Patchwork [v6,05/12] VMDK: add field BDRVVmdkState.desc_offset

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Submitter Feiran Zheng
Date July 1, 2011, 4:55 a.m.
Message ID <1309496142-14228-6-git-send-email-famcool@gmail.com>
Download mbox | patch
Permalink /patch/102862/
State New
Headers show

Comments

Feiran Zheng - July 1, 2011, 4:55 a.m.
There are several occurrence of magic number 0x200 as the descriptor
offset within mono sparse image file. This is not the case for images
with separate descriptor file. So a field is added to BDRVVmdkState to
hold the correct value.

Signed-off-by: Fam Zheng <famcool@gmail.com>
---
 block/vmdk.c |   26 ++++++++++++++++----------
 1 files changed, 16 insertions(+), 10 deletions(-)
Kevin Wolf - July 1, 2011, 1:08 p.m.
Am 01.07.2011 06:55, schrieb Fam Zheng:
> There are several occurrence of magic number 0x200 as the descriptor
> offset within mono sparse image file. This is not the case for images
> with separate descriptor file. So a field is added to BDRVVmdkState to
> hold the correct value.
> 
> Signed-off-by: Fam Zheng <famcool@gmail.com>
> ---
>  block/vmdk.c |   26 ++++++++++++++++----------
>  1 files changed, 16 insertions(+), 10 deletions(-)
> 

> @@ -296,7 +300,6 @@ static int vmdk_snapshot_create(const char *filename, const char *backing_file)
>          ret = -errno;
>          goto fail;
>      }
> -    /* the descriptor offset = 0x200 */
>      if (lseek(p_fd, 0x200, SEEK_SET) == -1) {
>          ret = -errno;
>          goto fail;

Is this comment wrong or why do you remove it? I think for the newly
created image it is correct and with this patch we have an unexplained
magic 0x200 in the code.

Kevin

Patch

diff --git a/block/vmdk.c b/block/vmdk.c
index 03248f3..9393ff9 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -81,6 +81,7 @@  typedef struct VmdkExtent {
 } VmdkExtent;
 
 typedef struct BDRVVmdkState {
+    int desc_offset;
     int num_extents;
     uint32_t parent_cid;
     VmdkExtent *extents;
@@ -173,10 +174,11 @@  static uint32_t vmdk_read_cid(BlockDriverState *bs, int parent)
     uint32_t cid;
     const char *p_name, *cid_str;
     size_t cid_str_size;
+    BDRVVmdkState *s = bs->opaque;
 
-    /* the descriptor offset = 0x200 */
-    if (bdrv_pread(bs->file, 0x200, desc, DESC_SIZE) != DESC_SIZE)
+    if (bdrv_pread(bs->file, s->desc_offset, desc, DESC_SIZE) != DESC_SIZE) {
         return 0;
+    }
 
     if (parent) {
         cid_str = "parentCID";
@@ -198,10 +200,11 @@  static int vmdk_write_cid(BlockDriverState *bs, uint32_t cid)
 {
     char desc[DESC_SIZE], tmp_desc[DESC_SIZE];
     char *p_name, *tmp_str;
+    BDRVVmdkState *s = bs->opaque;
 
-    /* the descriptor offset = 0x200 */
-    if (bdrv_pread(bs->file, 0x200, desc, DESC_SIZE) != DESC_SIZE)
-        return -1;
+    if (bdrv_pread(bs->file, s->desc_offset, desc, DESC_SIZE) != DESC_SIZE) {
+        return -EIO;
+    }
 
     tmp_str = strstr(desc,"parentCID");
     pstrcpy(tmp_desc, sizeof(tmp_desc), tmp_str);
@@ -211,8 +214,9 @@  static int vmdk_write_cid(BlockDriverState *bs, uint32_t cid)
         pstrcat(desc, sizeof(desc), tmp_desc);
     }
 
-    if (bdrv_pwrite_sync(bs->file, 0x200, desc, DESC_SIZE) < 0)
-        return -1;
+    if (bdrv_pwrite_sync(bs->file, s->desc_offset, desc, DESC_SIZE) < 0) {
+        return -EIO;
+    }
     return 0;
 }
 
@@ -296,7 +300,6 @@  static int vmdk_snapshot_create(const char *filename, const char *backing_file)
         ret = -errno;
         goto fail;
     }
-    /* the descriptor offset = 0x200 */
     if (lseek(p_fd, 0x200, SEEK_SET) == -1) {
         ret = -errno;
         goto fail;
@@ -400,10 +403,11 @@  static int vmdk_parent_open(BlockDriverState *bs)
 {
     char *p_name;
     char desc[DESC_SIZE];
+    BDRVVmdkState *s = bs->opaque;
 
-    /* the descriptor offset = 0x200 */
-    if (bdrv_pread(bs->file, 0x200, desc, DESC_SIZE) != DESC_SIZE)
+    if (bdrv_pread(bs->file, s->desc_offset, desc, DESC_SIZE) != DESC_SIZE) {
         return -1;
+    }
 
     if ((p_name = strstr(desc,"parentFileNameHint")) != NULL) {
         char *end_name;
@@ -531,6 +535,7 @@  static int vmdk_open_vmdk3(BlockDriverState *bs, int flags)
     VmdkExtent *extent;
     BDRVVmdkState *s = bs->opaque;
 
+    s->desc_offset = 0x200;
     ret = bdrv_pread(bs->file, sizeof(magic), &header, sizeof(header));
     if (ret != sizeof(header)) {
         ret = ret < 0 ? ret : -EIO;
@@ -561,6 +566,7 @@  static int vmdk_open_vmdk4(BlockDriverState *bs, int flags)
     BDRVVmdkState *s = bs->opaque;
     VmdkExtent *extent;
 
+    s->desc_offset = 0x200;
     ret = bdrv_pread(bs->file, sizeof(magic), &header, sizeof(header));
     if (ret != sizeof(header)) {
         ret = ret < 0 ? ret : -EIO;