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 <[email protected]>
> ---
> 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?
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;
>
