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Re: [Qemu-devel] [PATCH v1 3/3] qcow2: check for NULL l2meta


From: Max Reitz
Subject: Re: [Qemu-devel] [PATCH v1 3/3] qcow2: check for NULL l2meta
Date: Sun, 19 Jan 2014 17:18:05 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0

On 30.12.2013 06:29, Hu Tao wrote:
In case of do preallocating metadata with a large cluster size,
qcow2_alloc_cluster_offset() can allocate nothing and returns
a NULL l2meta. This patch checks for it and link2 l2 with only
valid l2meta.

Signed-off-by: Hu Tao <address@hidden>
---
  block/qcow2.c | 14 ++++++++------
  1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/block/qcow2.c b/block/qcow2.c
index 46860d5..380c240 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1399,18 +1399,20 @@ static int preallocate(BlockDriverState *bs)
      offset = 0;
while (nb_sectors) {
-        num = MIN(nb_sectors, INT_MAX >> 9);
+        num = MIN(nb_sectors, INT_MAX >> BDRV_SECTOR_BITS);

Well, if you're already adjusting this here, you could also replace the other occurrences of 9 and 512 in this function. ;-)

          ret = qcow2_alloc_cluster_offset(bs, offset, &num,
                                           &host_offset, &meta);
          if (ret < 0) {
              return ret;
          }
- ret = qcow2_alloc_cluster_link_l2(bs, meta);
-        if (ret < 0) {
-            qcow2_free_any_clusters(bs, meta->alloc_offset, meta->nb_clusters,
-                                    QCOW2_DISCARD_NEVER);
-            return ret;
+        if (meta) {
+            ret = qcow2_alloc_cluster_link_l2(bs, meta);
+            if (ret < 0) {
+                qcow2_free_any_clusters(bs, meta->alloc_offset,
+                                        meta->nb_clusters, 
QCOW2_DISCARD_NEVER);
+                return ret;
+            }
          }
/* There are no dependent requests, but we need to remove our request

But this doesn't make this patch wrong, so:

Reviewed-by: Max Reitz <address@hidden>



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