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[Qemu-devel] [PATCH v5 08/26] qcow2: Refcount overflow and qcow2_alloc_b
From: |
Max Reitz |
Subject: |
[Qemu-devel] [PATCH v5 08/26] qcow2: Refcount overflow and qcow2_alloc_bytes() |
Date: |
Mon, 15 Dec 2014 13:50:39 +0100 |
qcow2_alloc_bytes() may reuse a cluster multiple times, in which case
the refcount is increased accordingly. However, if this would lead to an
overflow the function should instead just not reuse this cluster and
allocate a new one.
Signed-off-by: Max Reitz <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
Reviewed-by: Stefan Hajnoczi <address@hidden>
---
block/qcow2-refcount.c | 31 ++++++++++++++++++++++++++++++-
1 file changed, 30 insertions(+), 1 deletion(-)
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index db81647..fd28a13 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -780,9 +780,11 @@ int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size)
BDRVQcowState *s = bs->opaque;
int64_t offset, cluster_offset, new_cluster;
int free_in_cluster, ret;
+ uint64_t refcount;
BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_ALLOC_BYTES);
assert(size > 0 && size <= s->cluster_size);
+ redo:
if (s->free_byte_offset == 0) {
offset = qcow2_alloc_clusters(bs, s->cluster_size);
if (offset < 0) {
@@ -790,12 +792,25 @@ int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size)
}
s->free_byte_offset = offset;
}
- redo:
+
free_in_cluster = s->cluster_size -
offset_into_cluster(s, s->free_byte_offset);
if (size <= free_in_cluster) {
/* enough space in current cluster */
offset = s->free_byte_offset;
+
+ if (offset_into_cluster(s, offset) != 0) {
+ /* We will have to increase the refcount of this cluster; if the
+ * maximum has been reached already, this cluster cannot be used */
+ ret = qcow2_get_refcount(bs, offset >> s->cluster_bits, &refcount);
+ if (ret < 0) {
+ return ret;
+ } else if (refcount == s->refcount_max) {
+ s->free_byte_offset = 0;
+ goto redo;
+ }
+ }
+
s->free_byte_offset += size;
free_in_cluster -= size;
if (free_in_cluster == 0)
@@ -816,6 +831,20 @@ int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size)
if ((cluster_offset + s->cluster_size) == new_cluster) {
/* we are lucky: contiguous data */
offset = s->free_byte_offset;
+
+ /* Same as above: In order to reuse the cluster, the refcount has
to
+ * be increased; if that will not work, we are not so lucky after
+ * all */
+ ret = qcow2_get_refcount(bs, offset >> s->cluster_bits, &refcount);
+ if (ret < 0) {
+ qcow2_free_clusters(bs, new_cluster, s->cluster_size,
+ QCOW2_DISCARD_NEVER);
+ return ret;
+ } else if (refcount == s->refcount_max) {
+ s->free_byte_offset = offset;
+ goto redo;
+ }
+
ret = qcow2_update_cluster_refcount(bs, offset >> s->cluster_bits,
1, false, QCOW2_DISCARD_NEVER);
if (ret < 0) {
--
1.9.3
- [Qemu-devel] [PATCH v5 00/26] qcow2: Support refcount orders != 4, Max Reitz, 2014/12/15
- [Qemu-devel] [PATCH v5 02/26] qcow2: Add refcount_bits to format-specific info, Max Reitz, 2014/12/15
- [Qemu-devel] [PATCH v5 03/26] qcow2: Do not return new value after refcount update, Max Reitz, 2014/12/15
- [Qemu-devel] [PATCH v5 04/26] qcow2: Only return status from qcow2_get_refcount, Max Reitz, 2014/12/15
- [Qemu-devel] [PATCH v5 01/26] qcow2: Add two new fields to BDRVQcowState, Max Reitz, 2014/12/15
- [Qemu-devel] [PATCH v5 06/26] qcow2: Use 64 bits for refcount values, Max Reitz, 2014/12/15
- [Qemu-devel] [PATCH v5 07/26] qcow2: Respect error in qcow2_alloc_bytes(), Max Reitz, 2014/12/15
- [Qemu-devel] [PATCH v5 05/26] qcow2: Use unsigned addend for update_refcount(), Max Reitz, 2014/12/15
- [Qemu-devel] [PATCH v5 08/26] qcow2: Refcount overflow and qcow2_alloc_bytes(),
Max Reitz <=
- [Qemu-devel] [PATCH v5 09/26] qcow2: Helper for refcount array reallocation, Max Reitz, 2014/12/15
- [Qemu-devel] [PATCH v5 10/26] qcow2: Helper function for refcount modification, Max Reitz, 2014/12/15
- [Qemu-devel] [PATCH v5 11/26] qcow2: More helpers for refcount modification, Max Reitz, 2014/12/15
- [Qemu-devel] [PATCH v5 12/26] qcow2: Open images with refcount order != 4, Max Reitz, 2014/12/15
- [Qemu-devel] [PATCH v5 13/26] qcow2: refcount_order parameter for qcow2_create2, Max Reitz, 2014/12/15
- [Qemu-devel] [PATCH v5 14/26] qcow2: Use symbolic macros in qcow2_amend_options, Max Reitz, 2014/12/15
- [Qemu-devel] [PATCH v5 15/26] iotests: Prepare for refcount_bits option, Max Reitz, 2014/12/15
- [Qemu-devel] [PATCH v5 16/26] qcow2: Allow creation with refcount order != 4, Max Reitz, 2014/12/15
- [Qemu-devel] [PATCH v5 17/26] progress: Allow regressing progress, Max Reitz, 2014/12/15
- [Qemu-devel] [PATCH v5 18/26] block: Add opaque value to the amend CB, Max Reitz, 2014/12/15