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raw-posix: Fix raw_co_get_block_status() after EOF 

As its comment states, raw_co_get_block_status() should unconditionally
return 0 and set *pnum to 0 for after EOF.

An assertion after lseek(..., SEEK_HOLE) tried to catch this case by
asserting that errno != -ENXIO (which would indicate a position after
the EOF); but it should be errno != ENXIO instead. Regardless of that,
there should be no such assertion at all. If bdrv_getlength() returned
an outdated value and the image has been resized outside of qemu,
lseek() will return with errno == ENXIO. Just return that value as an
error then.

Setting *pnum to 0 and returning 0 should not be done here, as in that
case we should update the device length as well. So, from qemu's
perspective, the file has not been resized; it's just that there was an
error querying sectors beyond a certain point (the actual file size).

Additionally, nb_sectors should be clamped against the image end. This
was probably not an issue if FIEMAP or SEEK_HOLE/SEEK_DATA worked, but
the fallback did not take this case into account.

Reported-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-id: 1414148280-17949-2-git-send-email-mreitz@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Max Reitz 2014-10-24 12:57:58 +02:00 committed by Stefan Hajnoczi
parent f76faeda4b
commit e6d7ec32dd
1 changed files with 10 additions and 4 deletions
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14
block/raw-posix.c
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@ -1535,10 +1535,6 @@ static int64_t try_seek_hole(BlockDriverState *bs, off_t start, off_t *data,
*hole = lseek(s->fd, start, SEEK_HOLE);
if (*hole == -1) {
/* -ENXIO indicates that sector_num was past the end of the file.
* There is a virtual hole there. */
assert(errno != -ENXIO);
return -errno;
}
@ -1578,6 +1574,7 @@ static int64_t coroutine_fn raw_co_get_block_status(BlockDriverState *bs,
int nb_sectors, int *pnum)
{
off_t start, data = 0, hole = 0;
int64_t total_size;
int64_t ret;
ret = fd_open(bs);
@ -1586,6 +1583,15 @@ static int64_t coroutine_fn raw_co_get_block_status(BlockDriverState *bs,
}
start = sector_num * BDRV_SECTOR_SIZE;
total_size = bdrv_getlength(bs);
if (total_size < 0) {
return total_size;
} else if (start >= total_size) {
*pnum = 0;
return 0;
} else if (start + nb_sectors * BDRV_SECTOR_SIZE > total_size) {
nb_sectors = DIV_ROUND_UP(total_size - start, BDRV_SECTOR_SIZE);
}
ret = try_seek_hole(bs, start, &data, &hole, pnum);
if (ret < 0) {