loop: support 4k physical blocksize

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>

1 files changed, 37 insertions, 6 deletions

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index fc706adff6a4..4d376c10a97a 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 @@ 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 */
@@ -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 @@ 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) &&
@@ -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;
                 }
@@ -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)