linux-kernel - Re: [RFC PATCH v1 21/57] sunrpc: Remove PAGE

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Message-ID: <Zw/SE9+AMYmzBprS@tissot.1015granger.net>
Date: Wed, 16 Oct 2024 10:47:47 -0400
From: Chuck Lever <chuck.lever@...cle.com>
To: Ryan Roberts <ryan.roberts@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
        Anna Schumaker <anna@...nel.org>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        David Hildenbrand <david@...hat.com>,
        Greg Marsden <greg.marsden@...cle.com>,
        Ivan Ivanov <ivan.ivanov@...e.com>,
        Kalesh Singh <kaleshsingh@...gle.com>, Marc Zyngier <maz@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Matthias Brugger <mbrugger@...e.com>, Miroslav Benes <mbenes@...e.cz>,
        Trond Myklebust <trondmy@...nel.org>, Will Deacon <will@...nel.org>,
        Jeff Layton <jlayton@...nel.org>, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-nfs@...r.kernel.org
Subject: Re: [RFC PATCH v1 21/57] sunrpc: Remove PAGE_SIZE compile-time
 constant assumption

On Wed, Oct 16, 2024 at 03:42:12PM +0100, Ryan Roberts wrote:
> + Chuck Lever, Jeff Layton
> 
> This was a rather tricky series to get the recipients correct for and my script
> did not realize that "supporter" was a pseudonym for "maintainer" so you were
> missed off the original post. Appologies!
> 
> More context in cover letter:
> https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@arm.com/
> 
> 
> On 14/10/2024 11:58, Ryan Roberts wrote:
> > To prepare for supporting boot-time page size selection, refactor code
> > to remove assumptions about PAGE_SIZE being compile-time constant. Code
> > intended to be equivalent when compile-time page size is active.
> > 
> > Updated array sizes in various structs to contain enough entries for the
> > smallest supported page size.
> > 
> > Signed-off-by: Ryan Roberts <ryan.roberts@....com>
> > ---
> > 
> > ***NOTE***
> > Any confused maintainers may want to read the cover note here for context:
> > https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@arm.com/
> > 
> >  include/linux/sunrpc/svc.h      | 8 +++++---
> >  include/linux/sunrpc/svc_rdma.h | 4 ++--
> >  include/linux/sunrpc/svcsock.h  | 2 +-
> >  3 files changed, 8 insertions(+), 6 deletions(-)
> > 
> > diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
> > index a7d0406b9ef59..dda44018b8f36 100644
> > --- a/include/linux/sunrpc/svc.h
> > +++ b/include/linux/sunrpc/svc.h
> > @@ -160,6 +160,8 @@ extern u32 svc_max_payload(const struct svc_rqst *rqstp);
> >   */
> >  #define RPCSVC_MAXPAGES		((RPCSVC_MAXPAYLOAD+PAGE_SIZE-1)/PAGE_SIZE \
> >  				+ 2 + 1)
> > +#define RPCSVC_MAXPAGES_MAX	((RPCSVC_MAXPAYLOAD+PAGE_SIZE_MIN-1)/PAGE_SIZE_MIN \
> > +				+ 2 + 1)

There is already a "MAX" in the name, so adding this new macro seems
superfluous to me. Can we get away with simply updating the
"RPCSVC_MAXPAGES" macro, instead of adding this new one?


> >  /*
> >   * The context of a single thread, including the request currently being
> > @@ -190,14 +192,14 @@ struct svc_rqst {
> >  	struct xdr_stream	rq_res_stream;
> >  	struct page		*rq_scratch_page;
> >  	struct xdr_buf		rq_res;
> > -	struct page		*rq_pages[RPCSVC_MAXPAGES + 1];
> > +	struct page		*rq_pages[RPCSVC_MAXPAGES_MAX + 1];
> >  	struct page *		*rq_respages;	/* points into rq_pages */
> >  	struct page *		*rq_next_page; /* next reply page to use */
> >  	struct page *		*rq_page_end;  /* one past the last page */
> >  
> >  	struct folio_batch	rq_fbatch;
> > -	struct kvec		rq_vec[RPCSVC_MAXPAGES]; /* generally useful.. */
> > -	struct bio_vec		rq_bvec[RPCSVC_MAXPAGES];
> > +	struct kvec		rq_vec[RPCSVC_MAXPAGES_MAX]; /* generally useful.. */
> > +	struct bio_vec		rq_bvec[RPCSVC_MAXPAGES_MAX];
> >  
> >  	__be32			rq_xid;		/* transmission id */
> >  	u32			rq_prog;	/* program number */
> > diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h
> > index d33bab33099ab..7c6441e8d6f7a 100644
> > --- a/include/linux/sunrpc/svc_rdma.h
> > +++ b/include/linux/sunrpc/svc_rdma.h
> > @@ -200,7 +200,7 @@ struct svc_rdma_recv_ctxt {
> >  	struct svc_rdma_pcl	rc_reply_pcl;
> >  
> >  	unsigned int		rc_page_count;
> > -	struct page		*rc_pages[RPCSVC_MAXPAGES];
> > +	struct page		*rc_pages[RPCSVC_MAXPAGES_MAX];
> >  };
> >  
> >  /*
> > @@ -242,7 +242,7 @@ struct svc_rdma_send_ctxt {
> >  	void			*sc_xprt_buf;
> >  	int			sc_page_count;
> >  	int			sc_cur_sge_no;
> > -	struct page		*sc_pages[RPCSVC_MAXPAGES];
> > +	struct page		*sc_pages[RPCSVC_MAXPAGES_MAX];
> >  	struct ib_sge		sc_sges[];
> >  };
> >  
> > diff --git a/include/linux/sunrpc/svcsock.h b/include/linux/sunrpc/svcsock.h
> > index 7c78ec6356b92..6c6bcc82685a3 100644
> > --- a/include/linux/sunrpc/svcsock.h
> > +++ b/include/linux/sunrpc/svcsock.h
> > @@ -40,7 +40,7 @@ struct svc_sock {
> >  
> >  	struct completion	sk_handshake_done;
> >  
> > -	struct page *		sk_pages[RPCSVC_MAXPAGES];	/* received data */
> > +	struct page *		sk_pages[RPCSVC_MAXPAGES_MAX];	/* received data */
> >  };
> >  
> >  static inline u32 svc_sock_reclen(struct svc_sock *svsk)
> 

-- 
Chuck Lever