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cloop: use pread 

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 12:44:38 +02:00 committed by Kevin Wolf
parent cb7cf0e3f4
commit c94304be3f
1 changed files with 17 additions and 15 deletions
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32
block/cloop.c
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@ -62,23 +62,22 @@ static int cloop_open(BlockDriverState *bs, const char *filename, int flags)
bs->read_only = 1;
/* read header */
if(lseek(s->fd,128,SEEK_SET)<0) {
cloop_close:
close(s->fd);
return -1;
if (pread(s->fd, &s->block_size, 4, 128) < 4) {
goto cloop_close;
}
if(read(s->fd,&s->block_size,4)<4)
goto cloop_close;
s->block_size=be32_to_cpu(s->block_size);
if(read(s->fd,&s->n_blocks,4)<4)
goto cloop_close;
s->n_blocks=be32_to_cpu(s->n_blocks);
s->block_size = be32_to_cpu(s->block_size);
if (pread(s->fd, &s->n_blocks, 4, 128 + 4) < 4) {
goto cloop_close;
}
s->n_blocks = be32_to_cpu(s->n_blocks);
/* read offsets */
offsets_size=s->n_blocks*sizeof(uint64_t);
s->offsets=(uint64_t*)qemu_malloc(offsets_size);
if(read(s->fd,s->offsets,offsets_size)<offsets_size)
offsets_size = s->n_blocks * sizeof(uint64_t);
s->offsets = qemu_malloc(offsets_size);
if (pread(s->fd, s->offsets, offsets_size, 128 + 4 + 4) < offsets_size) {
goto cloop_close;
}
for(i=0;i<s->n_blocks;i++) {
s->offsets[i]=be64_to_cpu(s->offsets[i]);
if(i>0) {
@ -98,6 +97,10 @@ cloop_close:
s->sectors_per_block = s->block_size/512;
bs->total_sectors = s->n_blocks*s->sectors_per_block;
return 0;
cloop_close:
close(s->fd);
return -1;
}
static inline int cloop_read_block(BDRVCloopState *s,int block_num)
@ -106,8 +109,7 @@ static inline int cloop_read_block(BDRVCloopState *s,int block_num)
int ret;
uint32_t bytes = s->offsets[block_num+1]-s->offsets[block_num];
lseek(s->fd, s->offsets[block_num], SEEK_SET);
ret = read(s->fd, s->compressed_block, bytes);
ret = pread(s->fd, s->compressed_block, bytes, s->offsets[block_num]);
if (ret != bytes)
return -1;