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Date: Sat, 12 Sep 2009 13:45:03 +0200
From: devzero@....de
To: linux-kernel@...r.kernel.org
Cc: Hannes Reinecke <hare@...e.de>,
"Randy.Dunlap" <rdunlap@...otime.net>
Subject: Re: [PATCH] Disable partition scan
Hello,
iirc i had a setup a while ago where i also found disabling partition scanning would be nice to have.
actually, we have a bugzilla entry for this - have a look at:
http://bugzilla.kernel.org/show_bug.cgi?id=8588
anyway, wouldn`t it be better to disable that on a per device basis or at least be able to exclude
the boot/system devices from being skipped?
regards
roland
>Hi all again,
>
>Hannes Reinecke wrote:
>> Hi all,
>>
>> for some setups (eg dmraid or multipathing) the in-kernel partition scan
>> is pointless; the (block) partitions won't be used anywhere. Instead the
>> system will be using kpartx-generated device-mapper devices.
>> Worse, on some setups (RAID0 dmraid or active/passive multipath devices)
>> the in-kernel partition scan will generate plenty of I/O errors as the
>> partitions table might not be accessible or invalid for this device.
>>
>> This patch implements a new kernel command-line option 'no_partition_scan'
>> which will switch off the partition scan globally. The partition scan can
>> be re-enabled for individual devices by echoing any positive number smaller
>> than the number of minors into
>> /sys/class/block/XXX/range
>>
>> and rescanning the device.
>>
>> Please apply.
>>
>Yeah, cool. One should take care not to mangle to patches.
>Should teach me to use git properly. Oh well.
>
>Corrected patch attached.
>
>Cheers,
>
>Hannes
>
>--
>Dr. Hannes Reinecke zSeries & Storage
>hare@...e.de +49 911 74053 688
>SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
>GF: Markus Rex, HRB 16746 (AG Nürnberg)
["no-partition-scan" (text/plain)]
Disable partition scan
For some setups (multipath or dmraid) the in-kernel partition scan
is pointless as the (block) partitions won't be used anywhere.
Worse, it might trigger I/O errors as the partition table might not
be accessible (eg for the passive path of a multipath device) or
even invalid (eg for RAID0 dmraid).
This patch allows to switch off the in-kernel partition scan by adding
'no_partition_scan' to the kernel commandline. Partitions scan can be
allowed for individual disk by echoing a positive number into
/sys/block/XXX/range and rescan the disk.
Signed-off-by: Hannes Reinecke <hare@...e.de>
diff --git a/block/genhd.c b/block/genhd.c
index 656c2c7..3d6a53b 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -173,6 +173,18 @@ static int exact_lock(dev_t devt, void *data)
return 0;
}
+static int __read_mostly no_partition_scan;
+
+static int __init no_partition_scan_setup(char *str)
+{
+ no_partition_scan = 1;
+ printk(KERN_INFO "genhd: omit partition scan.\n");
+
+ return 1;
+}
+
+__setup("no_partition_scan", no_partition_scan_setup);
+
/**
* add_disk - add partitioning information to kernel list
* @disk: per-device partitioning information
@@ -186,6 +198,8 @@ void add_disk(struct gendisk *disk)
int retval;
disk->flags |= GENHD_FL_UP;
+ if (no_partition_scan)
+ disk->flags |= GENHD_FL_NO_PARTITION_SCAN;
blk_register_region(MKDEV(disk->major, disk->first_minor),
disk->minors, NULL, exact_match, exact_lock, disk);
register_disk(disk);
@@ -419,7 +433,27 @@ static ssize_t disk_range_show(struct device *dev,
{
struct gendisk *disk = dev_to_disk(dev);
- return sprintf(buf, "%d\n", disk->minors);
+ return sprintf(buf, "%d\n",
+ (disk->flags & GENHD_FL_NO_PARTITION_SCAN ? 0 : disk->minors));
+}
+
+static ssize_t disk_range_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct gendisk *disk = dev_to_disk(dev);
+ int i;
+
+ if (count > 0 && sscanf(buf, "%d", &i) > 0) {
+ if (i == 0)
+ disk->flags |= GENHD_FL_NO_PARTITION_SCAN;
+ else if (i <= disk->minors)
+ disk->flags &= ~GENHD_FL_NO_PARTITION_SCAN;
+ else
+ count = -EINVAL;
+ }
+
+ return count;
}
static ssize_t disk_removable_show(struct device *dev,
@@ -509,7 +543,7 @@ static ssize_t disk_fail_store(struct device *dev,
#endif
-static DEVICE_ATTR(range, S_IRUGO, disk_range_show, NULL);
+static DEVICE_ATTR(range, S_IRUGO|S_IWUSR, disk_range_show, disk_range_store);
static DEVICE_ATTR(removable, S_IRUGO, disk_removable_show, NULL);
static DEVICE_ATTR(ro, S_IRUGO, disk_ro_show, NULL);
static DEVICE_ATTR(size, S_IRUGO, disk_size_show, NULL);
diff --git a/fs/partitions/check.c b/fs/partitions/check.c
index 7d6b34e..a73f6dc 100644
--- a/fs/partitions/check.c
+++ b/fs/partitions/check.c
@@ -485,6 +485,8 @@ int rescan_partitions(struct gendisk *disk, struct block_device *bdev)
delete_partition(disk, p);
if (disk->fops->revalidate_disk)
disk->fops->revalidate_disk(disk);
+ if (disk->flags & GENHD_FL_NO_PARTITION_SCAN)
+ return 0;
if (!get_capacity(disk) || !(state = check_partition(disk, bdev)))
return 0;
if (IS_ERR(state)) /* I/O error reading the partition table */
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 118216f..87c45ad 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -109,6 +109,7 @@ struct hd_struct {
#define GENHD_FL_UP 16
#define GENHD_FL_SUPPRESS_PARTITION_INFO 32
#define GENHD_FL_FAIL 64
+#define GENHD_FL_NO_PARTITION_SCAN 128
#define BLK_SCSI_MAX_CMDS (256)
#define BLK_SCSI_CMD_PER_LONG (BLK_SCSI_MAX_CMDS / (sizeof(long) * 8))
diff --git a/include/linux/virtio_blk.h b/include/linux/virtio_blk.h
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