LinuxLists.cc - [PATCH] Disable partition scan

2008-08-27 10:31:49

Subject: [PATCH] Disable partition scan

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 <[email protected]>

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/block/scsi_ioctl.c b/block/scsi_ioctl.c
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 4225109..dfcdef1 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -72,7 +72,7 @@ static void blk_done(struct virtqueue *vq)
static bool do_req(struct request_queue *q, struct virtio_blk *vblk,
struct request *req)
{
- unsigned long num, out, in;
+ unsigned long num, out = 1, in = 1;
struct virtblk_req *vbr;

vbr = mempool_alloc(vblk->pool, GFP_ATOMIC);
@@ -100,19 +100,26 @@ static bool do_req(struct request_queue *q, struct virtio_blk *vblk,
/* This init could be done at vblk creation time */
sg_init_table(vblk->sg, VIRTIO_MAX_SG);
sg_set_buf(&vblk->sg[0], &vbr->out_hdr, sizeof(vbr->out_hdr));
- num = blk_rq_map_sg(q, vbr->req, vblk->sg+1);
- sg_set_buf(&vblk->sg[num+1], &vbr->status, sizeof(vbr->status));
-
- if (rq_data_dir(vbr->req) == WRITE) {
- vbr->out_hdr.type |= VIRTIO_BLK_T_OUT;
- out = 1 + num;
- in = 1;
- } else {
- vbr->out_hdr.type |= VIRTIO_BLK_T_IN;
- out = 1;
- in = 1 + num;
+ if (blk_pc_request(vbr->req)) {
+ sg_set_buf(&vblk->sg[out], &vbr->req->cmd, vbr->req->cmd_len);
+ out++;
+ }
+ num = blk_rq_map_sg(q, vbr->req, vblk->sg+out);
+ sg_set_buf(&vblk->sg[num+out], &vbr->status, sizeof(vbr->status));
+ if (blk_pc_request(vbr->req)) {
+ sg_set_buf(&vblk->sg[num+out+1], &vbr->req->sense, 96);
+ in++;
}

+ if (vbr->req->data_len) {
+ if (rq_data_dir(vbr->req) == WRITE) {
+ vbr->out_hdr.type |= VIRTIO_BLK_T_OUT;
+ out += num;
+ } else {
+ vbr->out_hdr.type |= VIRTIO_BLK_T_IN;
+ in += num;
+ }
+ }
if (vblk->vq->vq_ops->add_buf(vblk->vq, vblk->sg, out, in, vbr)) {
mempool_free(vbr, vblk->pool);
return false;
diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
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

Attachments:

no-partition-scan (5.43 kB)

2008-08-27 12:30:18

by Hannes Reinecke

[permalink] [raw]

Subject: Re: [PATCH] Disable partition scan

Attachments:

no-partition-scan (3.62 kB)

2008-08-28 12:01:00

by Randy Dunlap

[permalink] [raw]

Subject: Re: [PATCH] Disable partition scan

On Wed, 27 Aug 2008, Hannes Reinecke wrote:

> Hi all again,
>
> Yeah, cool. One should take care not to mangle to patches.
> Should teach me to use git properly. Oh well.
>
> Corrected patch attached.

It's also missing an update to Documentation/kernel-parameters.txt ....
Please add that.

Thanks,
--
~Randy

2009-09-12 11:45:04

by Roland

[permalink] [raw]

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
>[email protected] +49 911 74053 688
>SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N?rnberg
>GF: Markus Rex, HRB 16746 (AG N?rnberg)

["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 <[email protected]>

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

2009-09-14 06:33:51

by Hannes Reinecke

[permalink] [raw]

Subject: Re: [PATCH] Disable partition scan

[email protected] wrote:
> 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?
>
Hmm. Not sure about this.
For once, you'd have to have a tool like kpartx anyway to generate the partition mappings for the
not-excluded devices. Hence it's not a big deal to use this tool _always_, ie for all devices.

But more importantly the commandline will be a killer. You would have to specify the device
to be excluded prior to driver probing. Which means you'd have to know how the driver would
enumerate the device and how the device to be excluded would be named.
But exactly this isn't guaranteed, so it'll be virtually impossible to do so.

Cheers,

Hannes
PS.: One wonders what'll happen to the patch. Maybe it'll linger forever in bugzilla as no-one
feels it important enough to have a look at it, let alone merge ...
So, if there are any users out there, please speak up to have it merged!
--
Dr. Hannes Reinecke zSeries & Storage
[email protected] +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N?rnberg
GF: Markus Rex, HRB 16746 (AG N?rnberg)

2009-09-14 20:59:50

by Roland

[permalink] [raw]

Subject: Re: [PATCH] Disable partition scan

> But more importantly the commandline will be a killer. You would have to specify the device
> to be excluded prior to driver probing. Which means you'd have to know how the driver would
> enumerate the device and how the device to be excluded would be named.
> But exactly this isn't guaranteed, so it'll be virtually impossible to do so.

ok, you`re right

>PS.: One wonders what'll happen to the patch. Maybe it'll linger forever in bugzilla as no-one
>feels it important enough to have a look at it, let alone merge ...
>So, if there are any users out there, please speak up to have it merged!

you did that patch for a reason (customer request?) and we have another request for it in bugzilla.
i think it`s useful.

maybe adding the new param to kernel-params.txt and adding some more people cc below the
signed-off will raise chances for acceptance.

> [email protected] wrote:
> > 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?
> >
> Hmm. Not sure about this.
> For once, you'd have to have a tool like kpartx anyway to generate the partition mappings for the
> not-excluded devices. Hence it's not a big deal to use this tool _always_, ie for all devices.
>
> But more importantly the commandline will be a killer. You would have to specify the device
> to be excluded prior to driver probing. Which means you'd have to know how the driver would
> enumerate the device and how the device to be excluded would be named.
> But exactly this isn't guaranteed, so it'll be virtually impossible to do so.
>
> Cheers,
>
> Hannes
> PS.: One wonders what'll happen to the patch. Maybe it'll linger forever in bugzilla as no-one
> feels it important enough to have a look at it, let alone merge ...
> So, if there are any users out there, please speak up to have it merged!
> --
> Dr. Hannes Reinecke zSeries & Storage
> [email protected] +49 911 74053 688
> SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N?rnberg
> GF: Markus Rex, HRB 16746 (AG N?rnberg)
>

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