[PATCH v6 04/15] block: add a helper to check if a zone is conventional

[Niklas Cassel <cassel@kernel.org>]

Whether a zone is conventional is encoded in the most significant bit of
the write pointer that the block layer keeps for it, so a caller that
wants to know has to reach into bs->wps->wp[] and apply BDRV_ZT_IS_CONV()
to the raw value. virtio-blk does that, which means a device model both
knows how a block driver stores its write pointers and knows what one of
the bits of a write pointer means.

Add an accessor next to bdrv_zone_index() and use it there, so that the
encoding stays with the code that chose it.

Unlike bdrv_zone_is_full(), this does not need the write pointer lock.
get_zones_wp() only ever sets the bit for a conventional zone and never
clears it, and a zone does not change type, so the answer cannot become
stale. The rest of the word does change, on every write, which is what
the lock is there for.

Signed-off-by: Niklas Cassel <cassel@kernel.org>
---
 block/io.c               | 7 +++++++
 hw/block/virtio-blk.c    | 2 +-
 include/block/block-io.h | 6 ++++++
 3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/block/io.c b/block/io.c
index cef23ee5bc..da61e641ac 100644
--- a/block/io.c
+++ b/block/io.c
@@ -3373,6 +3373,13 @@ uint32_t bdrv_zone_index(BlockDriverState *bs, uint64_t offset)
     return offset >> bs->bl.zone_size_bits;
 }
 
+bool bdrv_zone_is_conv(BlockDriverState *bs, uint32_t index)
+{
+    IO_CODE();
+
+    return BDRV_ZT_IS_CONV(bs->wps->wp[index]);
+}
+
 void *qemu_blockalign(BlockDriverState *bs, size_t size)
 {
     IO_CODE();
diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 6e4a7a4076..dd69d81532 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -524,7 +524,7 @@ static bool check_zoned_request(VirtIOBlock *s, int64_t offset, int64_t len,
         }
 
         index = bdrv_zone_index(bs, offset);
-        if (BDRV_ZT_IS_CONV(bs->wps->wp[index])) {
+        if (bdrv_zone_is_conv(bs, index)) {
             *status = VIRTIO_BLK_S_ZONE_INVALID_CMD;
             return false;
         }
diff --git a/include/block/block-io.h b/include/block/block-io.h
index 9d1c0eb7fb..e469df7061 100644
--- a/include/block/block-io.h
+++ b/include/block/block-io.h
@@ -128,6 +128,12 @@ int coroutine_fn GRAPH_RDLOCK bdrv_co_zone_append(BlockDriverState *bs,
                                                   BdrvRequestFlags flags);
 /* The index of the zone that @offset falls in. */
 uint32_t bdrv_zone_index(BlockDriverState *bs, uint64_t offset);
+/*
+ * True if the zone at @index is a conventional zone, which can be written
+ * anywhere in any order. The type of a zone does not change, so unlike
+ * bdrv_zone_is_full() this does not need the write pointer lock.
+ */
+bool bdrv_zone_is_conv(BlockDriverState *bs, uint32_t index);
 
 bool bdrv_can_write_zeroes_with_unmap(BlockDriverState *bs);
 
-- 
2.55.0