Messages in this thread | | | Subject | Re: [f2fs-dev] [PATCH v2] f2fs: fix to avoid deadlock of atomic file operations | From | Gao Xiang <> | Date | Mon, 25 Feb 2019 18:46:54 +0800 |
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On 2019/2/25 17:34, Chao Yu wrote: > 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@huawei.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?
No, except that it seems a little strange personally, I think it works... Ignore my comments..Sorry for annoying...
Thanks, Gao Xiang
> > 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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