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loop: support 4k physical blocksize
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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>
Signed-off-by: Jens Axboe <axboe@fb.com>
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Hannes Reinecke authored and Jens Axboe committed Jun 8, 2017
1 parent 51001b7 commit f2c6df7
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Showing 3 changed files with 41 additions and 6 deletions.
43 changes: 37 additions & 6 deletions drivers/block/loop.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand All @@ -233,6 +234,12 @@ figure_loop_size(struct loop_device *lo, loff_t offset, loff_t sizelimit)
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 */
Expand Down Expand Up @@ -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
Expand All @@ -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);
}

Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -1083,6 +1095,7 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
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) &&
Expand Down Expand Up @@ -1115,9 +1128,26 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
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;
}
Expand Down Expand Up @@ -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)
Expand Down
1 change: 1 addition & 0 deletions drivers/block/loop.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down
3 changes: 3 additions & 0 deletions include/uapi/linux/loop.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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 */
Expand Down Expand Up @@ -59,6 +60,8 @@ struct loop_info64 {
__u64 lo_init[2];
};

#define LO_INFO_BLOCKSIZE(l) (l)->lo_init[0]

/*
* Loop filter types
*/
Expand Down

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