[Qemu-devel] [PATCH v5 15/17] qcow2: Add overlap structure memory size options

[Max Reitz <mreitz@redhat.com>]

Add runtime options to qcow2 to control the size of the structures used
for metadata overlap prevention (one option to control the size of the
bitmap cache, another one to control the total memory size limit).

Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 block/qcow2.c | 35 +++++++++++++++++++++++++++++++++--
 block/qcow2.h |  2 ++
 2 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/block/qcow2.c b/block/qcow2.c
index d1257b1..d3f2e71 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -452,6 +452,18 @@ static QemuOptsList qcow2_runtime_opts = {
             .help = "Check for unintended writes into an inactive L2 table",
         },
         {
+            .name = QCOW2_OPT_OVERLAP_BITMAP_SIZE,
+            .type = QEMU_OPT_SIZE,
+            .help = "Size for the bitmap cache used by the metadata overlap "
+                    "check",
+        },
+        {
+            .name = QCOW2_OPT_OVERLAP_TOTAL_SIZE_LIMIT,
+            .type = QEMU_OPT_SIZE,
+            .help = "Maximum total memory size to be used for the metadata "
+                    "overlap check structures",
+        },
+        {
             .name = QCOW2_OPT_CACHE_SIZE,
             .type = QEMU_OPT_SIZE,
             .help = "Maximum combined metadata (L2 tables and refcount blocks) "
@@ -767,8 +779,27 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
     s->cluster_offset_mask = (1LL << s->csize_shift) - 1;
 
     if (s->overlap_check) {
-        /* TODO: Let the user override this default */
-        ret = qcow2_create_empty_metadata_list(bs, 65536, SIZE_MAX, errp);
+        uint64_t cache_size, total_size;
+
+        cache_size = qemu_opt_get_size(opts, QCOW2_OPT_OVERLAP_BITMAP_SIZE,
+                                       65536);
+        if (cache_size > SIZE_MAX) {
+            error_setg(errp, "qcow2 option '" QCOW2_OPT_OVERLAP_BITMAP_SIZE
+                       "' expects an argument less or equal to %zu", SIZE_MAX);
+            ret = -EINVAL;
+            goto fail;
+        }
+
+        total_size = qemu_opt_get_size(opts, QCOW2_OPT_OVERLAP_TOTAL_SIZE_LIMIT,
+                                       SIZE_MAX);
+        if (total_size > SIZE_MAX) {
+            error_setg(errp, "qcow2 option '" QCOW2_OPT_OVERLAP_TOTAL_SIZE_LIMIT
+                       "' expects an argument less or equal to %zu", SIZE_MAX);
+            ret = -EINVAL;
+            goto fail;
+        }
+
+        ret = qcow2_create_empty_metadata_list(bs, cache_size, total_size, errp);
         if (ret < 0) {
             goto fail;
         }
diff --git a/block/qcow2.h b/block/qcow2.h
index 7f4059e..400fe52 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -93,6 +93,8 @@
 #define QCOW2_OPT_OVERLAP_SNAPSHOT_TABLE "overlap-check.snapshot-table"
 #define QCOW2_OPT_OVERLAP_INACTIVE_L1 "overlap-check.inactive-l1"
 #define QCOW2_OPT_OVERLAP_INACTIVE_L2 "overlap-check.inactive-l2"
+#define QCOW2_OPT_OVERLAP_BITMAP_SIZE "overlap-structures.bitmap-size"
+#define QCOW2_OPT_OVERLAP_TOTAL_SIZE_LIMIT "overlap-structures.total-size-limit"
 #define QCOW2_OPT_CACHE_SIZE "cache-size"
 #define QCOW2_OPT_L2_CACHE_SIZE "l2-cache-size"
 #define QCOW2_OPT_REFCOUNT_CACHE_SIZE "refcount-cache-size"
-- 
2.4.6