Patchwork [2/2] qcow2: Fix error handling in l2_allocate

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Submitter Kevin Wolf
Date May 20, 2010, 2:48 p.m.
Message ID <1274366923-30095-2-git-send-email-kwolf@redhat.com>
Download mbox | patch
Permalink /patch/53075/
State New
Headers show

Comments

Kevin Wolf - May 20, 2010, 2:48 p.m.
l2_allocate has some intermediate states in which the image is inconsistent.
Change the order to write to the L1 table only after the new L2 table has
successfully been initialized.

Also reset the L2 cache in failure case, it's very likely wrong.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/qcow2-cluster.c |   23 +++++++++++++----------
 1 files changed, 13 insertions(+), 10 deletions(-)
Stefan Hajnoczi - May 21, 2010, 9:44 a.m.
On Thu, May 20, 2010 at 3:48 PM, Kevin Wolf <kwolf@redhat.com> wrote:
> l2_allocate has some intermediate states in which the image is inconsistent.
> Change the order to write to the L1 table only after the new L2 table has
> successfully been initialized.

Looks good.

Stefan

Patch

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index ed5c4b2..244b4a7 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -239,14 +239,6 @@  static int l2_allocate(BlockDriverState *bs, int l1_index, uint64_t **table)
         return l2_offset;
     }
 
-    /* update the L1 entry */
-
-    s->l1_table[l1_index] = l2_offset | QCOW_OFLAG_COPIED;
-    ret = write_l1_entry(bs, l1_index);
-    if (ret < 0) {
-        return ret;
-    }
-
     /* allocate a new entry in the l2 cache */
 
     min_index = l2_cache_new_entry(bs);
@@ -261,7 +253,7 @@  static int l2_allocate(BlockDriverState *bs, int l1_index, uint64_t **table)
         ret = bdrv_pread(bs->file, old_l2_offset, l2_table,
             s->l2_size * sizeof(uint64_t));
         if (ret < 0) {
-            return ret;
+            goto fail;
         }
     }
     /* write the l2 table to the file */
@@ -269,7 +261,14 @@  static int l2_allocate(BlockDriverState *bs, int l1_index, uint64_t **table)
     ret = bdrv_pwrite(bs->file, l2_offset, l2_table,
         s->l2_size * sizeof(uint64_t));
     if (ret < 0) {
-        return ret;
+        goto fail;
+    }
+
+    /* update the L1 entry */
+    s->l1_table[l1_index] = l2_offset | QCOW_OFLAG_COPIED;
+    ret = write_l1_entry(bs, l1_index);
+    if (ret < 0) {
+        goto fail;
     }
 
     /* update the l2 cache entry */
@@ -279,6 +278,10 @@  static int l2_allocate(BlockDriverState *bs, int l1_index, uint64_t **table)
 
     *table = l2_table;
     return 0;
+
+fail:
+    qcow2_l2_cache_reset(bs);
+    return ret;
 }
 
 static int count_contiguous_clusters(uint64_t nb_clusters, int cluster_size,