1 files changed, 39 insertions, 14 deletions

diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 0ff75329199c..7fbba19e076b 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -11,6 +11,7 @@
 
 #include <linux/types.h>
 #include <linux/kdev_t.h>
+#include <linux/rcupdate.h>
 
 #ifdef CONFIG_BLOCK
 
@@ -100,6 +101,7 @@ struct hd_struct {
 #else
         struct disk_stats dkstats;
 #endif
+        struct rcu_head rcu_head;
 };
 
 #define GENHD_FL_REMOVABLE                      1
@@ -120,7 +122,14 @@ struct gendisk {
                                          * disks that can't be partitioned. */
 
         char disk_name[32];             /* name of major driver */
-        struct hd_struct **part;        /* [indexed by minor - 1] */
+
+        /* Array of pointers to partitions indexed by partno - 1.
+         * Protected with matching bdev lock but stat and other
+         * non-critical accesses use RCU.  Always access through
+         * helpers.
+         */
+        struct hd_struct **__part;
+
         struct block_device_operations *fops;
         struct request_queue *queue;
         void *private_data;
@@ -171,25 +180,41 @@ static inline dev_t part_devt(struct hd_struct *part)
         return part->dev.devt;
 }
 
+extern struct hd_struct *disk_get_part(struct gendisk *disk, int partno);
+
+static inline void disk_put_part(struct hd_struct *part)
+{
+        if (likely(part))
+                put_device(&part->dev);
+}
+
+/*
+ * Smarter partition iterator without context limits.
+ */
+#define DISK_PITER_REVERSE      (1 << 0) /* iterate in the reverse direction */
+#define DISK_PITER_INCL_EMPTY   (1 << 1) /* include 0-sized parts */
+
+struct disk_part_iter {
+        struct gendisk          *disk;
+        struct hd_struct        *part;
+        int                     idx;
+        unsigned int            flags;
+};
+
+extern void disk_part_iter_init(struct disk_part_iter *piter,
+                                 struct gendisk *disk, unsigned int flags);
+extern struct hd_struct *disk_part_iter_next(struct disk_part_iter *piter);
+extern void disk_part_iter_exit(struct disk_part_iter *piter);
+
+extern struct hd_struct *disk_map_sector_rcu(struct gendisk *disk,
+                                             sector_t sector);
+
 /* 
  * Macros to operate on percpu disk statistics:
  *
  * The __ variants should only be called in critical sections. The full
  * variants disable/enable preemption.
  */
-static inline struct hd_struct *disk_map_sector(struct gendisk *gendiskp,
-                                                sector_t sector)
-{
-        struct hd_struct *part;
-        int i;
-        for (i = 0; i < disk_max_parts(gendiskp); i++) {
-                part = gendiskp->part[i];
-                if (part && part->start_sect <= sector
-                    && sector < part->start_sect + part->nr_sects)
-                        return part;
-        }
-        return NULL;
-}
 
 #ifdef  CONFIG_SMP
 #define __disk_stat_add(gendiskp, field, addnd)         \