system/qemu
system/qemu
1
0
Fork 0
mirror of https://gitlab.com/qemu-project/qemu synced 2024-10-15 15:32:51 +00:00
Code Issues Packages Projects Releases Wiki Activity

dmg: drop broken bdrv_pread() loop

Browse source 
It is not necessary to check errno for EINTR and the block layer does
not produce short reads.  Therefore we can drop the loop that attempts
to read a compressed chunk.

The loop is buggy because it incorrectly adds the transferred bytes
twice:

  do {
      ret = bdrv_pread(...);
      i += ret;
  } while (ret >= 0 && ret + i < s->lengths[chunk]);

Luckily we can drop the loop completely and perform a single
bdrv_pread().

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2014-03-26 13:05:56 +01:00
parent 73ed27ec28
commit b404bf8542
1 changed files with 2 additions and 13 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

15
block/dmg.c
View file

@ -298,21 +298,10 @@ static inline int dmg_read_chunk(BlockDriverState *bs, int sector_num)
s->current_chunk = s->n_chunks;
switch (s->types[chunk]) {
case 0x80000005: { /* zlib compressed */
int i;
/* we need to buffer, because only the chunk as whole can be
* inflated. */
i = 0;
do {
ret = bdrv_pread(bs->file, s->offsets[chunk] + i,
s->compressed_chunk + i,
s->lengths[chunk] - i);
if (ret < 0 && errno == EINTR) {
ret = 0;
}
i += ret;
} while (ret >= 0 && ret + i < s->lengths[chunk]);
ret = bdrv_pread(bs->file, s->offsets[chunk],
s->compressed_chunk, s->lengths[chunk]);
if (ret != s->lengths[chunk]) {
return -1;
}