Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262246AbTEHXTe (ORCPT ); Thu, 8 May 2003 19:19:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262249AbTEHXTd (ORCPT ); Thu, 8 May 2003 19:19:33 -0400 Received: from air-2.osdl.org ([65.172.181.6]:59783 "EHLO mail.osdl.org") by vger.kernel.org with ESMTP id S262246AbTEHXTb (ORCPT ); Thu, 8 May 2003 19:19:31 -0400 Subject: [PATCH 2.5.69 1/2] i_size atomic access (again) From: Daniel McNeil To: Andrew Morton Cc: Andrea Arcangeli , Linux Kernel Mailing List In-Reply-To: <1052436552.2492.32.camel@ibm-c.pdx.osdl.net> References: <1052436552.2492.32.camel@ibm-c.pdx.osdl.net> Content-Type: multipart/mixed; boundary="=-U+TLpLvmdTxTnP7zH1jl" Organization: Message-Id: <1052436725.2492.38.camel@ibm-c.pdx.osdl.net> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.2.1 Date: 08 May 2003 16:32:05 -0700 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2638 Lines: 95 --=-U+TLpLvmdTxTnP7zH1jl Content-Type: text/plain Content-Transfer-Encoding: 7bit With the patch attached. On Thu, 2003-05-08 at 16:29, Daniel McNeil wrote: > 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 2.5.69. > > 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=1834 -- Daniel McNeil --=-U+TLpLvmdTxTnP7zH1jl Content-Disposition: attachment; filename=patch-2.5.69-isize.1 Content-Type: text/x-patch; name=patch-2.5.69-isize.1; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit diff -rupN -X /home/daniel/dontdiff linux-2.5.69/include/linux/seqlock.h linux-2.5.69-isize/include/linux/seqlock.h --- linux-2.5.69/include/linux/seqlock.h Sun May 4 16:53:14 2003 +++ linux-2.5.69-isize/include/linux/seqlock.h Wed May 7 16:00:25 2003 @@ -94,6 +94,57 @@ static inline int read_seqretry(const se return (iv & 1) | (sl->sequence ^ iv); } + +/* + * Version using sequence counter only. + * 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) = (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 = 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 != 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); +} + + +/* + * Sequence counter only version assumes that callers are using their + * own mutexing. + */ +static inline void write_seqcntbegin(seqcnt_t *s) +{ + s->sequence++; + smp_wmb(); +} + +static inline void write_seqcntend(seqcnt_t *s) +{ + smp_wmb(); + s->sequence++; +} + /* * Possible sw/hw IRQ protected versions of the interfaces. */ --=-U+TLpLvmdTxTnP7zH1jl-- - 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/