[v4,1/2] vpc: Split off vpc_ignore_current_size() helper

Commit Message

Vitaly Kuznetsov Dec. 12, 2024, 1:45 p.m. UTC

In preparation to making changes to the logic deciding whether CHS or
'current_size' need to be used in determining the image size, split off
vpc_ignore_current_size() helper.

No functional change intended.

Signed-off-by: Vitaly Kuznetsov <[e-mail]>
---
 block/vpc.c | 67 +++++++++++++++++++++++++++++------------------------
 1 file changed, 37 insertions(+), 30 deletions(-)

Comments

Philippe Mathieu-Daudé Dec. 12, 2024, 2:13 p.m. UTC | #1

On 12/12/24 14:45, Vitaly Kuznetsov wrote:
> In preparation to making changes to the logic deciding whether CHS or
> 'current_size' need to be used in determining the image size, split off
> vpc_ignore_current_size() helper.
> 
> No functional change intended.
> 
> Signed-off-by: Vitaly Kuznetsov <[e-mail]>
> ---
>   block/vpc.c | 67 +++++++++++++++++++++++++++++------------------------
>   1 file changed, 37 insertions(+), 30 deletions(-)

Reviewed-by: Philippe Mathieu-Daudé <[e-mail]>

Patch

diff --git a/block/vpc.c b/block/vpc.c
index d95a204612b7..fb0ded1c4344 100644
--- a/block/vpc.c
+++ b/block/vpc.c
@@ -216,6 +216,41 @@  static void vpc_parse_options(BlockDriverState *bs, QemuOpts *opts,
     }
 }
 
+/*
+ * Microsoft Virtual PC and Microsoft Hyper-V produce and read
+ * VHD image sizes differently.  VPC will rely on CHS geometry,
+ * while Hyper-V and disk2vhd use the size specified in the footer.
+ *
+ * We use a couple of approaches to try and determine the correct method:
+ * look at the Creator App field, and look for images that have CHS
+ * geometry that is the maximum value.
+ *
+ * If the CHS geometry is the maximum CHS geometry, then we assume that
+ * the size is the footer->current_size to avoid truncation.  Otherwise,
+ * we follow the table based on footer->creator_app:
+ *
+ *  Known creator apps:
+ *      'vpc '  :  CHS              Virtual PC (uses disk geometry)
+ *      'qemu'  :  CHS              QEMU (uses disk geometry)
+ *      'qem2'  :  current_size     QEMU (uses current_size)
+ *      'win '  :  current_size     Hyper-V
+ *      'd2v '  :  current_size     Disk2vhd
+ *      'tap\0' :  current_size     XenServer
+ *      'CTXS'  :  current_size     XenConverter
+ *
+ *  The user can override the table values via drive options, however
+ *  even with an override we will still use current_size for images
+ *  that have CHS geometry of the maximum size.
+ */
+static bool vpc_ignore_current_size(VHDFooter *footer)
+{
+    return !!strncmp(footer->creator_app, "win ", 4) &&
+           !!strncmp(footer->creator_app, "qem2", 4) &&
+           !!strncmp(footer->creator_app, "d2v ", 4) &&
+           !!strncmp(footer->creator_app, "CTXS", 4) &&
+           !!memcmp(footer->creator_app, "tap", 4));
+}
+
 static int vpc_open(BlockDriverState *bs, QDict *options, int flags,
                     Error **errp)
 {
@@ -304,36 +339,8 @@  static int vpc_open(BlockDriverState *bs, QDict *options, int flags,
     bs->total_sectors = (int64_t)
         be16_to_cpu(footer->cyls) * footer->heads * footer->secs_per_cyl;
 
-    /* Microsoft Virtual PC and Microsoft Hyper-V produce and read
-     * VHD image sizes differently.  VPC will rely on CHS geometry,
-     * while Hyper-V and disk2vhd use the size specified in the footer.
-     *
-     * We use a couple of approaches to try and determine the correct method:
-     * look at the Creator App field, and look for images that have CHS
-     * geometry that is the maximum value.
-     *
-     * If the CHS geometry is the maximum CHS geometry, then we assume that
-     * the size is the footer->current_size to avoid truncation.  Otherwise,
-     * we follow the table based on footer->creator_app:
-     *
-     *  Known creator apps:
-     *      'vpc '  :  CHS              Virtual PC (uses disk geometry)
-     *      'qemu'  :  CHS              QEMU (uses disk geometry)
-     *      'qem2'  :  current_size     QEMU (uses current_size)
-     *      'win '  :  current_size     Hyper-V
-     *      'd2v '  :  current_size     Disk2vhd
-     *      'tap\0' :  current_size     XenServer
-     *      'CTXS'  :  current_size     XenConverter
-     *
-     *  The user can override the table values via drive options, however
-     *  even with an override we will still use current_size for images
-     *  that have CHS geometry of the maximum size.
-     */
-    use_chs = (!!strncmp(footer->creator_app, "win ", 4) &&
-               !!strncmp(footer->creator_app, "qem2", 4) &&
-               !!strncmp(footer->creator_app, "d2v ", 4) &&
-               !!strncmp(footer->creator_app, "CTXS", 4) &&
-               !!memcmp(footer->creator_app, "tap", 4)) || s->force_use_chs;
+    /* Use CHS or current_size to determine the image size. */
+    use_chs = vpc_ignore_current_size(footer) || s->force_use_chs;
 
     if (!use_chs || bs->total_sectors == VHD_MAX_GEOMETRY || s->force_use_sz) {
         bs->total_sectors = be64_to_cpu(footer->current_size) /