blob: 3ca739d6a0a70c4d2288583d2a959f95384a8fcf [file] [log] [blame]
From 54c209d2653b84ef44d66f108d3b1b99c456738e 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()
commit 9424ef56e13a1f14c57ea161eed3ecfdc7b2770e upstream.
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
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 488a4b92daa9..1901f683404a 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -1506,6 +1506,7 @@ 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;
--
2.7.4