From 8e50724313895a87057cc243ad805f2eb21feb9f Mon Sep 17 00:00:00 2001 From: Fam Zheng Date: Thu, 1 Aug 2013 18:12:17 +0800 Subject: vmdk: fix comment for vmdk_co_write_zeroes The comment was truncated. Add the missing parts, especially explain why we need zero_dry_run. Signed-off-by: Fam Zheng Signed-off-by: Michael Tokarev --- block/vmdk.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/block/vmdk.c b/block/vmdk.c index 3756333c60..e6c50b1e35 100644 --- a/block/vmdk.c +++ b/block/vmdk.c @@ -1200,8 +1200,10 @@ static coroutine_fn int vmdk_co_read(BlockDriverState *bs, int64_t sector_num, /** * vmdk_write: * @zeroed: buf is ignored (data is zero), use zeroed_grain GTE feature - * if possible, otherwise return -ENOTSUP. - * @zero_dry_run: used for zeroed == true only, don't update L2 table, just + * if possible, otherwise return -ENOTSUP. + * @zero_dry_run: used for zeroed == true only, don't update L2 table, just try + * with each cluster. By dry run we can find if the zero write + * is possible without modifying image data. * * Returns: error code with 0 for success. */ @@ -1328,6 +1330,8 @@ static int coroutine_fn vmdk_co_write_zeroes(BlockDriverState *bs, int ret; BDRVVmdkState *s = bs->opaque; qemu_co_mutex_lock(&s->lock); + /* write zeroes could fail if sectors not aligned to cluster, test it with + * dry_run == true before really updating image */ ret = vmdk_write(bs, sector_num, NULL, nb_sectors, true, true); if (!ret) { ret = vmdk_write(bs, sector_num, NULL, nb_sectors, true, false); -- cgit v1.2.3