[PATCHv8 0/2] loop: enable different logical blocksizes

[PATCHv8 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
Changes to v6:
- Include review from Ming Lei
Changes to v7:
- Reset logical blocksize on loop_set_fd()

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

 drivers/block/loop.c      | 47 +++++++++++++++++++++++++++++++++++++++--------
 drivers/block/loop.h      |  1 +
 include/uapi/linux/loop.h |  3 +++
 3 files changed, 43 insertions(+), 8 deletions(-)

-- 
1.8.5.6

[PATCHv8 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 28d9329..fc706ad 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1303,7 +1303,7 @@ 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;
@@ -1366,7 +1366,7 @@ 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

[PATCHv8 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      | 43 +++++++++++++++++++++++++++++++++++++------
 drivers/block/loop.h      |  1 +
 include/uapi/linux/loop.h |  3 +++
 3 files changed, 41 insertions(+), 6 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index fc706ad..4d376c1 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 */
@@ -810,6 +817,7 @@ 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 = 9;
 
 	/*
 	 * We use punch hole to reclaim the free space used by the
@@ -829,8 +837,11 @@ 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_write_zeroes_sectors(q, UINT_MAX >> 9);
+	if (lo->lo_flags & LO_FLAGS_BLOCKSIZE)
+		lo_bits = blksize_bits(lo->lo_logical_blocksize);
+
+	blk_queue_max_discard_sectors(q, UINT_MAX >> lo_bits);
+	blk_queue_max_write_zeroes_sectors(q, UINT_MAX >> lo_bits);
 	queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
 }
 
@@ -918,6 +929,7 @@ 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;
@@ -1083,6 +1095,7 @@ 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) &&
@@ -1115,9 +1128,26 @@ static int loop_clr_fd(struct loop_device *lo)
 	if (err)
 		goto exit;
 
+	if (info->lo_flags & LO_FLAGS_BLOCKSIZE) {
+		if (!(lo->lo_flags & LO_FLAGS_BLOCKSIZE))
+			lo->lo_logical_blocksize = 512;
+		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,
+				     LO_INFO_BLOCKSIZE(info)))
 			err = -EFBIG;
 			goto exit;
 		}
@@ -1308,7 +1338,8 @@ 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 fecd3f9..2c096b9 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: [PATCHv8 2/2] loop: support 4k physical blocksize

[Bart Van Assche]

On 06/08/17 04:46, Hannes Reinecke wrote:
>  	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,
> +				     LO_INFO_BLOCKSIZE(info)))
>  			err = -EFBIG;
>  			goto exit;
>  		}

Hello Hannes and Jens,

gcc reports the following for the above code:

drivers/block/loop.c:1149:3: warning: this 'if' clause does not guard...
[-Wmisleading-indentation]

Please review this code. Have the braces perhaps been misplaced?

Thanks,

Bart.

Re: [PATCHv8 2/2] loop: support 4k physical blocksize

[Jens Axboe]

On 06/09/2017 09:30 AM, Bart Van Assche wrote:
> On 06/08/17 04:46, Hannes Reinecke wrote:
>>  	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,
>> +				     LO_INFO_BLOCKSIZE(info)))
>>  			err = -EFBIG;
>>  			goto exit;
>>  		}
> 
> Hello Hannes and Jens,
> 
> gcc reports the following for the above code:
> 
> drivers/block/loop.c:1149:3: warning: this 'if' clause does not guard...
> [-Wmisleading-indentation]
> 
> Please review this code. Have the braces perhaps been misplaced?

It's clearly buggy, fix has gone in:

http://git.kernel.dk/cgit/linux-block/commit/?h=for-4.13/block&id=b040ad9cf6a169cc000a5324fcada695dfa1f4b3

-- 
Jens Axboe

Re: [PATCHv8 0/2] loop: enable different logical blocksizes

[Jens Axboe]

On 06/08/2017 05:46 AM, Hannes Reinecke wrote:
> 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.

Queued up for 4.13.

-- 
Jens Axboe