[Qemu-devel] [PATCH v6 2/3] block/qcow2: refactor threaded encryption code

[Maxim Levitsky <mlevitsk@redhat.com>]

Change the qcow2_co_encrypt to just receive full host and
guest offsets and in pariticular remove the
offset_in_cluster parameter of do_perform_cow_encrypt,
since it is misleading, because that offset can be larger than
cluster size currently.

Remove the do_perform_cow_encrypt by merging it with
qcow2_co_encrypt

Also document the qcow2_co_encrypt arguments to prevent
that bug from happening again

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/qcow2-cluster.c | 35 +++++--------------
 block/qcow2-threads.c | 81 ++++++++++++++++++++++++++++++++++++-------
 block/qcow2.c         |  5 +--
 block/qcow2.h         |  8 ++---
 4 files changed, 83 insertions(+), 46 deletions(-)

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index bfeb0241d7..f42b8a404c 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -462,28 +462,6 @@ static int coroutine_fn do_perform_cow_read(BlockDriverState *bs,
     return 0;
 }
 
-static bool coroutine_fn do_perform_cow_encrypt(BlockDriverState *bs,
-                                                uint64_t src_cluster_offset,
-                                                uint64_t cluster_offset,
-                                                unsigned offset_in_cluster,
-                                                uint8_t *buffer,
-                                                unsigned bytes)
-{
-    if (bytes && bs->encrypted) {
-        BDRVQcow2State *s = bs->opaque;
-        assert((offset_in_cluster & ~BDRV_SECTOR_MASK) == 0);
-        assert((bytes & ~BDRV_SECTOR_MASK) == 0);
-        assert(s->crypto);
-        if (qcow2_co_encrypt(bs,
-                start_of_cluster(s, cluster_offset + offset_in_cluster),
-                src_cluster_offset + offset_in_cluster,
-                buffer, bytes) < 0) {
-            return false;
-        }
-    }
-    return true;
-}
-
 static int coroutine_fn do_perform_cow_write(BlockDriverState *bs,
                                              uint64_t cluster_offset,
                                              unsigned offset_in_cluster,
@@ -891,11 +869,14 @@ static int perform_cow(BlockDriverState *bs, QCowL2Meta *m)
 
     /* Encrypt the data if necessary before writing it */
     if (bs->encrypted) {
-        if (!do_perform_cow_encrypt(bs, m->offset, m->alloc_offset,
-                                    start->offset, start_buffer,
-                                    start->nb_bytes) ||
-            !do_perform_cow_encrypt(bs, m->offset, m->alloc_offset,
-                                    end->offset, end_buffer, end->nb_bytes)) {
+        if (!qcow2_co_encrypt(bs,
+                              m->offset + start->offset,
+                              m->alloc_offset + start->offset,
+                              start_buffer, start->nb_bytes) ||
+            !qcow2_co_encrypt(bs,
+                              m->offset + end->offset,
+                              m->alloc_offset + end->offset,
+                              end_buffer, end->nb_bytes)) {
             ret = -EIO;
             goto fail;
         }
diff --git a/block/qcow2-threads.c b/block/qcow2-threads.c
index 3b1e63fe41..b31d45fb2b 100644
--- a/block/qcow2-threads.c
+++ b/block/qcow2-threads.c
@@ -234,15 +234,15 @@ static int qcow2_encdec_pool_func(void *opaque)
 }
 
 static int coroutine_fn
-qcow2_co_encdec(BlockDriverState *bs, uint64_t file_cluster_offset,
-                  uint64_t offset, void *buf, size_t len, Qcow2EncDecFunc func)
+qcow2_co_encdec(BlockDriverState *bs, uint64_t host_offset,
+                uint64_t guest_offset, void *buf, size_t len,
+                Qcow2EncDecFunc func)
 {
     BDRVQcow2State *s = bs->opaque;
+
     Qcow2EncDecData arg = {
         .block = s->crypto,
-        .offset = s->crypt_physical_offset ?
-                      file_cluster_offset + offset_into_cluster(s, offset) :
-                      offset,
+        .offset = s->crypt_physical_offset ? host_offset : guest_offset,
         .buf = buf,
         .len = len,
         .func = func,
@@ -251,18 +251,73 @@ qcow2_co_encdec(BlockDriverState *bs, uint64_t file_cluster_offset,
     return qcow2_co_process(bs, qcow2_encdec_pool_func, &arg);
 }
 
+
+/*
+ * qcow2_co_encrypt()
+ *
+ * Encrypts one or more contiguous aligned sectors
+ *
+ * @host_offset - underlying storage offset of the first sector of the
+ * data to be encrypted
+ *
+ * @guest_offset - guest (virtual) offset of the first sector of the
+ * data to be encrypted
+ *
+ * @buf - buffer with the data to encrypt, that after encryption
+ *        will be written to the underlying storage device at
+ *        @host_offset
+ *
+ * @len - length of the buffer (must be a BDRV_SECTOR_SIZE multiple)
+ *
+ * Depending on the encryption method, @host_offset and/or @guest_offset
+ * may be used for generating the initialization vector for
+ * encryption.
+ *
+ * Note that while the whole range must be aligned on sectors, it
+ * does not have to be aligned on clusters and can also cross cluster
+ * boundaries
+ */
 int coroutine_fn
-qcow2_co_encrypt(BlockDriverState *bs, uint64_t file_cluster_offset,
-                 uint64_t offset, void *buf, size_t len)
+qcow2_co_encrypt(BlockDriverState *bs, uint64_t host_offset,
+                 uint64_t guest_offset, void *buf, size_t len)
 {
-    return qcow2_co_encdec(bs, file_cluster_offset, offset, buf, len,
-                             qcrypto_block_encrypt);
+
+    BDRVQcow2State *s = bs->opaque;
+    assert(QEMU_IS_ALIGNED(guest_offset, BDRV_SECTOR_SIZE));
+    assert(QEMU_IS_ALIGNED(host_offset, BDRV_SECTOR_SIZE));
+    assert(QEMU_IS_ALIGNED(len, BDRV_SECTOR_SIZE));
+    assert(s->crypto);
+
+    if (!len) {
+        return 0;
+    }
+
+    return qcow2_co_encdec(bs, host_offset, guest_offset, buf, len,
+                           qcrypto_block_encrypt);
 }
 
+
+/*
+ * qcow2_co_decrypt()
+ *
+ * Decrypts one or more contiguous aligned sectors
+ * Similar to qcow2_co_encrypt
+ */
+
 int coroutine_fn
-qcow2_co_decrypt(BlockDriverState *bs, uint64_t file_cluster_offset,
-                 uint64_t offset, void *buf, size_t len)
+qcow2_co_decrypt(BlockDriverState *bs, uint64_t host_offset,
+                 uint64_t guest_offset, void *buf, size_t len)
 {
-    return qcow2_co_encdec(bs, file_cluster_offset, offset, buf, len,
-                             qcrypto_block_decrypt);
+    BDRVQcow2State *s = bs->opaque;
+    assert(QEMU_IS_ALIGNED(guest_offset, BDRV_SECTOR_SIZE));
+    assert(QEMU_IS_ALIGNED(host_offset, BDRV_SECTOR_SIZE));
+    assert(QEMU_IS_ALIGNED(len, BDRV_SECTOR_SIZE));
+    assert(s->crypto);
+
+    if (!len) {
+        return 0;
+    }
+
+    return qcow2_co_encdec(bs, host_offset, guest_offset, buf, len,
+                           qcrypto_block_decrypt);
 }
diff --git a/block/qcow2.c b/block/qcow2.c
index 57734f20cf..ac768092bb 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -2069,7 +2069,8 @@ static coroutine_fn int qcow2_co_preadv_part(BlockDriverState *bs,
 
                 assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
                 assert((cur_bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
-                if (qcow2_co_decrypt(bs, cluster_offset, offset,
+                if (qcow2_co_decrypt(bs, cluster_offset + offset_in_cluster,
+                                     offset,
                                      cluster_data, cur_bytes) < 0) {
                     ret = -EIO;
                     goto fail;
@@ -2288,7 +2289,7 @@ static coroutine_fn int qcow2_co_pwritev_part(
             qemu_iovec_to_buf(qiov, qiov_offset + bytes_done,
                               cluster_data, cur_bytes);
 
-            if (qcow2_co_encrypt(bs, cluster_offset, offset,
+            if (qcow2_co_encrypt(bs, cluster_offset + offset_in_cluster, offset,
                                  cluster_data, cur_bytes) < 0) {
                 ret = -EIO;
                 goto out_unlocked;
diff --git a/block/qcow2.h b/block/qcow2.h
index 998bcdaef1..a488d761ff 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -758,10 +758,10 @@ ssize_t coroutine_fn
 qcow2_co_decompress(BlockDriverState *bs, void *dest, size_t dest_size,
                     const void *src, size_t src_size);
 int coroutine_fn
-qcow2_co_encrypt(BlockDriverState *bs, uint64_t file_cluster_offset,
-                 uint64_t offset, void *buf, size_t len);
+qcow2_co_encrypt(BlockDriverState *bs, uint64_t host_offset,
+                 uint64_t guest_offset, void *buf, size_t len);
 int coroutine_fn
-qcow2_co_decrypt(BlockDriverState *bs, uint64_t file_cluster_offset,
-                 uint64_t offset, void *buf, size_t len);
+qcow2_co_decrypt(BlockDriverState *bs, uint64_t host_offset,
+                 uint64_t guest_offset, void *buf, size_t len);
 
 #endif
-- 
2.17.2