#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"
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;
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);
}
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:
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);