Re: [PATCH] fs/super: simplify superblock destroy action

["Zhang, Qiang" <Qiang.Zhang@xxxxxxxxxxxxx>]

Hello AI Viro
Can you review this patch?

Thanks
Qiang

________________________________________
From: Zhang, Qiang <qiang.zhang@xxxxxxxxxxxxx>
Sent: Tuesday, 25 May 2021 14:55
To: viro@xxxxxxxxxxxxxxxxxx; akpm@xxxxxxxxxxxxxxxxxxxx
Cc: linux-fsdevel@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
Subject: [PATCH] fs/super: simplify superblock destroy action

From: Zqiang <qiang.zhang@xxxxxxxxxxxxx>

The superblock is freed through call_rcu() and schedule_work(),
these two steps can be replaced by queue_rcu_work().

Signed-off-by: Zqiang <qiang.zhang@xxxxxxxxxxxxx>
---
 fs/super.c         | 15 +++++----------
 include/linux/fs.h |  3 +--
 2 files changed, 6 insertions(+), 12 deletions(-)

diff --git a/fs/super.c b/fs/super.c
index 11b7e7213fd1..6b796bbc5ba3 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -156,8 +156,8 @@ static unsigned long super_cache_count(struct shrinker *shrink,

 static void destroy_super_work(struct work_struct *work)
 {
-       struct super_block *s = container_of(work, struct super_block,
-                                                       destroy_work);
+       struct super_block *s = container_of(to_rcu_work(work), struct super_block,
+                                                       rcu_work);
        int i;

        for (i = 0; i < SB_FREEZE_LEVELS; i++)
@@ -165,12 +165,6 @@ static void destroy_super_work(struct work_struct *work)
        kfree(s);
 }

-static void destroy_super_rcu(struct rcu_head *head)
-{
-       struct super_block *s = container_of(head, struct super_block, rcu);
-       INIT_WORK(&s->destroy_work, destroy_super_work);
-       schedule_work(&s->destroy_work);
-}

 /* Free a superblock that has never been seen by anyone */
 static void destroy_unused_super(struct super_block *s)
@@ -185,7 +179,7 @@ static void destroy_unused_super(struct super_block *s)
        kfree(s->s_subtype);
        free_prealloced_shrinker(&s->s_shrink);
        /* no delays needed */
-       destroy_super_work(&s->destroy_work);
+       destroy_super_work(&s->rcu_work.work);
 }

 /**
@@ -249,6 +243,7 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags,
        spin_lock_init(&s->s_inode_list_lock);
        INIT_LIST_HEAD(&s->s_inodes_wb);
        spin_lock_init(&s->s_inode_wblist_lock);
+       INIT_RCU_WORK(&s->rcu_work, destroy_super_work);

        s->s_count = 1;
        atomic_set(&s->s_active, 1);
@@ -296,7 +291,7 @@ static void __put_super(struct super_block *s)
                fscrypt_sb_free(s);
                put_user_ns(s->s_user_ns);
                kfree(s->s_subtype);
-               call_rcu(&s->rcu, destroy_super_rcu);
+               queue_rcu_work(system_wq, &s->rcu_work);
        }
 }

diff --git a/include/linux/fs.h b/include/linux/fs.h
index c3c88fdb9b2a..2fe2b4d67af2 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1534,8 +1534,7 @@ struct super_block {
         */
        struct list_lru         s_dentry_lru;
        struct list_lru         s_inode_lru;
-       struct rcu_head         rcu;
-       struct work_struct      destroy_work;
+       struct rcu_work         rcu_work;

        struct mutex            s_sync_lock;    /* sync serialisation lock */

--
2.17.1