Re: [Qemu-devel] [PATCH v2 08/20] nfs: Handle failure for potentially large allocations

[Benoît Canet]

The Wednesday 28 May 2014 à 16:37:41 (+0200), Kevin Wolf wrote :
> Some code in the block layer makes potentially huge allocations. Failure
> is not completely unexpected there, so avoid aborting qemu and handle
> out-of-memory situations gracefully.
> 
> This patch addresses the allocations in the nfs block driver.
> 
> Signed-off-by: Kevin Wolf <address@hidden>
> Reviewed-by: Stefan Hajnoczi <address@hidden>
> ---
>  block/nfs.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/block/nfs.c b/block/nfs.c
> index 539bd95..e3d6216 100644
> --- a/block/nfs.c
> +++ b/block/nfs.c
> @@ -165,7 +165,11 @@ static int coroutine_fn nfs_co_writev(BlockDriverState 
> *bs,
>  
>      nfs_co_init_task(client, &task);
>  
> -    buf = g_malloc(nb_sectors * BDRV_SECTOR_SIZE);

Just wondering.

I see nothing in brv_write preventing write of nb_sectors == 0.
g_malloc return NULLL on zero allocation. If g_try_malloc behave the same this
case would make a spurious -ENOMEM report when a write of size 0 is done.


> +    buf = g_try_malloc(nb_sectors * BDRV_SECTOR_SIZE);
> +    if (buf == NULL) {
> +        return -ENOMEM;
> +    }
> +
>      qemu_iovec_to_buf(iov, 0, buf, nb_sectors * BDRV_SECTOR_SIZE);
>  
>      if (nfs_pwrite_async(client->context, client->fh,
> -- 
> 1.8.3.1
> 
>