Re: [Qemu-devel] [PATCH v2 6/9] block: Read only one sector for format probing

[Stefan Hajnoczi]

On Mon, Nov 10, 2014 at 03:48:52PM +0100, Max Reitz wrote:
> On 2014-11-07 at 20:39, Kevin Wolf wrote:
> >The only image format driver that even potentially accesses anything
> >after 512 bytes in its bdrv_probe() implementation is VMDK, which reads
> >a plain-text descriptor file. In practice, the field it's looking for
> >seems to come first and will be well within the first 512 bytes, too.
> >
> >Signed-off-by: Kevin Wolf <address@hidden>
> >Reviewed-by: Stefan Hajnoczi <address@hidden>
> >---
> >  block.c                   | 2 +-
> >  include/block/block_int.h | 2 ++
> >  2 files changed, 3 insertions(+), 1 deletion(-)
> >
> >diff --git a/block.c b/block.c
> >index 2fdc33f..1fd4b8e 100644
> >--- a/block.c
> >+++ b/block.c
> >@@ -682,7 +682,7 @@ static int find_image_format(BlockDriverState *bs, const 
> >char *filename,
> >                               BlockDriver **pdrv, Error **errp)
> >  {
> >      BlockDriver *drv;
> >-    uint8_t buf[2048];
> >+    uint8_t buf[BLOCK_PROBE_BUF_SIZE];
> >      int ret = 0;
> >      /* Return the raw BlockDriver * to scsi-generic devices or empty 
> > drives */
> >diff --git a/include/block/block_int.h b/include/block/block_int.h
> >index a1c17b9..cd94559 100644
> >--- a/include/block/block_int.h
> >+++ b/include/block/block_int.h
> >@@ -57,6 +57,8 @@
> >  #define BLOCK_OPT_REDUNDANCY        "redundancy"
> >  #define BLOCK_OPT_NOCOW             "nocow"
> >+#define BLOCK_PROBE_BUF_SIZE        512
> >+
> >  typedef struct BdrvTrackedRequest {
> >      BlockDriverState *bs;
> >      int64_t offset;
> 
> You should change the description of the buf_size parameter for
> bdrv_probe_all, as I wrote in my review for patch 5.
> 
> With that description fixed (either here or in patch 5):

Here please, since the value is still 2048 in Patch 5.

Stefan

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