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block: Minimize raw use of bds->total_sectors 

bdrv_is_allocated_above() was relying on intermediate->total_sectors,
which is a field that can have stale contents depending on the value
of intermediate->has_variable_length.  An audit shows that we are safe
(we were first calling through bdrv_co_get_block_status() which in
turn calls bdrv_nb_sectors() and therefore just refreshed the current
length), but it's nicer to favor our accessor functions to avoid having
to repeat such an audit, even if it means refresh_total_sectors() is
called more frequently.

Suggested-by: John Snow <jsnow@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Manos Pitsidianakis <el13635@mail.ntua.gr>
Reviewed-by: Jeff Cody <jcody@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Eric Blake 2017-07-07 07:44:58 -05:00 committed by Kevin Wolf
parent d6a644bbfe
commit c00716beb3
1 changed files with 6 additions and 8 deletions
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14
block/io.c
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@ -1947,6 +1947,7 @@ int bdrv_is_allocated_above(BlockDriverState *top,
intermediate = top;
while (intermediate && intermediate != base) {
int64_t pnum_inter;
int64_t size_inter;
int psectors_inter;
ret = bdrv_is_allocated(intermediate, sector_num * BDRV_SECTOR_SIZE,
@ -1962,15 +1963,12 @@ int bdrv_is_allocated_above(BlockDriverState *top,
return 1;
}
/*
* [sector_num, nb_sectors] is unallocated on top but intermediate
* might have
*
* [sector_num+x, nr_sectors] allocated.
*/
size_inter = bdrv_nb_sectors(intermediate);
if (size_inter < 0) {
return size_inter;
}
if (n > psectors_inter &&
(intermediate == top ||
sector_num + psectors_inter < intermediate->total_sectors)) {
(intermediate == top || sector_num + psectors_inter < size_inter)) {
n = psectors_inter;
}