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Subject[PATCHv5 2/2] loop: support 4k physical blocksize
Date
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 8dae865..776b3c6 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) &&
@@ -1116,9 +1126,24 @@ static int loop_clr_fd(struct loop_device *lo)
if (err)
return err;

+ 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]))
return -EFBIG;

loop_config_discard(lo);
@@ -1303,7 +1328,8 @@ 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
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