When running on files the physical blocksize is actually 4k,
so we should be announcing it as such. This is enabled with
a new LO_FLAGS_BLOCKSIZE flag value to the existing
loop_set_status ioctl.

Signed-off-by: Hannes Reinecke <h...@suse.de>
---
 drivers/block/loop.c      | 9 ++++++++-
 include/uapi/linux/loop.h | 1 +
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 3008dec..ff5c874 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -233,6 +233,8 @@ 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)
+               blk_queue_physical_block_size(lo->lo_queue, lo->lo_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 */
@@ -1087,6 +1089,7 @@ 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) &&
@@ -1116,8 +1119,12 @@ loop_set_status(struct loop_device *lo, const struct 
loop_info64 *info)
        if (err)
                return err;
 
+       if (info->lo_flags & LO_FLAGS_BLOCKSIZE)
+               lo->lo_flags |= LO_FLAGS_BLOCKSIZE;
+
        if (lo->lo_offset != info->lo_offset ||
-           lo->lo_sizelimit != info->lo_sizelimit)
+           lo->lo_sizelimit != info->lo_sizelimit ||
+           lo->lo_flags != lo_flags)
                if (figure_loop_size(lo, info->lo_offset, info->lo_sizelimit))
                        return -EFBIG;
 
diff --git a/include/uapi/linux/loop.h b/include/uapi/linux/loop.h
index c8125ec..2691c1c 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 */
-- 
2.6.6

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