X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=blobdiff_plain;f=drivers%2Fmd%2Flinear.c;h=a118c5a90dd793eafb080eac42763020690e68fe;hp=a82035867519c944b7e6b93f6aca110d5354a3ff;hb=a5a3182e50b5be88efd01050ba6f35e2d0aaee03;hpb=208bca0860406d16398145ddd950036a737c3c9d

diff --git a/drivers/md/linear.c b/drivers/md/linear.c
index a82035867519..a118c5a90dd7 100644
--- a/drivers/md/linear.c
+++ b/drivers/md/linear.c
@@ -19,6 +19,7 @@
 #include <linux/blkdev.h>
 #include <linux/raid/md_u.h>
 #include <linux/seq_file.h>
+#include <linux/module.h>
 #include <linux/slab.h>
 #include "md.h"
 #include "linear.h"
@@ -87,6 +88,12 @@ static int linear_mergeable_bvec(struct request_queue *q,
 	return maxsectors << 9;
 }
 
+/*
+ * In linear_congested() conf->raid_disks is used as a copy of
+ * mddev->raid_disks to iterate conf->disks[], because conf->raid_disks
+ * and conf->disks[] are created in linear_conf(), they are always
+ * consitent with each other, but mddev->raid_disks does not.
+ */
 static int linear_congested(void *data, int bits)
 {
 	struct mddev *mddev = data;
@@ -99,7 +106,7 @@ static int linear_congested(void *data, int bits)
 	rcu_read_lock();
 	conf = rcu_dereference(mddev->private);
 
-	for (i = 0; i < mddev->raid_disks && !ret ; i++) {
+	for (i = 0; i < conf->raid_disks && !ret ; i++) {
 		struct request_queue *q = bdev_get_queue(conf->disks[i].rdev->bdev);
 		ret |= bdi_congested(&q->backing_dev_info, bits);
 	}
@@ -187,6 +194,19 @@ static struct linear_conf *linear_conf(struct mddev *mddev, int raid_disks)
 			conf->disks[i-1].end_sector +
 			conf->disks[i].rdev->sectors;
 
+	/*
+	 * conf->raid_disks is copy of mddev->raid_disks. The reason to
+	 * keep a copy of mddev->raid_disks in struct linear_conf is,
+	 * mddev->raid_disks may not be consistent with pointers number of
+	 * conf->disks[] when it is updated in linear_add() and used to
+	 * iterate old conf->disks[] earray in linear_congested().
+	 * Here conf->raid_disks is always consitent with number of
+	 * pointers in conf->disks[] array, and mddev->private is updated
+	 * with rcu_assign_pointer() in linear_addr(), such race can be
+	 * avoided.
+	 */
+	conf->raid_disks = raid_disks;
+
 	return conf;
 
 out:
@@ -229,14 +249,23 @@ static int linear_add(struct mddev *mddev, struct md_rdev *rdev)
 		return -EINVAL;
 
 	rdev->raid_disk = rdev->saved_raid_disk;
+	rdev->saved_raid_disk = -1;
 
 	newconf = linear_conf(mddev,mddev->raid_disks+1);
 
 	if (!newconf)
 		return -ENOMEM;
 
+	/* newconf->raid_disks already keeps a copy of * the increased
+	 * value of mddev->raid_disks, WARN_ONCE() is just used to make
+	 * sure of this. It is possible that oldconf is still referenced
+	 * in linear_congested(), therefore kfree_rcu() is used to free
+	 * oldconf until no one uses it anymore.
+	 */
 	oldconf = rcu_dereference(mddev->private);
 	mddev->raid_disks++;
+	WARN_ONCE(mddev->raid_disks != newconf->raid_disks,
+		"copied raid_disks doesn't match mddev->raid_disks");
 	rcu_assign_pointer(mddev->private, newconf);
 	md_set_array_sectors(mddev, linear_size(mddev, 0, 0));
 	set_capacity(mddev->gendisk, mddev->array_sectors);