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Commit b7b17c9b authored by NeilBrown's avatar NeilBrown
Browse files

md: remove mddev_lock() from md_attr_show() 



Most attributes can be read safely without any locking.
A race might lead to a slightly out-dated value, but nothing wrong.

We already have locking in some places where needed.
All that remains is can_clear_show(), behind_writes_used_show()
and action_show() which are easily fixed.

Signed-off-by: default avatarNeilBrown <neilb@suse.de>
parent 7b1485ba

drivers/md/bitmap.c

+10 −3
Original line number Diff line number Diff line
@@ -2211,11 +2211,13 @@ __ATTR(metadata, S_IRUGO|S_IWUSR, metadata_show, metadata_store); 
static ssize_t can_clear_show(struct mddev *mddev, char *page)

{

	int len;

	spin_lock(&mddev->lock);

	if (mddev->bitmap)

		len = sprintf(page, "%s\n", (mddev->bitmap->need_sync ?

					     "false" : "true"));

	else

		len = sprintf(page, "\n");

	spin_unlock(&mddev->lock);

	return len;

}
@@ -2240,10 +2242,15 @@ __ATTR(can_clear, S_IRUGO|S_IWUSR, can_clear_show, can_clear_store); 
static ssize_t

behind_writes_used_show(struct mddev *mddev, char *page)

{

	ssize_t ret;

	spin_lock(&mddev->lock);

	if (mddev->bitmap == NULL)

		return sprintf(page, "0\n");

	return sprintf(page, "%lu\n",

		ret = sprintf(page, "0\n");

	else

		ret = sprintf(page, "%lu\n",

			      mddev->bitmap->behind_writes_used);

	spin_unlock(&mddev->lock);

	return ret;

}



static ssize_t

drivers/md/md.c

+10 −13
Original line number Diff line number Diff line
@@ -4042,20 +4042,21 @@ static ssize_t 
action_show(struct mddev *mddev, char *page)

{

	char *type = "idle";

	if (test_bit(MD_RECOVERY_FROZEN, &mddev->recovery))

	unsigned long recovery = mddev->recovery;

	if (test_bit(MD_RECOVERY_FROZEN, &recovery))

		type = "frozen";

	else if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) ||

	    (!mddev->ro && test_bit(MD_RECOVERY_NEEDED, &mddev->recovery))) {

		if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))

	else if (test_bit(MD_RECOVERY_RUNNING, &recovery) ||

	    (!mddev->ro && test_bit(MD_RECOVERY_NEEDED, &recovery))) {

		if (test_bit(MD_RECOVERY_RESHAPE, &recovery))

			type = "reshape";

		else if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {

			if (!test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))

		else if (test_bit(MD_RECOVERY_SYNC, &recovery)) {

			if (!test_bit(MD_RECOVERY_REQUESTED, &recovery))

				type = "resync";

			else if (test_bit(MD_RECOVERY_CHECK, &mddev->recovery))

			else if (test_bit(MD_RECOVERY_CHECK, &recovery))

				type = "check";

			else

				type = "repair";

		} else if (test_bit(MD_RECOVERY_RECOVER, &mddev->recovery))

		} else if (test_bit(MD_RECOVERY_RECOVER, &recovery))

			type = "recover";

	}

	return sprintf(page, "%s\n", type);
@@ -4572,11 +4573,7 @@ md_attr_show(struct kobject *kobj, struct attribute *attr, char *page) 
	mddev_get(mddev);

	spin_unlock(&all_mddevs_lock);



	rv = mddev_lock(mddev);

	if (!rv) {

	rv = entry->show(mddev, page);

		mddev_unlock(mddev);

	}

	mddev_put(mddev);

	return rv;

}