From 4899d10d142e97eea8f64141a3507b2ee1a64f52 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Mon, 19 Apr 2010 13:34:11 +0100 Subject: raw-posix: Use pread/pwrite instead of lseek+read/write 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 Signed-off-by: Kevin Wolf --- block/raw-posix.c | 37 ++++--------------------------------- 1 file changed, 4 insertions(+), 33 deletions(-) diff --git a/block/raw-posix.c b/block/raw-posix.c index 598ea19a77..7541ed2abe 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; -- cgit v1.2.1