=============================
[ BUG: Invalid wait context ]
6.13.0-rc1 #84 Tainted: G O
-----------------------------
cat/56160 is trying to lock:
ffff888105c86648 (&cprc->stat_lock){+.+.}-{3:3}, at:
update_general_status+0x32a/0x8c0 [f2fs]
other info that might help us debug this:
context-{5:5}
2 locks held by cat/56160:
#0: ffff88810a002a98 (&p->lock){+.+.}-{4:4}, at: seq_read_iter+0x56/0x4c0
#1: ffffffffa0462638 (f2fs_stat_lock){....}-{2:2}, at: stat_show+0x29/0x1020
[f2fs]
stack backtrace:
CPU: 0 UID: 0 PID: 56160 Comm: cat Tainted: G O 6.13.0-rc1 #84
Tainted: [O]=OOT_MODULE
Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
Call Trace:
<TASK>
dump_stack_lvl+0x88/0xd0
dump_stack+0x14/0x20
__lock_acquire+0x8d4/0xbb0
lock_acquire+0xd6/0x300
_raw_spin_lock+0x38/0x50
update_general_status+0x32a/0x8c0 [f2fs]
stat_show+0x50/0x1020 [f2fs]
seq_read_iter+0x116/0x4c0
seq_read+0xfa/0x130
full_proxy_read+0x66/0x90
vfs_read+0xc4/0x350
ksys_read+0x74/0xf0
__x64_sys_read+0x1d/0x20
x64_sys_call+0x17d9/0x1b80
do_syscall_64+0x68/0x130
entry_SYSCALL_64_after_hwframe+0x67/0x6f
RIP: 0033:0x7f2ca53147e2
- seq_read
- stat_show
- raw_spin_lock_irqsave(&f2fs_stat_lock, flags)
: f2fs_stat_lock is raw_spinlock_t type variable
- update_general_status
- spin_lock(&sbi->cprc_info.stat_lock);
: stat_lock is spinlock_t type variable
The root cause is the lock order is incorrect [1], we should not acquire
spinlock_t lock after raw_spinlock_t lock, as if CONFIG_PREEMPT_LOCK is
on, spinlock_t is implemented based on rtmutex, which can sleep after
holding the lock.
To fix this issue, let's use change f2fs_stat_lock lock type from
raw_spinlock_t to spinlock_t, it's safe due to:
- we don't need to use raw version of spinlock as the path is not
performance sensitive.
- we don't need to use irqsave version of spinlock as it won't be
used in irq context.
Quoted from [1]:
"Extend lockdep to validate lock wait-type context.
The current wait-types are:
LD_WAIT_FREE, /* wait free, rcu etc.. */
LD_WAIT_SPIN, /* spin loops, raw_spinlock_t etc.. */
LD_WAIT_CONFIG, /* CONFIG_PREEMPT_LOCK, spinlock_t etc.. */
LD_WAIT_SLEEP, /* sleeping locks, mutex_t etc.. */
Where lockdep validates that the current lock (the one being acquired)
fits in the current wait-context (as generated by the held stack).
This ensures that there is no attempt to acquire mutexes while holding
spinlocks, to acquire spinlocks while holding raw_spinlocks and so on. In
other words, its a more fancy might_sleep()."
[1] https://lore.kernel.org/all/20200321113242.427089...@linutronix.de
Fixes: 98237fcda4a2 ("f2fs: use spin_lock to avoid hang")
Signed-off-by: Chao Yu <c...@kernel.org>
---
fs/f2fs/debug.c | 17 +++++++----------
1 file changed, 7 insertions(+), 10 deletions(-)
diff --git a/fs/f2fs/debug.c b/fs/f2fs/debug.c
index 16c2dfb4f595..3417e7e550b2 100644
--- a/fs/f2fs/debug.c
+++ b/fs/f2fs/debug.c
@@ -21,7 +21,7 @@
#include "gc.h"
static LIST_HEAD(f2fs_stat_list);
-static DEFINE_RAW_SPINLOCK(f2fs_stat_lock);
+static DEFINE_SPINLOCK(f2fs_stat_lock);
#ifdef CONFIG_DEBUG_FS
static struct dentry *f2fs_debugfs_root;
#endif
@@ -439,9 +439,8 @@ static int stat_show(struct seq_file *s, void *v)
{
struct f2fs_stat_info *si;
int i = 0, j = 0;
- unsigned long flags;
- raw_spin_lock_irqsave(&f2fs_stat_lock, flags);
+ spin_lock(&f2fs_stat_lock);
list_for_each_entry(si, &f2fs_stat_list, stat_list) {
struct f2fs_sb_info *sbi = si->sbi;
@@ -753,7 +752,7 @@ static int stat_show(struct seq_file *s, void *v)
seq_printf(s, " - paged : %llu KB\n",
si->page_mem >> 10);
}
- raw_spin_unlock_irqrestore(&f2fs_stat_lock, flags);
+ spin_unlock(&f2fs_stat_lock);
return 0;
}
@@ -765,7 +764,6 @@ int f2fs_build_stats(struct f2fs_sb_info *sbi)
struct f2fs_super_block *raw_super = F2FS_RAW_SUPER(sbi);
struct f2fs_stat_info *si;
struct f2fs_dev_stats *dev_stats;
- unsigned long flags;
int i;
si = f2fs_kzalloc(sbi, sizeof(struct f2fs_stat_info), GFP_KERNEL);
@@ -817,9 +815,9 @@ int f2fs_build_stats(struct f2fs_sb_info *sbi)
atomic_set(&sbi->max_aw_cnt, 0);
- raw_spin_lock_irqsave(&f2fs_stat_lock, flags);
+ spin_lock(&f2fs_stat_lock);
list_add_tail(&si->stat_list, &f2fs_stat_list);
- raw_spin_unlock_irqrestore(&f2fs_stat_lock, flags);
+ spin_unlock(&f2fs_stat_lock);
return 0;
}
@@ -827,11 +825,10 @@ int f2fs_build_stats(struct f2fs_sb_info *sbi)
void f2fs_destroy_stats(struct f2fs_sb_info *sbi)
{
struct f2fs_stat_info *si = F2FS_STAT(sbi);
- unsigned long flags;
- raw_spin_lock_irqsave(&f2fs_stat_lock, flags);
+ spin_lock(&f2fs_stat_lock);
list_del(&si->stat_list);
- raw_spin_unlock_irqrestore(&f2fs_stat_lock, flags);
+ spin_unlock(&f2fs_stat_lock);
kfree(si->dev_stats);
kfree(si);
--
2.49.0
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