On 11.11.2013 14:20, Kevin Wolf wrote:
Am 24.10.2013 um 12:06 hat Peter Lieven geschrieben:
Reviewed-by: Eric Blake <ebl...@redhat.com>
Signed-off-by: Peter Lieven <p...@kamp.de>
---
block.c | 37 ++++++++++++++++++++++++++++++++++++-
1 file changed, 36 insertions(+), 1 deletion(-)
diff --git a/block.c b/block.c
index 0c0b0ac..b28dd42 100644
--- a/block.c
+++ b/block.c
@@ -4234,6 +4234,11 @@ static void coroutine_fn bdrv_discard_co_entry(void
*opaque)
rwco->ret = bdrv_co_discard(rwco->bs, rwco->sector_num, rwco->nb_sectors);
}
+/* if no limit is specified in the BlockLimits use a default
+ * of 32768 512-byte sectors (16 MiB) per request.
+ */
+#define MAX_DISCARD_DEFAULT 32768
+
int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num,
int nb_sectors)
{
@@ -4255,7 +4260,37 @@ int coroutine_fn bdrv_co_discard(BlockDriverState *bs,
int64_t sector_num,
}
if (bs->drv->bdrv_co_discard) {
- return bs->drv->bdrv_co_discard(bs, sector_num, nb_sectors);
+ int max_discard = bs->bl.max_discard ?
+ bs->bl.max_discard : MAX_DISCARD_DEFAULT;
+
+ while (nb_sectors > 0) {
+ int ret;
+ int num = nb_sectors;
+
+ /* align request */
+ if (bs->bl.discard_alignment &&
+ num >= bs->bl.discard_alignment &&
+ sector_num % bs->bl.discard_alignment) {
+ if (num > bs->bl.discard_alignment) {
+ num = bs->bl.discard_alignment;
+ }
+ num -= sector_num % bs->bl.discard_alignment;
+ }
+
+ /* limit request size */
+ if (num > max_discard) {
+ num = max_discard;
+ }
+
+ ret = bs->drv->bdrv_co_discard(bs, sector_num, num);
+ if (ret) {
+ return ret;
+ }
+
+ sector_num += num;
+ nb_sectors -= num;
+ }
+ return 0;
} else if (bs->drv->bdrv_aio_discard) {
BlockDriverAIOCB *acb;
CoroutineIOCompletion co = {
You're only optimising drivers which have a .bdrv_co_discard()
implementation, but not those with .bdrv_aio_discard(). Not very nice,
and it would have been easy to avoid this by putting the loop around the
whole if statement instead of inside the 'then' branch.
Good point. I wonder noone noticed before ;-)
Do you want me to respin or is ok to send a follow up patch?
Stefan has it already in block-next. This patch doesn't make
the situation worse and we need follow up patches for
all the drivers to supply alignment information anyway.
Peter
