Re: [Nbd] [PATCH] Fix size setup ioctls for small devices

[Wouter Verhelst <w@...112...>]

Hi Markus,

On Fri, Feb 12, 2016 at 04:08:17PM +0100, Markus Pargmann wrote:
> For devices smaller than 4096 the current code results in a blockdevice
> size of 0.
> 
> For devices with a different blocksize than 4096 the code potentially
> leads to more dropped blocks at the end of the file than necessary. For
> example a device with size 6144 would have only 4096 bytes available on
> client side even if the blocksize is set to 512.
> 
> This patch tries to use the user-given blocksize if possible. Otherwise
> it falls back to using 4096.
> 
> Signed-off-by: Markus Pargmann <mpa@...1897...>

Applied, thanks.

> ---
>  nbd-client.c | 21 ++++++++++++++++-----
>  1 file changed, 16 insertions(+), 5 deletions(-)
> 
> diff --git a/nbd-client.c b/nbd-client.c
> index 2c387f8c8c4c..40d6b7abac3c 100644
> --- a/nbd-client.c
> +++ b/nbd-client.c
> @@ -462,14 +462,25 @@ void setsizes(int nbd, u64 size64, int blocksize, u32 flags) {
>  	if (size64>>12 > (uint64_t)~0UL)
>  		err("Device too large.\n");
>  	else {
> -		if (ioctl(nbd, NBD_SET_BLKSIZE, 4096UL) < 0)
> +		int tmp_blocksize = 4096;
> +		if (size64 / (u64)blocksize <= (uint64_t)~0UL)
> +			tmp_blocksize = blocksize;
> +		if (ioctl(nbd, NBD_SET_BLKSIZE, tmp_blocksize) < 0) {
> +			fprintf(stderr, "Failed to set blocksize %d\n",
> +				tmp_blocksize);
>  			err("Ioctl/1.1a failed: %m\n");
> -		size = (unsigned long)(size64>>12);
> +		}
> +		size = (unsigned long)(size64 / (u64)tmp_blocksize);
>  		if (ioctl(nbd, NBD_SET_SIZE_BLOCKS, size) < 0)
>  			err("Ioctl/1.1b failed: %m\n");
> -		if (ioctl(nbd, NBD_SET_BLKSIZE, (unsigned long)blocksize) < 0)
> -			err("Ioctl/1.1c failed: %m\n");
> -		fprintf(stderr, "bs=%d, sz=%llu bytes\n", blocksize, 4096ULL*size);
> +		if (tmp_blocksize != blocksize) {
> +			if (ioctl(nbd, NBD_SET_BLKSIZE, (unsigned long)blocksize) < 0) {
> +				fprintf(stderr, "Failed to set blocksize %d\n",
> +					blocksize);
> +				err("Ioctl/1.1c failed: %m\n");
> +			}
> +		}
> +		fprintf(stderr, "bs=%d, sz=%llu bytes\n", blocksize, (u64)tmp_blocksize * size);
>  	}
>  
>  	ioctl(nbd, NBD_CLEAR_SOCK);
> -- 
> 2.7.0.rc3
> 
> 

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