quota: simplify drop_dquot_ref()

As Honza said, remove_inode_dquot_ref() currently does not release the
last dquot reference but instead adds the dquot to tofree_head list. This
is because dqput() can sleep while dropping of the last dquot reference
(writing back the dquot and calling ->release_dquot()) and that must not
happen under dq_list_lock. Now that dqput() queues the final dquot cleanup
into a workqueue, remove_inode_dquot_ref() can call dqput() unconditionally
and we can significantly simplify it.

Here we open code the simplified code of remove_inode_dquot_ref() into
remove_dquot_ref() and remove the function put_dquot_list() which is no
longer used.

Signed-off-by: Baokun Li <libaokun1@huawei.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Message-Id: <20230630110822.3881712-6-libaokun1@huawei.com>

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index c7afe43..e823224 100644 (file)
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -1072,59 +1072,7 @@ out:
        return err;
 }
 
-/*
- * Remove references to dquots from inode and add dquot to list for freeing
- * if we have the last reference to dquot
- */
-static void remove_inode_dquot_ref(struct inode *inode, int type,
-                                  struct list_head *tofree_head)
-{
-       struct dquot **dquots = i_dquot(inode);
-       struct dquot *dquot = dquots[type];
-
-       if (!dquot)
-               return;
-
-       dquots[type] = NULL;
-       if (list_empty(&dquot->dq_free)) {
-               /*
-                * The inode still has reference to dquot so it can't be in the
-                * free list
-                */
-               spin_lock(&dq_list_lock);
-               list_add(&dquot->dq_free, tofree_head);
-               spin_unlock(&dq_list_lock);
-       } else {
-               /*
-                * Dquot is already in a list to put so we won't drop the last
-                * reference here.
-                */
-               dqput(dquot);
-       }
-}
-
-/*
- * Free list of dquots
- * Dquots are removed from inodes and no new references can be got so we are
- * the only ones holding reference
- */
-static void put_dquot_list(struct list_head *tofree_head)
-{
-       struct list_head *act_head;
-       struct dquot *dquot;
-
-       act_head = tofree_head->next;
-       while (act_head != tofree_head) {
-               dquot = list_entry(act_head, struct dquot, dq_free);
-               act_head = act_head->next;
-               /* Remove dquot from the list so we won't have problems... */
-               list_del_init(&dquot->dq_free);
-               dqput(dquot);
-       }
-}
-
-static void remove_dquot_ref(struct super_block *sb, int type,
-               struct list_head *tofree_head)
+static void remove_dquot_ref(struct super_block *sb, int type)
 {
        struct inode *inode;
 #ifdef CONFIG_QUOTA_DEBUG
@@ -1141,11 +1089,16 @@ static void remove_dquot_ref(struct super_block *sb, int type,
                 */
                spin_lock(&dq_data_lock);
                if (!IS_NOQUOTA(inode)) {
+                       struct dquot **dquots = i_dquot(inode);
+                       struct dquot *dquot = dquots[type];
+
 #ifdef CONFIG_QUOTA_DEBUG
                        if (unlikely(inode_get_rsv_space(inode) > 0))
                                reserved = 1;
 #endif
-                       remove_inode_dquot_ref(inode, type, tofree_head);
+                       dquots[type] = NULL;
+                       if (dquot)
+                               dqput(dquot);
                }
                spin_unlock(&dq_data_lock);
        }
@@ -1162,13 +1115,8 @@ static void remove_dquot_ref(struct super_block *sb, int type,
 /* Gather all references from inodes and drop them */
 static void drop_dquot_ref(struct super_block *sb, int type)
 {
-       LIST_HEAD(tofree_head);
-
-       if (sb->dq_op) {
-               remove_dquot_ref(sb, type, &tofree_head);
-               synchronize_srcu(&dquot_srcu);
-               put_dquot_list(&tofree_head);
-       }
+       if (sb->dq_op)
+               remove_dquot_ref(sb, type);
 }
 
 static inline