From 3be020259d1627f335fe27aac1dc55e1249b7390 Mon Sep 17 00:00:00 2001
From: Max Reitz <mreitz@redhat.com>
Date: Sat, 13 Jun 2015 16:22:22 +0200
Subject: [PATCH 28/42] qcow2: Rebuild refcount structure during check
Message-id: <1434212556-3927-29-git-send-email-mreitz@redhat.com>
Patchwork-id: 66047
O-Subject: [RHEL-7.2 qemu-kvm PATCH 28/42] qcow2: Rebuild refcount structure during check
Bugzilla: 1129893
RH-Acked-by: Jeffrey Cody <jcody@redhat.com>
RH-Acked-by: Fam Zheng <famz@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
BZ: 1129893
The previous commit introduced the "rebuild" variable to qcow2's
implementation of the image consistency check. Now make use of this by
adding a function which creates a completely new refcount structure
based solely on the in-memory information gathered before.
The old refcount structure will be leaked, however. This leak will be
dealt with in a follow-up commit.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit c7c0681bc8a781e0319b7cf969b904dfe50d083e)
Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
block/qcow2-refcount.c | 311 ++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 305 insertions(+), 6 deletions(-)
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 3d66e7c..651ddb6 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -1660,6 +1660,285 @@ static void compare_refcounts(BlockDriverState *bs, BdrvCheckResult *res,
}
/*
+ * Allocates clusters using an in-memory refcount table (IMRT) in contrast to
+ * the on-disk refcount structures.
+ *
+ * On input, *first_free_cluster tells where to start looking, and need not
+ * actually be a free cluster; the returned offset will not be before that
+ * cluster. On output, *first_free_cluster points to the first gap found, even
+ * if that gap was too small to be used as the returned offset.
+ *
+ * Note that *first_free_cluster is a cluster index whereas the return value is
+ * an offset.
+ */
+static int64_t alloc_clusters_imrt(BlockDriverState *bs,
+ int cluster_count,
+ uint16_t **refcount_table,
+ int64_t *imrt_nb_clusters,
+ int64_t *first_free_cluster)
+{
+ BDRVQcowState *s = bs->opaque;
+ int64_t cluster = *first_free_cluster, i;
+ bool first_gap = true;
+ int contiguous_free_clusters;
+
+ /* Starting at *first_free_cluster, find a range of at least cluster_count
+ * continuously free clusters */
+ for (contiguous_free_clusters = 0;
+ cluster < *imrt_nb_clusters &&
+ contiguous_free_clusters < cluster_count;
+ cluster++)
+ {
+ if (!(*refcount_table)[cluster]) {
+ contiguous_free_clusters++;
+ if (first_gap) {
+ /* If this is the first free cluster found, update
+ * *first_free_cluster accordingly */
+ *first_free_cluster = cluster;
+ first_gap = false;
+ }
+ } else if (contiguous_free_clusters) {
+ contiguous_free_clusters = 0;
+ }
+ }
+
+ /* If contiguous_free_clusters is greater than zero, it contains the number
+ * of continuously free clusters until the current cluster; the first free
+ * cluster in the current "gap" is therefore
+ * cluster - contiguous_free_clusters */
+
+ /* If no such range could be found, grow the in-memory refcount table
+ * accordingly to append free clusters at the end of the image */
+ if (contiguous_free_clusters < cluster_count) {
+ int64_t old_imrt_nb_clusters = *imrt_nb_clusters;
+ uint16_t *new_refcount_table;
+
+ /* contiguous_free_clusters clusters are already empty at the image end;
+ * we need cluster_count clusters; therefore, we have to allocate
+ * cluster_count - contiguous_free_clusters new clusters at the end of
+ * the image (which is the current value of cluster; note that cluster
+ * may exceed old_imrt_nb_clusters if *first_free_cluster pointed beyond
+ * the image end) */
+ *imrt_nb_clusters = cluster + cluster_count - contiguous_free_clusters;
+ new_refcount_table = g_try_realloc(*refcount_table,
+ *imrt_nb_clusters *
+ sizeof(**refcount_table));
+ if (!new_refcount_table) {
+ *imrt_nb_clusters = old_imrt_nb_clusters;
+ return -ENOMEM;
+ }
+ *refcount_table = new_refcount_table;
+
+ memset(*refcount_table + old_imrt_nb_clusters, 0,
+ (*imrt_nb_clusters - old_imrt_nb_clusters) *
+ sizeof(**refcount_table));
+ }
+
+ /* Go back to the first free cluster */
+ cluster -= contiguous_free_clusters;
+ for (i = 0; i < cluster_count; i++) {
+ (*refcount_table)[cluster + i] = 1;
+ }
+
+ return cluster << s->cluster_bits;
+}
+
+/*
+ * Creates a new refcount structure based solely on the in-memory information
+ * given through *refcount_table. All necessary allocations will be reflected
+ * in that array.
+ *
+ * On success, the old refcount structure is leaked (it will be covered by the
+ * new refcount structure).
+ */
+static int rebuild_refcount_structure(BlockDriverState *bs,
+ BdrvCheckResult *res,
+ uint16_t **refcount_table,
+ int64_t *nb_clusters)
+{
+ BDRVQcowState *s = bs->opaque;
+ int64_t first_free_cluster = 0, reftable_offset = -1, cluster = 0;
+ int64_t refblock_offset, refblock_start, refblock_index;
+ uint32_t reftable_size = 0;
+ uint64_t *on_disk_reftable = NULL;
+ uint16_t *on_disk_refblock;
+ int i, ret = 0;
+ struct {
+ uint64_t reftable_offset;
+ uint32_t reftable_clusters;
+ } QEMU_PACKED reftable_offset_and_clusters;
+
+ qcow2_cache_empty(bs, s->refcount_block_cache);
+
+write_refblocks:
+ for (; cluster < *nb_clusters; cluster++) {
+ if (!(*refcount_table)[cluster]) {
+ continue;
+ }
+
+ refblock_index = cluster >> s->refcount_block_bits;
+ refblock_start = refblock_index << s->refcount_block_bits;
+
+ /* Don't allocate a cluster in a refblock already written to disk */
+ if (first_free_cluster < refblock_start) {
+ first_free_cluster = refblock_start;
+ }
+ refblock_offset = alloc_clusters_imrt(bs, 1, refcount_table,
+ nb_clusters, &first_free_cluster);
+ if (refblock_offset < 0) {
+ fprintf(stderr, "ERROR allocating refblock: %s\n",
+ strerror(-refblock_offset));
+ res->check_errors++;
+ ret = refblock_offset;
+ goto fail;
+ }
+
+ if (reftable_size <= refblock_index) {
+ uint32_t old_reftable_size = reftable_size;
+ uint64_t *new_on_disk_reftable;
+
+ reftable_size = ROUND_UP((refblock_index + 1) * sizeof(uint64_t),
+ s->cluster_size) / sizeof(uint64_t);
+ new_on_disk_reftable = g_try_realloc(on_disk_reftable,
+ reftable_size *
+ sizeof(uint64_t));
+ if (!new_on_disk_reftable) {
+ res->check_errors++;
+ ret = -ENOMEM;
+ goto fail;
+ }
+ on_disk_reftable = new_on_disk_reftable;
+
+ memset(on_disk_reftable + old_reftable_size, 0,
+ (reftable_size - old_reftable_size) * sizeof(uint64_t));
+
+ /* The offset we have for the reftable is now no longer valid;
+ * this will leak that range, but we can easily fix that by running
+ * a leak-fixing check after this rebuild operation */
+ reftable_offset = -1;
+ }
+ on_disk_reftable[refblock_index] = refblock_offset;
+
+ /* If this is apparently the last refblock (for now), try to squeeze the
+ * reftable in */
+ if (refblock_index == (*nb_clusters - 1) >> s->refcount_block_bits &&
+ reftable_offset < 0)
+ {
+ uint64_t reftable_clusters = size_to_clusters(s, reftable_size *
+ sizeof(uint64_t));
+ reftable_offset = alloc_clusters_imrt(bs, reftable_clusters,
+ refcount_table, nb_clusters,
+ &first_free_cluster);
+ if (reftable_offset < 0) {
+ fprintf(stderr, "ERROR allocating reftable: %s\n",
+ strerror(-reftable_offset));
+ res->check_errors++;
+ ret = reftable_offset;
+ goto fail;
+ }
+ }
+
+ ret = qcow2_pre_write_overlap_check(bs, 0, refblock_offset,
+ s->cluster_size);
+ if (ret < 0) {
+ fprintf(stderr, "ERROR writing refblock: %s\n", strerror(-ret));
+ goto fail;
+ }
+
+ on_disk_refblock = qemu_blockalign0(bs->file, s->cluster_size);
+ for (i = 0; i < s->refcount_block_size &&
+ refblock_start + i < *nb_clusters; i++)
+ {
+ on_disk_refblock[i] =
+ cpu_to_be16((*refcount_table)[refblock_start + i]);
+ }
+
+ ret = bdrv_write(bs->file, refblock_offset / BDRV_SECTOR_SIZE,
+ (void *)on_disk_refblock, s->cluster_sectors);
+ qemu_vfree(on_disk_refblock);
+ if (ret < 0) {
+ fprintf(stderr, "ERROR writing refblock: %s\n", strerror(-ret));
+ goto fail;
+ }
+
+ /* Go to the end of this refblock */
+ cluster = refblock_start + s->refcount_block_size - 1;
+ }
+
+ if (reftable_offset < 0) {
+ uint64_t post_refblock_start, reftable_clusters;
+
+ post_refblock_start = ROUND_UP(*nb_clusters, s->refcount_block_size);
+ reftable_clusters = size_to_clusters(s,
+ reftable_size * sizeof(uint64_t));
+ /* Not pretty but simple */
+ if (first_free_cluster < post_refblock_start) {
+ first_free_cluster = post_refblock_start;
+ }
+ reftable_offset = alloc_clusters_imrt(bs, reftable_clusters,
+ refcount_table, nb_clusters,
+ &first_free_cluster);
+ if (reftable_offset < 0) {
+ fprintf(stderr, "ERROR allocating reftable: %s\n",
+ strerror(-reftable_offset));
+ res->check_errors++;
+ ret = reftable_offset;
+ goto fail;
+ }
+
+ goto write_refblocks;
+ }
+
+ assert(on_disk_reftable);
+
+ for (refblock_index = 0; refblock_index < reftable_size; refblock_index++) {
+ cpu_to_be64s(&on_disk_reftable[refblock_index]);
+ }
+
+ ret = qcow2_pre_write_overlap_check(bs, 0, reftable_offset,
+ reftable_size * sizeof(uint64_t));
+ if (ret < 0) {
+ fprintf(stderr, "ERROR writing reftable: %s\n", strerror(-ret));
+ goto fail;
+ }
+
+ assert(reftable_size < INT_MAX / sizeof(uint64_t));
+ ret = bdrv_pwrite(bs->file, reftable_offset, on_disk_reftable,
+ reftable_size * sizeof(uint64_t));
+ if (ret < 0) {
+ fprintf(stderr, "ERROR writing reftable: %s\n", strerror(-ret));
+ goto fail;
+ }
+
+ /* Enter new reftable into the image header */
+ cpu_to_be64w(&reftable_offset_and_clusters.reftable_offset,
+ reftable_offset);
+ cpu_to_be32w(&reftable_offset_and_clusters.reftable_clusters,
+ size_to_clusters(s, reftable_size * sizeof(uint64_t)));
+ ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader,
+ refcount_table_offset),
+ &reftable_offset_and_clusters,
+ sizeof(reftable_offset_and_clusters));
+ if (ret < 0) {
+ fprintf(stderr, "ERROR setting reftable: %s\n", strerror(-ret));
+ goto fail;
+ }
+
+ for (refblock_index = 0; refblock_index < reftable_size; refblock_index++) {
+ be64_to_cpus(&on_disk_reftable[refblock_index]);
+ }
+ s->refcount_table = on_disk_reftable;
+ s->refcount_table_offset = reftable_offset;
+ s->refcount_table_size = reftable_size;
+
+ return 0;
+
+fail:
+ g_free(on_disk_reftable);
+ return ret;
+}
+
+/*
* Checks an image for refcount consistency.
*
* Returns 0 if no errors are found, the number of errors in case the image is
@@ -1669,6 +1948,7 @@ int qcow2_check_refcounts(BlockDriverState *bs, BdrvCheckResult *res,
BdrvCheckMode fix)
{
BDRVQcowState *s = bs->opaque;
+ BdrvCheckResult pre_compare_res;
int64_t size, highest_cluster, nb_clusters;
uint16_t *refcount_table = NULL;
bool rebuild = false;
@@ -1695,14 +1975,33 @@ int qcow2_check_refcounts(BlockDriverState *bs, BdrvCheckResult *res,
goto fail;
}
- compare_refcounts(bs, res, fix, &rebuild, &highest_cluster, refcount_table,
+ /* In case we don't need to rebuild the refcount structure (but want to fix
+ * something), this function is immediately called again, in which case the
+ * result should be ignored */
+ pre_compare_res = *res;
+ compare_refcounts(bs, res, 0, &rebuild, &highest_cluster, refcount_table,
nb_clusters);
- if (rebuild) {
- fprintf(stderr, "ERROR need to rebuild refcount structures\n");
- res->check_errors++;
- /* Just carry on, the rest does not rely on the on-disk refcount
- * structures */
+ if (rebuild && (fix & BDRV_FIX_ERRORS)) {
+ fprintf(stderr, "Rebuilding refcount structure\n");
+ ret = rebuild_refcount_structure(bs, res, &refcount_table,
+ &nb_clusters);
+ if (ret < 0) {
+ goto fail;
+ }
+ } else if (fix) {
+ if (rebuild) {
+ fprintf(stderr, "ERROR need to rebuild refcount structures\n");
+ res->check_errors++;
+ ret = -EIO;
+ goto fail;
+ }
+
+ if (res->leaks || res->corruptions) {
+ *res = pre_compare_res;
+ compare_refcounts(bs, res, fix, &rebuild, &highest_cluster,
+ refcount_table, nb_clusters);
+ }
}
/* check OFLAG_COPIED */
--
1.8.3.1