From mboxrd@z Thu Jan 1 00:00:00 1970 From: akpm@linux-foundation.org Subject: [patch 056/115] fs/dcache.c: fix spin lockup issue on nlru->lock Date: Mon, 10 Jul 2017 15:50:00 -0700 Message-ID: <20170710225000.9GwuJooq8%akpm@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from mail.linuxfoundation.org ([140.211.169.12]:42958 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932151AbdGJWuB (ORCPT ); Mon, 10 Jul 2017 18:50:01 -0400 Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: akpm@linux-foundation.org, apolyakov@beget.ru, jack@suse.cz, mm-commits@vger.kernel.org, stable@vger.kernel.org, stummala@codeaurora.org, torvalds@linux-foundation.org, vdavydov.dev@gmail.com, viro@zeniv.linux.org.uk From: Sahitya Tummala Subject: fs/dcache.c: fix spin lockup issue on nlru->lock __list_lru_walk_one() acquires nlru spin lock (nlru->lock) for longer duration if there are more number of items in the lru list. As per the current code, it can hold the spin lock for upto maximum UINT_MAX entries at a time. So if there are more number of items in the lru list, then "BUG: spinlock lockup suspected" is observed in the below path - [] spin_bug+0x90 [] do_raw_spin_lock+0xfc [] _raw_spin_lock+0x28 [] list_lru_add+0x28 [] dput+0x1c8 [] path_put+0x20 [] terminate_walk+0x3c [] path_lookupat+0x100 [] filename_lookup+0x6c [] user_path_at_empty+0x54 [] SyS_faccessat+0xd0 [] el0_svc_naked+0x24 This nlru->lock is acquired by another CPU in this path - [] d_lru_shrink_move+0x34 [] dentry_lru_isolate_shrink+0x48 [] __list_lru_walk_one.isra.10+0x94 [] list_lru_walk_node+0x40 [] shrink_dcache_sb+0x60 [] do_remount_sb+0xbc [] do_emergency_remount+0xb0 [] process_one_work+0x228 [] worker_thread+0x2e0 [] kthread+0xf4 [] ret_from_fork+0x10 Fix this lockup by reducing the number of entries to be shrinked from the lru list to 1024 at once. Also, add cond_resched() before processing the lru list again. Link: http://marc.info/?t=149722864900001&r=1&w=2 Link: http://lkml.kernel.org/r/1498707575-2472-1-git-send-email-stummala@codeaurora.org Signed-off-by: Sahitya Tummala Suggested-by: Jan Kara Suggested-by: Vladimir Davydov Acked-by: Vladimir Davydov Cc: Alexander Polakov Cc: Al Viro Cc: Signed-off-by: Andrew Morton --- fs/dcache.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff -puN fs/dcache.c~fs-dcachec-fix-spin-lockup-issue-on-nlru-lock fs/dcache.c --- a/fs/dcache.c~fs-dcachec-fix-spin-lockup-issue-on-nlru-lock +++ a/fs/dcache.c @@ -1160,11 +1160,12 @@ void shrink_dcache_sb(struct super_block LIST_HEAD(dispose); freed = list_lru_walk(&sb->s_dentry_lru, - dentry_lru_isolate_shrink, &dispose, UINT_MAX); + dentry_lru_isolate_shrink, &dispose, 1024); this_cpu_sub(nr_dentry_unused, freed); shrink_dentry_list(&dispose); - } while (freed > 0); + cond_resched(); + } while (list_lru_count(&sb->s_dentry_lru) > 0); } EXPORT_SYMBOL(shrink_dcache_sb); _