---

yaml
---
r: 217804
b: refs/heads/master
c: f991bd2
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 7de9c6ee3ecffd99e1628e81a5ea5468f7581a1f
+refs/heads/master: f991bd2e14210fb93d722cb23e54991de20e8a3d

trunk/fs/inode.c

@@ -717,6 +717,43 @@ static struct inode *find_inode_fast(struct super_block *sb,
 	return NULL;
 }
 
+/*
+ * Each cpu owns a range of LAST_INO_BATCH numbers.
+ * 'shared_last_ino' is dirtied only once out of LAST_INO_BATCH allocations,
+ * to renew the exhausted range.
+ *
+ * This does not significantly increase overflow rate because every CPU can
+ * consume at most LAST_INO_BATCH-1 unused inode numbers. So there is
+ * NR_CPUS*(LAST_INO_BATCH-1) wastage. At 4096 and 1024, this is ~0.1% of the
+ * 2^32 range, and is a worst-case. Even a 50% wastage would only increase
+ * overflow rate by 2x, which does not seem too significant.
+ *
+ * On a 32bit, non LFS stat() call, glibc will generate an EOVERFLOW
+ * error if st_ino won't fit in target struct field. Use 32bit counter
+ * here to attempt to avoid that.
+ */
+#define LAST_INO_BATCH 1024
+static DEFINE_PER_CPU(unsigned int, last_ino);
+
+static unsigned int get_next_ino(void)
+{
+	unsigned int *p = &get_cpu_var(last_ino);
+	unsigned int res = *p;
+
+#ifdef CONFIG_SMP
+	if (unlikely((res & (LAST_INO_BATCH-1)) == 0)) {
+		static atomic_t shared_last_ino;
+		int next = atomic_add_return(LAST_INO_BATCH, &shared_last_ino);
+
+		res = next - LAST_INO_BATCH;
+	}
+#endif
+
+	*p = ++res;
+	put_cpu_var(last_ino);
+	return res;
+}
+
 /**
  *	new_inode 	- obtain an inode
  *	@sb: superblock
@@ -731,12 +768,6 @@ static struct inode *find_inode_fast(struct super_block *sb,
  */
 struct inode *new_inode(struct super_block *sb)
 {
-	/*
-	 * On a 32bit, non LFS stat() call, glibc will generate an EOVERFLOW
-	 * error if st_ino won't fit in target struct field. Use 32bit counter
-	 * here to attempt to avoid that.
-	 */
-	static unsigned int last_ino;
 	struct inode *inode;
 
 	spin_lock_prefetch(&inode_lock);
@@ -745,7 +776,7 @@ struct inode *new_inode(struct super_block *sb)
 	if (inode) {
 		spin_lock(&inode_lock);
 		__inode_sb_list_add(inode);
-		inode->i_ino = ++last_ino;
+		inode->i_ino = get_next_ino();
 		inode->i_state = 0;
 		spin_unlock(&inode_lock);
 	}