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Subject[PATCH AUTOSEL 4.19 005/192] f2fs: fix to avoid deadlock of atomic file operations
Date
From: Chao Yu <yuchao0@huawei.com>

[ Upstream commit 48432984d718c95cf13e26d487c2d1b697c3c01f ]

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>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 30779aaa9dba..1fa6f8185766 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -216,7 +216,8 @@ 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;
@@ -228,7 +229,16 @@ 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;
+ } else {
+ lock_page(page);
+ }

f2fs_wait_on_page_writeback(page, DATA, true);

@@ -317,13 +327,19 @@ 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;
@@ -427,12 +443,15 @@ 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;
--
2.19.1
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