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authorSahitya Tummala2017-07-10 17:50:00 -0500
committerGreg Kroah-Hartman2017-07-21 00:44:56 -0500
commit68b0f5d85b3a25ee452424e18fe06b93da8dd4d2 (patch)
tree6d321b722d4b790388e8637dec804dc96ec0f71d /fs
parent2d0db02d2e8f45e215fd2e646820c669c6e70159 (diff)
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fs/dcache.c: fix spin lockup issue on nlru->lock
commit b17c070fb624cf10162cf92ea5e1ec25cd8ac176 upstream. __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 <stummala@codeaurora.org> Suggested-by: Jan Kara <jack@suse.cz> Suggested-by: Vladimir Davydov <vdavydov.dev@gmail.com> Acked-by: Vladimir Davydov <vdavydov.dev@gmail.com> Cc: Alexander Polakov <apolyakov@beget.ru> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/dcache.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/fs/dcache.c b/fs/dcache.c
index 849c1c1e787b..3000cbb54949 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1128,11 +1128,12 @@ void shrink_dcache_sb(struct super_block *sb)
1128 LIST_HEAD(dispose); 1128 LIST_HEAD(dispose);
1129 1129
1130 freed = list_lru_walk(&sb->s_dentry_lru, 1130 freed = list_lru_walk(&sb->s_dentry_lru,
1131 dentry_lru_isolate_shrink, &dispose, UINT_MAX); 1131 dentry_lru_isolate_shrink, &dispose, 1024);
1132 1132
1133 this_cpu_sub(nr_dentry_unused, freed); 1133 this_cpu_sub(nr_dentry_unused, freed);
1134 shrink_dentry_list(&dispose); 1134 shrink_dentry_list(&dispose);
1135 } while (freed > 0); 1135 cond_resched();
1136 } while (list_lru_count(&sb->s_dentry_lru) > 0);
1136} 1137}
1137EXPORT_SYMBOL(shrink_dcache_sb); 1138EXPORT_SYMBOL(shrink_dcache_sb);
1138 1139