qcow2: Add the 'extended_l2' option and the QCOW2_INCOMPAT_EXTL2 bit

Now that the implementation of subclusters is complete we can finally
add the necessary options to create and read images with this feature,
which we call "extended L2 entries".

Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <6476caaa73216bd05b7bb2d504a20415e1665176.1594396418.git.berto@igalia.com>
[mreitz: %s/5\.1/5.2/; fixed 302's and 303's reference output]
Signed-off-by: Max Reitz <mreitz@redhat.com>

2 files changed, 65 insertions, 9 deletions

diff --git a/block/qcow2.c b/block/qcow2.c
index 7c03d41170..00cda5696b 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1449,6 +1449,12 @@ static int coroutine_fn qcow2_do_open(BlockDriverState *bs, QDict *options,
     s->subcluster_size = s->cluster_size / s->subclusters_per_cluster;
     s->subcluster_bits = ctz32(s->subcluster_size);
 
+    if (s->subcluster_size < (1 << MIN_CLUSTER_BITS)) {
+        error_setg(errp, "Unsupported subcluster size: %d", s->subcluster_size);
+        ret = -EINVAL;
+        goto fail;
+    }
+
     /* Check support for various header values */
     if (header.refcount_order > 6) {
         error_setg(errp, "Reference count entry width too large; may not "
@@ -2935,6 +2941,11 @@ int qcow2_update_header(BlockDriverState *bs)
                 .name = "compression type",
             },
             {
+                .type = QCOW2_FEAT_TYPE_INCOMPATIBLE,
+                .bit  = QCOW2_INCOMPAT_EXTL2_BITNR,
+                .name = "extended L2 entries",
+            },
+            {
                 .type = QCOW2_FEAT_TYPE_COMPATIBLE,
                 .bit  = QCOW2_COMPAT_LAZY_REFCOUNTS_BITNR,
                 .name = "lazy refcounts",
@@ -3270,7 +3281,8 @@ static int64_t qcow2_calc_prealloc_size(int64_t total_size,
     return meta_size + aligned_total_size;
 }
 
-static bool validate_cluster_size(size_t cluster_size, Error **errp)
+static bool validate_cluster_size(size_t cluster_size, bool extended_l2,
+                                  Error **errp)
 {
     int cluster_bits = ctz32(cluster_size);
     if (cluster_bits < MIN_CLUSTER_BITS || cluster_bits > MAX_CLUSTER_BITS ||
@@ -3280,16 +3292,28 @@ static bool validate_cluster_size(size_t cluster_size, Error **errp)
                    "%dk", 1 << MIN_CLUSTER_BITS, 1 << (MAX_CLUSTER_BITS - 10));
         return false;
     }
+
+    if (extended_l2) {
+        unsigned min_cluster_size =
+            (1 << MIN_CLUSTER_BITS) * QCOW_EXTL2_SUBCLUSTERS_PER_CLUSTER;
+        if (cluster_size < min_cluster_size) {
+            error_setg(errp, "Extended L2 entries are only supported with "
+                       "cluster sizes of at least %u bytes", min_cluster_size);
+            return false;
+        }
+    }
+
     return true;
 }
 
-static size_t qcow2_opt_get_cluster_size_del(QemuOpts *opts, Error **errp)
+static size_t qcow2_opt_get_cluster_size_del(QemuOpts *opts, bool extended_l2,
+                                             Error **errp)
 {
     size_t cluster_size;
 
     cluster_size = qemu_opt_get_size_del(opts, BLOCK_OPT_CLUSTER_SIZE,
                                          DEFAULT_CLUSTER_SIZE);
-    if (!validate_cluster_size(cluster_size, errp)) {
+    if (!validate_cluster_size(cluster_size, extended_l2, errp)) {
         return 0;
     }
     return cluster_size;
@@ -3403,7 +3427,20 @@ qcow2_co_create(BlockdevCreateOptions *create_options, Error **errp)
         cluster_size = DEFAULT_CLUSTER_SIZE;
     }
 
-    if (!validate_cluster_size(cluster_size, errp)) {
+    if (!qcow2_opts->has_extended_l2) {
+        qcow2_opts->extended_l2 = false;
+    }
+    if (qcow2_opts->extended_l2) {
+        if (version < 3) {
+            error_setg(errp, "Extended L2 entries are only supported with "
+                       "compatibility level 1.1 and above (use version=v3 or "
+                       "greater)");
+            ret = -EINVAL;
+            goto out;
+        }
+    }
+
+    if (!validate_cluster_size(cluster_size, qcow2_opts->extended_l2, errp)) {
         ret = -EINVAL;
         goto out;
     }
@@ -3554,6 +3591,11 @@ qcow2_co_create(BlockdevCreateOptions *create_options, Error **errp)
             cpu_to_be64(QCOW2_INCOMPAT_COMPRESSION);
     }
 
+    if (qcow2_opts->extended_l2) {
+        header->incompatible_features |=
+            cpu_to_be64(QCOW2_INCOMPAT_EXTL2);
+    }
+
     ret = blk_pwrite(blk, 0, header, cluster_size, 0);
     g_free(header);
     if (ret < 0) {
@@ -3731,6 +3773,7 @@ static int coroutine_fn qcow2_co_create_opts(BlockDriver *drv,
         { BLOCK_OPT_BACKING_FMT,        "backing-fmt" },
         { BLOCK_OPT_CLUSTER_SIZE,       "cluster-size" },
         { BLOCK_OPT_LAZY_REFCOUNTS,     "lazy-refcounts" },
+        { BLOCK_OPT_EXTL2,              "extended-l2" },
         { BLOCK_OPT_REFCOUNT_BITS,      "refcount-bits" },
         { BLOCK_OPT_ENCRYPT,            BLOCK_OPT_ENCRYPT_FORMAT },
         { BLOCK_OPT_COMPAT_LEVEL,       "version" },
@@ -4847,11 +4890,14 @@ static BlockMeasureInfo *qcow2_measure(QemuOpts *opts, BlockDriverState *in_bs,
     PreallocMode prealloc;
     bool has_backing_file;
     bool has_luks;
-    bool extended_l2 = false; /* Set to false until the option is added */
+    bool extended_l2;
     size_t l2e_size;
 
     /* Parse image creation options */
-    cluster_size = qcow2_opt_get_cluster_size_del(opts, &local_err);
+    extended_l2 = qemu_opt_get_bool_del(opts, BLOCK_OPT_EXTL2, false);
+
+    cluster_size = qcow2_opt_get_cluster_size_del(opts, extended_l2,
+                                                  &local_err);
     if (local_err) {
         goto err;
     }
@@ -5047,6 +5093,8 @@ static ImageInfoSpecific *qcow2_get_specific_info(BlockDriverState *bs,
             .corrupt            = s->incompatible_features &
                                   QCOW2_INCOMPAT_CORRUPT,
             .has_corrupt        = true,
+            .has_extended_l2    = true,
+            .extended_l2        = has_subclusters(s),
             .refcount_bits      = s->refcount_bits,
             .has_bitmaps        = !!bitmaps,
             .bitmaps            = bitmaps,
@@ -5775,6 +5823,12 @@ static QemuOptsList qcow2_create_opts = {
             .def_value_str = stringify(DEFAULT_CLUSTER_SIZE)            \
         },                                                              \
         {                                                               \
+            .name = BLOCK_OPT_EXTL2,                                    \
+            .type = QEMU_OPT_BOOL,                                      \
+            .help = "Extended L2 tables",                               \
+            .def_value_str = "off"                                      \
+        },                                                              \
+        {                                                               \
             .name = BLOCK_OPT_PREALLOC,                                 \
             .type = QEMU_OPT_STRING,                                    \
             .help = "Preallocation mode (allowed values: off, "         \
diff --git a/block/qcow2.h b/block/qcow2.h
index f3499e53bf..065ec3df0b 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -246,15 +246,18 @@ enum {
     QCOW2_INCOMPAT_CORRUPT_BITNR    = 1,
     QCOW2_INCOMPAT_DATA_FILE_BITNR  = 2,
     QCOW2_INCOMPAT_COMPRESSION_BITNR = 3,
+    QCOW2_INCOMPAT_EXTL2_BITNR      = 4,
     QCOW2_INCOMPAT_DIRTY            = 1 << QCOW2_INCOMPAT_DIRTY_BITNR,
     QCOW2_INCOMPAT_CORRUPT          = 1 << QCOW2_INCOMPAT_CORRUPT_BITNR,
     QCOW2_INCOMPAT_DATA_FILE        = 1 << QCOW2_INCOMPAT_DATA_FILE_BITNR,
     QCOW2_INCOMPAT_COMPRESSION      = 1 << QCOW2_INCOMPAT_COMPRESSION_BITNR,
+    QCOW2_INCOMPAT_EXTL2            = 1 << QCOW2_INCOMPAT_EXTL2_BITNR,
 
     QCOW2_INCOMPAT_MASK             = QCOW2_INCOMPAT_DIRTY
                                     | QCOW2_INCOMPAT_CORRUPT
                                     | QCOW2_INCOMPAT_DATA_FILE
-                                    | QCOW2_INCOMPAT_COMPRESSION,
+                                    | QCOW2_INCOMPAT_COMPRESSION
+                                    | QCOW2_INCOMPAT_EXTL2,
 };
 
 /* Compatible feature bits */
@@ -581,8 +584,7 @@ typedef enum QCow2MetadataOverlap {
 
 static inline bool has_subclusters(BDRVQcow2State *s)
 {
-    /* FIXME: Return false until this feature is complete */
-    return false;
+    return s->incompatible_features & QCOW2_INCOMPAT_EXTL2;
 }
 
 static inline size_t l2_entry_size(BDRVQcow2State *s)