|
From: | Max Reitz |
Subject: | Re: [Qemu-devel] [PATCH v6 09/11] qcow2: Clean up after refcount rebuild |
Date: | Tue, 21 Oct 2014 16:55:14 +0200 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 |
On 2014-10-21 at 12:16, Max Reitz wrote:
On 2014-10-21 at 11:59, Kevin Wolf wrote:Am 20.10.2014 um 16:35 hat Max Reitz geschrieben:Because the old refcount structure will be leaked after having rebuiltit, we need to recalculate the refcounts and run a leak-fixing operationafterwards (if leaks should be fixed at all). Signed-off-by: Max Reitz <address@hidden> Reviewed-by: BenoƮt Canet <address@hidden> --- block/qcow2-refcount.c | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c index 75e726b..3730be2 100644 --- a/block/qcow2-refcount.c +++ b/block/qcow2-refcount.c@@ -1956,12 +1956,47 @@ int qcow2_check_refcounts(BlockDriverState *bs, BdrvCheckResult *res,nb_clusters); if (rebuild && (fix & BDRV_FIX_ERRORS)) { + BdrvCheckResult old_res = *res; + fprintf(stderr, "Rebuilding refcount structure\n"); ret = rebuild_refcount_structure(bs, res, &refcount_table, &nb_clusters); if (ret < 0) { goto fail; } + + res->corruptions = 0; + res->leaks = 0; ++ /* Because the old reftable has been exchanged for a new one the+ * references have to be recalculated */ + rebuild = false; + memset(refcount_table, 0, nb_clusters * sizeof(uint16_t));+ ret = calculate_refcounts(bs, res, 0, &rebuild, &refcount_table,+ &nb_clusters); + if (ret < 0) { + goto fail; + } + + if (fix & BDRV_FIX_LEAKS) {+ /* The old refcount structures are now leaked, fix it; the result+ * can be ignored */ + pre_compare_res = *res;I would prefer using another local variable here. At the first sight it's not quite clear which references to pre_compare_res correspond to which state.Why not.+ compare_refcounts(bs, res, BDRV_FIX_LEAKS, &rebuild,+ &highest_cluster, refcount_table, nb_clusters);+ if (rebuild) {+ fprintf(stderr, "ERROR rebuilt refcount structure is still "+ "broken\n"); + } + *res = pre_compare_res; + } + + if (res->corruptions < old_res.corruptions) {+ res->corruptions_fixed += old_res.corruptions - res->corruptions;+ } + if (res->leaks < old_res.leaks) { + res->leaks_fixed += old_res.leaks - res->leaks; + }For these numbers to be accurate, don't we need to run compare_refcounts() unconditionally and only make BDRV_FIX_LEAKS conditional?Actually, there is no difference, because at the point of this patch, you cannot use BDRV_FIX_ERRORS without BDRV_FIX_LEAKS. But it'd be more correct, right.
Wait, it would not be more correct. The result of the compare_refcounts() call inside of the "if (fix & BDRV_FIX_LEAKS)" conditional block is ignored, its only purpose is to fix leaks resulting from rebuild_refcount_structure().
So the question is whether we should discard the result of that compare_refcounts() call. I think we should. Its sole purpose is to fix leaks due to the rebuilt refcount structures, and qemu-img will double check anyway.
Max
Thanks, MaxNow that I've read the rest of the series, comparing res and old_res actually makes sense, so maybe it's not necessary to introduce a Qcow2CheckResult.} else if (fix) { if (rebuild) {fprintf(stderr, "ERROR need to rebuild refcount structures\n");-- 2.1.2Kevin
[Prev in Thread] | Current Thread | [Next in Thread] |