Re: [Qemu-devel] [PATCH 2/6] VMDK: add twoGbMaxExtentSparse support

[Stefan Hajnoczi]

On Thu, Aug 4, 2011 at 3:35 AM, Fam Zheng <address@hidden> wrote:
> On Tue, Aug 2, 2011 at 6:32 PM, Stefan Hajnoczi <address@hidden> wrote:
>> On Wed, Jul 27, 2011 at 10:27 AM, Fam Zheng <address@hidden> wrote:
>>> Add twoGbMaxExtentSparse support. Only opening code is changed.
>>>
>>> Signed-off-by: Fam Zheng <address@hidden>
>>> ---
>>>  block/vmdk.c |  124 
>>> ++++++++++++++++++++++++++++++++++++----------------------
>>>  1 files changed, 77 insertions(+), 47 deletions(-)
>>>
>>> diff --git a/block/vmdk.c b/block/vmdk.c
>>> index 9e6c67a..9d1ae32 100644
>>> --- a/block/vmdk.c
>>> +++ b/block/vmdk.c
>>> @@ -357,7 +357,9 @@ static int vmdk_init_tables(BlockDriverState *bs, 
>>> VmdkExtent *extent)
>>>     return ret;
>>>  }
>>>
>>> -static int vmdk_open_vmdk3(BlockDriverState *bs, int flags)
>>> +static int vmdk_open_vmdk3(BlockDriverState *bs,
>>> +                           BlockDriverState *file,
>>> +                           int flags)
>>>  {
>>>     int ret;
>>>     uint32_t magic;
>>> @@ -365,10 +367,9 @@ static int vmdk_open_vmdk3(BlockDriverState *bs, int 
>>> flags)
>>>     BDRVVmdkState *s = bs->opaque;
>>>     VmdkExtent *extent;
>>>
>>> -    s->desc_offset = 0x200;
>>> -    ret = bdrv_pread(bs->file, sizeof(magic), &header, sizeof(header));
>>> +    ret = bdrv_pread(file, sizeof(magic), &header, sizeof(header));
>>>     if (ret < 0) {
>>> -        goto fail;
>>> +        return ret;
>>>     }
>>>     extent = vmdk_add_extent(bs,
>>>                              bs->file, false,
>>> @@ -378,17 +379,16 @@ static int vmdk_open_vmdk3(BlockDriverState *bs, int 
>>> flags)
>>>                              le32_to_cpu(header.granularity));
>>>     ret = vmdk_init_tables(bs, extent);
>>>     if (ret) {
>>> -        /* vmdk_init_tables cleans up on fail, so only free allocation of
>>> -         * vmdk_add_extent here. */
>>> -        goto fail;
>>> +        /* free extent allocated by vmdk_add_extent */
>>> +        s->num_extents--;
>>> +        qemu_realloc(s->extents, s->num_extents * sizeof(VmdkExtent));
>>
>> The return value of qemu_realloc() is the new address of s->extents[].
>>  You are ignoring the new address and continue to use the old one.
>>
>> Please add a vmdk_free_last_extent() function that encapsulates this.
>> The rest of the vmdk.c code should not manipulate
>> s->extents[]/s->num_extents.  Use vmdk_add_extent(),
>> vmdk_free_last_extent(), vmdk_free_extents() instead of spreading the
>> extent management code in various places.
>>
>>>     }
>>> -    return 0;
>>> - fail:
>>> -    vmdk_free_extents(bs);
>>>     return ret;
>>>  }
>>>
>>> -static int vmdk_open_vmdk4(BlockDriverState *bs, int flags)
>>> +static int vmdk_open_vmdk4(BlockDriverState *bs,
>>> +                           BlockDriverState *file,
>>> +                           int flags)
>>>  {
>>>     int ret;
>>>     uint32_t magic;
>>> @@ -397,39 +397,30 @@ 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));
>>> +    ret = bdrv_pread(file, sizeof(magic), &header, sizeof(header));
>>>     if (ret < 0) {
>>> -        goto fail;
>>> +        return ret;
>>>     }
>>>     l1_entry_sectors = le32_to_cpu(header.num_gtes_per_gte)
>>>                         * le64_to_cpu(header.granularity);
>>> +    if (l1_entry_sectors <= 0) {
>>> +        return -EINVAL;
>>> +    }
>>>     l1_size = (le64_to_cpu(header.capacity) + l1_entry_sectors - 1)
>>>                 / l1_entry_sectors;
>>> -    extent = vmdk_add_extent(bs, bs->file, false,
>>> +    extent = vmdk_add_extent(bs, file, false,
>>>                           le64_to_cpu(header.capacity),
>>>                           le64_to_cpu(header.gd_offset) << 9,
>>>                           le64_to_cpu(header.rgd_offset) << 9,
>>>                           l1_size,
>>>                           le32_to_cpu(header.num_gtes_per_gte),
>>>                           le64_to_cpu(header.granularity));
>>> -    if (extent->l1_entry_sectors <= 0) {
>>> -        ret = -EINVAL;
>>> -        goto fail;
>>> -    }
>>> -    /* try to open parent images, if exist */
>>> -    ret = vmdk_parent_open(bs);
>>> -    if (ret) {
>>> -        goto fail;
>>> -    }
>>> -    s->parent_cid = vmdk_read_cid(bs, 1);
>>>     ret = vmdk_init_tables(bs, extent);
>>>     if (ret) {
>>> -        goto fail;
>>> +        /* free extent allocated by vmdk_add_extent */
>>> +        s->num_extents--;
>>> +        qemu_realloc(s->extents, s->num_extents * sizeof(VmdkExtent));
>>
>> Same bug.
>>
>>>     }
>>> -    return 0;
>>> - fail:
>>> -    vmdk_free_extents(bs);
>>>     return ret;
>>>  }
>>>
>>> @@ -460,6 +451,35 @@ static int vmdk_parse_description(const char *desc, 
>>> const char *opt_name,
>>>     return 0;
>>>  }
>>>
>>> +/* Open an extent file and append to bs array */
>>> +static int vmdk_open_sparse(BlockDriverState *bs,
>>> +                            BlockDriverState *file,
>>> +                            int flags)
>>> +{
>>> +    int ret;
>>> +    uint32_t magic;
>>> +
>>> +    if (bdrv_pread(file, 0, &magic, sizeof(magic)) != sizeof(magic)) {
>>> +        return -EIO;
>>> +    }
>>> +
>>> +    magic = be32_to_cpu(magic);
>>> +    if (magic == VMDK3_MAGIC) {
>>> +        ret = vmdk_open_vmdk3(bs, file, flags);
>>> +        if (ret) {
>>> +            return ret;
>>> +        }
>>> +    } else if (magic == VMDK4_MAGIC) {
>>> +        ret = vmdk_open_vmdk4(bs, file, flags);
>>> +        if (ret) {
>>> +            return ret;
>>> +        }
>>> +    } else {
>>> +        return -EINVAL;
>>> +    }
>>> +    return 0;
>>
>> Shorter way of writing this (ret is no longer necessary):
>>
>> switch (magic) {
>> case VMDK3_MAGIC:
>>    return vmdk_open_vmdk3(bs, file, flags);
>> case VMDK4_MAGIC:
>>    return vmdk_open_vmdk4(bs, file, flags);
>> default:
>>    return -EINVAL;
>> }
>>
>>> +}
>>> +
>>>  static int vmdk_parse_extents(const char *desc, BlockDriverState *bs,
>>>         const char *desc_file_path)
>>>  {
>>> @@ -470,6 +490,8 @@ static int vmdk_parse_extents(const char *desc, 
>>> BlockDriverState *bs,
>>>     const char *p = desc;
>>>     int64_t sectors = 0;
>>>     int64_t flat_offset;
>>> +    char extent_path[PATH_MAX];
>>> +    BlockDriverState *extent_file;
>>>
>>>     while (*p) {
>>>         /* parse extent line:
>>> @@ -504,22 +526,28 @@ static int vmdk_parse_extents(const char *desc, 
>>> BlockDriverState *bs,
>>>             goto next_line;
>>>         }
>>>
>>> +        path_combine(extent_path, sizeof(extent_path),
>>> +                desc_file_path, fname);
>>> +        ret = bdrv_file_open(&extent_file, extent_path, bs->open_flags);
>>> +        if (ret) {
>>> +            return ret;
>>> +        }
>>> +
>>>         /* save to extents array */
>>>         if (!strcmp(type, "FLAT")) {
>>>             /* FLAT extent */
>>> -            char extent_path[PATH_MAX];
>>> -            BlockDriverState *extent_file;
>>>             VmdkExtent *extent;
>>>
>>> -            path_combine(extent_path, sizeof(extent_path),
>>> -                    desc_file_path, fname);
>>> -            ret = bdrv_file_open(&extent_file, extent_path, 
>>> bs->open_flags);
>>> -            if (ret) {
>>> -                return ret;
>>> -            }
>>>             extent = vmdk_add_extent(bs, extent_file, true, sectors,
>>>                             0, 0, 0, 0, sectors);
>>>             extent->flat_start_offset = flat_offset;
>>> +        } else if (!strcmp(type, "SPARSE")) {
>>> +            /* SPARSE extent */
>>> +            ret = vmdk_open_sparse(bs, extent_file, bs->open_flags);
>>> +            if (ret) {
>>> +                bdrv_delete(extent_file);
>>> +                return ret;
>>> +            }
>>>         } else {
>>>             /* SPARSE extent, not supported for now */
>>
>> This comment is outdated.
>>
>>>             fprintf(stderr,
>>> @@ -552,6 +580,7 @@ static int vmdk_open_desc_file(BlockDriverState *bs, 
>>> int flags)
>>>         return -EINVAL;
>>>     }
>>>     if (strcmp(ct, "monolithicFlat") &&
>>> +        strcmp(ct, "twoGbMaxExtentSparse") &&
>>>         strcmp(ct, "twoGbMaxExtentFlat")) {
>>>         fprintf(stderr,
>>>                 "VMDK: Not supported image type \"%s\""".\n", ct);
>>> @@ -574,17 +603,18 @@ static int vmdk_open_desc_file(BlockDriverState *bs, 
>>> int flags)
>>>
>>>  static int vmdk_open(BlockDriverState *bs, int flags)
>>>  {
>>> -    uint32_t magic;
>>> -
>>> -    if (bdrv_pread(bs->file, 0, &magic, sizeof(magic)) != sizeof(magic)) {
>>> -        return -EIO;
>>> -    }
>>> +    int ret;
>>> +    BDRVVmdkState *s = bs->opaque;
>>>
>>> -    magic = be32_to_cpu(magic);
>>> -    if (magic == VMDK3_MAGIC) {
>>> -        return vmdk_open_vmdk3(bs, flags);
>>> -    } else if (magic == VMDK4_MAGIC) {
>>> -        return vmdk_open_vmdk4(bs, flags);
>>> +    if (vmdk_open_sparse(bs, bs->file, flags) == 0) {
>>> +        s->desc_offset = 0x200;
>>> +        /* try to open parent images, if exist */
>>> +        ret = vmdk_parent_open(bs);
>>> +        if (ret) {
>>> +            return ret;
>>
>> What needs to be freed here?
>>
>
> No resource allocation in vmdk_parent_open, so I think none.

But what about vmdk_open_sparse(), which succeeded?  This function is
a .bdrv_open().  If you return an error then bs->file will be deleted
and bs->opaque is freed - but you need to clean up all image
format-specific resources *before* returning error.  bdrv_close() will
not be called if bdrv_open() returns error.

Stefan