| Message ID | 1498707575-2472-1-git-send-email-stummala@codeaurora.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, 29 Jun 2017 09:09:35 +0530 Sahitya Tummala <stummala@codeaurora.org> wrote: > __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 - > > ... > > 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. > > ... > > --- a/fs/dcache.c > +++ b/fs/dcache.c > @@ -1133,11 +1133,12 @@ void shrink_dcache_sb(struct super_block *sb) > 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); I'll add a cc:stable to this one - a large dentry list is a relatively common thing. I'm assumng that [1/2] does not need to be backported, OK?
On 6/30/2017 4:18 AM, Andrew Morton wrote: > >> --- a/fs/dcache.c >> +++ b/fs/dcache.c >> @@ -1133,11 +1133,12 @@ void shrink_dcache_sb(struct super_block *sb) >> 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); > I'll add a cc:stable to this one - a large dentry list is a relatively > common thing. > > I'm assumng that [1/2] does not need to be backported, OK? I think we should include [1/2] as well along with this patch, as this patch is using list_lru_count(), which can return incorrect count if [1/2] is not included. Also, all the previous patches submitted for fixing this issue must be dropped i.e, mm/list_lru.c: use cond_resched_lock() for nlru->lock must be dropped.
On Thu, Jun 29, 2017 at 09:09:35AM +0530, Sahitya Tummala wrote: > __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 - > > [<ffffff8eca0fb0bc>] spin_bug+0x90 > [<ffffff8eca0fb220>] do_raw_spin_lock+0xfc > [<ffffff8ecafb7798>] _raw_spin_lock+0x28 > [<ffffff8eca1ae884>] list_lru_add+0x28 > [<ffffff8eca1f5dac>] dput+0x1c8 > [<ffffff8eca1eb46c>] path_put+0x20 > [<ffffff8eca1eb73c>] terminate_walk+0x3c > [<ffffff8eca1eee58>] path_lookupat+0x100 > [<ffffff8eca1f00fc>] filename_lookup+0x6c > [<ffffff8eca1f0264>] user_path_at_empty+0x54 > [<ffffff8eca1e066c>] SyS_faccessat+0xd0 > [<ffffff8eca084e30>] el0_svc_naked+0x24 > > This nlru->lock is acquired by another CPU in this path - > > [<ffffff8eca1f5fd0>] d_lru_shrink_move+0x34 > [<ffffff8eca1f6180>] dentry_lru_isolate_shrink+0x48 > [<ffffff8eca1aeafc>] __list_lru_walk_one.isra.10+0x94 > [<ffffff8eca1aec34>] list_lru_walk_node+0x40 > [<ffffff8eca1f6620>] shrink_dcache_sb+0x60 > [<ffffff8eca1e56a8>] do_remount_sb+0xbc > [<ffffff8eca1e583c>] do_emergency_remount+0xb0 > [<ffffff8eca0ba510>] process_one_work+0x228 > [<ffffff8eca0bb158>] worker_thread+0x2e0 > [<ffffff8eca0c040c>] kthread+0xf4 > [<ffffff8eca084dd0>] 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 > Fix-suggested-by: Jan kara <jack@suse.cz> > Fix-suggested-by: Vladimir Davydov <vdavydov.dev@gmail.com> > Signed-off-by: Sahitya Tummala <stummala@codeaurora.org> Acked-by: Vladimir Davydov <vdavydov.dev@gmail.com>
diff --git a/fs/dcache.c b/fs/dcache.c index a9f995f..1161390 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -1133,11 +1133,12 @@ void shrink_dcache_sb(struct super_block *sb) 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);
__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 - [<ffffff8eca0fb0bc>] spin_bug+0x90 [<ffffff8eca0fb220>] do_raw_spin_lock+0xfc [<ffffff8ecafb7798>] _raw_spin_lock+0x28 [<ffffff8eca1ae884>] list_lru_add+0x28 [<ffffff8eca1f5dac>] dput+0x1c8 [<ffffff8eca1eb46c>] path_put+0x20 [<ffffff8eca1eb73c>] terminate_walk+0x3c [<ffffff8eca1eee58>] path_lookupat+0x100 [<ffffff8eca1f00fc>] filename_lookup+0x6c [<ffffff8eca1f0264>] user_path_at_empty+0x54 [<ffffff8eca1e066c>] SyS_faccessat+0xd0 [<ffffff8eca084e30>] el0_svc_naked+0x24 This nlru->lock is acquired by another CPU in this path - [<ffffff8eca1f5fd0>] d_lru_shrink_move+0x34 [<ffffff8eca1f6180>] dentry_lru_isolate_shrink+0x48 [<ffffff8eca1aeafc>] __list_lru_walk_one.isra.10+0x94 [<ffffff8eca1aec34>] list_lru_walk_node+0x40 [<ffffff8eca1f6620>] shrink_dcache_sb+0x60 [<ffffff8eca1e56a8>] do_remount_sb+0xbc [<ffffff8eca1e583c>] do_emergency_remount+0xb0 [<ffffff8eca0ba510>] process_one_work+0x228 [<ffffff8eca0bb158>] worker_thread+0x2e0 [<ffffff8eca0c040c>] kthread+0xf4 [<ffffff8eca084dd0>] 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 Fix-suggested-by: Jan kara <jack@suse.cz> Fix-suggested-by: Vladimir Davydov <vdavydov.dev@gmail.com> Signed-off-by: Sahitya Tummala <stummala@codeaurora.org> --- fs/dcache.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)