block: fix disk->part[] dereferencing race

[linux-2.6-omap-h63xx.git] / include / linux / genhd.h

diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 0ff75329199c38e4ab2ad78f5b32eda45c65f327..7fbba19e076bedf62b31664c9aaf227953b6e4a6 100644 (file)
--- 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)        \