svn commit: r269807 - in head/sys: kern sys

[Konstantin Belousov]

On Mon, Aug 11, 2014 at 12:59:55PM +0000, Gleb Smirnoff wrote:
> Author: glebius
> Date: Mon Aug 11 12:59:55 2014
> New Revision: 269807
> URL: http://svnweb.freebsd.org/changeset/base/269807
> 
> Log:
>   Provide sf_buf_ref() to optimize refcounting of already allocated
>   sendfile(2) buffers.
>   
>   Sponsored by:	Netflix
>   Sponsored by:	Nginx, Inc.
> 
> Modified:
>   head/sys/kern/subr_sfbuf.c
>   head/sys/kern/uipc_syscalls.c
>   head/sys/sys/sf_buf.h
> 
> Modified: head/sys/kern/subr_sfbuf.c
> ==============================================================================
> --- head/sys/kern/subr_sfbuf.c	Mon Aug 11 12:26:48 2014	(r269806)
> +++ head/sys/kern/subr_sfbuf.c	Mon Aug 11 12:59:55 2014	(r269807)
> @@ -201,6 +201,22 @@ sf_buf_free(struct sf_buf *sf)
>  	mtx_unlock(&sf_buf_lock);
>  }
>  
> +void
> +sf_buf_ref(struct sf_buf *sf)
> +{
> +
> +#ifdef SFBUF_OPTIONAL_DIRECT_MAP
> +	if (SFBUF_OPTIONAL_DIRECT_MAP)
> +		return;
> +#endif
> +
> +	KASSERT(sf->ref_count > 0, ("%s: sf %p not allocated", __func__, sf));
> +
> +	mtx_lock(&sf_buf_lock);
> +	sf->ref_count++;
> +	mtx_unlock(&sf_buf_lock);
> +}

I think assert could be usefully moved under the mutex protected region.
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