/*
* Dquot List Management:
- * The quota code uses four lists for dquot management: the inuse_list,
- * free_dquots, dqi_dirty_list, and dquot_hash[] array. A single dquot
- * structure may be on some of those lists, depending on its current state.
+ * The quota code uses five lists for dquot management: the inuse_list,
+ * releasing_dquots, free_dquots, dqi_dirty_list, and dquot_hash[] array.
+ * A single dquot structure may be on some of those lists, depending on
+ * its current state.
*
* All dquots are placed to the end of inuse_list when first created, and this
* list is used for invalidate operation, which must look at every dquot.
*
+ * When the last reference of a dquot will be dropped, the dquot will be
+ * added to releasing_dquots. We'd then queue work item which would call
+ * synchronize_srcu() and after that perform the final cleanup of all the
+ * dquots on the list. Both releasing_dquots and free_dquots use the
+ * dq_free list_head in the dquot struct. When a dquot is removed from
+ * releasing_dquots, a reference count is always subtracted, and if
+ * dq_count == 0 at that point, the dquot will be added to the free_dquots.
+ *
* Unused dquots (dq_count == 0) are added to the free_dquots list when freed,
* and this list is searched whenever we need an available dquot. Dquots are
* removed from the list as soon as they are used again, and
static LIST_HEAD(inuse_list);
static LIST_HEAD(free_dquots);
+static LIST_HEAD(releasing_dquots);
static unsigned int dq_hash_bits, dq_hash_mask;
static struct hlist_head *dquot_hash;
static qsize_t __inode_get_rsv_space(struct inode *inode);
static int __dquot_initialize(struct inode *inode, int type);
+static void quota_release_workfn(struct work_struct *work);
+static DECLARE_DELAYED_WORK(quota_release_work, quota_release_workfn);
+
static inline unsigned int
hashfn(const struct super_block *sb, struct kqid qid)
{
dqstats_inc(DQST_FREE_DQUOTS);
}
+static inline void put_releasing_dquots(struct dquot *dquot)
+{
+ list_add_tail(&dquot->dq_free, &releasing_dquots);
+}
+
static inline void remove_free_dquot(struct dquot *dquot)
{
if (list_empty(&dquot->dq_free))
return;
list_del_init(&dquot->dq_free);
- dqstats_dec(DQST_FREE_DQUOTS);
+ if (!atomic_read(&dquot->dq_count))
+ dqstats_dec(DQST_FREE_DQUOTS);
}
static inline void put_inuse(struct dquot *dquot)
struct dquot *dquot, *tmp;
restart:
+ flush_delayed_work("a_release_work);
+
spin_lock(&dq_list_lock);
list_for_each_entry_safe(dquot, tmp, &inuse_list, dq_inuse) {
if (dquot->dq_sb != sb)
continue;
/* Wait for dquot users */
if (atomic_read(&dquot->dq_count)) {
+ /* dquot in releasing_dquots, flush and retry */
+ if (!list_empty(&dquot->dq_free)) {
+ spin_unlock(&dq_list_lock);
+ goto restart;
+ }
+
atomic_inc(&dquot->dq_count);
spin_unlock(&dq_list_lock);
/*
.seeks = DEFAULT_SEEKS,
};
+/*
+ * Safely release dquot and put reference to dquot.
+ */
+static void quota_release_workfn(struct work_struct *work)
+{
+ struct dquot *dquot;
+ struct list_head rls_head;
+
+ spin_lock(&dq_list_lock);
+ /* Exchange the list head to avoid livelock. */
+ list_replace_init(&releasing_dquots, &rls_head);
+ spin_unlock(&dq_list_lock);
+
+restart:
+ synchronize_srcu(&dquot_srcu);
+ spin_lock(&dq_list_lock);
+ while (!list_empty(&rls_head)) {
+ dquot = list_first_entry(&rls_head, struct dquot, dq_free);
+ /* Dquot got used again? */
+ if (atomic_read(&dquot->dq_count) > 1) {
+ remove_free_dquot(dquot);
+ atomic_dec(&dquot->dq_count);
+ continue;
+ }
+ if (dquot_dirty(dquot)) {
+ spin_unlock(&dq_list_lock);
+ /* Commit dquot before releasing */
+ dquot_write_dquot(dquot);
+ goto restart;
+ }
+ if (dquot_active(dquot)) {
+ spin_unlock(&dq_list_lock);
+ dquot->dq_sb->dq_op->release_dquot(dquot);
+ goto restart;
+ }
+ /* Dquot is inactive and clean, now move it to free list */
+ remove_free_dquot(dquot);
+ atomic_dec(&dquot->dq_count);
+ put_dquot_last(dquot);
+ }
+ spin_unlock(&dq_list_lock);
+}
+
/*
* Put reference to dquot
*/
}
#endif
dqstats_inc(DQST_DROPS);
-we_slept:
+
spin_lock(&dq_list_lock);
if (atomic_read(&dquot->dq_count) > 1) {
/* We have more than one user... nothing to do */
spin_unlock(&dq_list_lock);
return;
}
+
/* Need to release dquot? */
- if (dquot_dirty(dquot)) {
- spin_unlock(&dq_list_lock);
- /* Commit dquot before releasing */
- dquot_write_dquot(dquot);
- goto we_slept;
- }
- if (dquot_active(dquot)) {
- spin_unlock(&dq_list_lock);
- dquot->dq_sb->dq_op->release_dquot(dquot);
- goto we_slept;
- }
- atomic_dec(&dquot->dq_count);
#ifdef CONFIG_QUOTA_DEBUG
/* sanity check */
BUG_ON(!list_empty(&dquot->dq_free));
#endif
- put_dquot_last(dquot);
+ put_releasing_dquots(dquot);
spin_unlock(&dq_list_lock);
+ queue_delayed_work(system_unbound_wq, "a_release_work, 1);
}
EXPORT_SYMBOL(dqput);