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[Qemu-devel] [PATCH 1/2] parallels: use pread
From: |
Christoph Hellwig |
Subject: |
[Qemu-devel] [PATCH 1/2] parallels: use pread |
Date: |
Thu, 6 May 2010 22:04:34 +0200 |
User-agent: |
Mutt/1.3.28i |
Use pread instead of lseek + read in preparation of using the qemu
block API.
Signed-off-by: Christoph Hellwig <address@hidden>
Index: qemu-kevin/block/parallels.c
===================================================================
--- qemu-kevin.orig/block/parallels.c 2010-05-06 21:59:25.809255629 +0200
+++ qemu-kevin/block/parallels.c 2010-05-06 22:01:11.343284544 +0200
@@ -83,7 +83,7 @@ static int parallels_open(BlockDriverSta
s->fd = fd;
- if (read(fd, &ph, sizeof(ph)) != sizeof(ph))
+ if (pread(fd, &ph, sizeof(ph), 0) != sizeof(ph))
goto fail;
if (memcmp(ph.magic, HEADER_MAGIC, 16) ||
@@ -93,14 +93,11 @@ static int parallels_open(BlockDriverSta
bs->total_sectors = le32_to_cpu(ph.nb_sectors);
- if (lseek(s->fd, 64, SEEK_SET) != 64)
- goto fail;
-
s->tracks = le32_to_cpu(ph.tracks);
s->catalog_size = le32_to_cpu(ph.catalog_entries);
s->catalog_bitmap = qemu_malloc(s->catalog_size * 4);
- if (read(s->fd, s->catalog_bitmap, s->catalog_size * 4) !=
+ if (pread(s->fd, s->catalog_bitmap, s->catalog_size * 4, 64) !=
s->catalog_size * 4)
goto fail;
for (i = 0; i < s->catalog_size; i++)
@@ -114,28 +111,18 @@ fail:
return -1;
}
-static inline int seek_to_sector(BlockDriverState *bs, int64_t sector_num)
+static int64_t seek_to_sector(BlockDriverState *bs, int64_t sector_num)
{
BDRVParallelsState *s = bs->opaque;
uint32_t index, offset;
- uint64_t position;
index = sector_num / s->tracks;
offset = sector_num % s->tracks;
- // not allocated
+ /* not allocated */
if ((index > s->catalog_size) || (s->catalog_bitmap[index] == 0))
return -1;
-
- position = (uint64_t)(s->catalog_bitmap[index] + offset) * 512;
-
-// fprintf(stderr, "sector: %llx index=%x offset=%x pointer=%x
position=%x\n",
-// sector_num, index, offset, s->catalog_bitmap[index], position);
-
- if (lseek(s->fd, position, SEEK_SET) != position)
- return -1;
-
- return 0;
+ return (uint64_t)(s->catalog_bitmap[index] + offset) * 512;
}
static int parallels_read(BlockDriverState *bs, int64_t sector_num,
@@ -144,11 +131,13 @@ static int parallels_read(BlockDriverSta
BDRVParallelsState *s = bs->opaque;
while (nb_sectors > 0) {
- if (!seek_to_sector(bs, sector_num)) {
- if (read(s->fd, buf, 512) != 512)
- return -1;
- } else
+ int64_t position = seek_to_sector(bs, sector_num);
+ if (position >= 0) {
+ if (pread(s->fd, buf, 512, position) != 512)
+ return -1;
+ } else {
memset(buf, 0, 512);
+ }
nb_sectors--;
sector_num++;
buf += 512;
- [Qemu-devel] [PATCH 1/2] parallels: use pread,
Christoph Hellwig <=