• Ye Bin's avatar
    jbd2: fix soft lockup in journal_finish_inode_data_buffers() · 6c02757c
    Ye Bin authored
    There's issue when do io test:
    WARN: soft lockup - CPU#45 stuck for 11s! [jbd2/dm-2-8:4170]
    CPU: 45 PID: 4170 Comm: jbd2/dm-2-8 Kdump: loaded Tainted: G  OE
    Call trace:
     dump_backtrace+0x0/0x1a0
     show_stack+0x24/0x30
     dump_stack+0xb0/0x100
     watchdog_timer_fn+0x254/0x3f8
     __hrtimer_run_queues+0x11c/0x380
     hrtimer_interrupt+0xfc/0x2f8
     arch_timer_handler_phys+0x38/0x58
     handle_percpu_devid_irq+0x90/0x248
     generic_handle_irq+0x3c/0x58
     __handle_domain_irq+0x68/0xc0
     gic_handle_irq+0x90/0x320
     el1_irq+0xcc/0x180
     queued_spin_lock_slowpath+0x1d8/0x320
     jbd2_journal_commit_transaction+0x10f4/0x1c78 [jbd2]
     kjournald2+0xec/0x2f0 [jbd2]
     kthread+0x134/0x138
     ret_from_fork+0x10/0x18
    
    Analyzed informations from vmcore as follows:
    (1) There are about 5k+ jbd2_inode in 'commit_transaction->t_inode_list';
    (2) Now is processing the 855th jbd2_inode;
    (3) JBD2 task has TIF_NEED_RESCHED flag;
    (4) There's no pags in address_space around the 855th jbd2_inode;
    (5) There are some process is doing drop caches;
    (6) Mounted with 'nodioread_nolock' option;
    (7) 128 CPUs;
    
    According to informations from vmcore we know 'journal->j_list_lock' spin lock
    competition is fierce. So journal_finish_inode_data_buffers() maybe process
    slowly. Theoretically, there is scheduling point in the filemap_fdatawait_range_keep_errors().
    However, if inode's address_space has no pages which taged with PAGECACHE_TAG_WRITEBACK,
    will not call cond_resched(). So may lead to soft lockup.
    journal_finish_inode_data_buffers
      filemap_fdatawait_range_keep_errors
        __filemap_fdatawait_range
          while (index <= end)
            nr_pages = pagevec_lookup_range_tag(&pvec, mapping, &index, end, PAGECACHE_TAG_WRITEBACK);
            if (!nr_pages)
               break;    --> If 'nr_pages' is equal zero will break, then will not call cond_resched()
            for (i = 0; i < nr_pages; i++)
              wait_on_page_writeback(page);
            cond_resched();
    
    To solve above issue, add scheduling point in the journal_finish_inode_data_buffers();
    Signed-off-by: default avatarYe Bin <yebin10@huawei.com>
    Reviewed-by: default avatarJan Kara <jack@suse.cz>
    Link: https://lore.kernel.org/r/20231211112544.3879780-1-yebin10@huawei.comSigned-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
    6c02757c
commit.c 35.2 KB