From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Shawn O. Pearce" Subject: [PATCH 2/7] Switch git_mmap to use pread. Date: Sun, 24 Dec 2006 00:45:47 -0500 Message-ID: <20061224054547.GB8146@spearce.org> References: <487c7d0ea81f2f82f330e277e0aea38a66ca7cfe.1166939109.git.spearce@spearce.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: git@vger.kernel.org X-From: git-owner@vger.kernel.org Sun Dec 24 06:45:58 2006 Return-path: Envelope-to: gcvg-git@gmane.org Received: from vger.kernel.org ([209.132.176.167]) by dough.gmane.org with esmtp (Exim 4.50) id 1GyMBG-0001QZ-QX for gcvg-git@gmane.org; Sun, 24 Dec 2006 06:45:55 +0100 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754111AbWLXFpv (ORCPT ); Sun, 24 Dec 2006 00:45:51 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754115AbWLXFpv (ORCPT ); Sun, 24 Dec 2006 00:45:51 -0500 Received: from corvette.plexpod.net ([64.38.20.226]:53720 "EHLO corvette.plexpod.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754111AbWLXFpu (ORCPT ); Sun, 24 Dec 2006 00:45:50 -0500 Received: from cpe-74-70-48-173.nycap.res.rr.com ([74.70.48.173] helo=asimov.home.spearce.org) by corvette.plexpod.net with esmtpa (Exim 4.52) id 1GyMBB-0008LO-23; Sun, 24 Dec 2006 00:45:49 -0500 Received: by asimov.home.spearce.org (Postfix, from userid 1000) id 5077420FB65; Sun, 24 Dec 2006 00:45:47 -0500 (EST) To: Junio C Hamano Content-Disposition: inline In-Reply-To: <487c7d0ea81f2f82f330e277e0aea38a66ca7cfe.1166939109.git.spearce@spearce.org> User-Agent: Mutt/1.5.11 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - corvette.plexpod.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [0 0] / [47 12] X-AntiAbuse: Sender Address Domain - spearce.org X-Source: X-Source-Args: X-Source-Dir: Sender: git-owner@vger.kernel.org Precedence: bulk X-Mailing-List: git@vger.kernel.org Archived-At: Now that Git depends on pread in index-pack its safe to say we can also depend on it within the git_mmap emulation we activate when NO_MMAP is set. On most systems pread should be slightly faster than an lseek/read/lseek sequence as its one system call vs. three system calls. We also now honor EAGAIN and EINTR error codes from pread and restart the prior read. Signed-off-by: Shawn O. Pearce --- compat/mmap.c | 17 ++++------------- 1 files changed, 4 insertions(+), 13 deletions(-) diff --git a/compat/mmap.c b/compat/mmap.c index bb34c7e..98056f0 100644 --- a/compat/mmap.c +++ b/compat/mmap.c @@ -2,17 +2,11 @@ void *git_mmap(void *start, size_t length, int prot, int flags, int fd, off_t offset) { - int n = 0; - off_t current_offset = lseek(fd, 0, SEEK_CUR); + size_t n = 0; if (start != NULL || !(flags & MAP_PRIVATE)) die("Invalid usage of mmap when built with NO_MMAP"); - if (lseek(fd, offset, SEEK_SET) < 0) { - errno = EINVAL; - return MAP_FAILED; - } - start = xmalloc(length); if (start == NULL) { errno = ENOMEM; @@ -20,7 +14,7 @@ void *git_mmap(void *start, size_t length, int prot, int flags, int fd, off_t of } while (n < length) { - int count = read(fd, start+n, length-n); + ssize_t count = pread(fd, start + n, length - n, offset + n); if (count == 0) { memset(start+n, 0, length-n); @@ -28,6 +22,8 @@ void *git_mmap(void *start, size_t length, int prot, int flags, int fd, off_t of } if (count < 0) { + if (errno == EAGAIN || errno == EINTR) + continue; free(start); errno = EACCES; return MAP_FAILED; @@ -36,11 +32,6 @@ void *git_mmap(void *start, size_t length, int prot, int flags, int fd, off_t of n += count; } - if (current_offset != lseek(fd, current_offset, SEEK_SET)) { - errno = EINVAL; - return MAP_FAILED; - } - return start; } -- 1.4.4.3.g2e63