linux-kernel - Re: [PATCH v4 01/11] net/9p: Adjust maximum MSIZE to account for p9 header

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Message-ID: <Y/CDUtk3CNIMaf+B@codewreck.org>
Date:   Sat, 18 Feb 2023 16:50:42 +0900
From:   asmadeus@...ewreck.org
To:     Eric Van Hensbergen <ericvh@...nel.org>
Cc:     v9fs-developer@...ts.sourceforge.net, rminnich@...il.com,
        lucho@...kov.net, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux_oss@...debyte.com
Subject: Re: [PATCH v4 01/11] net/9p: Adjust maximum MSIZE to account for p9
 header

Eric Van Hensbergen wrote on Sat, Feb 18, 2023 at 12:33:13AM +0000:
> Add maximum p9 header size to MSIZE to make sure we can
> have page aligned data.
> 
> Signed-off-by: Eric Van Hensbergen <ericvh@...nel.org>

I'd be tempted to round that up to the next PAGE_SIZE, but it likely
won't make any difference in practice if we want to round the actual
payload. Let's go for this.

Reviewed-by: Dominique Martinet <asmadeus@...ewreck.org>

> ---
>  net/9p/client.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/net/9p/client.c b/net/9p/client.c
> index 622ec6a586ee..6c2a768a6ab1 100644
> --- a/net/9p/client.c
> +++ b/net/9p/client.c
> @@ -28,7 +28,11 @@
>  #define CREATE_TRACE_POINTS
>  #include <trace/events/9p.h>
>  
> -#define DEFAULT_MSIZE (128 * 1024)
> +/* DEFAULT MSIZE = 32 pages worth of payload + P9_HDRSZ +
> + * room for write (16 extra) or read (11 extra) operands.
> + */
> +
> +#define DEFAULT_MSIZE ((128 * 1024) + P9_IOHDRSZ)
>  
>  /* Client Option Parsing (code inspired by NFS code)
>   *  - a little lazy - parse all client options