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authorChristoph Hellwig <hch@lst.de>2010-06-07 12:06:28 +0200
committerKevin Wolf <kwolf@redhat.com>2010-06-15 09:41:59 +0200
commit122bb9e32df488accad35ce6a52c3a2a5c33e4be (patch)
treeb7f489428b243d65386b8e8525c66b0708c5d513
parent68dba0bf455e60061bb3c9c40ef0d82916372664 (diff)
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cow: use pread/pwrite
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>
-rw-r--r--block/cow.c10
1 files changed, 5 insertions, 5 deletions
diff --git a/block/cow.c b/block/cow.c
index fde066e..1a48ac0 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++)