6.16-stable review patch. If anyone has any objections, please let me know.
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From: Chao Yu chao@kernel.org
[ Upstream commit 90d5c9ba3ed91950f1546bf123a7a57cd958b452 ]
============================= [ 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/20200321113242.427089655@linutronix.de
Fixes: 98237fcda4a2 ("f2fs: use spin_lock to avoid hang") Signed-off-by: Chao Yu chao@kernel.org Signed-off-by: Jaegeuk Kim jaegeuk@kernel.org Signed-off-by: Sasha Levin sashal@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);