Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S265877AbTFSSCj (ORCPT ); Thu, 19 Jun 2003 14:02:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S265879AbTFSSCj (ORCPT ); Thu, 19 Jun 2003 14:02:39 -0400 Received: from air-2.osdl.org ([65.172.181.6]:40922 "EHLO mail.osdl.org") by vger.kernel.org with ESMTP id S265877AbTFSSCf (ORCPT ); Thu, 19 Jun 2003 14:02:35 -0400 Subject: [PATCH 2.5.72 1/2] i_size atomic access From: Daniel McNeil To: Andrew Morton , Linux Kernel Mailing List Cc: Andrea Arcangeli Content-Type: multipart/mixed; boundary="=-5fZdQvXIMEaAytk7UvwN" X-Mailer: Ximian Evolution 1.0.8 (1.0.8-10) Date: 19 Jun 2003 11:16:56 -0700 Message-Id: <1056046616.17359.18.camel@dell_ss5.pdx.osdl.net> Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2601 Lines: 95 --=-5fZdQvXIMEaAytk7UvwN Content-Type: text/plain Content-Transfer-Encoding: 7bit This adds a sequence counter only version of the reader/writer consistent mechanism to seqlock.h This is used in the second part of this patch give atomic access to i_size. re-diff against 2.5.72. The patch is also available for download from OSDL's patch lifecycle manager (PLM): http://www.osdl.org/cgi-bin/plm?module=patch_info&patch_id=1939 Daneil McNeil --=-5fZdQvXIMEaAytk7UvwN Content-Disposition: attachment; filename=patch.2.5.72-isize.1 Content-Transfer-Encoding: quoted-printable Content-Type: text/x-patch; name=patch.2.5.72-isize.1; charset=ISO-8859-1 diff -rupN -X /home/daniel_nfs/dontdiff linux-2.5.72/include/linux/seqlock.= h linux-2.5.72-isize/include/linux/seqlock.h --- linux-2.5.72/include/linux/seqlock.h 2003-06-16 21:20:00.000000000 -070= 0 +++ linux-2.5.72-isize/include/linux/seqlock.h 2003-06-17 16:56:25.15995628= 9 -0700 @@ -94,6 +94,57 @@ static inline int read_seqretry(const se return (iv & 1) | (sl->sequence ^ iv); } =20 + +/* + * Version using sequence counter only.=20 + * This can be used when code has its own mutex protecting the + * updating starting before the write_seqcntbeqin() and ending + * after the write_seqcntend(). + */ + +typedef struct seqcnt { + unsigned sequence; +} seqcnt_t; + +#define SEQCNT_ZERO { 0 } +#define seqcnt_init(x) do { *(x) =3D (seqcnt_t) SEQCNT_ZERO; } while (0) + +/* Start of read using pointer to a sequence counter only. */ +static inline unsigned read_seqcntbegin(const seqcnt_t *s) +{ + unsigned ret =3D s->sequence; + smp_rmb(); + return ret; +} + +/* Test if reader processed invalid data. + * Equivalent to: iv is odd or sequence number has changed. + * (iv & 1) || (*s !=3D iv) + * Using xor saves one conditional branch. + */ +static inline int read_seqcntretry(const seqcnt_t *s, unsigned iv) +{ + smp_rmb(); + return (iv & 1) | (s->sequence ^ iv); +} + + +/*=20 + * Sequence counter only version assumes that callers are using their + * own mutexing. + */ +static inline void write_seqcntbegin(seqcnt_t *s) +{ + s->sequence++; + smp_wmb(); =09 +}=09 + +static inline void write_seqcntend(seqcnt_t *s)=20 +{ + smp_wmb(); + s->sequence++; +} + /* * Possible sw/hw IRQ protected versions of the interfaces. */ --=-5fZdQvXIMEaAytk7UvwN-- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/