[Qemu-devel] [PATCH v2 04/13] block: Switch bdrv_write_zeroes() to byte interface

[Eric Blake <eblake@redhat.com>]

Rename to bdrv_pwrite_zeroes() to let the compiler ensure we
cater to the updated semantics.  Do the same for
bdrv_aio_write_zeroes() and bdrv_co_write_zeroes().  Two of the
three places map to the byte-based counterparts; but for now,
since we have no byte-based aio write, we still require sector
alignment in those callers, via assertions.

Signed-off-by: Eric Blake <eblake@redhat.com>
---
 include/block/block.h  | 16 ++++++++--------
 block/blkreplay.c      |  4 +++-
 block/io.c             | 45 ++++++++++++++++++++++++++++-----------------
 block/parallels.c      |  4 +++-
 block/qcow2-cluster.c  |  3 +--
 block/qcow2.c          |  9 ++++-----
 block/raw_bsd.c        |  3 ++-
 migration/block.c      |  5 +++--
 tests/qemu-iotests/034 |  2 +-
 tests/qemu-iotests/154 |  2 +-
 trace-events           |  4 ++--
 11 files changed, 56 insertions(+), 41 deletions(-)

diff --git a/include/block/block.h b/include/block/block.h
index 0c3e709..7e87451 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -33,7 +33,7 @@ typedef struct BlockDriverInfo {
      * True if the driver can optimize writing zeroes by unmapping
      * sectors. This is equivalent to the BLKDISCARDZEROES ioctl in Linux
      * with the difference that in qemu a discard is allowed to silently
-     * fail. Therefore we have to use bdrv_write_zeroes with the
+     * fail. Therefore we have to use bdrv_pwrite_zeroes with the
      * BDRV_REQ_MAY_UNMAP flag for an optimized zero write with unmapping.
      * After this call the driver has to guarantee that the contents read
      * back as zero. It is additionally required that the block device is
@@ -227,11 +227,11 @@ int bdrv_read(BlockDriverState *bs, int64_t sector_num,
               uint8_t *buf, int nb_sectors);
 int bdrv_write(BlockDriverState *bs, int64_t sector_num,
                const uint8_t *buf, int nb_sectors);
-int bdrv_write_zeroes(BlockDriverState *bs, int64_t sector_num,
-               int nb_sectors, BdrvRequestFlags flags);
-BlockAIOCB *bdrv_aio_write_zeroes(BlockDriverState *bs, int64_t sector_num,
-                                  int nb_sectors, BdrvRequestFlags flags,
-                                  BlockCompletionFunc *cb, void *opaque);
+int bdrv_pwrite_zeroes(BlockDriverState *bs, int64_t offset,
+                       int count, BdrvRequestFlags flags);
+BlockAIOCB *bdrv_aio_pwrite_zeroes(BlockDriverState *bs, int64_t offset,
+                                   int count, BdrvRequestFlags flags,
+                                   BlockCompletionFunc *cb, void *opaque);
 int bdrv_make_zero(BlockDriverState *bs, BdrvRequestFlags flags);
 int bdrv_pread(BlockDriverState *bs, int64_t offset,
                void *buf, int count);
@@ -250,8 +250,8 @@ int coroutine_fn bdrv_co_writev(BlockDriverState *bs, int64_t sector_num,
  * function is not suitable for zeroing the entire image in a single request
  * because it may allocate memory for the entire region.
  */
-int coroutine_fn bdrv_co_write_zeroes(BlockDriverState *bs, int64_t sector_num,
-    int nb_sectors, BdrvRequestFlags flags);
+int coroutine_fn bdrv_co_pwrite_zeroes(BlockDriverState *bs, int64_t offset,
+    int count, BdrvRequestFlags flags);
 BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs,
     const char *backing_file);
 int bdrv_get_backing_file_depth(BlockDriverState *bs);
diff --git a/block/blkreplay.c b/block/blkreplay.c
index 42f1813..1a721ad 100755
--- a/block/blkreplay.c
+++ b/block/blkreplay.c
@@ -107,7 +107,9 @@ static int coroutine_fn blkreplay_co_write_zeroes(BlockDriverState *bs,
     int64_t sector_num, int nb_sectors, BdrvRequestFlags flags)
 {
     uint64_t reqid = request_id++;
-    int ret = bdrv_co_write_zeroes(bs->file->bs, sector_num, nb_sectors, flags);
+    int ret = bdrv_co_pwrite_zeroes(bs->file->bs,
+                                    sector_num << BDRV_SECTOR_BITS,
+                                    nb_sectors << BDRV_SECTOR_BITS, flags);
     block_request_create(reqid, bs, qemu_coroutine_self());
     qemu_coroutine_yield();

diff --git a/block/io.c b/block/io.c
index 3fe7576..5f021d5 100644
--- a/block/io.c
+++ b/block/io.c
@@ -620,18 +620,25 @@ int bdrv_write(BlockDriverState *bs, int64_t sector_num,
     return bdrv_rw_co(bs, sector_num, (uint8_t *)buf, nb_sectors, true, 0);
 }

-int bdrv_write_zeroes(BlockDriverState *bs, int64_t sector_num,
-                      int nb_sectors, BdrvRequestFlags flags)
+int bdrv_pwrite_zeroes(BlockDriverState *bs, int64_t offset,
+                       int count, BdrvRequestFlags flags)
 {
-    return bdrv_rw_co(bs, sector_num, NULL, nb_sectors, true,
-                      BDRV_REQ_ZERO_WRITE | flags);
+    QEMUIOVector qiov;
+    struct iovec iov = {
+        .iov_base = NULL,
+        .iov_len = count,
+    };
+
+    qemu_iovec_init_external(&qiov, &iov, 1);
+    return bdrv_prwv_co(bs, offset, &qiov, true,
+                        BDRV_REQ_ZERO_WRITE | flags);
 }

 /*
- * Completely zero out a block device with the help of bdrv_write_zeroes.
+ * Completely zero out a block device with the help of bdrv_pwrite_zeroes.
  * The operation is sped up by checking the block status and only writing
  * zeroes to the device if they currently do not return zeroes. Optional
- * flags are passed through to bdrv_write_zeroes (e.g. BDRV_REQ_MAY_UNMAP,
+ * flags are passed through to bdrv_pwrite_zeroes (e.g. BDRV_REQ_MAY_UNMAP,
  * BDRV_REQ_FUA).
  *
  * Returns < 0 on error, 0 on success. For error codes see bdrv_write().
@@ -662,7 +669,8 @@ int bdrv_make_zero(BlockDriverState *bs, BdrvRequestFlags flags)
             sector_num += n;
             continue;
         }
-        ret = bdrv_write_zeroes(bs, sector_num, n, flags);
+        ret = bdrv_pwrite_zeroes(bs, sector_num << BDRV_SECTOR_BITS,
+                                 n << BDRV_SECTOR_BITS, flags);
         if (ret < 0) {
             error_report("error writing zeroes at sector %" PRId64 ": %s",
                          sector_num, strerror(-ret));
@@ -1518,18 +1526,18 @@ int coroutine_fn bdrv_co_writev(BlockDriverState *bs, int64_t sector_num,
     return bdrv_co_do_writev(bs, sector_num, nb_sectors, qiov, 0);
 }

-int coroutine_fn bdrv_co_write_zeroes(BlockDriverState *bs,
-                                      int64_t sector_num, int nb_sectors,
-                                      BdrvRequestFlags flags)
+int coroutine_fn bdrv_co_pwrite_zeroes(BlockDriverState *bs,
+                                       int64_t offset, int count,
+                                       BdrvRequestFlags flags)
 {
-    trace_bdrv_co_write_zeroes(bs, sector_num, nb_sectors, flags);
+    trace_bdrv_co_pwrite_zeroes(bs, offset, count, flags);

     if (!(bs->open_flags & BDRV_O_UNMAP)) {
         flags &= ~BDRV_REQ_MAY_UNMAP;
     }

-    return bdrv_co_do_writev(bs, sector_num, nb_sectors, NULL,
-                             BDRV_REQ_ZERO_WRITE | flags);
+    return bdrv_co_pwritev(bs, offset, count, NULL,
+                           BDRV_REQ_ZERO_WRITE | flags);
 }

 typedef struct BdrvCoGetBlockStatusData {
@@ -1881,13 +1889,16 @@ BlockAIOCB *bdrv_aio_writev(BlockDriverState *bs, int64_t sector_num,
                                  cb, opaque, true);
 }

-BlockAIOCB *bdrv_aio_write_zeroes(BlockDriverState *bs,
-        int64_t sector_num, int nb_sectors, BdrvRequestFlags flags,
+BlockAIOCB *bdrv_aio_pwrite_zeroes(BlockDriverState *bs,
+        int64_t offset, int count, BdrvRequestFlags flags,
         BlockCompletionFunc *cb, void *opaque)
 {
-    trace_bdrv_aio_write_zeroes(bs, sector_num, nb_sectors, flags, opaque);
+    trace_bdrv_aio_pwrite_zeroes(bs, offset, count, flags, opaque);
+    assert(offset % BDRV_SECTOR_SIZE == 0);
+    assert(count % BDRV_SECTOR_SIZE == 0);

-    return bdrv_co_aio_rw_vector(bs, sector_num, NULL, nb_sectors,
+    return bdrv_co_aio_rw_vector(bs, offset >> BDRV_SECTOR_BITS, NULL,
+                                 count >> BDRV_SECTOR_BITS,
                                  BDRV_REQ_ZERO_WRITE | flags,
                                  cb, opaque, true);
 }
diff --git a/block/parallels.c b/block/parallels.c
index 99fc0f7..4621553 100644
--- a/block/parallels.c
+++ b/block/parallels.c
@@ -210,7 +210,9 @@ static int64_t allocate_clusters(BlockDriverState *bs, int64_t sector_num,
         int ret;
         space += s->prealloc_size;
         if (s->prealloc_mode == PRL_PREALLOC_MODE_FALLOCATE) {
-            ret = bdrv_write_zeroes(bs->file->bs, s->data_end, space, 0);
+            ret = bdrv_pwrite_zeroes(bs->file->bs,
+                                     s->data_end << BDRV_SECTOR_BITS,
+                                     space << BDRV_SECTOR_BITS, 0);
         } else {
             ret = bdrv_truncate(bs->file->bs,
                                 (s->data_end + space) << BDRV_SECTOR_BITS);
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 892e0fb..d901d89 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -1765,8 +1765,7 @@ static int expand_zero_clusters_in_l1(BlockDriverState *bs, uint64_t *l1_table,
                 goto fail;
             }

-            ret = bdrv_write_zeroes(bs->file->bs, offset / BDRV_SECTOR_SIZE,
-                                    s->cluster_sectors, 0);
+            ret = bdrv_pwrite_zeroes(bs->file->bs, offset, s->cluster_size, 0);
             if (ret < 0) {
                 if (!preallocated) {
                     qcow2_free_clusters(bs, offset, s->cluster_size,
diff --git a/block/qcow2.c b/block/qcow2.c
index a6ea6cb..cc59efc 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -2655,8 +2655,8 @@ static int make_completely_empty(BlockDriverState *bs)
     /* After this call, neither the in-memory nor the on-disk refcount
      * information accurately describe the actual references */

-    ret = bdrv_write_zeroes(bs->file->bs, s->l1_table_offset / BDRV_SECTOR_SIZE,
-                            l1_clusters * s->cluster_sectors, 0);
+    ret = bdrv_pwrite_zeroes(bs->file->bs, s->l1_table_offset,
+                             l1_clusters * s->cluster_size, 0);
     if (ret < 0) {
         goto fail_broken_refcounts;
     }
@@ -2669,9 +2669,8 @@ static int make_completely_empty(BlockDriverState *bs)
      * overwrite parts of the existing refcount and L1 table, which is not
      * an issue because the dirty flag is set, complete data loss is in fact
      * desired and partial data loss is consequently fine as well */
-    ret = bdrv_write_zeroes(bs->file->bs, s->cluster_size / BDRV_SECTOR_SIZE,
-                            (2 + l1_clusters) * s->cluster_size /
-                            BDRV_SECTOR_SIZE, 0);
+    ret = bdrv_pwrite_zeroes(bs->file->bs, s->cluster_size,
+                             (2 + l1_clusters) * s->cluster_size, 0);
     /* This call (even if it failed overall) may have overwritten on-disk
      * refcount structures; in that case, the in-memory refcount information
      * will probably differ from the on-disk information which makes the BDS
diff --git a/block/raw_bsd.c b/block/raw_bsd.c
index 3385ed4..d9adf90 100644
--- a/block/raw_bsd.c
+++ b/block/raw_bsd.c
@@ -131,7 +131,8 @@ static int coroutine_fn raw_co_write_zeroes(BlockDriverState *bs,
                                             int64_t sector_num, int nb_sectors,
                                             BdrvRequestFlags flags)
 {
-    return bdrv_co_write_zeroes(bs->file->bs, sector_num, nb_sectors, flags);
+    return bdrv_co_pwrite_zeroes(bs->file->bs, sector_num << BDRV_SECTOR_BITS,
+                                 nb_sectors << BDRV_SECTOR_BITS, flags);
 }

 static int coroutine_fn raw_co_discard(BlockDriverState *bs,
diff --git a/migration/block.c b/migration/block.c
index e0628d1..16cc1f8 100644
--- a/migration/block.c
+++ b/migration/block.c
@@ -883,8 +883,9 @@ static int block_load(QEMUFile *f, void *opaque, int version_id)
             }

             if (flags & BLK_MIG_FLAG_ZERO_BLOCK) {
-                ret = bdrv_write_zeroes(bs, addr, nr_sectors,
-                                        BDRV_REQ_MAY_UNMAP);
+                ret = bdrv_pwrite_zeroes(bs, addr << BDRV_SECTOR_BITS,
+                                         nr_sectors << BDRV_SECTOR_BITS,
+                                         BDRV_REQ_MAY_UNMAP);
             } else {
                 buf = g_malloc(BLOCK_SIZE);
                 qemu_get_buffer(f, buf, BLOCK_SIZE);
diff --git a/tests/qemu-iotests/034 b/tests/qemu-iotests/034
index c711cfc..1b28bda 100755
--- a/tests/qemu-iotests/034
+++ b/tests/qemu-iotests/034
@@ -1,6 +1,6 @@
 #!/bin/bash
 #
-# Test bdrv_write_zeroes with backing files
+# Test bdrv_pwrite_zeroes with backing files (see also 154)
 #
 # Copyright (C) 2012 Red Hat, Inc.
 #
diff --git a/tests/qemu-iotests/154 b/tests/qemu-iotests/154
index 5905c55..7ca7219 100755
--- a/tests/qemu-iotests/154
+++ b/tests/qemu-iotests/154
@@ -1,6 +1,6 @@
 #!/bin/bash
 #
-# qcow2 specific bdrv_write_zeroes tests with backing files (complements 034)
+# qcow2 specific bdrv_pwrite_zeroes tests with backing files (complements 034)
 #
 # Copyright (C) 2016 Red Hat, Inc.
 #
diff --git a/trace-events b/trace-events
index da930d5..6329c01 100644
--- a/trace-events
+++ b/trace-events
@@ -70,10 +70,10 @@ bdrv_aio_discard(void *bs, int64_t sector_num, int nb_sectors, void *opaque) "bs
 bdrv_aio_flush(void *bs, void *opaque) "bs %p opaque %p"
 bdrv_aio_readv(void *bs, int64_t sector_num, int nb_sectors, void *opaque) "bs %p sector_num %"PRId64" nb_sectors %d opaque %p"
 bdrv_aio_writev(void *bs, int64_t sector_num, int nb_sectors, void *opaque) "bs %p sector_num %"PRId64" nb_sectors %d opaque %p"
-bdrv_aio_write_zeroes(void *bs, int64_t sector_num, int nb_sectors, int flags, void *opaque) "bs %p sector_num %"PRId64" nb_sectors %d flags %#x opaque %p"
+bdrv_aio_pwrite_zeroes(void *bs, int64_t offset, int count, int flags, void *opaque) "bs %p offset %"PRId64" count %d flags %#x opaque %p"
 bdrv_co_readv(void *bs, int64_t sector_num, int nb_sector) "bs %p sector_num %"PRId64" nb_sectors %d"
 bdrv_co_writev(void *bs, int64_t sector_num, int nb_sector) "bs %p sector_num %"PRId64" nb_sectors %d"
-bdrv_co_write_zeroes(void *bs, int64_t sector_num, int nb_sector, int flags) "bs %p sector_num %"PRId64" nb_sectors %d flags %#x"
+bdrv_co_pwrite_zeroes(void *bs, int64_t offset, int count, int flags) "bs %p offset %"PRId64" count %d flags %#x"
 bdrv_co_do_copy_on_readv(void *bs, int64_t sector_num, int nb_sectors, int64_t cluster_sector_num, int cluster_nb_sectors) "bs %p sector_num %"PRId64" nb_sectors %d cluster_sector_num %"PRId64" cluster_nb_sectors %d"

 # block/stream.c
-- 
2.5.5