[PATCHv6 0/2] loop: enable different logical blocksizes

[PATCHv6 0/2] loop: enable different logical blocksizes

[Hannes Reinecke]

Currently the loop driver just simulates 512-byte blocks. When
creating bootable images for virtual machines it might be required
to use a different physical blocksize (eg 4k for S/390 DASD), as
the some bootloaders (like lilo or zipl for S/390) need to know
the physical block addresses of the kernel and initrd.

With this patchset the loop driver will export the logical and
physical blocksize and the current LOOP_SET_STATUS64 ioctl is
extended to set the logical blocksize by re-using the existing
'init' fields, which are currently unused.

As usual, comments and reviews are welcome.

Changes to v1:
- Move LO_FLAGS_BLOCKSIZE definition
- Reshuffle patches
Changes to v2:
- Include reviews from Ming Lei
Changes to v3:
- Include reviews from Christoph
- Merge patches
Changes to v4:
- Add LO_INFO_BLOCKSIZE definition
Changes to v5:
- Rediff to latest upstream

Hannes Reinecke (2):
  loop: Remove unused 'bdev' argument from loop_set_capacity
  loop: support 4k physical blocksize

 drivers/block/loop.c      | 40 +++++++++++++++++++++++++++++++++-------
 drivers/block/loop.h      |  1 +
 include/uapi/linux/loop.h |  3 +++
 3 files changed, 37 insertions(+), 7 deletions(-)

-- 
1.8.5.6

[PATCHv6 1/2] loop: Remove unused 'bdev' argument from loop_set_capacity

[Hannes Reinecke]

Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 drivers/block/loop.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index cc981f3..81b3900 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1307,7 +1307,7 @@ static int loop_clr_fd(struct loop_device *lo)
 	return err;
 }
 
-static int loop_set_capacity(struct loop_device *lo, struct block_device *bdev)
+static int loop_set_capacity(struct loop_device *lo)
 {
 	if (unlikely(lo->lo_state != Lo_bound))
 		return -ENXIO;
@@ -1370,7 +1370,7 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode,
 	case LOOP_SET_CAPACITY:
 		err = -EPERM;
 		if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN))
-			err = loop_set_capacity(lo, bdev);
+			err = loop_set_capacity(lo);
 		break;
 	case LOOP_SET_DIRECT_IO:
 		err = -EPERM;
-- 
1.8.5.6

Re: [PATCHv6 1/2] loop: Remove unused 'bdev' argument from loop_set_capacity

[Ming Lei]

On Fri, Apr 07, 2017 at 08:58:57AM +0200, Hannes Reinecke wrote:
> Signed-off-by: Hannes Reinecke <hare@suse.de>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> ---
>  drivers/block/loop.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> index cc981f3..81b3900 100644
> --- a/drivers/block/loop.c
> +++ b/drivers/block/loop.c
> @@ -1307,7 +1307,7 @@ static int loop_clr_fd(struct loop_device *lo)
>  	return err;
>  }
>  
> -static int loop_set_capacity(struct loop_device *lo, struct block_device *bdev)
> +static int loop_set_capacity(struct loop_device *lo)
>  {
>  	if (unlikely(lo->lo_state != Lo_bound))
>  		return -ENXIO;
> @@ -1370,7 +1370,7 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode,
>  	case LOOP_SET_CAPACITY:
>  		err = -EPERM;
>  		if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN))
> -			err = loop_set_capacity(lo, bdev);
> +			err = loop_set_capacity(lo);
>  		break;
>  	case LOOP_SET_DIRECT_IO:
>  		err = -EPERM;

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


Thanks,
Ming

[PATCHv6 2/2] loop: support 4k physical blocksize

[Hannes Reinecke]

When generating bootable VM images certain systems (most notably
s390x) require devices with 4k blocksize. This patch implements
a new flag 'LO_FLAGS_BLOCKSIZE' which will set the physical
blocksize to that of the underlying device, and allow to change
the logical blocksize for up to the physical blocksize.

Signed-off-by: Hannes Reinecke <hare@suse.com>
---
 drivers/block/loop.c      | 36 +++++++++++++++++++++++++++++++-----
 drivers/block/loop.h      |  1 +
 include/uapi/linux/loop.h |  3 +++
 3 files changed, 35 insertions(+), 5 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 81b3900..f098681 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -221,7 +221,8 @@ static void __loop_update_dio(struct loop_device *lo, bool dio)
 }
 
 static int
-figure_loop_size(struct loop_device *lo, loff_t offset, loff_t sizelimit)
+figure_loop_size(struct loop_device *lo, loff_t offset, loff_t sizelimit,
+		 loff_t logical_blocksize)
 {
 	loff_t size = get_size(offset, sizelimit, lo->lo_backing_file);
 	sector_t x = (sector_t)size;
@@ -233,6 +234,12 @@ static void __loop_update_dio(struct loop_device *lo, bool dio)
 		lo->lo_offset = offset;
 	if (lo->lo_sizelimit != sizelimit)
 		lo->lo_sizelimit = sizelimit;
+	if (lo->lo_flags & LO_FLAGS_BLOCKSIZE) {
+		lo->lo_logical_blocksize = logical_blocksize;
+		blk_queue_physical_block_size(lo->lo_queue, lo->lo_blocksize);
+		blk_queue_logical_block_size(lo->lo_queue,
+					     lo->lo_logical_blocksize);
+	}
 	set_capacity(lo->lo_disk, x);
 	bd_set_size(bdev, (loff_t)get_capacity(bdev->bd_disk) << 9);
 	/* let user-space know about the new size */
@@ -814,6 +821,7 @@ static void loop_config_discard(struct loop_device *lo)
 	struct file *file = lo->lo_backing_file;
 	struct inode *inode = file->f_mapping->host;
 	struct request_queue *q = lo->lo_queue;
+	int lo_bits = blksize_bits(lo->lo_logical_blocksize);
 
 	/*
 	 * We use punch hole to reclaim the free space used by the
@@ -833,7 +841,7 @@ static void loop_config_discard(struct loop_device *lo)
 
 	q->limits.discard_granularity = inode->i_sb->s_blocksize;
 	q->limits.discard_alignment = 0;
-	blk_queue_max_discard_sectors(q, UINT_MAX >> 9);
+	blk_queue_max_discard_sectors(q, UINT_MAX >> lo_bits);
 	q->limits.discard_zeroes_data = 1;
 	queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
 }
@@ -922,6 +930,7 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
 
 	lo->use_dio = false;
 	lo->lo_blocksize = lo_blocksize;
+	lo->lo_logical_blocksize = 512;
 	lo->lo_device = bdev;
 	lo->lo_flags = lo_flags;
 	lo->lo_backing_file = file;
@@ -1087,6 +1096,7 @@ static int loop_clr_fd(struct loop_device *lo)
 	int err;
 	struct loop_func_table *xfer;
 	kuid_t uid = current_uid();
+	int lo_flags = lo->lo_flags;
 
 	if (lo->lo_encrypt_key_size &&
 	    !uid_eq(lo->lo_key_owner, uid) &&
@@ -1119,9 +1129,24 @@ static int loop_clr_fd(struct loop_device *lo)
 	if (err)
 		goto exit;
 
+	if (info->lo_flags & LO_FLAGS_BLOCKSIZE) {
+		lo->lo_flags |= LO_FLAGS_BLOCKSIZE;
+		if (LO_INFO_BLOCKSIZE(info) != 512 &&
+		    LO_INFO_BLOCKSIZE(info) != 1024 &&
+		    LO_INFO_BLOCKSIZE(info) != 2048 &&
+		    LO_INFO_BLOCKSIZE(info) != 4096)
+			return -EINVAL;
+		if (LO_INFO_BLOCKSIZE(info) > lo->lo_blocksize)
+			return -EINVAL;
+	}
+
 	if (lo->lo_offset != info->lo_offset ||
-	    lo->lo_sizelimit != info->lo_sizelimit)
-		if (figure_loop_size(lo, info->lo_offset, info->lo_sizelimit)) {
+	    lo->lo_sizelimit != info->lo_sizelimit ||
+	    lo->lo_flags != lo_flags ||
+	    ((lo->lo_flags & LO_FLAGS_BLOCKSIZE) &&
+	     lo->lo_logical_blocksize != LO_INFO_BLOCKSIZE(info))) {
+		if (figure_loop_size(lo, info->lo_offset, info->lo_sizelimit,
+				     info->lo_init[0]))
 			err = -EFBIG;
 			goto exit;
 		}
@@ -1312,7 +1337,8 @@ static int loop_set_capacity(struct loop_device *lo)
 	if (unlikely(lo->lo_state != Lo_bound))
 		return -ENXIO;
 
-	return figure_loop_size(lo, lo->lo_offset, lo->lo_sizelimit);
+	return figure_loop_size(lo, lo->lo_offset, lo->lo_sizelimit,
+				lo->lo_logical_blocksize);
 }
 
 static int loop_set_dio(struct loop_device *lo, unsigned long arg)
diff --git a/drivers/block/loop.h b/drivers/block/loop.h
index fb2237c..579f2f7 100644
--- a/drivers/block/loop.h
+++ b/drivers/block/loop.h
@@ -49,6 +49,7 @@ struct loop_device {
 	struct file *	lo_backing_file;
 	struct block_device *lo_device;
 	unsigned	lo_blocksize;
+	unsigned	lo_logical_blocksize;
 	void		*key_data; 
 
 	gfp_t		old_gfp_mask;
diff --git a/include/uapi/linux/loop.h b/include/uapi/linux/loop.h
index c8125ec..a3960f9 100644
--- a/include/uapi/linux/loop.h
+++ b/include/uapi/linux/loop.h
@@ -22,6 +22,7 @@ enum {
 	LO_FLAGS_AUTOCLEAR	= 4,
 	LO_FLAGS_PARTSCAN	= 8,
 	LO_FLAGS_DIRECT_IO	= 16,
+	LO_FLAGS_BLOCKSIZE	= 32,
 };
 
 #include <asm/posix_types.h>	/* for __kernel_old_dev_t */
@@ -59,6 +60,8 @@ struct loop_info64 {
 	__u64		   lo_init[2];
 };
 
+#define LO_INFO_BLOCKSIZE(l) (l)->lo_init[0]
+
 /*
  * Loop filter types
  */
-- 
1.8.5.6

Re: [PATCHv6 2/2] loop: support 4k physical blocksize

[Ming Lei]

On Fri, Apr 07, 2017 at 08:58:58AM +0200, Hannes Reinecke wrote:
> When generating bootable VM images certain systems (most notably
> s390x) require devices with 4k blocksize. This patch implements
> a new flag 'LO_FLAGS_BLOCKSIZE' which will set the physical
> blocksize to that of the underlying device, and allow to change
> the logical blocksize for up to the physical blocksize.

Actually this UAPI flag is only for setting logical block size. 

> 
> Signed-off-by: Hannes Reinecke <hare@suse.com>
> ---
>  drivers/block/loop.c      | 36 +++++++++++++++++++++++++++++++-----
>  drivers/block/loop.h      |  1 +
>  include/uapi/linux/loop.h |  3 +++
>  3 files changed, 35 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> index 81b3900..f098681 100644
> --- a/drivers/block/loop.c
> +++ b/drivers/block/loop.c
> @@ -221,7 +221,8 @@ static void __loop_update_dio(struct loop_device *lo, bool dio)
>  }
>  
>  static int
> -figure_loop_size(struct loop_device *lo, loff_t offset, loff_t sizelimit)
> +figure_loop_size(struct loop_device *lo, loff_t offset, loff_t sizelimit,
> +		 loff_t logical_blocksize)
>  {
>  	loff_t size = get_size(offset, sizelimit, lo->lo_backing_file);
>  	sector_t x = (sector_t)size;
> @@ -233,6 +234,12 @@ static void __loop_update_dio(struct loop_device *lo, bool dio)
>  		lo->lo_offset = offset;
>  	if (lo->lo_sizelimit != sizelimit)
>  		lo->lo_sizelimit = sizelimit;
> +	if (lo->lo_flags & LO_FLAGS_BLOCKSIZE) {
> +		lo->lo_logical_blocksize = logical_blocksize;
> +		blk_queue_physical_block_size(lo->lo_queue, lo->lo_blocksize);
> +		blk_queue_logical_block_size(lo->lo_queue,
> +					     lo->lo_logical_blocksize);
> +	}

We can move setting physical block size into loop_set_fd(), and set
512 bytes as default logical block size in loop_set_fd() too.

>  	set_capacity(lo->lo_disk, x);
>  	bd_set_size(bdev, (loff_t)get_capacity(bdev->bd_disk) << 9);
>  	/* let user-space know about the new size */
> @@ -814,6 +821,7 @@ static void loop_config_discard(struct loop_device *lo)
>  	struct file *file = lo->lo_backing_file;
>  	struct inode *inode = file->f_mapping->host;
>  	struct request_queue *q = lo->lo_queue;
> +	int lo_bits = blksize_bits(lo->lo_logical_blocksize);
>  
>  	/*
>  	 * We use punch hole to reclaim the free space used by the
> @@ -833,7 +841,7 @@ static void loop_config_discard(struct loop_device *lo)
>  
>  	q->limits.discard_granularity = inode->i_sb->s_blocksize;
>  	q->limits.discard_alignment = 0;
> -	blk_queue_max_discard_sectors(q, UINT_MAX >> 9);
> +	blk_queue_max_discard_sectors(q, UINT_MAX >> lo_bits);
>  	q->limits.discard_zeroes_data = 1;
>  	queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
>  }
> @@ -922,6 +930,7 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
>  
>  	lo->use_dio = false;
>  	lo->lo_blocksize = lo_blocksize;
> +	lo->lo_logical_blocksize = 512;

It isn't enough to just this local vaiable as 512 here, since the last
logical block size is still kept in queue's setting.

>  	lo->lo_device = bdev;
>  	lo->lo_flags = lo_flags;
>  	lo->lo_backing_file = file;
> @@ -1087,6 +1096,7 @@ static int loop_clr_fd(struct loop_device *lo)
>  	int err;
>  	struct loop_func_table *xfer;
>  	kuid_t uid = current_uid();
> +	int lo_flags = lo->lo_flags;
>  
>  	if (lo->lo_encrypt_key_size &&
>  	    !uid_eq(lo->lo_key_owner, uid) &&
> @@ -1119,9 +1129,24 @@ static int loop_clr_fd(struct loop_device *lo)
>  	if (err)
>  		goto exit;
>  
> +	if (info->lo_flags & LO_FLAGS_BLOCKSIZE) {
> +		lo->lo_flags |= LO_FLAGS_BLOCKSIZE;
> +		if (LO_INFO_BLOCKSIZE(info) != 512 &&
> +		    LO_INFO_BLOCKSIZE(info) != 1024 &&
> +		    LO_INFO_BLOCKSIZE(info) != 2048 &&
> +		    LO_INFO_BLOCKSIZE(info) != 4096)
> +			return -EINVAL;
> +		if (LO_INFO_BLOCKSIZE(info) > lo->lo_blocksize)
> +			return -EINVAL;
> +	}
> +
>  	if (lo->lo_offset != info->lo_offset ||
> -	    lo->lo_sizelimit != info->lo_sizelimit)
> -		if (figure_loop_size(lo, info->lo_offset, info->lo_sizelimit)) {
> +	    lo->lo_sizelimit != info->lo_sizelimit ||
> +	    lo->lo_flags != lo_flags ||
> +	    ((lo->lo_flags & LO_FLAGS_BLOCKSIZE) &&
> +	     lo->lo_logical_blocksize != LO_INFO_BLOCKSIZE(info))) {
> +		if (figure_loop_size(lo, info->lo_offset, info->lo_sizelimit,
> +				     info->lo_init[0]))
>  			err = -EFBIG;
>  			goto exit;
>  		}
> @@ -1312,7 +1337,8 @@ static int loop_set_capacity(struct loop_device *lo)
>  	if (unlikely(lo->lo_state != Lo_bound))
>  		return -ENXIO;
>  
> -	return figure_loop_size(lo, lo->lo_offset, lo->lo_sizelimit);
> +	return figure_loop_size(lo, lo->lo_offset, lo->lo_sizelimit,
> +				lo->lo_logical_blocksize);
>  }
>  
>  static int loop_set_dio(struct loop_device *lo, unsigned long arg)
> diff --git a/drivers/block/loop.h b/drivers/block/loop.h
> index fb2237c..579f2f7 100644
> --- a/drivers/block/loop.h
> +++ b/drivers/block/loop.h
> @@ -49,6 +49,7 @@ struct loop_device {
>  	struct file *	lo_backing_file;
>  	struct block_device *lo_device;
>  	unsigned	lo_blocksize;
> +	unsigned	lo_logical_blocksize;
>  	void		*key_data; 
>  
>  	gfp_t		old_gfp_mask;
> diff --git a/include/uapi/linux/loop.h b/include/uapi/linux/loop.h
> index c8125ec..a3960f9 100644
> --- a/include/uapi/linux/loop.h
> +++ b/include/uapi/linux/loop.h
> @@ -22,6 +22,7 @@ enum {
>  	LO_FLAGS_AUTOCLEAR	= 4,
>  	LO_FLAGS_PARTSCAN	= 8,
>  	LO_FLAGS_DIRECT_IO	= 16,
> +	LO_FLAGS_BLOCKSIZE	= 32,
>  };
>  
>  #include <asm/posix_types.h>	/* for __kernel_old_dev_t */
> @@ -59,6 +60,8 @@ struct loop_info64 {
>  	__u64		   lo_init[2];
>  };
>  
> +#define LO_INFO_BLOCKSIZE(l) (l)->lo_init[0]
> +
>  /*
>   * Loop filter types
>   */
> -- 
> 1.8.5.6
> 

-- 
Ming

Re: [PATCHv6 2/2] loop: support 4k physical blocksize

[Hannes Reinecke]

On 04/07/2017 11:34 AM, Ming Lei wrote:
> On Fri, Apr 07, 2017 at 08:58:58AM +0200, Hannes Reinecke wrote:
>> When generating bootable VM images certain systems (most notably
>> s390x) require devices with 4k blocksize. This patch implements
>> a new flag 'LO_FLAGS_BLOCKSIZE' which will set the physical
>> blocksize to that of the underlying device, and allow to change
>> the logical blocksize for up to the physical blocksize.
> 
> Actually this UAPI flag is only for setting logical block size. 
> 
Hmm? No, we're setting the physical blocksize, too.
Or am I missing something?

>>
>> Signed-off-by: Hannes Reinecke <hare@suse.com>
>> ---
>>  drivers/block/loop.c      | 36 +++++++++++++++++++++++++++++++-----
>>  drivers/block/loop.h      |  1 +
>>  include/uapi/linux/loop.h |  3 +++
>>  3 files changed, 35 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
>> index 81b3900..f098681 100644
>> --- a/drivers/block/loop.c
>> +++ b/drivers/block/loop.c
>> @@ -221,7 +221,8 @@ static void __loop_update_dio(struct loop_device *lo, bool dio)
>>  }
>>  
>>  static int
>> -figure_loop_size(struct loop_device *lo, loff_t offset, loff_t sizelimit)
>> +figure_loop_size(struct loop_device *lo, loff_t offset, loff_t sizelimit,
>> +		 loff_t logical_blocksize)
>>  {
>>  	loff_t size = get_size(offset, sizelimit, lo->lo_backing_file);
>>  	sector_t x = (sector_t)size;
>> @@ -233,6 +234,12 @@ static void __loop_update_dio(struct loop_device *lo, bool dio)
>>  		lo->lo_offset = offset;
>>  	if (lo->lo_sizelimit != sizelimit)
>>  		lo->lo_sizelimit = sizelimit;
>> +	if (lo->lo_flags & LO_FLAGS_BLOCKSIZE) {
>> +		lo->lo_logical_blocksize = logical_blocksize;
>> +		blk_queue_physical_block_size(lo->lo_queue, lo->lo_blocksize);
>> +		blk_queue_logical_block_size(lo->lo_queue,
>> +					     lo->lo_logical_blocksize);
>> +	}
> 
> We can move setting physical block size into loop_set_fd(), and set
> 512 bytes as default logical block size in loop_set_fd() too.
> 
Okay.

>>  	set_capacity(lo->lo_disk, x);
>>  	bd_set_size(bdev, (loff_t)get_capacity(bdev->bd_disk) << 9);
>>  	/* let user-space know about the new size */
>> @@ -814,6 +821,7 @@ static void loop_config_discard(struct loop_device *lo)
>>  	struct file *file = lo->lo_backing_file;
>>  	struct inode *inode = file->f_mapping->host;
>>  	struct request_queue *q = lo->lo_queue;
>> +	int lo_bits = blksize_bits(lo->lo_logical_blocksize);
>>  
>>  	/*
>>  	 * We use punch hole to reclaim the free space used by the
>> @@ -833,7 +841,7 @@ static void loop_config_discard(struct loop_device *lo)
>>  
>>  	q->limits.discard_granularity = inode->i_sb->s_blocksize;
>>  	q->limits.discard_alignment = 0;
>> -	blk_queue_max_discard_sectors(q, UINT_MAX >> 9);
>> +	blk_queue_max_discard_sectors(q, UINT_MAX >> lo_bits);
>>  	q->limits.discard_zeroes_data = 1;
>>  	queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
>>  }
>> @@ -922,6 +930,7 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
>>  
>>  	lo->use_dio = false;
>>  	lo->lo_blocksize = lo_blocksize;
>> +	lo->lo_logical_blocksize = 512;
> 
> It isn't enough to just this local vaiable as 512 here, since the last
> logical block size is still kept in queue's setting.
> 
Right. Will be updating the queue setting, too.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
hare@suse.de			               +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 N�rnberg
GF: F. Imend�rffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG N�rnberg)

Re: [PATCHv6 2/2] loop: support 4k physical blocksize

[Hannes Reinecke]

On 04/07/2017 11:38 AM, Hannes Reinecke wrote:
> On 04/07/2017 11:34 AM, Ming Lei wrote:
>> On Fri, Apr 07, 2017 at 08:58:58AM +0200, Hannes Reinecke wrote:
>>> When generating bootable VM images certain systems (most notably
>>> s390x) require devices with 4k blocksize. This patch implements
>>> a new flag 'LO_FLAGS_BLOCKSIZE' which will set the physical
>>> blocksize to that of the underlying device, and allow to change
>>> the logical blocksize for up to the physical blocksize.
>>
>> Actually this UAPI flag is only for setting logical block size. 
>>
> Hmm? No, we're setting the physical blocksize, too.
> Or am I missing something?
> 
>>>
>>> Signed-off-by: Hannes Reinecke <hare@suse.com>
>>> ---
>>>  drivers/block/loop.c      | 36 +++++++++++++++++++++++++++++++-----
>>>  drivers/block/loop.h      |  1 +
>>>  include/uapi/linux/loop.h |  3 +++
>>>  3 files changed, 35 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
>>> index 81b3900..f098681 100644
>>> --- a/drivers/block/loop.c
>>> +++ b/drivers/block/loop.c
>>> @@ -221,7 +221,8 @@ static void __loop_update_dio(struct loop_device *lo, bool dio)
>>>  }
>>>  
>>>  static int
>>> -figure_loop_size(struct loop_device *lo, loff_t offset, loff_t sizelimit)
>>> +figure_loop_size(struct loop_device *lo, loff_t offset, loff_t sizelimit,
>>> +		 loff_t logical_blocksize)
>>>  {
>>>  	loff_t size = get_size(offset, sizelimit, lo->lo_backing_file);
>>>  	sector_t x = (sector_t)size;
>>> @@ -233,6 +234,12 @@ static void __loop_update_dio(struct loop_device *lo, bool dio)
>>>  		lo->lo_offset = offset;
>>>  	if (lo->lo_sizelimit != sizelimit)
>>>  		lo->lo_sizelimit = sizelimit;
>>> +	if (lo->lo_flags & LO_FLAGS_BLOCKSIZE) {
>>> +		lo->lo_logical_blocksize = logical_blocksize;
>>> +		blk_queue_physical_block_size(lo->lo_queue, lo->lo_blocksize);
>>> +		blk_queue_logical_block_size(lo->lo_queue,
>>> +					     lo->lo_logical_blocksize);
>>> +	}
>>
>> We can move setting physical block size into loop_set_fd(), and set
>> 512 bytes as default logical block size in loop_set_fd() too.
>>
> Okay.
> 
After thinking about it some more I'm not sure if I agree with that
reasoning.

One of the goals of this patchset is to keep compability with existing
installations.
If we move setting the physical blocksize into loop_set_fd() (which
needs to be called before loop_set_status()) the physical blocksize
would always be set.
Which would induce a user-visible change.

Hence I've formulated my patch to _not_ change the default setup if the
new flag isn't set.

If this is of no concern, however, I can easily modify the patch to
always set the physical blocksize; in fact, that's what I did
originally, but that was deemed bad style.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
hare@suse.de			               +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 N�rnberg
GF: F. Imend�rffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG N�rnberg)

Re: [PATCHv6 2/2] loop: support 4k physical blocksize

[Ming Lei]

On Fri, Apr 07, 2017 at 11:52:27AM +0200, Hannes Reinecke wrote:
> On 04/07/2017 11:38 AM, Hannes Reinecke wrote:
> > On 04/07/2017 11:34 AM, Ming Lei wrote:
> >> On Fri, Apr 07, 2017 at 08:58:58AM +0200, Hannes Reinecke wrote:
> >>> When generating bootable VM images certain systems (most notably
> >>> s390x) require devices with 4k blocksize. This patch implements
> >>> a new flag 'LO_FLAGS_BLOCKSIZE' which will set the physical
> >>> blocksize to that of the underlying device, and allow to change
> >>> the logical blocksize for up to the physical blocksize.
> >>
> >> Actually this UAPI flag is only for setting logical block size. 
> >>
> > Hmm? No, we're setting the physical blocksize, too.
> > Or am I missing something?
> > 
> >>>
> >>> Signed-off-by: Hannes Reinecke <hare@suse.com>
> >>> ---
> >>>  drivers/block/loop.c      | 36 +++++++++++++++++++++++++++++++-----
> >>>  drivers/block/loop.h      |  1 +
> >>>  include/uapi/linux/loop.h |  3 +++
> >>>  3 files changed, 35 insertions(+), 5 deletions(-)
> >>>
> >>> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> >>> index 81b3900..f098681 100644
> >>> --- a/drivers/block/loop.c
> >>> +++ b/drivers/block/loop.c
> >>> @@ -221,7 +221,8 @@ static void __loop_update_dio(struct loop_device *lo, bool dio)
> >>>  }
> >>>  
> >>>  static int
> >>> -figure_loop_size(struct loop_device *lo, loff_t offset, loff_t sizelimit)
> >>> +figure_loop_size(struct loop_device *lo, loff_t offset, loff_t sizelimit,
> >>> +		 loff_t logical_blocksize)
> >>>  {
> >>>  	loff_t size = get_size(offset, sizelimit, lo->lo_backing_file);
> >>>  	sector_t x = (sector_t)size;
> >>> @@ -233,6 +234,12 @@ static void __loop_update_dio(struct loop_device *lo, bool dio)
> >>>  		lo->lo_offset = offset;
> >>>  	if (lo->lo_sizelimit != sizelimit)
> >>>  		lo->lo_sizelimit = sizelimit;
> >>> +	if (lo->lo_flags & LO_FLAGS_BLOCKSIZE) {
> >>> +		lo->lo_logical_blocksize = logical_blocksize;
> >>> +		blk_queue_physical_block_size(lo->lo_queue, lo->lo_blocksize);
> >>> +		blk_queue_logical_block_size(lo->lo_queue,
> >>> +					     lo->lo_logical_blocksize);
> >>> +	}
> >>
> >> We can move setting physical block size into loop_set_fd(), and set
> >> 512 bytes as default logical block size in loop_set_fd() too.
> >>
> > Okay.
> > 
> After thinking about it some more I'm not sure if I agree with that
> reasoning.
> 
> One of the goals of this patchset is to keep compability with existing
> installations.
> If we move setting the physical blocksize into loop_set_fd() (which
> needs to be called before loop_set_status()) the physical blocksize
> would always be set.
> Which would induce a user-visible change.
> 
> Hence I've formulated my patch to _not_ change the default setup if the
> new flag isn't set.

OK, better to not break current users, :-)

Thanks,
Ming