qcow2: Add runtime options for cache sizes

Add options for specifying the size of the metadata caches. This can
either be done directly for each cache (if only one is given, the other
will be derived according to a default ratio) or combined for both.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

2 files changed, 103 insertions, 11 deletions

diff --git a/block/qcow2.c b/block/qcow2.c
index 0f1be2e..f9e045f 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -442,6 +442,22 @@ static QemuOptsList qcow2_runtime_opts = {
             .type = QEMU_OPT_BOOL,
             .help = "Check for unintended writes into an inactive L2 table",
         },
+        {
+            .name = QCOW2_OPT_CACHE_SIZE,
+            .type = QEMU_OPT_SIZE,
+            .help = "Maximum combined metadata (L2 tables and refcount blocks) "
+                    "cache size",
+        },
+        {
+            .name = QCOW2_OPT_L2_CACHE_SIZE,
+            .type = QEMU_OPT_SIZE,
+            .help = "Maximum L2 table cache size",
+        },
+        {
+            .name = QCOW2_OPT_REFCOUNT_CACHE_SIZE,
+            .type = QEMU_OPT_SIZE,
+            .help = "Maximum refcount block cache size",
+        },
         { /* end of list */ }
     },
 };
@@ -457,6 +473,61 @@ static const char *overlap_bool_option_names[QCOW2_OL_MAX_BITNR] = {
     [QCOW2_OL_INACTIVE_L2_BITNR]    = QCOW2_OPT_OVERLAP_INACTIVE_L2,
 };
 
+static void read_cache_sizes(QemuOpts *opts, uint64_t *l2_cache_size,
+                             uint64_t *refcount_cache_size, Error **errp)
+{
+    uint64_t combined_cache_size;
+    bool l2_cache_size_set, refcount_cache_size_set, combined_cache_size_set;
+
+    combined_cache_size_set = qemu_opt_get(opts, QCOW2_OPT_CACHE_SIZE);
+    l2_cache_size_set = qemu_opt_get(opts, QCOW2_OPT_L2_CACHE_SIZE);
+    refcount_cache_size_set = qemu_opt_get(opts, QCOW2_OPT_REFCOUNT_CACHE_SIZE);
+
+    combined_cache_size = qemu_opt_get_size(opts, QCOW2_OPT_CACHE_SIZE, 0);
+    *l2_cache_size = qemu_opt_get_size(opts, QCOW2_OPT_L2_CACHE_SIZE, 0);
+    *refcount_cache_size = qemu_opt_get_size(opts,
+                                             QCOW2_OPT_REFCOUNT_CACHE_SIZE, 0);
+
+    if (combined_cache_size_set) {
+        if (l2_cache_size_set && refcount_cache_size_set) {
+            error_setg(errp, QCOW2_OPT_CACHE_SIZE ", " QCOW2_OPT_L2_CACHE_SIZE
+                       " and " QCOW2_OPT_REFCOUNT_CACHE_SIZE " may not be set "
+                       "the same time");
+            return;
+        } else if (*l2_cache_size > combined_cache_size) {
+            error_setg(errp, QCOW2_OPT_L2_CACHE_SIZE " may not exceed "
+                       QCOW2_OPT_CACHE_SIZE);
+            return;
+        } else if (*refcount_cache_size > combined_cache_size) {
+            error_setg(errp, QCOW2_OPT_REFCOUNT_CACHE_SIZE " may not exceed "
+                       QCOW2_OPT_CACHE_SIZE);
+            return;
+        }
+
+        if (l2_cache_size_set) {
+            *refcount_cache_size = combined_cache_size - *l2_cache_size;
+        } else if (refcount_cache_size_set) {
+            *l2_cache_size = combined_cache_size - *refcount_cache_size;
+        } else {
+            *refcount_cache_size = combined_cache_size
+                                 / (DEFAULT_L2_REFCOUNT_SIZE_RATIO + 1);
+            *l2_cache_size = combined_cache_size - *refcount_cache_size;
+        }
+    } else {
+        if (!l2_cache_size_set && !refcount_cache_size_set) {
+            *l2_cache_size = DEFAULT_L2_CACHE_BYTE_SIZE;
+            *refcount_cache_size = *l2_cache_size
+                                 / DEFAULT_L2_REFCOUNT_SIZE_RATIO;
+        } else if (!l2_cache_size_set) {
+            *l2_cache_size = *refcount_cache_size
+                           * DEFAULT_L2_REFCOUNT_SIZE_RATIO;
+        } else if (!refcount_cache_size_set) {
+            *refcount_cache_size = *l2_cache_size
+                                 / DEFAULT_L2_REFCOUNT_SIZE_RATIO;
+        }
+    }
+}
+
 static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
                       Error **errp)
 {
@@ -707,17 +778,43 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
         }
     }
 
-    /* alloc L2 table/refcount block cache */
-    l2_cache_size = DEFAULT_L2_CACHE_BYTE_SIZE / s->cluster_size;
+    /* get L2 table/refcount block cache size from command line options */
+    opts = qemu_opts_create(&qcow2_runtime_opts, NULL, 0, &error_abort);
+    qemu_opts_absorb_qdict(opts, options, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        ret = -EINVAL;
+        goto fail;
+    }
+
+    read_cache_sizes(opts, &l2_cache_size, &refcount_cache_size, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        ret = -EINVAL;
+        goto fail;
+    }
+
+    l2_cache_size /= s->cluster_size;
     if (l2_cache_size < MIN_L2_CACHE_SIZE) {
         l2_cache_size = MIN_L2_CACHE_SIZE;
     }
+    if (l2_cache_size > INT_MAX) {
+        error_setg(errp, "L2 cache size too big");
+        ret = -EINVAL;
+        goto fail;
+    }
 
-    refcount_cache_size = l2_cache_size / DEFAULT_L2_REFCOUNT_SIZE_RATIO;
+    refcount_cache_size /= s->cluster_size;
     if (refcount_cache_size < MIN_REFCOUNT_CACHE_SIZE) {
         refcount_cache_size = MIN_REFCOUNT_CACHE_SIZE;
     }
+    if (refcount_cache_size > INT_MAX) {
+        error_setg(errp, "Refcount cache size too big");
+        ret = -EINVAL;
+        goto fail;
+    }
 
+    /* alloc L2 table/refcount block cache */
     s->l2_table_cache = qcow2_cache_create(bs, l2_cache_size);
     s->refcount_block_cache = qcow2_cache_create(bs, refcount_cache_size);
     if (s->l2_table_cache == NULL || s->refcount_block_cache == NULL) {
@@ -809,14 +906,6 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
     }
 
     /* Enable lazy_refcounts according to image and command line options */
-    opts = qemu_opts_create(&qcow2_runtime_opts, NULL, 0, &error_abort);
-    qemu_opts_absorb_qdict(opts, options, &local_err);
-    if (local_err) {
-        error_propagate(errp, local_err);
-        ret = -EINVAL;
-        goto fail;
-    }
-
     s->use_lazy_refcounts = qemu_opt_get_bool(opts, QCOW2_OPT_LAZY_REFCOUNTS,
         (s->compatible_features & QCOW2_COMPAT_LAZY_REFCOUNTS));
 
diff --git a/block/qcow2.h b/block/qcow2.h
index 671783d..6aeb7ea 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -91,6 +91,9 @@
 #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_CACHE_SIZE "cache-size"
+#define QCOW2_OPT_L2_CACHE_SIZE "l2-cache-size"
+#define QCOW2_OPT_REFCOUNT_CACHE_SIZE "refcount-cache-size"
 
 typedef struct QCowHeader {
     uint32_t magic;