[Qemu-devel] Re: [PATCH 2/2] Add proper -errno error return values to qcow2_open()

[Kevin Wolf <kwolf@redhat.com>]

Am 16.12.2010 17:05, schrieb Jes.Sorensen@redhat.com:
> From: Jes Sorensen <Jes.Sorensen@redhat.com>
> 
> In addition this adds missing braces to the function to be consistent
> with the coding style.
> 
> Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
> ---
>  block/qcow2.c |   61 ++++++++++++++++++++++++++++++++++++++++----------------
>  1 files changed, 43 insertions(+), 18 deletions(-)
> 
> diff --git a/block/qcow2.c b/block/qcow2.c
> index d7fd167..b4a9e5e 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -140,12 +140,14 @@ static int qcow2_read_extensions(BlockDriverState *bs, uint64_t start_offset,
>  static int qcow2_open(BlockDriverState *bs, int flags)
>  {
>      BDRVQcowState *s = bs->opaque;
> -    int len, i;
> +    int len, i, ret = 0;
>      QCowHeader header;
>      uint64_t ext_end;
>  
> -    if (bdrv_pread(bs->file, 0, &header, sizeof(header)) != sizeof(header))
> +    if (bdrv_pread(bs->file, 0, &header, sizeof(header)) != sizeof(header)) {
> +        ret = -EIO; 
>          goto fail;
> +    }

ret = bdrv_pread(...);
if (ret < 0) {
    goto fail;
}

We have a specific error code, so why throw it away?

>      be32_to_cpus(&header.magic);
>      be32_to_cpus(&header.version);
>      be64_to_cpus(&header.backing_file_offset);
> @@ -160,16 +162,23 @@ static int qcow2_open(BlockDriverState *bs, int flags)
>      be64_to_cpus(&header.snapshots_offset);
>      be32_to_cpus(&header.nb_snapshots);
>  
> -    if (header.magic != QCOW_MAGIC || header.version != QCOW_VERSION)
> +    if (header.magic != QCOW_MAGIC || header.version != QCOW_VERSION) {
> +        ret = -EINVAL;
>          goto fail;
> +    }
>      if (header.cluster_bits < MIN_CLUSTER_BITS ||
> -        header.cluster_bits > MAX_CLUSTER_BITS)
> +        header.cluster_bits > MAX_CLUSTER_BITS) {
> +        ret = -EINVAL;
>          goto fail;
> -    if (header.crypt_method > QCOW_CRYPT_AES)
> +    }
> +    if (header.crypt_method > QCOW_CRYPT_AES) {
> +        ret = -EINVAL;
>          goto fail;
> +    }
>      s->crypt_method_header = header.crypt_method;
> -    if (s->crypt_method_header)
> +    if (s->crypt_method_header) {
>          bs->encrypted = 1;
> +    }
>      s->cluster_bits = header.cluster_bits;
>      s->cluster_size = 1 << s->cluster_bits;
>      s->cluster_sectors = 1 << (s->cluster_bits - 9);
> @@ -191,15 +200,20 @@ static int qcow2_open(BlockDriverState *bs, int flags)
>      s->l1_vm_state_index = size_to_l1(s, header.size);
>      /* the L1 table must contain at least enough entries to put
>         header.size bytes */
> -    if (s->l1_size < s->l1_vm_state_index)
> +    if (s->l1_size < s->l1_vm_state_index) {
> +        ret = -EINVAL;
>          goto fail;
> +    }
>      s->l1_table_offset = header.l1_table_offset;
>      if (s->l1_size > 0) {
>          s->l1_table = qemu_mallocz(
>              align_offset(s->l1_size * sizeof(uint64_t), 512));
> -        if (bdrv_pread(bs->file, s->l1_table_offset, s->l1_table, s->l1_size * sizeof(uint64_t)) !=
> -            s->l1_size * sizeof(uint64_t))
> +        if (bdrv_pread(bs->file, s->l1_table_offset, s->l1_table,
> +                       s->l1_size * sizeof(uint64_t)) !=
> +            s->l1_size * sizeof(uint64_t)) {
> +            ret = -EIO;
>              goto fail;
> +        }

Same here.

>          for(i = 0;i < s->l1_size; i++) {
>              be64_to_cpus(&s->l1_table[i]);
>          }
> @@ -212,35 +226,46 @@ static int qcow2_open(BlockDriverState *bs, int flags)
>                                    + 512);
>      s->cluster_cache_offset = -1;
>  
> -    if (qcow2_refcount_init(bs) < 0)
> +    ret = qcow2_refcount_init(bs);
> +    if (ret != 0) {
>          goto fail;
> +    }
>  
>      QLIST_INIT(&s->cluster_allocs);
>  
>      /* read qcow2 extensions */
> -    if (header.backing_file_offset)
> +    if (header.backing_file_offset) {
>          ext_end = header.backing_file_offset;
> -    else
> +    } else {
>          ext_end = s->cluster_size;
> -    if (qcow2_read_extensions(bs, sizeof(header), ext_end))
> +    }
> +    if (qcow2_read_extensions(bs, sizeof(header), ext_end)) {
> +        ret = -EINVAL;
>          goto fail;
> +    }
>  
>      /* read the backing file name */
>      if (header.backing_file_offset != 0) {
>          len = header.backing_file_size;
> -        if (len > 1023)
> +        if (len > 1023) {
>              len = 1023;
> -        if (bdrv_pread(bs->file, header.backing_file_offset, bs->backing_file, len) != len)
> +        }
> +        if (bdrv_pread(bs->file, header.backing_file_offset,
> +                       bs->backing_file, len) != len) {
> +            ret = -EIO;
>              goto fail;
> +        }

And here.

Otherwise the patch looks good to me.

Kevin