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bochs: use pread

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Use pread instead of lseek + read in preparation of using the qemu
block API.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Christoph Hellwig 2010-05-04 12:44:08 +02:00 committed by Kevin Wolf
parent 38d8dfa193
commit efbca10f10
1 changed files with 20 additions and 43 deletions
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59
block/bochs.c
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@ -125,7 +125,7 @@ static int bochs_open(BlockDriverState *bs, const char *filename, int flags)
s->fd = fd;
if (read(fd, &bochs, sizeof(bochs)) != sizeof(bochs)) {
if (pread(fd, &bochs, sizeof(bochs), 0) != sizeof(bochs)) {
goto fail;
}
@ -144,14 +144,10 @@ static int bochs_open(BlockDriverState *bs, const char *filename, int flags)
bs->total_sectors = le64_to_cpu(bochs.extra.redolog.disk) / 512;
}
if (lseek(s->fd, le32_to_cpu(bochs.header), SEEK_SET) == (off_t)-1) {
goto fail;
}
s->catalog_size = le32_to_cpu(bochs.extra.redolog.catalog);
s->catalog_bitmap = qemu_malloc(s->catalog_size * 4);
if (read(s->fd, s->catalog_bitmap, s->catalog_size * 4) !=
s->catalog_size * 4)
if (pread(s->fd, s->catalog_bitmap, s->catalog_size * 4,
le32_to_cpu(bochs.header)) != s->catalog_size * 4)
goto fail;
for (i = 0; i < s->catalog_size; i++)
le32_to_cpus(&s->catalog_bitmap[i]);
@ -169,54 +165,35 @@ static int bochs_open(BlockDriverState *bs, const char *filename, int flags)
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)
{
BDRVBochsState *s = bs->opaque;
int64_t offset = sector_num * 512;
int64_t extent_index, extent_offset, bitmap_offset, block_offset;
int64_t extent_index, extent_offset, bitmap_offset;
char bitmap_entry;
// seek to sector
extent_index = offset / s->extent_size;
extent_offset = (offset % s->extent_size) / 512;
if (s->catalog_bitmap[extent_index] == 0xffffffff)
{
// fprintf(stderr, "page not allocated [%x - %x:%x]\n",
// sector_num, extent_index, extent_offset);
return -1; // not allocated
if (s->catalog_bitmap[extent_index] == 0xffffffff) {
return -1; /* not allocated */
}
bitmap_offset = s->data_offset + (512 * s->catalog_bitmap[extent_index] *
(s->extent_blocks + s->bitmap_blocks));
block_offset = bitmap_offset + (512 * (s->bitmap_blocks + extent_offset));
// fprintf(stderr, "sect: %x [ext i: %x o: %x] -> %x bitmap: %x block: %x\n",
// sector_num, extent_index, extent_offset,
// le32_to_cpu(s->catalog_bitmap[extent_index]),
// bitmap_offset, block_offset);
// read in bitmap for current extent
if (lseek(s->fd, bitmap_offset + (extent_offset / 8), SEEK_SET) ==
(off_t)-1) {
/* read in bitmap for current extent */
if (pread(s->fd, &bitmap_entry, 1, bitmap_offset + (extent_offset / 8))
!= 1) {
return -1;
}
if (read(s->fd, &bitmap_entry, 1) != 1)
return -1;
if (!((bitmap_entry >> (extent_offset % 8)) & 1))
{
// fprintf(stderr, "sector (%x) in bitmap not allocated\n",
// sector_num);
return -1; // not allocated
if (!((bitmap_entry >> (extent_offset % 8)) & 1)) {
return -1; /* not allocated */
}
if (lseek(s->fd, block_offset, SEEK_SET) == (off_t)-1) {
return -1;
}
return 0;
return bitmap_offset + (512 * (s->bitmap_blocks + extent_offset));
}
static int bochs_read(BlockDriverState *bs, int64_t sector_num,
@ -226,13 +203,13 @@ static int bochs_read(BlockDriverState *bs, int64_t sector_num,
int ret;
while (nb_sectors > 0) {
if (!seek_to_sector(bs, sector_num))
{
ret = read(s->fd, buf, 512);
if (ret != 512)
int64_t block_offset = seek_to_sector(bs, sector_num);
if (block_offset >= 0) {
ret = pread(s->fd, buf, 512, block_offset);
if (ret != 512) {
return -1;
}
else
} else
memset(buf, 0, 512);
nb_sectors--;
sector_num++;