[patch 15/58] block: include empty disks in /proc/diskstats

[Greg KH <gregkh@suse.de>]

[-- Attachment #1: block-include-empty-disks-in-proc-diskstats.patch --]
[-- Type: text/plain, Size: 2817 bytes --]

2.6.29-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Tejun Heo <tj@kernel.org>

commit 71982a409f12c50d011325a4471aa20666bb908d upstream.

/proc/diskstats used to show stats for all disks whether they're
zero-sized or not and their non-zero partitions.  Commit
074a7aca7afa6f230104e8e65eba3420263714a5 accidentally changed the
behavior such that it doesn't print out zero sized disks.  This patch
implements DISK_PITER_INCL_EMPTY_PART0 flag to partition iterator and
uses it in diskstats_show() such that empty part0 is shown in
/proc/diskstats.

Reported and bisectd by Dianel Collins.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Daniel Collins <solemnwarning@solemnwarning.no-ip.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 block/genhd.c         |   12 ++++++++----
 include/linux/genhd.h |    1 +
 2 files changed, 9 insertions(+), 4 deletions(-)

--- a/block/genhd.c
+++ b/block/genhd.c
@@ -98,7 +98,7 @@ void disk_part_iter_init(struct disk_par
 
 	if (flags & DISK_PITER_REVERSE)
 		piter->idx = ptbl->len - 1;
-	else if (flags & DISK_PITER_INCL_PART0)
+	else if (flags & (DISK_PITER_INCL_PART0 | DISK_PITER_INCL_EMPTY_PART0))
 		piter->idx = 0;
 	else
 		piter->idx = 1;
@@ -134,7 +134,8 @@ struct hd_struct *disk_part_iter_next(st
 	/* determine iteration parameters */
 	if (piter->flags & DISK_PITER_REVERSE) {
 		inc = -1;
-		if (piter->flags & DISK_PITER_INCL_PART0)
+		if (piter->flags & (DISK_PITER_INCL_PART0 |
+				    DISK_PITER_INCL_EMPTY_PART0))
 			end = -1;
 		else
 			end = 0;
@@ -150,7 +151,10 @@ struct hd_struct *disk_part_iter_next(st
 		part = rcu_dereference(ptbl->part[piter->idx]);
 		if (!part)
 			continue;
-		if (!(piter->flags & DISK_PITER_INCL_EMPTY) && !part->nr_sects)
+		if (!part->nr_sects &&
+		    !(piter->flags & DISK_PITER_INCL_EMPTY) &&
+		    !(piter->flags & DISK_PITER_INCL_EMPTY_PART0 &&
+		      piter->idx == 0))
 			continue;
 
 		get_device(part_to_dev(part));
@@ -1011,7 +1015,7 @@ static int diskstats_show(struct seq_fil
 				"\n\n");
 	*/
  
-	disk_part_iter_init(&piter, gp, DISK_PITER_INCL_PART0);
+	disk_part_iter_init(&piter, gp, DISK_PITER_INCL_EMPTY_PART0);
 	while ((hd = disk_part_iter_next(&piter))) {
 		cpu = part_stat_lock();
 		part_round_stats(cpu, hd);
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -214,6 +214,7 @@ static inline void disk_put_part(struct 
 #define DISK_PITER_REVERSE	(1 << 0) /* iterate in the reverse direction */
 #define DISK_PITER_INCL_EMPTY	(1 << 1) /* include 0-sized parts */
 #define DISK_PITER_INCL_PART0	(1 << 2) /* include partition 0 */
+#define DISK_PITER_INCL_EMPTY_PART0 (1 << 3) /* include empty partition 0 */
 
 struct disk_part_iter {
 	struct gendisk		*disk;