From: ebiederm@xmission•com (Eric W. Biederman)
To: Andrei Vagin <avagin@gmail•com>
Cc: Andrei Vagin <avagin@virtuozzo•com>,
Konstantin Khlebnikov <khlebnikov@yandex-team•ru>,
linux-fsdevel <linux-fsdevel@vger•kernel.org>,
Linux Kernel Network Developers <netdev@vger•kernel.org>,
Linux Containers <containers@lists•linux-foundation.org>,
LKML <linux-kernel@vger•kernel.org>,
"criu\@openvz.org" <criu@openvz•org>
Subject: Re: [CRIU] BUG: Dentry ffff9f795a08fe60{i=af565f, n=lo} still in use (1) [unmount of proc proc]
Date: Thu, 06 Jul 2017 08:41:00 -0500 [thread overview]
Message-ID: <87van54r9v.fsf@xmission.com> (raw)
In-Reply-To: <20170703163646.GA9346@gmail.com> (Andrei Vagin's message of "Mon, 3 Jul 2017 09:36:48 -0700")
Andrei Vagin <avagin@gmail•com> writes:
> I did a few experiments and found that the bug is reproduced for 6-12
> hours on the our test server. Then I reverted two patches and the server
> is working normally for more than 24 hours already, so the bug is
> probably in one of these patches.
>
> commit e3d0065ab8535cbeee69a4c46a59f4d7360803ae
> Author: Andrei Vagin <avagin@openvz•org>
> Date: Sun Jul 2 07:41:25 2017 +0200
>
> Revert "proc/sysctl: prune stale dentries during unregistering"
>
> This reverts commit d6cffbbe9a7e51eb705182965a189457c17ba8a3.
>
> commit 2d3c50dac81011c1da4d2f7a63b84bd75287e320
> Author: Andrei Vagin <avagin@openvz•org>
> Date: Sun Jul 2 07:40:08 2017 +0200
>
> Revert "proc/sysctl: Don't grab i_lock under sysctl_lock."
>
> This reverts commit ace0c791e6c3cf5ef37cad2df69f0d90ccc40ffb.
>
>
> FYI: This bug has been reproduced on 4.11.7
Instead of the revert could you test the patch below?
This should fix the issue by grabbing a s_active reference
to the proc super block for every inode we flush.
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index c5ae09b6c726..18694598bebf 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -67,7 +67,7 @@ struct proc_inode {
struct proc_dir_entry *pde;
struct ctl_table_header *sysctl;
struct ctl_table *sysctl_entry;
- struct list_head sysctl_inodes;
+ struct hlist_node sysctl_inodes;
const struct proc_ns_operations *ns_ops;
struct inode vfs_inode;
};
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 67985a7233c2..9bf06e2b1284 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -191,7 +191,7 @@ static void init_header(struct ctl_table_header *head,
head->set = set;
head->parent = NULL;
head->node = node;
- INIT_LIST_HEAD(&head->inodes);
+ INIT_HLIST_HEAD(&head->inodes);
if (node) {
struct ctl_table *entry;
for (entry = table; entry->procname; entry++, node++)
@@ -261,25 +261,42 @@ static void unuse_table(struct ctl_table_header *p)
complete(p->unregistering);
}
-/* called under sysctl_lock */
static void proc_sys_prune_dcache(struct ctl_table_header *head)
{
- struct inode *inode, *prev = NULL;
+ struct inode *inode;
struct proc_inode *ei;
+ struct hlist_node *node;
+ struct super_block *sb;
rcu_read_lock();
- list_for_each_entry_rcu(ei, &head->inodes, sysctl_inodes) {
- inode = igrab(&ei->vfs_inode);
- if (inode) {
- rcu_read_unlock();
- iput(prev);
- prev = inode;
- d_prune_aliases(inode);
+ for (;;) {
+ node = hlist_first_rcu(&head->inodes);
+ if (!node)
+ break;
+ ei = hlist_entry(node, struct proc_inode, sysctl_inodes);
+ spin_lock(&sysctl_lock);
+ hlist_del_init_rcu(&ei->sysctl_inodes);
+ spin_unlock(&sysctl_lock);
+
+ inode = &ei->vfs_inode;
+ sb = inode->i_sb;
+ if (!atomic_inc_not_zero(&sb->s_active))
+ continue;
+ inode = igrab(inode);
+ rcu_read_unlock();
+ if (unlikely(!inode)) {
+ deactivate_super(sb);
rcu_read_lock();
+ continue;
}
+
+ d_prune_aliases(inode);
+ iput(inode);
+ deactivate_super(sb);
+
+ rcu_read_lock();
}
rcu_read_unlock();
- iput(prev);
}
/* called under sysctl_lock, will reacquire if has to wait */
@@ -461,7 +478,7 @@ static struct inode *proc_sys_make_inode(struct super_block *sb,
}
ei->sysctl = head;
ei->sysctl_entry = table;
- list_add_rcu(&ei->sysctl_inodes, &head->inodes);
+ hlist_add_head_rcu(&ei->sysctl_inodes, &head->inodes);
head->count++;
spin_unlock(&sysctl_lock);
@@ -489,7 +506,7 @@ static struct inode *proc_sys_make_inode(struct super_block *sb,
void proc_sys_evict_inode(struct inode *inode, struct ctl_table_header *head)
{
spin_lock(&sysctl_lock);
- list_del_rcu(&PROC_I(inode)->sysctl_inodes);
+ hlist_del_init_rcu(&PROC_I(inode)->sysctl_inodes);
if (!--head->count)
kfree_rcu(head, rcu);
spin_unlock(&sysctl_lock);
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 80d07816def0..1c04a26bfd2f 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -143,7 +143,7 @@ struct ctl_table_header
struct ctl_table_set *set;
struct ctl_dir *parent;
struct ctl_node *node;
- struct list_head inodes; /* head for proc_inode->sysctl_inodes */
+ struct hlist_head inodes; /* head for proc_inode->sysctl_inodes */
};
struct ctl_dir {
next prev parent reply other threads:[~2017-07-06 13:41 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-29 18:38 BUG: Dentry ffff9f795a08fe60{i=af565f, n=lo} still in use (1) [unmount of proc proc] Andrei Vagin
[not found] ` <CANaxB-yneyRrUhJp1uwvHcaC88n3yyF5Jjr=1A869hWQsXfNEg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-06-29 19:06 ` Eric W. Biederman
2017-06-29 20:15 ` BUG: Dentry ffff9f795a08fe60{i=af565f,n=lo} " Andrei Vagin
[not found] ` <CANaxB-z-K=A2_OfMsXqROttsef0SXSeACX8Wj9ik2NJ1Dkz_Fw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-06-30 1:42 ` BUG: Dentry ffff9f795a08fe60{i=af565f, n=lo} " Eric W. Biederman
2017-06-30 19:11 ` [CRIU] " Andrei Vagin
[not found] ` <20170630191106.GB8899-1ViLX0X+lBJGNQ1M2rI3KwRV3xvJKrda@public.gmane.org>
2017-07-03 16:36 ` Andrei Vagin
[not found] ` <20170703163646.GA9346-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2017-07-05 20:16 ` Eric W. Biederman
2017-07-06 13:41 ` Eric W. Biederman [this message]
2017-07-07 20:34 ` Andrei Vagin
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