[PATCH] nbd: set the max segment size to UINT_MAX

[PATCH] nbd: set the max segment size to UINT_MAX

[Josef Bacik]

NBD doesn't care about limiting the segment size, let the user push the
largest bio's they want.  This allows us to control the request size
solely through max_sectors_kb.

Signed-off-by: Josef Bacik <jbacik@fb.com>
---
 drivers/block/nbd.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index d220045..0f62d86 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1469,6 +1469,8 @@ static int nbd_dev_add(int index)
 	queue_flag_clear_unlocked(QUEUE_FLAG_ADD_RANDOM, disk->queue);
 	disk->queue->limits.discard_granularity = 512;
 	blk_queue_max_discard_sectors(disk->queue, UINT_MAX);
+	blk_queue_max_segment_size(disk->queue, UINT_MAX);
+
 	disk->queue->limits.discard_zeroes_data = 0;
 	blk_queue_max_hw_sectors(disk->queue, 65536);
 	disk->queue->limits.max_sectors = 256;
-- 
2.7.4

Re: [PATCH] nbd: set the max segment size to UINT_MAX

[Jens Axboe]

On 04/17/2017 07:44 AM, Josef Bacik wrote:
> NBD doesn't care about limiting the segment size, let the user push the
> largest bio's they want.  This allows us to control the request size
> solely through max_sectors_kb.

Doesn't apply to the 4.12 branch.

-- 
Jens Axboe

Re: [PATCH] nbd: set the max segment size to UINT_MAX

[Jens Axboe]

On 04/17/2017 09:55 AM, Jens Axboe wrote:
> On 04/17/2017 07:44 AM, Josef Bacik wrote:
>> NBD doesn't care about limiting the segment size, let the user push the
>> largest bio's they want.  This allows us to control the request size
>> solely through max_sectors_kb.
> 
> Doesn't apply to the 4.12 branch.

Maybe it does on top of your previous series. I'll check.

-- 
Jens Axboe

Re: [PATCH] nbd: set the max segment size to UINT_MAX

[Jens Axboe]

On 04/17/2017 09:57 AM, Jens Axboe wrote:
> On 04/17/2017 09:55 AM, Jens Axboe wrote:
>> On 04/17/2017 07:44 AM, Josef Bacik wrote:
>>> NBD doesn't care about limiting the segment size, let the user push the
>>> largest bio's they want.  This allows us to control the request size
>>> solely through max_sectors_kb.
>>
>> Doesn't apply to the 4.12 branch.
> 
> Maybe it does on top of your previous series. I'll check.

Nope, does not.

-- 
Jens Axboe

Re: [Nbd] [PATCH] nbd: set the max segment size to UINT_MAX

[Alex Bligh]

> On 17 Apr 2017, at 15:44, Josef Bacik <josef@toxicpanda.com> wrote:
>=20
> NBD doesn't care about limiting the segment size, let the user push =
the
> largest bio's they want.  This allows us to control the request size
> solely through max_sectors_kb.

I'm a bit lost around the various knobs in the kernel for maximum block
sizes, but note that the NBD protocol is (with an extension, soon
to be made mainstream by the looks of it) capable of negotiating
block size minima, maxima and preferred sizes - see here:

=
https://github.com/NetworkBlockDevice/nbd/blob/extension-info/doc/proto.md=
#block-size-constraints

These are server block sizes (obviously) which would normally be passed
from userland client to kernel client via an ioctl. I suspect such
ioctls may not be implemented at the moment, and kernel support for
them would be much appreciated.

--=20
Alex Bligh

[PATCH] nbd: set the max segment size to UINT_MAX

[Josef Bacik]

NBD doesn't care about limiting the segment size, let the user push the
largest bio's they want.  This allows us to control the request size
solely through max_sectors_kb.

Signed-off-by: Josef Bacik <jbacik@fb.com>
---
 drivers/block/nbd.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index b78f23c..6e592c2 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1469,6 +1469,7 @@ static int nbd_dev_add(int index)
 	queue_flag_clear_unlocked(QUEUE_FLAG_ADD_RANDOM, disk->queue);
 	disk->queue->limits.discard_granularity = 512;
 	blk_queue_max_discard_sectors(disk->queue, UINT_MAX);
+	blk_queue_max_segment_size(disk->queue, UINT_MAX);
 	blk_queue_max_hw_sectors(disk->queue, 65536);
 	disk->queue->limits.max_sectors = 256;
 
-- 
2.7.4

Re: [PATCH] nbd: set the max segment size to UINT_MAX

[Ming Lei]

On Wed, Apr 19, 2017 at 4:22 AM, Josef Bacik <josef@toxicpanda.com> wrote:
> NBD doesn't care about limiting the segment size, let the user push the
> largest bio's they want.  This allows us to control the request size
> solely through max_sectors_kb.
>
> Signed-off-by: Josef Bacik <jbacik@fb.com>
> ---
>  drivers/block/nbd.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> index b78f23c..6e592c2 100644
> --- a/drivers/block/nbd.c
> +++ b/drivers/block/nbd.c
> @@ -1469,6 +1469,7 @@ static int nbd_dev_add(int index)
>         queue_flag_clear_unlocked(QUEUE_FLAG_ADD_RANDOM, disk->queue);
>         disk->queue->limits.discard_granularity = 512;
>         blk_queue_max_discard_sectors(disk->queue, UINT_MAX);
> +       blk_queue_max_segment_size(disk->queue, UINT_MAX);
>         blk_queue_max_hw_sectors(disk->queue, 65536);
>         disk->queue->limits.max_sectors = 256;

The change is fine, since the segment size limit should be from hw itself.

Reviewed-by: Ming Lei <ming.lei@redhat.com>

Thanks,
Ming Lei

Re: [PATCH] nbd: set the max segment size to UINT_MAX

[Jens Axboe]

On 04/18/2017 02:22 PM, Josef Bacik wrote:
> NBD doesn't care about limiting the segment size, let the user push the
> largest bio's they want.  This allows us to control the request size
> solely through max_sectors_kb.

Thanks Josef, applied for 4.12.

-- 
Jens Axboe