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

Ming Lei
2017-04-07T09:34:34Z

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