Changeset 64829 in vbox for trunk/src/VBox

Timestamp:

Dec 12, 2016 8:08:31 AM (8 years ago)

Author:

vboxsync

Message:

Storage/QCOW: Remember an L2 table if it was just created so it can be accessed when another read or write happens in the same area at the same time. Fixes assertion in VD layer

File:

• trunk/src/VBox/Storage/QCOW.cpp (modified) (6 diffs)

trunk/src/VBox/Storage/QCOW.cpp

@@ -248 +248 @@
     uint32_t            cL2Shift;
 
+    /** Pointer to the L2 table we are currently allocating
+     * (can be only one at a time). */
+    PQCOWL2CACHEENTRY   pL2TblAlloc;
+
 } QCOWIMAGE, *PQCOWIMAGE;
 
@@ -500 +504 @@
 static PQCOWL2CACHEENTRY qcowL2TblCacheRetain(PQCOWIMAGE pImage, uint64_t offL2Tbl)
 {
+    if (   pImage->pL2TblAlloc
+        && pImage->pL2TblAlloc->offL2Tbl == offL2Tbl)
+    {
+        pImage->pL2TblAlloc->cRefs++;
+        return pImage->pL2TblAlloc;
+    }
+
     PQCOWL2CACHEENTRY pL2Entry;
     RTListForEach(&pImage->ListSearch, pL2Entry, QCOWL2CACHEENTRY, NodeSearch)
@@ -1322 +1333 @@
             /* Revert the L1 table entry */
             pImage->paL1Table[pClusterAlloc->idxL1] = 0;
+            pImage->pL2TblAlloc = NULL;
 
             /* Assumption right now is that the L1 table is not modified on storage if the link fails. */
             rc = vdIfIoIntFileSetSize(pImage->pIfIo, pImage->pStorage, pClusterAlloc->offNextClusterOld);
             qcowL2TblCacheEntryRelease(pClusterAlloc->pL2Entry); /* Release L2 cache entry. */
+            Assert(!pClusterAlloc->pL2Entry->cRefs);
             qcowL2TblCacheEntryFree(pImage, pClusterAlloc->pL2Entry); /* Free it, it is not in the cache yet. */
             break;
@@ -1394 +1407 @@
             uint64_t offData = qcowClusterAllocate(pImage, 1);
 
+            pImage->pL2TblAlloc = NULL;
             qcowL2TblCacheEntryInsert(pImage, pClusterAlloc->pL2Entry);
 
@@ -1763 +1777 @@
                         pL2ClusterAlloc->cbToWrite         = cbToWrite;
                         pL2ClusterAlloc->pL2Entry          = pL2Entry;
+
+                        pImage->pL2TblAlloc = pL2Entry;
+
+                        LogFlowFunc(("Allocating new L2 table at cluster offset %llu\n", offL2Tbl));
 
                         /*
@@ -1785 +1803 @@
                     else
                     {
+                        LogFlowFunc(("Fetching L2 table at cluster offset %llu\n", pImage->paL1Table[idxL1]));
+
                         rc = qcowL2TblCacheFetch(pImage, pIoCtx, pImage->paL1Table[idxL1],
                                                  &pL2Entry);