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authorShijie Luo <luoshijie1@huawei.com>2020-02-15 11:02:06 +0300
committerTheodore Ts'o <tytso@mit.edu>2020-02-20 07:53:52 +0300
commit9424ef56e13a1f14c57ea161eed3ecfdc7b2770e (patch)
tree97d0b9e3336559fce90677cf6fdf1057a206ff23 /fs/ext4
parent35df4299a6487f323b0aca120ea3f485dfee2ae3 (diff)
downloadlinux-9424ef56e13a1f14c57ea161eed3ecfdc7b2770e.tar.xz
ext4: add cond_resched() to __ext4_find_entry()
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
Diffstat (limited to 'fs/ext4')
-rw-r--r--fs/ext4/namei.c1
1 files changed, 1 insertions, 0 deletions
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 @@ restart:
/*
* We deal with the read-ahead logic here.
*/
+ cond_resched();
if (ra_ptr >= ra_max) {
/* Refill the readahead buffer */
ra_ptr = 0;