From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1O3qAs-0001aM-V1 for qemu-devel@nongnu.org; Mon, 19 Apr 2010 08:34:03 -0400 Received: from [140.186.70.92] (port=57364 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1O3qAo-0001Ys-9g for qemu-devel@nongnu.org; Mon, 19 Apr 2010 08:34:02 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1O3qAl-0000Ld-D5 for qemu-devel@nongnu.org; Mon, 19 Apr 2010 08:33:58 -0400 Received: from mtagate2.uk.ibm.com ([194.196.100.162]:43009) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1O3qAl-0000L6-5p for qemu-devel@nongnu.org; Mon, 19 Apr 2010 08:33:55 -0400 Received: from d06nrmr1407.portsmouth.uk.ibm.com (d06nrmr1407.portsmouth.uk.ibm.com [9.149.38.185]) by mtagate2.uk.ibm.com (8.13.1/8.13.1) with ESMTP id o3JCXqjH029239 for ; Mon, 19 Apr 2010 12:33:52 GMT Received: from d06av04.portsmouth.uk.ibm.com (d06av04.portsmouth.uk.ibm.com [9.149.37.216]) by d06nrmr1407.portsmouth.uk.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id o3JCXpwp913448 for ; Mon, 19 Apr 2010 13:33:51 +0100 Received: from d06av04.portsmouth.uk.ibm.com (loopback [127.0.0.1]) by d06av04.portsmouth.uk.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id o3JCXp3o005615 for ; Mon, 19 Apr 2010 13:33:51 +0100 From: Stefan Hajnoczi Date: Mon, 19 Apr 2010 13:34:11 +0100 Message-Id: <1271680452-24121-1-git-send-email-stefanha@linux.vnet.ibm.com> Subject: [Qemu-devel] [PATCH 1/2] raw-posix: Use pread/pwrite instead of lseek+read/write List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Kevin Wolf , Jan Kiszka , Christoph Hellwig , Stefan Hajnoczi This patch combines the lseek+read/write calls to use pread/pwrite instead. This will result in fewer system calls and is already used by AIO. Thanks to Jan Kiszka for identifying excessive lseek and Christoph Hellwig for confirming that this approach should work. Signed-off-by: Stefan Hajnoczi --- block/raw-posix.c | 37 ++++--------------------------------- 1 files changed, 4 insertions(+), 33 deletions(-) diff --git a/block/raw-posix.c b/block/raw-posix.c index 598ea19..7541ed2 100644 --- a/block/raw-posix.c +++ b/block/raw-posix.c @@ -105,7 +105,6 @@ typedef struct BDRVRawState { int fd; int type; - unsigned int lseek_err_cnt; int open_flags; #if defined(__linux__) /* linux floppy specific */ @@ -134,8 +133,6 @@ static int raw_open_common(BlockDriverState *bs, const char *filename, BDRVRawState *s = bs->opaque; int fd, ret; - s->lseek_err_cnt = 0; - s->open_flags = open_flags | O_BINARY; s->open_flags &= ~O_ACCMODE; if (bdrv_flags & BDRV_O_RDWR) { @@ -243,19 +240,7 @@ static int raw_pread_aligned(BlockDriverState *bs, int64_t offset, if (ret < 0) return ret; - if (offset >= 0 && lseek(s->fd, offset, SEEK_SET) == (off_t)-1) { - ++(s->lseek_err_cnt); - if(s->lseek_err_cnt <= 10) { - DEBUG_BLOCK_PRINT("raw_pread(%d:%s, %" PRId64 ", %p, %d) [%" PRId64 - "] lseek failed : %d = %s\n", - s->fd, bs->filename, offset, buf, count, - bs->total_sectors, errno, strerror(errno)); - } - return -1; - } - s->lseek_err_cnt=0; - - ret = read(s->fd, buf, count); + ret = pread(s->fd, buf, count, offset); if (ret == count) goto label__raw_read__success; @@ -276,12 +261,10 @@ static int raw_pread_aligned(BlockDriverState *bs, int64_t offset, /* Try harder for CDrom. */ if (bs->type == BDRV_TYPE_CDROM) { - lseek(s->fd, offset, SEEK_SET); - ret = read(s->fd, buf, count); + ret = pread(s->fd, buf, count, offset); if (ret == count) goto label__raw_read__success; - lseek(s->fd, offset, SEEK_SET); - ret = read(s->fd, buf, count); + ret = pread(s->fd, buf, count, offset); if (ret == count) goto label__raw_read__success; @@ -313,19 +296,7 @@ static int raw_pwrite_aligned(BlockDriverState *bs, int64_t offset, if (ret < 0) return -errno; - if (offset >= 0 && lseek(s->fd, offset, SEEK_SET) == (off_t)-1) { - ++(s->lseek_err_cnt); - if(s->lseek_err_cnt) { - DEBUG_BLOCK_PRINT("raw_pwrite(%d:%s, %" PRId64 ", %p, %d) [%" - PRId64 "] lseek failed : %d = %s\n", - s->fd, bs->filename, offset, buf, count, - bs->total_sectors, errno, strerror(errno)); - } - return -EIO; - } - s->lseek_err_cnt = 0; - - ret = write(s->fd, buf, count); + ret = pwrite(s->fd, buf, count, offset); if (ret == count) goto label__raw_write__success; -- 1.7.0