[PATCH 5.4 109/183] quota: simplify drop_dquot_ref()

Sasha Levin
2024-03-24T23:48:30Z

From: Baokun Li <libaokun1@huawei.com>

[ Upstream commit 7bce48f0fec602b3b6c335963b26d9eefa417788 ]

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>
Stable-dep-of: 179b8c97ebf6 ("quota: Fix rcu annotations of inode dquot pointers")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/quota/dquot.c | 70 +++++++-----------------------------------------
1 file changed, 9 insertions(+), 61 deletions(-)

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index d9da4a8c4317c..08ca5b1a5fba5 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -1075,59 +1075,7 @@ static int add_dquot_ref(struct super_block *sb, int type)
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
@@ -1144,11 +1092,16 @@ 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);
}
@@ -1165,13 +1118,8 @@ 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
--
2.43.0