linux-kernel - [PATCH 07/10] proc: Generalize proc_sys_prune_dcache into proc_prune_siblings

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Date:   Fri,  4 Dec 2020 02:32:01 +0800
From:   Wen Yang <wenyang@...ux.alibaba.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Sasha Levin <sashal@...nel.org>
Cc:     Xunlei Pang <xlpang@...ux.alibaba.com>,
        linux-kernel@...r.kernel.org,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        stable@...r.kernel.org, Wen Yang <wenyang@...ux.alibaba.com>
Subject: [PATCH 07/10] proc: Generalize proc_sys_prune_dcache into proc_prune_siblings_dcache

From: "Eric W. Biederman" <ebiederm@...ssion.com>

[ Upstream commit 26dbc60f385ff9cff475ea2a3bad02e80fd6fa43 ]

This prepares the way for allowing the pid part of proc to use this
dcache pruning code as well.

Signed-off-by: Eric W. Biederman <ebiederm@...ssion.com>
Cc: <stable@...r.kernel.org> # 4.9.x
(proc: fix up cherry-pick conflicts for 26dbc60f385f)
Signed-off-by: Wen Yang <wenyang@...ux.alibaba.com>
---
 fs/proc/inode.c       | 38 ++++++++++++++++++++++++++++++++++++++
 fs/proc/internal.h    |  1 +
 fs/proc/proc_sysctl.c | 35 +----------------------------------
 3 files changed, 40 insertions(+), 34 deletions(-)

diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 14d9c1d..920c761 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -101,6 +101,44 @@ void __init proc_init_inodecache(void)
 					     init_once);
 }
 
+void proc_prune_siblings_dcache(struct hlist_head *inodes, spinlock_t *lock)
+{
+	struct inode *inode;
+	struct proc_inode *ei;
+	struct hlist_node *node;
+	struct super_block *sb;
+
+	rcu_read_lock();
+	for (;;) {
+		node = hlist_first_rcu(inodes);
+		if (!node)
+			break;
+		ei = hlist_entry(node, struct proc_inode, sibling_inodes);
+		spin_lock(lock);
+		hlist_del_init_rcu(&ei->sibling_inodes);
+		spin_unlock(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();
+}
+
 static int proc_show_options(struct seq_file *seq, struct dentry *root)
 {
 	struct super_block *sb = root->d_sb;
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index 409b5c5..9bc44a1 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -200,6 +200,7 @@ struct pde_opener {
 extern const struct inode_operations proc_pid_link_inode_operations;
 
 extern void proc_init_inodecache(void);
+void proc_prune_siblings_dcache(struct hlist_head *inodes, spinlock_t *lock);
 extern struct inode *proc_get_inode(struct super_block *, struct proc_dir_entry *);
 extern int proc_fill_super(struct super_block *, void *data, int flags);
 extern void proc_entry_rundown(struct proc_dir_entry *);
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 671490e..f19063b 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -262,40 +262,7 @@ static void unuse_table(struct ctl_table_header *p)
 
 static void proc_sys_prune_dcache(struct ctl_table_header *head)
 {
-	struct inode *inode;
-	struct proc_inode *ei;
-	struct hlist_node *node;
-	struct super_block *sb;
-
-	rcu_read_lock();
-	for (;;) {
-		node = hlist_first_rcu(&head->inodes);
-		if (!node)
-			break;
-		ei = hlist_entry(node, struct proc_inode, sibling_inodes);
-		spin_lock(&sysctl_lock);
-		hlist_del_init_rcu(&ei->sibling_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();
+	proc_prune_siblings_dcache(&head->inodes, &sysctl_lock);
 }
 
 /* called under sysctl_lock, will reacquire if has to wait */
-- 
1.8.3.1