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>

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index fc706adff6a45b58a6243ae87beb3af7576f9a01..4d376c10a97a2beba0877346e3785a309238dec3 100644 (file)
--- 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)

diff --git a/drivers/block/loop.h b/drivers/block/loop.h
index fecd3f97ef8c7cd9f825e6c58777a1a2bc6f3461..2c096b9a17b8ccd756065d5102b293796a5833ad 100644 (file)
--- 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 c8125ec1f4f2270a5a01a358832425cd57edb11a..a3960f98679c13567c3db4ecb7919cd14a70cfb0 100644 (file)
--- 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
  */