On 28.06.21 21:10, Eric Blake wrote:
+++ b/include/block/block_int.h
@@ -347,6 +347,11 @@ struct BlockDriver {
* clamped to bdrv_getlength() and aligned to request_alignment,
* as well as non-NULL pnum, map, and file; in turn, the driver
* must return an error or set pnum to an aligned non-zero value.
+ *
+ * Note that @bytes is just a hint on how big of a region the
+ * caller wants to inspect. It is not a limit on *pnum.
+ * Implementations are free to return larger values of *pnum if
+ * doing so does not incur a performance penalty.
Worth mention that the cache will benefit of it?
Oh, right, absolutely. Like so:
"block/io.c's bdrv_co_block_status() will clamp *pnum before returning it to
its caller, but it itself can still make use of the unclamped *pnum value.
Specifically, the block-status cache for protocol nodes will benefit from
storing as large a region as possible."
How about this tweak to the wording to make it flow a little better:
block/io.c's bdrv_co_block_status() will utilize an unclamped *pnum
value for the block-status cache on protocol nodes, prior to clamping
*pnum for return to its caller.
Sure, thanks!
Max
