From 9424ef56e13a1f14c57ea161eed3ecfdc7b2770e Mon Sep 17 00:00:00 2001
From: Shijie Luo <luoshijie1@huawei.com>
Date: Sat, 15 Feb 2020 03:02:06 -0500
Subject: [PATCH] ext4: add cond_resched() to __ext4_find_entry()
Git-commit: 9424ef56e13a1f14c57ea161eed3ecfdc7b2770e
Patch-mainline: v5.6-rc3
References: bsc#1166862
We tested a soft lockup problem in linux 4.19 which could also
be found in linux 5.x.
When dir inode takes up a large number of blocks, and if the
directory is growing when we are searching, it's possible the
restart branch could be called many times, and the do while loop
could hold cpu a long time.
Here is the call trace in linux 4.19.
[ 473.756186] Call trace:
[ 473.756196] dump_backtrace+0x0/0x198
[ 473.756199] show_stack+0x24/0x30
[ 473.756205] dump_stack+0xa4/0xcc
[ 473.756210] watchdog_timer_fn+0x300/0x3e8
[ 473.756215] __hrtimer_run_queues+0x114/0x358
[ 473.756217] hrtimer_interrupt+0x104/0x2d8
[ 473.756222] arch_timer_handler_virt+0x38/0x58
[ 473.756226] handle_percpu_devid_irq+0x90/0x248
[ 473.756231] generic_handle_irq+0x34/0x50
[ 473.756234] __handle_domain_irq+0x68/0xc0
[ 473.756236] gic_handle_irq+0x6c/0x150
[ 473.756238] el1_irq+0xb8/0x140
[ 473.756286] ext4_es_lookup_extent+0xdc/0x258 [ext4]
[ 473.756310] ext4_map_blocks+0x64/0x5c0 [ext4]
[ 473.756333] ext4_getblk+0x6c/0x1d0 [ext4]
[ 473.756356] ext4_bread_batch+0x7c/0x1f8 [ext4]
[ 473.756379] ext4_find_entry+0x124/0x3f8 [ext4]
[ 473.756402] ext4_lookup+0x8c/0x258 [ext4]
[ 473.756407] __lookup_hash+0x8c/0xe8
[ 473.756411] filename_create+0xa0/0x170
[ 473.756413] do_mkdirat+0x6c/0x140
[ 473.756415] __arm64_sys_mkdirat+0x28/0x38
[ 473.756419] el0_svc_common+0x78/0x130
[ 473.756421] el0_svc_handler+0x38/0x78
[ 473.756423] el0_svc+0x8/0xc
[ 485.755156] watchdog: BUG: soft lockup - CPU#2 stuck for 22s! [tmp:5149]
Add cond_resched() to avoid soft lockup and to provide a better
system responding.
Link: https://lore.kernel.org/r/20200215080206.13293-1-luoshijie1@huawei.com
Signed-off-by: Shijie Luo <luoshijie1@huawei.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: stable@kernel.org
Acked-by: Jan Kara <jack@suse.cz>
---
fs/ext4/namei.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index ceff4b4b1877..b05ea72f38fd 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -1511,6 +1511,7 @@ static struct buffer_head *__ext4_find_entry(struct inode *dir,
/*
* We deal with the read-ahead logic here.
*/
+ cond_resched();
if (ra_ptr >= ra_max) {
/* Refill the readahead buffer */
ra_ptr = 0;
--
2.16.4