Commit c00716be authored Jul 07, 2017 by Eric Blake Committed by Kevin Wolf Jul 10, 2017

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>

parent d6a644bb

block/io.c

+6 −8

Original line number	Diff line number	Diff line
		@@ -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;
		}