From f9674fc2928586d07b60ef0d46dcd0dce417955d Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Tue, 14 Feb 2012 11:13:39 +0100
Subject: [PATCH 14/99] cow: use pread/pwrite
RH-Author: Kevin Wolf <kwolf@redhat.com>
Message-id: <1329218101-24213-15-git-send-email-kwolf@redhat.com>
Patchwork-id: 37208
O-Subject: [RHEL-6.3 qemu-kvm PATCH v2 14/96] cow: use pread/pwrite
Bugzilla: 783950
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Marcelo Tosatti <mtosatti@redhat.com>
RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
From: Christoph Hellwig <hch@lst.de>
Bugzilla: 783950
Use pread/pwrite instead of lseek + read/write in preparation of using the
qemu block API.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 122bb9e32df488accad35ce6a52c3a2a5c33e4be)
---
block/cow.c | 10 +++++-----
1 files changed, 5 insertions(+), 5 deletions(-)
Signed-off-by: Michal Novotny <minovotn@redhat.com>
---
block/cow.c | 10 +++++-----
1 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/block/cow.c b/block/cow.c
index 8e21f02..932daee 100644
--- a/block/cow.c
+++ b/block/cow.c
@@ -78,7 +78,7 @@ static int cow_open(BlockDriverState *bs, const char *filename, int flags)
}
s->fd = fd;
/* see if it is a cow image */
- if (read(fd, &cow_header, sizeof(cow_header)) != sizeof(cow_header)) {
+ if (pread(fd, &cow_header, sizeof(cow_header), 0) != sizeof(cow_header)) {
goto fail;
}
@@ -159,8 +159,8 @@ static int cow_read(BlockDriverState *bs, int64_t sector_num,
while (nb_sectors > 0) {
if (is_changed(s->cow_bitmap, sector_num, nb_sectors, &n)) {
- lseek(s->fd, s->cow_sectors_offset + sector_num * 512, SEEK_SET);
- ret = read(s->fd, buf, n * 512);
+ ret = pread(s->fd, buf, n * 512,
+ s->cow_sectors_offset + sector_num * 512);
if (ret != n * 512)
return -1;
} else {
@@ -186,8 +186,8 @@ static int cow_write(BlockDriverState *bs, int64_t sector_num,
BDRVCowState *s = bs->opaque;
int ret, i;
- lseek(s->fd, s->cow_sectors_offset + sector_num * 512, SEEK_SET);
- ret = write(s->fd, buf, nb_sectors * 512);
+ ret = pwrite(s->fd, buf, nb_sectors * 512,
+ s->cow_sectors_offset + sector_num * 512);
if (ret != nb_sectors * 512)
return -1;
for (i = 0; i < nb_sectors; i++)
--
1.7.7.5