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Date: Mon, 25 Feb 2019 17:34:42 +0800
From: Chao Yu <yuchao0@...wei.com>
To: Gao Xiang <gaoxiang25@...wei.com>
CC: <jaegeuk@...nel.org>, <linux-kernel@...r.kernel.org>,
<linux-f2fs-devel@...ts.sourceforge.net>
Subject: Re: [f2fs-dev] [PATCH v2] f2fs: fix to avoid deadlock of atomic file
operations
Hi Xiang,
On 2019/2/25 17:25, Gao Xiang wrote:
> Hi Chao,
>
> On 2019/2/25 17:11, Chao Yu wrote:
>> Thread A Thread B
>> - __fput
>> - f2fs_release_file
>> - drop_inmem_pages
>> - mutex_lock(&fi->inmem_lock)
>> - __revoke_inmem_pages
>> - lock_page(page)
>> - open
>> - f2fs_setattr
>> - truncate_setsize
>> - truncate_inode_pages_range
>> - lock_page(page)
>> - truncate_cleanup_page
>> - f2fs_invalidate_page
>> - drop_inmem_page
>> - mutex_lock(&fi->inmem_lock);
>>
>> We may encounter above ABBA deadlock as reported by Kyungtae Kim:
>>
>> I'm reporting a bug in linux-4.17.19: "INFO: task hung in
>> drop_inmem_page" (no reproducer)
>>
>> I think this might be somehow related to the following:
>> https://groups.google.com/forum/#!searchin/syzkaller-bugs/INFO$3A$20task$20hung$20in$20%7Csort:date/syzkaller-bugs/c6soBTrdaIo/AjAzPeIzCgAJ
>>
>> =========================================
>> INFO: task syz-executor7:10822 blocked for more than 120 seconds.
>> Not tainted 4.17.19 #1
>> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
>> syz-executor7 D27024 10822 6346 0x00000004
>> Call Trace:
>> context_switch kernel/sched/core.c:2867 [inline]
>> __schedule+0x721/0x1e60 kernel/sched/core.c:3515
>> schedule+0x88/0x1c0 kernel/sched/core.c:3559
>> schedule_preempt_disabled+0x18/0x30 kernel/sched/core.c:3617
>> __mutex_lock_common kernel/locking/mutex.c:833 [inline]
>> __mutex_lock+0x5bd/0x1410 kernel/locking/mutex.c:893
>> mutex_lock_nested+0x1b/0x20 kernel/locking/mutex.c:908
>> drop_inmem_page+0xcb/0x810 fs/f2fs/segment.c:327
>> f2fs_invalidate_page+0x337/0x5e0 fs/f2fs/data.c:2401
>> do_invalidatepage mm/truncate.c:165 [inline]
>> truncate_cleanup_page+0x261/0x330 mm/truncate.c:187
>> truncate_inode_pages_range+0x552/0x1610 mm/truncate.c:367
>> truncate_inode_pages mm/truncate.c:478 [inline]
>> truncate_pagecache+0x6d/0x90 mm/truncate.c:801
>> truncate_setsize+0x81/0xa0 mm/truncate.c:826
>> f2fs_setattr+0x44f/0x1270 fs/f2fs/file.c:781
>> notify_change+0xa62/0xe80 fs/attr.c:313
>> do_truncate+0x12e/0x1e0 fs/open.c:63
>> do_last fs/namei.c:2955 [inline]
>> path_openat+0x2042/0x29f0 fs/namei.c:3505
>> do_filp_open+0x1bd/0x2c0 fs/namei.c:3540
>> do_sys_open+0x35e/0x4e0 fs/open.c:1101
>> __do_sys_open fs/open.c:1119 [inline]
>> __se_sys_open fs/open.c:1114 [inline]
>> __x64_sys_open+0x89/0xc0 fs/open.c:1114
>> do_syscall_64+0xc4/0x4e0 arch/x86/entry/common.c:287
>> entry_SYSCALL_64_after_hwframe+0x49/0xbe
>> RIP: 0033:0x4497b9
>> RSP: 002b:00007f734e459c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
>> RAX: ffffffffffffffda RBX: 00007f734e45a6cc RCX: 00000000004497b9
>> RDX: 0000000000000104 RSI: 00000000000a8280 RDI: 0000000020000080
>> RBP: 000000000071bea0 R08: 0000000000000000 R09: 0000000000000000
>> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
>> R13: 0000000000007230 R14: 00000000006f02d0 R15: 00007f734e45a700
>> INFO: task syz-executor7:10858 blocked for more than 120 seconds.
>> Not tainted 4.17.19 #1
>> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
>> syz-executor7 D28880 10858 6346 0x00000004
>> Call Trace:
>> context_switch kernel/sched/core.c:2867 [inline]
>> __schedule+0x721/0x1e60 kernel/sched/core.c:3515
>> schedule+0x88/0x1c0 kernel/sched/core.c:3559
>> __rwsem_down_write_failed_common kernel/locking/rwsem-xadd.c:565 [inline]
>> rwsem_down_write_failed+0x5e6/0xc90 kernel/locking/rwsem-xadd.c:594
>> call_rwsem_down_write_failed+0x17/0x30 arch/x86/lib/rwsem.S:117
>> __down_write arch/x86/include/asm/rwsem.h:142 [inline]
>> down_write+0x58/0xa0 kernel/locking/rwsem.c:72
>> inode_lock include/linux/fs.h:713 [inline]
>> do_truncate+0x120/0x1e0 fs/open.c:61
>> do_last fs/namei.c:2955 [inline]
>> path_openat+0x2042/0x29f0 fs/namei.c:3505
>> do_filp_open+0x1bd/0x2c0 fs/namei.c:3540
>> do_sys_open+0x35e/0x4e0 fs/open.c:1101
>> __do_sys_open fs/open.c:1119 [inline]
>> __se_sys_open fs/open.c:1114 [inline]
>> __x64_sys_open+0x89/0xc0 fs/open.c:1114
>> do_syscall_64+0xc4/0x4e0 arch/x86/entry/common.c:287
>> entry_SYSCALL_64_after_hwframe+0x49/0xbe
>> RIP: 0033:0x4497b9
>> RSP: 002b:00007f734e3b4c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
>> RAX: ffffffffffffffda RBX: 00007f734e3b56cc RCX: 00000000004497b9
>> RDX: 0000000000000104 RSI: 00000000000a8280 RDI: 0000000020000080
>> RBP: 000000000071c238 R08: 0000000000000000 R09: 0000000000000000
>> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
>> R13: 0000000000007230 R14: 00000000006f02d0 R15: 00007f734e3b5700
>> INFO: task syz-executor5:10829 blocked for more than 120 seconds.
>> Not tainted 4.17.19 #1
>> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
>> syz-executor5 D28760 10829 6308 0x80000002
>> Call Trace:
>> context_switch kernel/sched/core.c:2867 [inline]
>> __schedule+0x721/0x1e60 kernel/sched/core.c:3515
>> schedule+0x88/0x1c0 kernel/sched/core.c:3559
>> io_schedule+0x21/0x80 kernel/sched/core.c:5179
>> wait_on_page_bit_common mm/filemap.c:1100 [inline]
>> __lock_page+0x2b5/0x390 mm/filemap.c:1273
>> lock_page include/linux/pagemap.h:483 [inline]
>> __revoke_inmem_pages+0xb35/0x11c0 fs/f2fs/segment.c:231
>> drop_inmem_pages+0xa3/0x3e0 fs/f2fs/segment.c:306
>> f2fs_release_file+0x2c7/0x330 fs/f2fs/file.c:1556
>> __fput+0x2c7/0x780 fs/file_table.c:209
>> ____fput+0x1a/0x20 fs/file_table.c:243
>> task_work_run+0x151/0x1d0 kernel/task_work.c:113
>> exit_task_work include/linux/task_work.h:22 [inline]
>> do_exit+0x8ba/0x30a0 kernel/exit.c:865
>> do_group_exit+0x13b/0x3a0 kernel/exit.c:968
>> get_signal+0x6bb/0x1650 kernel/signal.c:2482
>> do_signal+0x84/0x1b70 arch/x86/kernel/signal.c:810
>> exit_to_usermode_loop+0x155/0x190 arch/x86/entry/common.c:162
>> prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
>> syscall_return_slowpath arch/x86/entry/common.c:265 [inline]
>> do_syscall_64+0x445/0x4e0 arch/x86/entry/common.c:290
>> entry_SYSCALL_64_after_hwframe+0x49/0xbe
>> RIP: 0033:0x4497b9
>> RSP: 002b:00007f1c68e74ce8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
>> RAX: fffffffffffffe00 RBX: 000000000071bf80 RCX: 00000000004497b9
>> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000071bf80
>> RBP: 000000000071bf80 R08: 0000000000000000 R09: 000000000071bf58
>> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
>> R13: 0000000000000000 R14: 00007f1c68e759c0 R15: 00007f1c68e75700
>>
>> This patch tries to use trylock_page to mitigate such deadlock condition
>> for fix.
>>
>> Signed-off-by: Chao Yu <yuchao0@...wei.com>
>> ---
>> v2:
>> - fix wrong mutex_unlock position.
>> fs/f2fs/segment.c | 43 +++++++++++++++++++++++++++++++------------
>> 1 file changed, 31 insertions(+), 12 deletions(-)
>>
>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>> index fdd8cd21522f..ca786913b2c6 100644
>> --- a/fs/f2fs/segment.c
>> +++ b/fs/f2fs/segment.c
>> @@ -215,7 +215,8 @@ void f2fs_register_inmem_page(struct inode *inode, struct page *page)
>> }
>>
>> static int __revoke_inmem_pages(struct inode *inode,
>> - struct list_head *head, bool drop, bool recover)
>> + struct list_head *head, bool drop, bool recover,
>> + bool trylock)
>> {
>> struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>> struct inmem_pages *cur, *tmp;
>> @@ -227,7 +228,16 @@ static int __revoke_inmem_pages(struct inode *inode,
>> if (drop)
>> trace_f2fs_commit_inmem_page(page, INMEM_DROP);
>>
>> - lock_page(page);
>> + if (trylock) {
>> + /*
>> + * to avoid deadlock in between page lock and
>> + * inmem_lock.
>> + */
>> + if (!trylock_page(page))
>> + continue;
>
> Will it cause memleak? since revoke_list is a temporary local linked list...
> Is there a better way than just simplily skip it?
@trylock will only be true in f2fs_drop_inmem_pages(), and it passes global
link list &fi->inmem_pages, and there is a loop being introduced to make
sure that each entry can be released in that list, so any missing case here?
Thanks,
>
> Thanks,
> Gao Xiang
>
>> + } else {
>> + lock_page(page);
>> + }
>>
>> f2fs_wait_on_page_writeback(page, DATA, true, true);
>>
>> @@ -318,13 +328,19 @@ void f2fs_drop_inmem_pages(struct inode *inode)
>> struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>> struct f2fs_inode_info *fi = F2FS_I(inode);
>>
>> - mutex_lock(&fi->inmem_lock);
>> - __revoke_inmem_pages(inode, &fi->inmem_pages, true, false);
>> - spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
>> - if (!list_empty(&fi->inmem_ilist))
>> - list_del_init(&fi->inmem_ilist);
>> - spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
>> - mutex_unlock(&fi->inmem_lock);
>> + while (!list_empty(&fi->inmem_pages)) {
>> + mutex_lock(&fi->inmem_lock);
>> + __revoke_inmem_pages(inode, &fi->inmem_pages,
>> + true, false, true);
>> +
>> + if (list_empty(&fi->inmem_pages)) {
>> + spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
>> + if (!list_empty(&fi->inmem_ilist))
>> + list_del_init(&fi->inmem_ilist);
>> + spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
>> + }
>> + mutex_unlock(&fi->inmem_lock);
>> + }
>>
>> clear_inode_flag(inode, FI_ATOMIC_FILE);
>> fi->i_gc_failures[GC_FAILURE_ATOMIC] = 0;
>> @@ -429,12 +445,15 @@ static int __f2fs_commit_inmem_pages(struct inode *inode)
>> * recovery or rewrite & commit last transaction. For other
>> * error number, revoking was done by filesystem itself.
>> */
>> - err = __revoke_inmem_pages(inode, &revoke_list, false, true);
>> + err = __revoke_inmem_pages(inode, &revoke_list,
>> + false, true, false);
>>
>> /* drop all uncommitted pages */
>> - __revoke_inmem_pages(inode, &fi->inmem_pages, true, false);
>> + __revoke_inmem_pages(inode, &fi->inmem_pages,
>> + true, false, false);
>> } else {
>> - __revoke_inmem_pages(inode, &revoke_list, false, false);
>> + __revoke_inmem_pages(inode, &revoke_list,
>> + false, false, false);
>> }
>>
>> return err;
>>
>
> .
>
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