d5 >> devid 2 size 279.39GB used 233.70GB path /dev/cciss/c0d2 >> devid 15 size 279.39GB used 209.33GB path /dev/cciss/c1d6 >> devid 10 size 279.39GB used 208.33GB path /dev/cciss/c1d13 >> devid 7 size 279.39GB used 208.33GB path /dev/cciss/c1d10 >> devid 18 size 279.39GB used 208.34GB path /dev/cciss/c1d9 >> Btrfs v0.19-16-g075587c-dirty >> >> The filesystem, mounted in /mnt/btrfs is hanging, no existing or new >> process can access it, however 'df' still displays the disk usage (3TB out >> of 5). The disks appear to be physically healthy. Please note that a >> significant number of files were placed on this filesystem, between 20 and >> 30 million files. >> >> The relevant kernel messages are displayed below: >> >> INFO: task btrfs-submit-0:4220 blocked for more than 120 seconds. >> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >> btrfs-submit- D 000000010042e12f 0 4220 2 0x00000000 >> ffff8803e584ac70 0000000000000046 0000000000004000 0000000000011680 >> ffff8803f7349fd8 ffff8803f7349fd8 ffff8803e584ac70 0000000000011680 >> 0000000000000001 ffff8803ff99d250 ffffffff8149f020 0000000081150ab0 >> Call Trace: >> [<ffffffff813089f3>] ? io_schedule+0x71/0xb1 >> [<ffffffff811470be>] ? get_request_wait+0xab/0x140 >> [<ffffffff810406f4>] ? autoremove_wake_function+0x0/0x2e >> [<ffffffff81143a4d>] ? elv_rq_merge_ok+0x89/0x97 >> [<ffffffff8114a245>] ? blk_recount_segments+0x17/0x27 >> [<ffffffff81147429>] ? __make_request+0x2d6/0x3fc >> [<ffffffff81145b16>] ? generic_make_request+0x207/0x268 >> [<ffffffff81145c12>] ? submit_bio+0x9b/0xa2 >> [<ffffffffa01aa081>] ? btrfs_requeue_work+0xd7/0xe1 [btrfs] >> [<ffffffffa01a5365>] ? run_scheduled_bios+0x297/0x48f [btrfs] >> [<ffffffffa01aa687>] ? worker_loop+0x17c/0x452 [btrfs] >> [<ffffffffa01aa50b>] ? worker_loop+0x0/0x452 [btrfs] >> [<ffffffff81040331>] ? kthread+0x79/0x81 >> [<ffffffff81003674>] ? kernel_thread_helper+0x4/0x10 >> [<ffffffff810402b8>] ? kthread+0x0/0x81 >> [<ffffffff81003670>] ? kernel_thread_helper+0x0/0x10 > This looks like the issue we saw too, http://lkml.org/lkml/2010/6/8/375. > This is reproduceable in our setup. I think I know the cause of http://lkml.org/lkml/2010/6/8/375. The code in the first do-while loop in btrfs_commit_transaction set current process to TASK_UNINTERRUPTIBLE state, then calls btrfs_start_delalloc_inodes, btrfs_wait_ordered_extents and btrfs_run_ordered_operations(). All of these function may call cond_resched(). -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
