Merge remote-tracking branch 'mreitz/tags/pull-block-2017-10-06' into queue-block

Block patches

# gpg: Signature made Fri Oct  6 16:30:57 2017 CEST
# gpg:                using RSA key F407DB0061D5CF40
# gpg: Good signature from "Max Reitz <mreitz@redhat.com>"
# Primary key fingerprint: 91BE B60A 30DB 3E88 57D1  1829 F407 DB00 61D5 CF40

* mreitz/tags/pull-block-2017-10-06:
  block/mirror: check backing in bdrv_mirror_top_flush
  qcow2: truncate the tail of the image file after shrinking the image
  qcow2: fix return error code in qcow2_truncate()
  iotests: Fix 195 if IMGFMT is part of TEST_DIR
  block/mirror: check backing in bdrv_mirror_top_refresh_filename
  block: support passthrough of BDRV_REQ_FUA in crypto driver
  block: convert qcrypto_block_encrypt|decrypt to take bytes offset
  block: convert crypto driver to bdrv_co_preadv|pwritev
  block: fix data type casting for crypto payload offset
  crypto: expose encryption sector size in APIs
  block: use 1 MB bounce buffers for crypto instead of 16KB

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

13 files changed, 209 insertions, 101 deletions

diff --git a/block/crypto.c b/block/crypto.c
index 58ef6f2f52..60ddf8623e 100644
--- a/block/crypto.c
+++ b/block/crypto.c
@@ -279,6 +279,9 @@ static int block_crypto_open_generic(QCryptoBlockFormat format,
         return -EINVAL;
     }
 
+    bs->supported_write_flags = BDRV_REQ_FUA &
+        bs->file->bs->supported_write_flags;
+
     opts = qemu_opts_create(opts_spec, NULL, 0, &error_abort);
     qemu_opts_absorb_qdict(opts, options, &local_err);
     if (local_err) {
@@ -364,8 +367,9 @@ static int block_crypto_truncate(BlockDriverState *bs, int64_t offset,
                                  PreallocMode prealloc, Error **errp)
 {
     BlockCrypto *crypto = bs->opaque;
-    size_t payload_offset =
+    uint64_t payload_offset =
         qcrypto_block_get_payload_offset(crypto->block);
+    assert(payload_offset < (INT64_MAX - offset));
 
     offset += payload_offset;
 
@@ -379,66 +383,65 @@ static void block_crypto_close(BlockDriverState *bs)
 }
 
 
-#define BLOCK_CRYPTO_MAX_SECTORS 32
+/*
+ * 1 MB bounce buffer gives good performance / memory tradeoff
+ * when using cache=none|directsync.
+ */
+#define BLOCK_CRYPTO_MAX_IO_SIZE (1024 * 1024)
 
 static coroutine_fn int
-block_crypto_co_readv(BlockDriverState *bs, int64_t sector_num,
-                      int remaining_sectors, QEMUIOVector *qiov)
+block_crypto_co_preadv(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
+                       QEMUIOVector *qiov, int flags)
 {
     BlockCrypto *crypto = bs->opaque;
-    int cur_nr_sectors; /* number of sectors in current iteration */
+    uint64_t cur_bytes; /* number of bytes in current iteration */
     uint64_t bytes_done = 0;
     uint8_t *cipher_data = NULL;
     QEMUIOVector hd_qiov;
     int ret = 0;
-    size_t payload_offset =
-        qcrypto_block_get_payload_offset(crypto->block) / 512;
+    uint64_t sector_size = qcrypto_block_get_sector_size(crypto->block);
+    uint64_t payload_offset = qcrypto_block_get_payload_offset(crypto->block);
+
+    assert(!flags);
+    assert(payload_offset < INT64_MAX);
+    assert(QEMU_IS_ALIGNED(offset, sector_size));
+    assert(QEMU_IS_ALIGNED(bytes, sector_size));
 
     qemu_iovec_init(&hd_qiov, qiov->niov);
 
-    /* Bounce buffer so we have a linear mem region for
-     * entire sector. XXX optimize so we avoid bounce
-     * buffer in case that qiov->niov == 1
+    /* Bounce buffer because we don't wish to expose cipher text
+     * in qiov which points to guest memory.
      */
     cipher_data =
-        qemu_try_blockalign(bs->file->bs, MIN(BLOCK_CRYPTO_MAX_SECTORS * 512,
+        qemu_try_blockalign(bs->file->bs, MIN(BLOCK_CRYPTO_MAX_IO_SIZE,
                                               qiov->size));
     if (cipher_data == NULL) {
         ret = -ENOMEM;
         goto cleanup;
     }
 
-    while (remaining_sectors) {
-        cur_nr_sectors = remaining_sectors;
-
-        if (cur_nr_sectors > BLOCK_CRYPTO_MAX_SECTORS) {
-            cur_nr_sectors = BLOCK_CRYPTO_MAX_SECTORS;
-        }
+    while (bytes) {
+        cur_bytes = MIN(bytes, BLOCK_CRYPTO_MAX_IO_SIZE);
 
         qemu_iovec_reset(&hd_qiov);
-        qemu_iovec_add(&hd_qiov, cipher_data, cur_nr_sectors * 512);
+        qemu_iovec_add(&hd_qiov, cipher_data, cur_bytes);
 
-        ret = bdrv_co_readv(bs->file,
-                            payload_offset + sector_num,
-                            cur_nr_sectors, &hd_qiov);
+        ret = bdrv_co_preadv(bs->file, payload_offset + offset + bytes_done,
+                             cur_bytes, &hd_qiov, 0);
         if (ret < 0) {
             goto cleanup;
         }
 
-        if (qcrypto_block_decrypt(crypto->block,
-                                  sector_num,
-                                  cipher_data, cur_nr_sectors * 512,
-                                  NULL) < 0) {
+        if (qcrypto_block_decrypt(crypto->block, offset + bytes_done,
+                                  cipher_data, cur_bytes, NULL) < 0) {
             ret = -EIO;
             goto cleanup;
         }
 
-        qemu_iovec_from_buf(qiov, bytes_done,
-                            cipher_data, cur_nr_sectors * 512);
+        qemu_iovec_from_buf(qiov, bytes_done, cipher_data, cur_bytes);
 
-        remaining_sectors -= cur_nr_sectors;
-        sector_num += cur_nr_sectors;
-        bytes_done += cur_nr_sectors * 512;
+        bytes -= cur_bytes;
+        bytes_done += cur_bytes;
     }
 
  cleanup:
@@ -450,63 +453,58 @@ block_crypto_co_readv(BlockDriverState *bs, int64_t sector_num,
 
 
 static coroutine_fn int
-block_crypto_co_writev(BlockDriverState *bs, int64_t sector_num,
-                       int remaining_sectors, QEMUIOVector *qiov)
+block_crypto_co_pwritev(BlockDriverState *bs, uint64_t offset, uint64_t bytes,
+                        QEMUIOVector *qiov, int flags)
 {
     BlockCrypto *crypto = bs->opaque;
-    int cur_nr_sectors; /* number of sectors in current iteration */
+    uint64_t cur_bytes; /* number of bytes in current iteration */
     uint64_t bytes_done = 0;
     uint8_t *cipher_data = NULL;
     QEMUIOVector hd_qiov;
     int ret = 0;
-    size_t payload_offset =
-        qcrypto_block_get_payload_offset(crypto->block) / 512;
+    uint64_t sector_size = qcrypto_block_get_sector_size(crypto->block);
+    uint64_t payload_offset = qcrypto_block_get_payload_offset(crypto->block);
+
+    assert(!(flags & ~BDRV_REQ_FUA));
+    assert(payload_offset < INT64_MAX);
+    assert(QEMU_IS_ALIGNED(offset, sector_size));
+    assert(QEMU_IS_ALIGNED(bytes, sector_size));
 
     qemu_iovec_init(&hd_qiov, qiov->niov);
 
-    /* Bounce buffer so we have a linear mem region for
-     * entire sector. XXX optimize so we avoid bounce
-     * buffer in case that qiov->niov == 1
+    /* Bounce buffer because we're not permitted to touch
+     * contents of qiov - it points to guest memory.
      */
     cipher_data =
-        qemu_try_blockalign(bs->file->bs, MIN(BLOCK_CRYPTO_MAX_SECTORS * 512,
+        qemu_try_blockalign(bs->file->bs, MIN(BLOCK_CRYPTO_MAX_IO_SIZE,
                                               qiov->size));
     if (cipher_data == NULL) {
         ret = -ENOMEM;
         goto cleanup;
     }
 
-    while (remaining_sectors) {
-        cur_nr_sectors = remaining_sectors;
+    while (bytes) {
+        cur_bytes = MIN(bytes, BLOCK_CRYPTO_MAX_IO_SIZE);
 
-        if (cur_nr_sectors > BLOCK_CRYPTO_MAX_SECTORS) {
-            cur_nr_sectors = BLOCK_CRYPTO_MAX_SECTORS;
-        }
-
-        qemu_iovec_to_buf(qiov, bytes_done,
-                          cipher_data, cur_nr_sectors * 512);
+        qemu_iovec_to_buf(qiov, bytes_done, cipher_data, cur_bytes);
 
-        if (qcrypto_block_encrypt(crypto->block,
-                                  sector_num,
-                                  cipher_data, cur_nr_sectors * 512,
-                                  NULL) < 0) {
+        if (qcrypto_block_encrypt(crypto->block, offset + bytes_done,
+                                  cipher_data, cur_bytes, NULL) < 0) {
             ret = -EIO;
             goto cleanup;
         }
 
         qemu_iovec_reset(&hd_qiov);
-        qemu_iovec_add(&hd_qiov, cipher_data, cur_nr_sectors * 512);
+        qemu_iovec_add(&hd_qiov, cipher_data, cur_bytes);
 
-        ret = bdrv_co_writev(bs->file,
-                             payload_offset + sector_num,
-                             cur_nr_sectors, &hd_qiov);
+        ret = bdrv_co_pwritev(bs->file, payload_offset + offset + bytes_done,
+                              cur_bytes, &hd_qiov, flags);
         if (ret < 0) {
             goto cleanup;
         }
 
-        remaining_sectors -= cur_nr_sectors;
-        sector_num += cur_nr_sectors;
-        bytes_done += cur_nr_sectors * 512;
+        bytes -= cur_bytes;
+        bytes_done += cur_bytes;
     }
 
  cleanup:
@@ -516,13 +514,22 @@ block_crypto_co_writev(BlockDriverState *bs, int64_t sector_num,
     return ret;
 }
 
+static void block_crypto_refresh_limits(BlockDriverState *bs, Error **errp)
+{
+    BlockCrypto *crypto = bs->opaque;
+    uint64_t sector_size = qcrypto_block_get_sector_size(crypto->block);
+    bs->bl.request_alignment = sector_size; /* No sub-sector I/O */
+}
+
 
 static int64_t block_crypto_getlength(BlockDriverState *bs)
 {
     BlockCrypto *crypto = bs->opaque;
     int64_t len = bdrv_getlength(bs->file->bs);
 
-    ssize_t offset = qcrypto_block_get_payload_offset(crypto->block);
+    uint64_t offset = qcrypto_block_get_payload_offset(crypto->block);
+    assert(offset < INT64_MAX);
+    assert(offset < len);
 
     len -= offset;
 
@@ -613,8 +620,9 @@ BlockDriver bdrv_crypto_luks = {
     .bdrv_truncate      = block_crypto_truncate,
     .create_opts        = &block_crypto_create_opts_luks,
 
-    .bdrv_co_readv      = block_crypto_co_readv,
-    .bdrv_co_writev     = block_crypto_co_writev,
+    .bdrv_refresh_limits = block_crypto_refresh_limits,
+    .bdrv_co_preadv     = block_crypto_co_preadv,
+    .bdrv_co_pwritev    = block_crypto_co_pwritev,
     .bdrv_getlength     = block_crypto_getlength,
     .bdrv_get_info      = block_crypto_get_info_luks,
     .bdrv_get_specific_info = block_crypto_get_specific_info_luks,
diff --git a/block/mirror.c b/block/mirror.c
index 459b80f8f3..153758ca9f 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -1041,6 +1041,10 @@ static int coroutine_fn bdrv_mirror_top_pwritev(BlockDriverState *bs,
 
 static int coroutine_fn bdrv_mirror_top_flush(BlockDriverState *bs)
 {
+    if (bs->backing == NULL) {
+        /* we can be here after failed bdrv_append in mirror_start_job */
+        return 0;
+    }
     return bdrv_co_flush(bs->backing->bs);
 }
 
@@ -1058,6 +1062,11 @@ static int coroutine_fn bdrv_mirror_top_pdiscard(BlockDriverState *bs,
 
 static void bdrv_mirror_top_refresh_filename(BlockDriverState *bs, QDict *opts)
 {
+    if (bs->backing == NULL) {
+        /* we can be here after failed bdrv_attach_child in
+         * bdrv_set_backing_hd */
+        return;
+    }
     bdrv_refresh_filename(bs->backing->bs);
     pstrcpy(bs->exact_filename, sizeof(bs->exact_filename),
             bs->backing->bs->filename);
diff --git a/block/qcow.c b/block/qcow.c
index f450b00cfc..9569deeaf0 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -478,7 +478,9 @@ static int get_cluster_offset(BlockDriverState *bs,
                     for(i = 0; i < s->cluster_sectors; i++) {
                         if (i < n_start || i >= n_end) {
                             memset(s->cluster_data, 0x00, 512);
-                            if (qcrypto_block_encrypt(s->crypto, start_sect + i,
+                            if (qcrypto_block_encrypt(s->crypto,
+                                                      (start_sect + i) *
+                                                      BDRV_SECTOR_SIZE,
                                                       s->cluster_data,
                                                       BDRV_SECTOR_SIZE,
                                                       NULL) < 0) {
@@ -668,7 +670,8 @@ static coroutine_fn int qcow_co_readv(BlockDriverState *bs, int64_t sector_num,
             }
             if (bs->encrypted) {
                 assert(s->crypto);
-                if (qcrypto_block_decrypt(s->crypto, sector_num, buf,
+                if (qcrypto_block_decrypt(s->crypto,
+                                          sector_num * BDRV_SECTOR_SIZE, buf,
                                           n * BDRV_SECTOR_SIZE, NULL) < 0) {
                     ret = -EIO;
                     break;
@@ -740,8 +743,8 @@ static coroutine_fn int qcow_co_writev(BlockDriverState *bs, int64_t sector_num,
         }
         if (bs->encrypted) {
             assert(s->crypto);
-            if (qcrypto_block_encrypt(s->crypto, sector_num, buf,
-                                      n * BDRV_SECTOR_SIZE, NULL) < 0) {
+            if (qcrypto_block_encrypt(s->crypto, sector_num * BDRV_SECTOR_SIZE,
+                                      buf, n * BDRV_SECTOR_SIZE, NULL) < 0) {
                 ret = -EIO;
                 break;
             }
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index d2518d1893..0e5aec81cb 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -446,15 +446,13 @@ static bool coroutine_fn do_perform_cow_encrypt(BlockDriverState *bs,
 {
     if (bytes && bs->encrypted) {
         BDRVQcow2State *s = bs->opaque;
-        int64_t sector = (s->crypt_physical_offset ?
+        int64_t offset = (s->crypt_physical_offset ?
                           (cluster_offset + offset_in_cluster) :
-                          (src_cluster_offset + offset_in_cluster))
-                         >> BDRV_SECTOR_BITS;
+                          (src_cluster_offset + offset_in_cluster));
         assert((offset_in_cluster & ~BDRV_SECTOR_MASK) == 0);
         assert((bytes & ~BDRV_SECTOR_MASK) == 0);
         assert(s->crypto);
-        if (qcrypto_block_encrypt(s->crypto, sector, buffer,
-                                  bytes, NULL) < 0) {
+        if (qcrypto_block_encrypt(s->crypto, offset, buffer, bytes, NULL) < 0) {
             return false;
         }
     }
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 88d5a3f1ad..aa3fd6cf17 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -3181,3 +3181,25 @@ out:
     g_free(reftable_tmp);
     return ret;
 }
+
+int64_t qcow2_get_last_cluster(BlockDriverState *bs, int64_t size)
+{
+    BDRVQcow2State *s = bs->opaque;
+    int64_t i;
+
+    for (i = size_to_clusters(s, size) - 1; i >= 0; i--) {
+        uint64_t refcount;
+        int ret = qcow2_get_refcount(bs, i, &refcount);
+        if (ret < 0) {
+            fprintf(stderr, "Can't get refcount for cluster %" PRId64 ": %s\n",
+                    i, strerror(-ret));
+            return ret;
+        }
+        if (refcount > 0) {
+            return i;
+        }
+    }
+    qcow2_signal_corruption(bs, true, -1, -1,
+                            "There are no references in the refcount table.");
+    return -EIO;
+}
diff --git a/block/qcow2.c b/block/qcow2.c
index b8da8ca105..f63d1831f8 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1811,7 +1811,7 @@ static coroutine_fn int qcow2_co_preadv(BlockDriverState *bs, uint64_t offset,
                 if (qcrypto_block_decrypt(s->crypto,
                                           (s->crypt_physical_offset ?
                                            cluster_offset + offset_in_cluster :
-                                           offset) >> BDRV_SECTOR_BITS,
+                                           offset),
                                           cluster_data,
                                           cur_bytes,
                                           NULL) < 0) {
@@ -1946,7 +1946,7 @@ static coroutine_fn int qcow2_co_pwritev(BlockDriverState *bs, uint64_t offset,
             if (qcrypto_block_encrypt(s->crypto,
                                       (s->crypt_physical_offset ?
                                        cluster_offset + offset_in_cluster :
-                                       offset) >> BDRV_SECTOR_BITS,
+                                       offset),
                                       cluster_data,
                                       cur_bytes, NULL) < 0) {
                 ret = -EIO;
@@ -3107,6 +3107,7 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset,
     new_l1_size = size_to_l1(s, offset);
 
     if (offset < old_length) {
+        int64_t last_cluster, old_file_size;
         if (prealloc != PREALLOC_MODE_OFF) {
             error_setg(errp,
                        "Preallocation can't be used for shrinking an image");
@@ -3135,6 +3136,28 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset,
                              "Failed to discard unused refblocks");
             return ret;
         }
+
+        old_file_size = bdrv_getlength(bs->file->bs);
+        if (old_file_size < 0) {
+            error_setg_errno(errp, -old_file_size,
+                             "Failed to inquire current file length");
+            return old_file_size;
+        }
+        last_cluster = qcow2_get_last_cluster(bs, old_file_size);
+        if (last_cluster < 0) {
+            error_setg_errno(errp, -last_cluster,
+                             "Failed to find the last cluster");
+            return last_cluster;
+        }
+        if ((last_cluster + 1) * s->cluster_size < old_file_size) {
+            ret = bdrv_truncate(bs->file, (last_cluster + 1) * s->cluster_size,
+                                PREALLOC_MODE_OFF, NULL);
+            if (ret < 0) {
+                warn_report("Failed to truncate the tail of the image: %s",
+                            strerror(-ret));
+                ret = 0;
+            }
+        }
     } else {
         ret = qcow2_grow_l1_table(bs, new_l1_size, true);
         if (ret < 0) {
@@ -3167,7 +3190,7 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset,
         if (old_file_size < 0) {
             error_setg_errno(errp, -old_file_size,
                              "Failed to inquire current file length");
-            return ret;
+            return old_file_size;
         }
 
         nb_new_data_clusters = DIV_ROUND_UP(offset - old_length,
@@ -3196,7 +3219,7 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset,
         if (allocation_start < 0) {
             error_setg_errno(errp, -allocation_start,
                              "Failed to resize refcount structures");
-            return -allocation_start;
+            return allocation_start;
         }
 
         clusters_allocated = qcow2_alloc_clusters_at(bs, allocation_start,
diff --git a/block/qcow2.h b/block/qcow2.h
index 5a289a81e2..782a206ecb 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -597,6 +597,7 @@ int qcow2_change_refcount_order(BlockDriverState *bs, int refcount_order,
                                 BlockDriverAmendStatusCB *status_cb,
                                 void *cb_opaque, Error **errp);
 int qcow2_shrink_reftable(BlockDriverState *bs);
+int64_t qcow2_get_last_cluster(BlockDriverState *bs, int64_t size);
 
 /* qcow2-cluster.c functions */
 int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size,
diff --git a/crypto/block-luks.c b/crypto/block-luks.c
index 36bc856084..d418ac30b8 100644
--- a/crypto/block-luks.c
+++ b/crypto/block-luks.c
@@ -846,8 +846,9 @@ qcrypto_block_luks_open(QCryptoBlock *block,
         }
     }
 
+    block->sector_size = QCRYPTO_BLOCK_LUKS_SECTOR_SIZE;
     block->payload_offset = luks->header.payload_offset *
-        QCRYPTO_BLOCK_LUKS_SECTOR_SIZE;
+        block->sector_size;
 
     luks->cipher_alg = cipheralg;
     luks->cipher_mode = ciphermode;
@@ -1240,8 +1241,9 @@ qcrypto_block_luks_create(QCryptoBlock *block,
                    QCRYPTO_BLOCK_LUKS_SECTOR_SIZE)) *
          QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS);
 
+    block->sector_size = QCRYPTO_BLOCK_LUKS_SECTOR_SIZE;
     block->payload_offset = luks->header.payload_offset *
-        QCRYPTO_BLOCK_LUKS_SECTOR_SIZE;
+        block->sector_size;
 
     /* Reserve header space to match payload offset */
     initfunc(block, block->payload_offset, opaque, &local_err);
@@ -1397,29 +1399,33 @@ static void qcrypto_block_luks_cleanup(QCryptoBlock *block)
 
 static int
 qcrypto_block_luks_decrypt(QCryptoBlock *block,
-                           uint64_t startsector,
+                           uint64_t offset,
                            uint8_t *buf,
                            size_t len,
                            Error **errp)
 {
+    assert(QEMU_IS_ALIGNED(offset, QCRYPTO_BLOCK_LUKS_SECTOR_SIZE));
+    assert(QEMU_IS_ALIGNED(len, QCRYPTO_BLOCK_LUKS_SECTOR_SIZE));
     return qcrypto_block_decrypt_helper(block->cipher,
                                         block->niv, block->ivgen,
                                         QCRYPTO_BLOCK_LUKS_SECTOR_SIZE,
-                                        startsector, buf, len, errp);
+                                        offset, buf, len, errp);
 }
 
 
 static int
 qcrypto_block_luks_encrypt(QCryptoBlock *block,
-                           uint64_t startsector,
+                           uint64_t offset,
                            uint8_t *buf,
                            size_t len,
                            Error **errp)
 {
+    assert(QEMU_IS_ALIGNED(offset, QCRYPTO_BLOCK_LUKS_SECTOR_SIZE));
+    assert(QEMU_IS_ALIGNED(len, QCRYPTO_BLOCK_LUKS_SECTOR_SIZE));
     return qcrypto_block_encrypt_helper(block->cipher,
                                         block->niv, block->ivgen,
                                         QCRYPTO_BLOCK_LUKS_SECTOR_SIZE,
-                                        startsector, buf, len, errp);
+                                        offset, buf, len, errp);
 }
 
 
diff --git a/crypto/block-qcow.c b/crypto/block-qcow.c
index a456fe338b..8817d6aaa7 100644
--- a/crypto/block-qcow.c
+++ b/crypto/block-qcow.c
@@ -80,6 +80,7 @@ qcrypto_block_qcow_init(QCryptoBlock *block,
         goto fail;
     }
 
+    block->sector_size = QCRYPTO_BLOCK_QCOW_SECTOR_SIZE;
     block->payload_offset = 0;
 
     return 0;
@@ -142,29 +143,33 @@ qcrypto_block_qcow_cleanup(QCryptoBlock *block)
 
 static int
 qcrypto_block_qcow_decrypt(QCryptoBlock *block,
-                           uint64_t startsector,
+                           uint64_t offset,
                            uint8_t *buf,
                            size_t len,
                            Error **errp)
 {
+    assert(QEMU_IS_ALIGNED(offset, QCRYPTO_BLOCK_QCOW_SECTOR_SIZE));
+    assert(QEMU_IS_ALIGNED(len, QCRYPTO_BLOCK_QCOW_SECTOR_SIZE));
     return qcrypto_block_decrypt_helper(block->cipher,
                                         block->niv, block->ivgen,
                                         QCRYPTO_BLOCK_QCOW_SECTOR_SIZE,
-                                        startsector, buf, len, errp);
+                                        offset, buf, len, errp);
 }
 
 
 static int
 qcrypto_block_qcow_encrypt(QCryptoBlock *block,
-                           uint64_t startsector,
+                           uint64_t offset,
                            uint8_t *buf,
                            size_t len,
                            Error **errp)
 {
+    assert(QEMU_IS_ALIGNED(offset, QCRYPTO_BLOCK_QCOW_SECTOR_SIZE));
+    assert(QEMU_IS_ALIGNED(len, QCRYPTO_BLOCK_QCOW_SECTOR_SIZE));
     return qcrypto_block_encrypt_helper(block->cipher,
                                         block->niv, block->ivgen,
                                         QCRYPTO_BLOCK_QCOW_SECTOR_SIZE,
-                                        startsector, buf, len, errp);
+                                        offset, buf, len, errp);
 }
 
 
diff --git a/crypto/block.c b/crypto/block.c
index c382393d9a..f206d5eea8 100644
--- a/crypto/block.c
+++ b/crypto/block.c
@@ -127,22 +127,22 @@ QCryptoBlockInfo *qcrypto_block_get_info(QCryptoBlock *block,
 
 
 int qcrypto_block_decrypt(QCryptoBlock *block,
-                          uint64_t startsector,
+                          uint64_t offset,
                           uint8_t *buf,
                           size_t len,
                           Error **errp)
 {
-    return block->driver->decrypt(block, startsector, buf, len, errp);
+    return block->driver->decrypt(block, offset, buf, len, errp);
 }
 
 
 int qcrypto_block_encrypt(QCryptoBlock *block,
-                          uint64_t startsector,
+                          uint64_t offset,
                           uint8_t *buf,
                           size_t len,
                           Error **errp)
 {
-    return block->driver->encrypt(block, startsector, buf, len, errp);
+    return block->driver->encrypt(block, offset, buf, len, errp);
 }
 
 
@@ -170,6 +170,12 @@ uint64_t qcrypto_block_get_payload_offset(QCryptoBlock *block)
 }
 
 
+uint64_t qcrypto_block_get_sector_size(QCryptoBlock *block)
+{
+    return block->sector_size;
+}
+
+
 void qcrypto_block_free(QCryptoBlock *block)
 {
     if (!block) {
@@ -188,13 +194,17 @@ int qcrypto_block_decrypt_helper(QCryptoCipher *cipher,
                                  size_t niv,
                                  QCryptoIVGen *ivgen,
                                  int sectorsize,
-                                 uint64_t startsector,
+                                 uint64_t offset,
                                  uint8_t *buf,
                                  size_t len,
                                  Error **errp)
 {
     uint8_t *iv;
     int ret = -1;
+    uint64_t startsector = offset / sectorsize;
+
+    assert(QEMU_IS_ALIGNED(offset, sectorsize));
+    assert(QEMU_IS_ALIGNED(len, sectorsize));
 
     iv = niv ? g_new0(uint8_t, niv) : NULL;
 
@@ -237,13 +247,17 @@ int qcrypto_block_encrypt_helper(QCryptoCipher *cipher,
                                  size_t niv,
                                  QCryptoIVGen *ivgen,
                                  int sectorsize,
-                                 uint64_t startsector,
+                                 uint64_t offset,
                                  uint8_t *buf,
                                  size_t len,
                                  Error **errp)
 {
     uint8_t *iv;
     int ret = -1;
+    uint64_t startsector = offset / sectorsize;
+
+    assert(QEMU_IS_ALIGNED(offset, sectorsize));
+    assert(QEMU_IS_ALIGNED(len, sectorsize));
 
     iv = niv ? g_new0(uint8_t, niv) : NULL;
 
diff --git a/crypto/blockpriv.h b/crypto/blockpriv.h
index 0edb810e22..41840abcec 100644
--- a/crypto/blockpriv.h
+++ b/crypto/blockpriv.h
@@ -36,6 +36,7 @@ struct QCryptoBlock {
     QCryptoHashAlgorithm kdfhash;
     size_t niv;
     uint64_t payload_offset; /* In bytes */
+    uint64_t sector_size; /* In bytes */
 };
 
 struct QCryptoBlockDriver {
@@ -81,7 +82,7 @@ int qcrypto_block_decrypt_helper(QCryptoCipher *cipher,
                                  size_t niv,
                                  QCryptoIVGen *ivgen,
                                  int sectorsize,
-                                 uint64_t startsector,
+                                 uint64_t offset,
                                  uint8_t *buf,
                                  size_t len,
                                  Error **errp);
@@ -90,7 +91,7 @@ int qcrypto_block_encrypt_helper(QCryptoCipher *cipher,
                                  size_t niv,
                                  QCryptoIVGen *ivgen,
                                  int sectorsize,
-                                 uint64_t startsector,
+                                 uint64_t offset,
                                  uint8_t *buf,
                                  size_t len,
                                  Error **errp);
diff --git a/include/crypto/block.h b/include/crypto/block.h
index f0e543bee1..cd18f46d56 100644
--- a/include/crypto/block.h
+++ b/include/crypto/block.h
@@ -161,18 +161,19 @@ QCryptoBlockInfo *qcrypto_block_get_info(QCryptoBlock *block,
 /**
  * @qcrypto_block_decrypt:
  * @block: the block encryption object
- * @startsector: the sector from which @buf was read
+ * @offset: the position at which @iov was read
  * @buf: the buffer to decrypt
  * @len: the length of @buf in bytes
  * @errp: pointer to a NULL-initialized error object
  *
  * Decrypt @len bytes of cipher text in @buf, writing
- * plain text back into @buf
+ * plain text back into @buf. @len and @offset must be
+ * a multiple of the encryption format sector size.
  *
  * Returns 0 on success, -1 on failure
  */
 int qcrypto_block_decrypt(QCryptoBlock *block,
-                          uint64_t startsector,
+                          uint64_t offset,
                           uint8_t *buf,
                           size_t len,
                           Error **errp);
@@ -180,18 +181,19 @@ int qcrypto_block_decrypt(QCryptoBlock *block,
 /**
  * @qcrypto_block_encrypt:
  * @block: the block encryption object
- * @startsector: the sector to which @buf will be written
+ * @offset: the position at which @iov will be written
  * @buf: the buffer to decrypt
  * @len: the length of @buf in bytes
  * @errp: pointer to a NULL-initialized error object
  *
  * Encrypt @len bytes of plain text in @buf, writing
- * cipher text back into @buf
+ * cipher text back into @buf. @len and @offset must be
+ * a multiple of the encryption format sector size.
  *
  * Returns 0 on success, -1 on failure
  */
 int qcrypto_block_encrypt(QCryptoBlock *block,
-                          uint64_t startsector,
+                          uint64_t offset,
                           uint8_t *buf,
                           size_t len,
                           Error **errp);
@@ -241,6 +243,21 @@ QCryptoHashAlgorithm qcrypto_block_get_kdf_hash(QCryptoBlock *block);
 uint64_t qcrypto_block_get_payload_offset(QCryptoBlock *block);
 
 /**
+ * qcrypto_block_get_sector_size:
+ * @block: the block encryption object
+ *
+ * Get the size of sectors used for payload encryption. A new
+ * IV is used at the start of each sector. The encryption
+ * sector size is not required to match the sector size of the
+ * underlying storage. For example LUKS will always use a 512
+ * byte sector size, even if the volume is on a disk with 4k
+ * sectors.
+ *
+ * Returns: the sector in bytes
+ */
+uint64_t qcrypto_block_get_sector_size(QCryptoBlock *block);
+
+/**
  * qcrypto_block_free:
  * @block: the block encryption object
  *
diff --git a/tests/qemu-iotests/195 b/tests/qemu-iotests/195
index 05a239cbf5..e7a403ded2 100755
--- a/tests/qemu-iotests/195
+++ b/tests/qemu-iotests/195
@@ -44,15 +44,16 @@ _supported_os Linux
 
 function do_run_qemu()
 {
-    echo Testing: "$@" | _filter_imgfmt
+    echo Testing: "$@"
     $QEMU -nographic -qmp-pretty stdio -serial none "$@"
     echo
 }
 
 function run_qemu()
 {
-    do_run_qemu "$@" 2>&1 | _filter_testdir | _filter_qemu | _filter_qmp \
-                          | _filter_qemu_io | _filter_generated_node_ids
+    do_run_qemu "$@" 2>&1 | _filter_testdir | _filter_imgfmt | _filter_qemu \
+                          | _filter_qmp | _filter_qemu_io \
+                          | _filter_generated_node_ids
 }
 
 size=64M