GFS2: change gfs2_quota_scan into a shrinker

Deallocation of gfs2_quota_data objects now happens on-demand through a
shrinker instead of routinely deallocating through the quotad daemon.

Signed-off-by: Abhijith Das <adas@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

1 files changed, 98 insertions, 67 deletions

diff --git a/fs/gfs2/quota.c b/fs/gfs2/quota.c
index b08d09696b3e..2ada6e10d07b 100644
--- a/fs/gfs2/quota.c
+++ b/fs/gfs2/quota.c
@@ -80,6 +80,53 @@ struct gfs2_quota_change_host {
         u32 qc_id;
 };
 
+static LIST_HEAD(qd_lru_list);
+static atomic_t qd_lru_count = ATOMIC_INIT(0);
+static spinlock_t qd_lru_lock = SPIN_LOCK_UNLOCKED;
+
+int gfs2_shrink_qd_memory(int nr, gfp_t gfp_mask)
+{
+        struct gfs2_quota_data *qd;
+        struct gfs2_sbd *sdp;
+
+        if (nr == 0)
+                goto out;
+
+        if (!(gfp_mask & __GFP_FS))
+                return -1;
+
+        spin_lock(&qd_lru_lock);
+        while (nr && !list_empty(&qd_lru_list)) {
+                qd = list_entry(qd_lru_list.next,
+                                struct gfs2_quota_data, qd_reclaim);
+                sdp = qd->qd_gl->gl_sbd;
+
+                /* Free from the filesystem-specific list */
+                list_del(&qd->qd_list);
+
+                spin_lock(&sdp->sd_quota_spin);
+                gfs2_assert_warn(sdp, !qd->qd_change);
+                gfs2_assert_warn(sdp, !qd->qd_slot_count);
+                gfs2_assert_warn(sdp, !qd->qd_bh_count);
+
+                gfs2_lvb_unhold(qd->qd_gl);
+                spin_unlock(&sdp->sd_quota_spin);
+                atomic_dec(&sdp->sd_quota_count);
+
+                /* Delete it from the common reclaim list */
+                list_del_init(&qd->qd_reclaim);
+                atomic_dec(&qd_lru_count);
+                spin_unlock(&qd_lru_lock);
+                kmem_cache_free(gfs2_quotad_cachep, qd);
+                spin_lock(&qd_lru_lock);
+                nr--;
+        }
+        spin_unlock(&qd_lru_lock);
+
+out:
+        return (atomic_read(&qd_lru_count) * sysctl_vfs_cache_pressure) / 100;
+}
+
 static u64 qd2offset(struct gfs2_quota_data *qd)
 {
         u64 offset;
@@ -100,11 +147,12 @@ static int qd_alloc(struct gfs2_sbd *sdp, int user, u32 id,
         if (!qd)
                 return -ENOMEM;
 
-        qd->qd_count = 1;
+        atomic_set(&qd->qd_count, 1);
         qd->qd_id = id;
         if (user)
                 set_bit(QDF_USER, &qd->qd_flags);
         qd->qd_slot = -1;
+        INIT_LIST_HEAD(&qd->qd_reclaim);
 
         error = gfs2_glock_get(sdp, 2 * (u64)id + !user,
                               &gfs2_quota_glops, CREATE, &qd->qd_gl);
@@ -135,11 +183,17 @@ static int qd_get(struct gfs2_sbd *sdp, int user, u32 id, int create,
 
         for (;;) {
                 found = 0;
-                spin_lock(&sdp->sd_quota_spin);
+                spin_lock(&qd_lru_lock);
                 list_for_each_entry(qd, &sdp->sd_quota_list, qd_list) {
                         if (qd->qd_id == id &&
                             !test_bit(QDF_USER, &qd->qd_flags) == !user) {
-                                qd->qd_count++;
+                                if (!atomic_read(&qd->qd_count) &&
+                                    !list_empty(&qd->qd_reclaim)) {
+                                        /* Remove it from reclaim list */
+                                        list_del_init(&qd->qd_reclaim);
+                                        atomic_dec(&qd_lru_count);
+                                }
+                                atomic_inc(&qd->qd_count);
                                 found = 1;
                                 break;
                         }
@@ -155,7 +209,7 @@ static int qd_get(struct gfs2_sbd *sdp, int user, u32 id, int create,
                         new_qd = NULL;
                 }
 
-                spin_unlock(&sdp->sd_quota_spin);
+                spin_unlock(&qd_lru_lock);
 
                 if (qd || !create) {
                         if (new_qd) {
@@ -175,21 +229,18 @@ static int qd_get(struct gfs2_sbd *sdp, int user, u32 id, int create,
 static void qd_hold(struct gfs2_quota_data *qd)
 {
         struct gfs2_sbd *sdp = qd->qd_gl->gl_sbd;
-
-        spin_lock(&sdp->sd_quota_spin);
-        gfs2_assert(sdp, qd->qd_count);
-        qd->qd_count++;
-        spin_unlock(&sdp->sd_quota_spin);
+        gfs2_assert(sdp, atomic_read(&qd->qd_count));
+        atomic_inc(&qd->qd_count);
 }
 
 static void qd_put(struct gfs2_quota_data *qd)
 {
-        struct gfs2_sbd *sdp = qd->qd_gl->gl_sbd;
-        spin_lock(&sdp->sd_quota_spin);
-        gfs2_assert(sdp, qd->qd_count);
-        if (!--qd->qd_count)
-                qd->qd_last_touched = jiffies;
-        spin_unlock(&sdp->sd_quota_spin);
+        if (atomic_dec_and_lock(&qd->qd_count, &qd_lru_lock)) {
+                /* Add to the reclaim list */
+                list_add_tail(&qd->qd_reclaim, &qd_lru_list);
+                atomic_inc(&qd_lru_count);
+                spin_unlock(&qd_lru_lock);
+        }
 }
 
 static int slot_get(struct gfs2_quota_data *qd)
@@ -330,6 +381,7 @@ static int qd_fish(struct gfs2_sbd *sdp, struct gfs2_quota_data **qdp)
         if (sdp->sd_vfs->s_flags & MS_RDONLY)
                 return 0;
 
+        spin_lock(&qd_lru_lock);
         spin_lock(&sdp->sd_quota_spin);
 
         list_for_each_entry(qd, &sdp->sd_quota_list, qd_list) {
@@ -341,8 +393,8 @@ static int qd_fish(struct gfs2_sbd *sdp, struct gfs2_quota_data **qdp)
                 list_move_tail(&qd->qd_list, &sdp->sd_quota_list);
 
                 set_bit(QDF_LOCKED, &qd->qd_flags);
-                gfs2_assert_warn(sdp, qd->qd_count);
-                qd->qd_count++;
+                gfs2_assert_warn(sdp, atomic_read(&qd->qd_count));
+                atomic_inc(&qd->qd_count);
                 qd->qd_change_sync = qd->qd_change;
                 gfs2_assert_warn(sdp, qd->qd_slot_count);
                 qd->qd_slot_count++;
@@ -355,6 +407,7 @@ static int qd_fish(struct gfs2_sbd *sdp, struct gfs2_quota_data **qdp)
                 qd = NULL;
 
         spin_unlock(&sdp->sd_quota_spin);
+        spin_unlock(&qd_lru_lock);
 
         if (qd) {
                 gfs2_assert_warn(sdp, qd->qd_change_sync);
@@ -379,24 +432,27 @@ static int qd_trylock(struct gfs2_quota_data *qd)
         if (sdp->sd_vfs->s_flags & MS_RDONLY)
                 return 0;
 
+        spin_lock(&qd_lru_lock);
         spin_lock(&sdp->sd_quota_spin);
 
         if (test_bit(QDF_LOCKED, &qd->qd_flags) ||
             !test_bit(QDF_CHANGE, &qd->qd_flags)) {
                 spin_unlock(&sdp->sd_quota_spin);
+                spin_unlock(&qd_lru_lock);
                 return 0;
         }
 
         list_move_tail(&qd->qd_list, &sdp->sd_quota_list);
 
         set_bit(QDF_LOCKED, &qd->qd_flags);
-        gfs2_assert_warn(sdp, qd->qd_count);
-        qd->qd_count++;
+        gfs2_assert_warn(sdp, atomic_read(&qd->qd_count));
+        atomic_inc(&qd->qd_count);
         qd->qd_change_sync = qd->qd_change;
         gfs2_assert_warn(sdp, qd->qd_slot_count);
         qd->qd_slot_count++;
 
         spin_unlock(&sdp->sd_quota_spin);
+        spin_unlock(&qd_lru_lock);
 
         gfs2_assert_warn(sdp, qd->qd_change_sync);
         if (bh_get(qd)) {
@@ -802,8 +858,8 @@ restart:
                 loff_t pos;
                 gfs2_glock_dq_uninit(q_gh);
                 error = gfs2_glock_nq_init(qd->qd_gl,
-                                          LM_ST_EXCLUSIVE, GL_NOCACHE,
-                                          q_gh);
+                                           LM_ST_EXCLUSIVE, GL_NOCACHE,
+                                           q_gh);
                 if (error)
                         return error;
 
@@ -820,7 +876,6 @@ restart:
 
                 gfs2_glock_dq_uninit(&i_gh);
 
-
                 gfs2_quota_in(&q, buf);
                 qlvb = (struct gfs2_quota_lvb *)qd->qd_gl->gl_lvb;
                 qlvb->qb_magic = cpu_to_be32(GFS2_MAGIC);
@@ -1171,13 +1226,14 @@ int gfs2_quota_init(struct gfs2_sbd *sdp)
                         qd->qd_change = qc.qc_change;
                         qd->qd_slot = slot;
                         qd->qd_slot_count = 1;
-                        qd->qd_last_touched = jiffies;
 
+                        spin_lock(&qd_lru_lock);
                         spin_lock(&sdp->sd_quota_spin);
                         gfs2_icbit_munge(sdp, sdp->sd_quota_bitmap, slot, 1);
+                        spin_unlock(&sdp->sd_quota_spin);
                         list_add(&qd->qd_list, &sdp->sd_quota_list);
                         atomic_inc(&sdp->sd_quota_count);
-                        spin_unlock(&sdp->sd_quota_spin);
+                        spin_unlock(&qd_lru_lock);
 
                         found++;
                 }
@@ -1197,61 +1253,39 @@ fail:
         return error;
 }
 
-static void gfs2_quota_scan(struct gfs2_sbd *sdp)
-{
-        struct gfs2_quota_data *qd, *safe;
-        LIST_HEAD(dead);
-
-        spin_lock(&sdp->sd_quota_spin);
-        list_for_each_entry_safe(qd, safe, &sdp->sd_quota_list, qd_list) {
-                if (!qd->qd_count &&
-                    time_after_eq(jiffies, qd->qd_last_touched +
-                                gfs2_tune_get(sdp, gt_quota_cache_secs) * HZ)) {
-                        list_move(&qd->qd_list, &dead);
-                        gfs2_assert_warn(sdp,
-                                         atomic_read(&sdp->sd_quota_count) > 0);
-                        atomic_dec(&sdp->sd_quota_count);
-                }
-        }
-        spin_unlock(&sdp->sd_quota_spin);
-
-        while (!list_empty(&dead)) {
-                qd = list_entry(dead.next, struct gfs2_quota_data, qd_list);
-                list_del(&qd->qd_list);
-
-                gfs2_assert_warn(sdp, !qd->qd_change);
-                gfs2_assert_warn(sdp, !qd->qd_slot_count);
-                gfs2_assert_warn(sdp, !qd->qd_bh_count);
-
-                gfs2_lvb_unhold(qd->qd_gl);
-                kmem_cache_free(gfs2_quotad_cachep, qd);
-        }
-}
-
 void gfs2_quota_cleanup(struct gfs2_sbd *sdp)
 {
         struct list_head *head = &sdp->sd_quota_list;
         struct gfs2_quota_data *qd;
         unsigned int x;
 
-        spin_lock(&sdp->sd_quota_spin);
+        spin_lock(&qd_lru_lock);
         while (!list_empty(head)) {
                 qd = list_entry(head->prev, struct gfs2_quota_data, qd_list);
 
-                if (qd->qd_count > 1 ||
-                    (qd->qd_count && !test_bit(QDF_CHANGE, &qd->qd_flags))) {
-                        list_move(&qd->qd_list, head);
+                spin_lock(&sdp->sd_quota_spin);
+                if (atomic_read(&qd->qd_count) > 1 ||
+                    (atomic_read(&qd->qd_count) &&
+                     !test_bit(QDF_CHANGE, &qd->qd_flags))) {
                         spin_unlock(&sdp->sd_quota_spin);
+                        list_move(&qd->qd_list, head);
+                        spin_unlock(&qd_lru_lock);
                         schedule();
-                        spin_lock(&sdp->sd_quota_spin);
+                        spin_lock(&qd_lru_lock);
                         continue;
                 }
+                spin_unlock(&sdp->sd_quota_spin);
 
                 list_del(&qd->qd_list);
+                /* Also remove if this qd exists in the reclaim list */
+                if (!list_empty(&qd->qd_reclaim)) {
+                        list_del_init(&qd->qd_reclaim);
+                        atomic_dec(&qd_lru_count);
+                }
                 atomic_dec(&sdp->sd_quota_count);
-                spin_unlock(&sdp->sd_quota_spin);
+                spin_unlock(&qd_lru_lock);
 
-                if (!qd->qd_count) {
+                if (!atomic_read(&qd->qd_count)) {
                         gfs2_assert_warn(sdp, !qd->qd_change);
                         gfs2_assert_warn(sdp, !qd->qd_slot_count);
                 } else
@@ -1261,9 +1295,9 @@ void gfs2_quota_cleanup(struct gfs2_sbd *sdp)
                 gfs2_lvb_unhold(qd->qd_gl);
                 kmem_cache_free(gfs2_quotad_cachep, qd);
 
-                spin_lock(&sdp->sd_quota_spin);
+                spin_lock(&qd_lru_lock);
         }
-        spin_unlock(&sdp->sd_quota_spin);
+        spin_unlock(&qd_lru_lock);
 
         gfs2_assert_warn(sdp, !atomic_read(&sdp->sd_quota_count));
 
@@ -1341,9 +1375,6 @@ int gfs2_quotad(void *data)
                 quotad_check_timeo(sdp, "sync", gfs2_quota_sync, t,
                                    &quotad_timeo, &tune->gt_quota_quantum);
 
-                /* FIXME: This should be turned into a shrinker */
-                gfs2_quota_scan(sdp);
-
                 /* Check for & recover partially truncated inodes */
                 quotad_check_trunc_list(sdp);