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authorKevin Wolf <kwolf@redhat.com>2011-11-16 12:43:59 +0100
committerKevin Wolf <kwolf@redhat.com>2011-12-05 14:51:36 +0100
commitd1ea98d56dc2485b4637a1ca19feef786b3aee8f (patch)
treee2f7b247199b3f261b696af7e3f55ae34cca8044
parent03343166f703d5c8f02b8519f8493c56e5541ae7 (diff)
downloadqemu-arm-d1ea98d56dc2485b4637a1ca19feef786b3aee8f.tar.gz
qcow2: Rework qcow2_snapshot_create error handling
Increase refcounts only after allocating a new L1 table has succeeded in order to make leaks less likely. If writing the snapshot table fails, revert in-memory state to be consistent with that on disk. While at it, make it return the real error codes instead of -1. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
-rw-r--r--block/qcow2-snapshot.c55
1 files changed, 41 insertions, 14 deletions
diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
index 53d9233ba9..a8add9c857 100644
--- a/block/qcow2-snapshot.c
+++ b/block/qcow2-snapshot.c
@@ -277,7 +277,9 @@ static int find_snapshot_by_id_or_name(BlockDriverState *bs, const char *name)
int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
{
BDRVQcowState *s = bs->opaque;
- QCowSnapshot *snapshots1, sn1, *sn = &sn1;
+ QCowSnapshot *new_snapshot_list = NULL;
+ QCowSnapshot *old_snapshot_list = NULL;
+ QCowSnapshot sn1, *sn = &sn1;
int i, ret;
uint64_t *l1_table = NULL;
int64_t l1_table_offset;
@@ -303,16 +305,12 @@ int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
sn->date_nsec = sn_info->date_nsec;
sn->vm_clock_nsec = sn_info->vm_clock_nsec;
- ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 1);
- if (ret < 0)
- goto fail;
-
/* Allocate the L1 table of the snapshot and copy the current one there. */
l1_table_offset = qcow2_alloc_clusters(bs, s->l1_size * sizeof(uint64_t));
if (l1_table_offset < 0) {
+ ret = l1_table_offset;
goto fail;
}
- bdrv_flush(bs->file);
sn->l1_table_offset = l1_table_offset;
sn->l1_size = s->l1_size;
@@ -321,22 +319,50 @@ int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
for(i = 0; i < s->l1_size; i++) {
l1_table[i] = cpu_to_be64(s->l1_table[i]);
}
- if (bdrv_pwrite_sync(bs->file, sn->l1_table_offset,
- l1_table, s->l1_size * sizeof(uint64_t)) < 0)
+
+ ret = bdrv_pwrite(bs->file, sn->l1_table_offset, l1_table,
+ s->l1_size * sizeof(uint64_t));
+ if (ret < 0) {
goto fail;
+ }
+
g_free(l1_table);
l1_table = NULL;
- snapshots1 = g_malloc((s->nb_snapshots + 1) * sizeof(QCowSnapshot));
+ /*
+ * Increase the refcounts of all clusters and make sure everything is
+ * stable on disk before updating the snapshot table to contain a pointer
+ * to the new L1 table.
+ */
+ ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 1);
+ if (ret < 0) {
+ goto fail;
+ }
+
+ ret = bdrv_flush(bs);
+ if (ret < 0) {
+ goto fail;
+ }
+
+ /* Append the new snapshot to the snapshot list */
+ new_snapshot_list = g_malloc((s->nb_snapshots + 1) * sizeof(QCowSnapshot));
if (s->snapshots) {
- memcpy(snapshots1, s->snapshots, s->nb_snapshots * sizeof(QCowSnapshot));
- g_free(s->snapshots);
+ memcpy(new_snapshot_list, s->snapshots,
+ s->nb_snapshots * sizeof(QCowSnapshot));
+ old_snapshot_list = s->snapshots;
}
- s->snapshots = snapshots1;
+ s->snapshots = new_snapshot_list;
s->snapshots[s->nb_snapshots++] = *sn;
- if (qcow2_write_snapshots(bs) < 0)
+ ret = qcow2_write_snapshots(bs);
+ if (ret < 0) {
+ g_free(s->snapshots);
+ s->snapshots = old_snapshot_list;
goto fail;
+ }
+
+ g_free(old_snapshot_list);
+
#ifdef DEBUG_ALLOC
{
BdrvCheckResult result = {0};
@@ -349,7 +375,8 @@ fail:
g_free(sn->id_str);
g_free(sn->name);
g_free(l1_table);
- return -1;
+
+ return ret;
}
/* copy the snapshot 'snapshot_name' into the current disk image */