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block: return BDRV_BLOCK_ZERO past end of backing file

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If the sectors are unallocated and we are past the end of the
backing file, they will read as zero.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Paolo Bonzini 2013-09-04 19:00:32 +02:00 committed by Stefan Hajnoczi
parent 415b5b013c
commit f0ad5712d5
1 changed files with 10 additions and 2 deletions
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12
block.c
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@ -3102,8 +3102,16 @@ static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs,
return ret;
}
if (!(ret & BDRV_BLOCK_DATA) && bdrv_has_zero_init(bs)) {
ret |= BDRV_BLOCK_ZERO;
if (!(ret & BDRV_BLOCK_DATA)) {
if (bdrv_has_zero_init(bs)) {
ret |= BDRV_BLOCK_ZERO;
} else {
BlockDriverState *bs2 = bs->backing_hd;
int64_t length2 = bdrv_getlength(bs2);
if (length2 >= 0 && sector_num >= (length2 >> BDRV_SECTOR_BITS)) {
ret |= BDRV_BLOCK_ZERO;
}
}
}
return ret;
}