1 files changed, 33 insertions, 5 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index 2593153471cf..aac41adf4743 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -119,6 +119,7 @@ struct dentry_stat_t dentry_stat = {
 
 static DEFINE_PER_CPU(long, nr_dentry);
 static DEFINE_PER_CPU(long, nr_dentry_unused);
+static DEFINE_PER_CPU(long, nr_dentry_negative);
 
 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
 
@@ -152,11 +153,22 @@ static long get_nr_dentry_unused(void)
         return sum < 0 ? 0 : sum;
 }
 
+static long get_nr_dentry_negative(void)
+{
+        int i;
+        long sum = 0;
+
+        for_each_possible_cpu(i)
+                sum += per_cpu(nr_dentry_negative, i);
+        return sum < 0 ? 0 : sum;
+}
+
 int proc_nr_dentry(struct ctl_table *table, int write, void __user *buffer,
                    size_t *lenp, loff_t *ppos)
 {
         dentry_stat.nr_dentry = get_nr_dentry();
         dentry_stat.nr_unused = get_nr_dentry_unused();
+        dentry_stat.nr_negative = get_nr_dentry_negative();
         return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
 }
 #endif
@@ -317,6 +329,8 @@ static inline void __d_clear_type_and_inode(struct dentry *dentry)
         flags &= ~(DCACHE_ENTRY_TYPE | DCACHE_FALLTHRU);
         WRITE_ONCE(dentry->d_flags, flags);
         dentry->d_inode = NULL;
+        if (dentry->d_flags & DCACHE_LRU_LIST)
+                this_cpu_inc(nr_dentry_negative);
 }
 
 static void dentry_free(struct dentry *dentry)
@@ -371,6 +385,11 @@ static void dentry_unlink_inode(struct dentry * dentry)
  * The per-cpu "nr_dentry_unused" counters are updated with
  * the DCACHE_LRU_LIST bit.
  *
+ * The per-cpu "nr_dentry_negative" counters are only updated
+ * when deleted from or added to the per-superblock LRU list, not
+ * from/to the shrink list. That is to avoid an unneeded dec/inc
+ * pair when moving from LRU to shrink list in select_collect().
+ *
  * These helper functions make sure we always follow the
  * rules. d_lock must be held by the caller.
  */
@@ -380,6 +399,8 @@ static void d_lru_add(struct dentry *dentry)
         D_FLAG_VERIFY(dentry, 0);
         dentry->d_flags |= DCACHE_LRU_LIST;
         this_cpu_inc(nr_dentry_unused);
+        if (d_is_negative(dentry))
+                this_cpu_inc(nr_dentry_negative);
         WARN_ON_ONCE(!list_lru_add(&dentry->d_sb->s_dentry_lru, &dentry->d_lru));
 }
 
@@ -388,6 +409,8 @@ static void d_lru_del(struct dentry *dentry)
         D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
         dentry->d_flags &= ~DCACHE_LRU_LIST;
         this_cpu_dec(nr_dentry_unused);
+        if (d_is_negative(dentry))
+                this_cpu_dec(nr_dentry_negative);
         WARN_ON_ONCE(!list_lru_del(&dentry->d_sb->s_dentry_lru, &dentry->d_lru));
 }
 
@@ -418,6 +441,8 @@ static void d_lru_isolate(struct list_lru_one *lru, struct dentry *dentry)
         D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
         dentry->d_flags &= ~DCACHE_LRU_LIST;
         this_cpu_dec(nr_dentry_unused);
+        if (d_is_negative(dentry))
+                this_cpu_dec(nr_dentry_negative);
         list_lru_isolate(lru, &dentry->d_lru);
 }
 
@@ -426,6 +451,8 @@ static void d_lru_shrink_move(struct list_lru_one *lru, struct dentry *dentry,
 {
         D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
         dentry->d_flags |= DCACHE_SHRINK_LIST;
+        if (d_is_negative(dentry))
+                this_cpu_dec(nr_dentry_negative);
         list_lru_isolate_move(lru, &dentry->d_lru, list);
 }
 
@@ -1188,15 +1215,11 @@ static enum lru_status dentry_lru_isolate_shrink(struct list_head *item,
  */
 void shrink_dcache_sb(struct super_block *sb)
 {
-        long freed;
-
         do {
                 LIST_HEAD(dispose);
 
-                freed = list_lru_walk(&sb->s_dentry_lru,
+                list_lru_walk(&sb->s_dentry_lru,
                         dentry_lru_isolate_shrink, &dispose, 1024);
-
-                this_cpu_sub(nr_dentry_unused, freed);
                 shrink_dentry_list(&dispose);
         } while (list_lru_count(&sb->s_dentry_lru) > 0);
 }
@@ -1820,6 +1843,11 @@ static void __d_instantiate(struct dentry *dentry, struct inode *inode)
         WARN_ON(d_in_lookup(dentry));
 
         spin_lock(&dentry->d_lock);
+        /*
+         * Decrement negative dentry count if it was in the LRU list.
+         */
+        if (dentry->d_flags & DCACHE_LRU_LIST)
+                this_cpu_dec(nr_dentry_negative);
         hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
         raw_write_seqcount_begin(&dentry->d_seq);
         __d_set_inode_and_type(dentry, inode, add_flags);