1 files changed, 187 insertions, 31 deletions

diff --git a/block/genhd.c b/block/genhd.c
index fa32d09fda2..b431d654394 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -26,6 +26,158 @@ struct kobject *block_depr;
 
 static struct device_type disk_type;
 
+/**
+ * disk_get_part - get partition
+ * @disk: disk to look partition from
+ * @partno: partition number
+ *
+ * Look for partition @partno from @disk.  If found, increment
+ * reference count and return it.
+ *
+ * CONTEXT:
+ * Don't care.
+ *
+ * RETURNS:
+ * Pointer to the found partition on success, NULL if not found.
+ */
+struct hd_struct *disk_get_part(struct gendisk *disk, int partno)
+{
+	struct hd_struct *part;
+
+	if (unlikely(partno < 1 || partno > disk_max_parts(disk)))
+		return NULL;
+	rcu_read_lock();
+	part = rcu_dereference(disk->__part[partno - 1]);
+	if (part)
+		get_device(&part->dev);
+	rcu_read_unlock();
+
+	return part;
+}
+EXPORT_SYMBOL_GPL(disk_get_part);
+
+/**
+ * disk_part_iter_init - initialize partition iterator
+ * @piter: iterator to initialize
+ * @disk: disk to iterate over
+ * @flags: DISK_PITER_* flags
+ *
+ * Initialize @piter so that it iterates over partitions of @disk.
+ *
+ * CONTEXT:
+ * Don't care.
+ */
+void disk_part_iter_init(struct disk_part_iter *piter, struct gendisk *disk,
+			  unsigned int flags)
+{
+	piter->disk = disk;
+	piter->part = NULL;
+
+	if (flags & DISK_PITER_REVERSE)
+		piter->idx = disk_max_parts(piter->disk) - 1;
+	else
+		piter->idx = 0;
+
+	piter->flags = flags;
+}
+EXPORT_SYMBOL_GPL(disk_part_iter_init);
+
+/**
+ * disk_part_iter_next - proceed iterator to the next partition and return it
+ * @piter: iterator of interest
+ *
+ * Proceed @piter to the next partition and return it.
+ *
+ * CONTEXT:
+ * Don't care.
+ */
+struct hd_struct *disk_part_iter_next(struct disk_part_iter *piter)
+{
+	int inc, end;
+
+	/* put the last partition */
+	disk_put_part(piter->part);
+	piter->part = NULL;
+
+	rcu_read_lock();
+
+	/* determine iteration parameters */
+	if (piter->flags & DISK_PITER_REVERSE) {
+		inc = -1;
+		end = -1;
+	} else {
+		inc = 1;
+		end = disk_max_parts(piter->disk);
+	}
+
+	/* iterate to the next partition */
+	for (; piter->idx != end; piter->idx += inc) {
+		struct hd_struct *part;
+
+		part = rcu_dereference(piter->disk->__part[piter->idx]);
+		if (!part)
+			continue;
+		if (!(piter->flags & DISK_PITER_INCL_EMPTY) && !part->nr_sects)
+			continue;
+
+		get_device(&part->dev);
+		piter->part = part;
+		piter->idx += inc;
+		break;
+	}
+
+	rcu_read_unlock();
+
+	return piter->part;
+}
+EXPORT_SYMBOL_GPL(disk_part_iter_next);
+
+/**
+ * disk_part_iter_exit - finish up partition iteration
+ * @piter: iter of interest
+ *
+ * Called when iteration is over.  Cleans up @piter.
+ *
+ * CONTEXT:
+ * Don't care.
+ */
+void disk_part_iter_exit(struct disk_part_iter *piter)
+{
+	disk_put_part(piter->part);
+	piter->part = NULL;
+}
+EXPORT_SYMBOL_GPL(disk_part_iter_exit);
+
+/**
+ * disk_map_sector_rcu - map sector to partition
+ * @disk: gendisk of interest
+ * @sector: sector to map
+ *
+ * Find out which partition @sector maps to on @disk.  This is
+ * primarily used for stats accounting.
+ *
+ * CONTEXT:
+ * RCU read locked.  The returned partition pointer is valid only
+ * while preemption is disabled.
+ *
+ * RETURNS:
+ * Found partition on success, NULL if there's no matching partition.
+ */
+struct hd_struct *disk_map_sector_rcu(struct gendisk *disk, sector_t sector)
+{
+	int i;
+
+	for (i = 0; i < disk_max_parts(disk); i++) {
+		struct hd_struct *part = rcu_dereference(disk->__part[i]);
+
+		if (part && part->start_sect <= sector &&
+		    sector < part->start_sect + part->nr_sects)
+			return part;
+	}
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(disk_map_sector_rcu);
+
 /*
  * Can be deleted altogether. Later.
  *
@@ -245,10 +397,12 @@ extern struct block_device *bdget_disk(struct gendisk *disk, int partno)
 	if (partno == 0)
 		devt = disk_devt(disk);
 	else {
-		struct hd_struct *part = disk->part[partno - 1];
+		struct hd_struct *part;
 
+		part = disk_get_part(disk, partno);
 		if (part && part->nr_sects)
 			devt = part_devt(part);
+		disk_put_part(part);
 	}
 
 	if (likely(devt != MKDEV(0, 0)))
@@ -270,8 +424,9 @@ void __init printk_all_partitions(void)
 	class_dev_iter_init(&iter, &block_class, NULL, &disk_type);
 	while ((dev = class_dev_iter_next(&iter))) {
 		struct gendisk *disk = dev_to_disk(dev);
+		struct disk_part_iter piter;
+		struct hd_struct *part;
 		char buf[BDEVNAME_SIZE];
-		int n;
 
 		/*
 		 * Don't show empty devices or things that have been
@@ -298,16 +453,13 @@ void __init printk_all_partitions(void)
 			printk(" (driver?)\n");
 
 		/* now show the partitions */
-		for (n = 0; n < disk_max_parts(disk); ++n) {
-			struct hd_struct *part = disk->part[n];
-
-			if (!part || !part->nr_sects)
-				continue;
+		disk_part_iter_init(&piter, disk, 0);
+		while ((part = disk_part_iter_next(&piter)))
 			printk("  %02x%02x %10llu %s\n",
 			       MAJOR(part_devt(part)), MINOR(part_devt(part)),
 			       (unsigned long long)part->nr_sects >> 1,
 			       disk_name(disk, part->partno, buf));
-		}
+		disk_part_iter_exit(&piter);
 	}
 	class_dev_iter_exit(&iter);
 }
@@ -371,7 +523,8 @@ static void *show_partition_start(struct seq_file *seqf, loff_t *pos)
 static int show_partition(struct seq_file *seqf, void *v)
 {
 	struct gendisk *sgp = v;
-	int n;
+	struct disk_part_iter piter;
+	struct hd_struct *part;
 	char buf[BDEVNAME_SIZE];
 
 	/* Don't show non-partitionable removeable devices or empty devices */
@@ -386,17 +539,14 @@ static int show_partition(struct seq_file *seqf, void *v)
 		MAJOR(disk_devt(sgp)), MINOR(disk_devt(sgp)),
 		(unsigned long long)get_capacity(sgp) >> 1,
 		disk_name(sgp, 0, buf));
-	for (n = 0; n < disk_max_parts(sgp); n++) {
-		struct hd_struct *part = sgp->part[n];
-		if (!part)
-			continue;
-		if (part->nr_sects == 0)
-			continue;
+
+	disk_part_iter_init(&piter, sgp, 0);
+	while ((part = disk_part_iter_next(&piter)))
 		seq_printf(seqf, "%4d  %4d %10llu %s\n",
 			   MAJOR(part_devt(part)), MINOR(part_devt(part)),
 			   (unsigned long long)part->nr_sects >> 1,
 			   disk_name(sgp, part->partno, buf));
-	}
+	disk_part_iter_exit(&piter);
 
 	return 0;
 }
@@ -571,7 +721,7 @@ static void disk_release(struct device *dev)
 	struct gendisk *disk = dev_to_disk(dev);
 
 	kfree(disk->random);
-	kfree(disk->part);
+	kfree(disk->__part);
 	free_disk_stats(disk);
 	kfree(disk);
 }
@@ -596,8 +746,9 @@ static struct device_type disk_type = {
 static int diskstats_show(struct seq_file *seqf, void *v)
 {
 	struct gendisk *gp = v;
+	struct disk_part_iter piter;
+	struct hd_struct *hd;
 	char buf[BDEVNAME_SIZE];
-	int n;
 
 	/*
 	if (&gp->dev.kobj.entry == block_class.devices.next)
@@ -624,12 +775,8 @@ static int diskstats_show(struct seq_file *seqf, void *v)
 		jiffies_to_msecs(disk_stat_read(gp, time_in_queue)));
 
 	/* now show all non-0 size partitions of it */
-	for (n = 0; n < disk_max_parts(gp); n++) {
-		struct hd_struct *hd = gp->part[n];
-
-		if (!hd || !hd->nr_sects)
-			continue;
-
+	disk_part_iter_init(&piter, gp, 0);
+	while ((hd = disk_part_iter_next(&piter))) {
 		preempt_disable();
 		part_round_stats(hd);
 		preempt_enable();
@@ -650,6 +797,7 @@ static int diskstats_show(struct seq_file *seqf, void *v)
 			   jiffies_to_msecs(part_stat_read(hd, time_in_queue))
 			);
 	}
+	disk_part_iter_exit(&piter);
  
 	return 0;
 }
@@ -703,12 +851,16 @@ dev_t blk_lookup_devt(const char *name, int partno)
 		if (partno == 0)
 			devt = disk_devt(disk);
 		else {
-			struct hd_struct *part = disk->part[partno - 1];
+			struct hd_struct *part;
 
-			if (!part || !part->nr_sects)
+			part = disk_get_part(disk, partno);
+			if (!part || !part->nr_sects) {
+				disk_put_part(part);
 				continue;
+			}
 
 			devt = part_devt(part);
+			disk_put_part(part);
 		}
 		break;
 	}
@@ -735,9 +887,9 @@ struct gendisk *alloc_disk_node(int minors, int node_id)
 		}
 		if (minors > 1) {
 			int size = (minors - 1) * sizeof(struct hd_struct *);
-			disk->part = kmalloc_node(size,
+			disk->__part = kmalloc_node(size,
 				GFP_KERNEL | __GFP_ZERO, node_id);
-			if (!disk->part) {
+			if (!disk->__part) {
 				free_disk_stats(disk);
 				kfree(disk);
 				return NULL;
@@ -798,10 +950,14 @@ EXPORT_SYMBOL(set_device_ro);
 
 void set_disk_ro(struct gendisk *disk, int flag)
 {
-	int i;
+	struct disk_part_iter piter;
+	struct hd_struct *part;
+
 	disk->policy = flag;
-	for (i = 0; i < disk_max_parts(disk); i++)
-		if (disk->part[i]) disk->part[i]->policy = flag;
+	disk_part_iter_init(&piter, disk, DISK_PITER_INCL_EMPTY);
+	while ((part = disk_part_iter_next(&piter)))
+		part->policy = flag;
+	disk_part_iter_exit(&piter);
 }
 
 EXPORT_SYMBOL(set_disk_ro);