---

yaml
---
r: 123301
b: refs/heads/master
c: a6f2365
h: refs/heads/master
i:
  123299: 7148b02
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 30e0dc28bff9dc456cdfc2aae4aca78b8b1a1cec
+refs/heads/master: a6f23657d3072bde6844055bbc2290e497f33fbc

trunk/block/genhd.c

@@ -181,6 +181,12 @@ void disk_part_iter_exit(struct disk_part_iter *piter)
 }
 EXPORT_SYMBOL_GPL(disk_part_iter_exit);
 
+static inline int sector_in_part(struct hd_struct *part, sector_t sector)
+{
+	return part->start_sect <= sector &&
+		sector < part->start_sect + part->nr_sects;
+}
+
 /**
  * disk_map_sector_rcu - map sector to partition
  * @disk: gendisk of interest
@@ -199,16 +205,22 @@ EXPORT_SYMBOL_GPL(disk_part_iter_exit);
 struct hd_struct *disk_map_sector_rcu(struct gendisk *disk, sector_t sector)
 {
 	struct disk_part_tbl *ptbl;
+	struct hd_struct *part;
 	int i;
 
 	ptbl = rcu_dereference(disk->part_tbl);
 
+	part = rcu_dereference(ptbl->last_lookup);
+	if (part && sector_in_part(part, sector))
+		return part;
+
 	for (i = 1; i < ptbl->len; i++) {
-		struct hd_struct *part = rcu_dereference(ptbl->part[i]);
+		part = rcu_dereference(ptbl->part[i]);
 
-		if (part && part->start_sect <= sector &&
-		    sector < part->start_sect + part->nr_sects)
+		if (part && sector_in_part(part, sector)) {
+			rcu_assign_pointer(ptbl->last_lookup, part);
 			return part;
+		}
 	}
 	return &disk->part0;
 }
@@ -888,8 +900,11 @@ static void disk_replace_part_tbl(struct gendisk *disk,
 	struct disk_part_tbl *old_ptbl = disk->part_tbl;
 
 	rcu_assign_pointer(disk->part_tbl, new_ptbl);
-	if (old_ptbl)
+
+	if (old_ptbl) {
+		rcu_assign_pointer(old_ptbl->last_lookup, NULL);
 		call_rcu(&old_ptbl->rcu_head, disk_free_ptbl_rcu_cb);
+	}
 }
 
 /**

trunk/include/linux/genhd.h

@@ -126,6 +126,7 @@ struct blk_scsi_cmd_filter {
 struct disk_part_tbl {
 	struct rcu_head rcu_head;
 	int len;
+	struct hd_struct *last_lookup;
 	struct hd_struct *part[];
 };