[Qemu-devel] [PATCH 2/3] file: Expose some protocol-specific information

[Eric Blake <eblake@redhat.com>]

When analyzing performance, it might be nice to let 'qemu-img info'
expose details that it learned from the underlying file or block
device.  Start the process by picking a few useful items determined
during raw_open_common().

Signed-off-by: Eric Blake <eblake@redhat.com>
---
 qapi/block-core.json | 24 +++++++++++++++++++++++-
 block/file-posix.c   | 21 +++++++++++++++++++++
 2 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/qapi/block-core.json b/qapi/block-core.json
index f28d5f5fc76..296c22a1003 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -101,6 +101,25 @@
       'extents': ['ImageInfo']
   } }

+##
+# @ImageInfoSpecificFile:
+#
+# Details about a file protocol BDS.
+#
+# @align: Alignment in use
+#
+# @discard: True if discard operations can be attempted
+#
+# @write-zero: True if efficient write zero operations can be attempted
+#
+# @discard-zero: True if discarding is known to read back as zero
+#
+# Since: 4.0
+##
+{ 'struct': 'ImageInfoSpecificFile',
+  'data': { 'align': 'int', 'discard': 'bool', 'write-zero': 'bool',
+            '*discard-zero': 'bool' } }
+
 ##
 # @ImageInfoSpecific:
 #
@@ -110,12 +129,15 @@
 ##
 { 'union': 'ImageInfoSpecific',
   'data': {
+      # Format drivers:
       'qcow2': 'ImageInfoSpecificQCow2',
       'vmdk': 'ImageInfoSpecificVmdk',
       # If we need to add block driver specific parameters for
       # LUKS in future, then we'll subclass QCryptoBlockInfoLUKS
       # to define a ImageInfoSpecificLUKS
-      'luks': 'QCryptoBlockInfoLUKS'
+      'luks': 'QCryptoBlockInfoLUKS',
+      # Protocol drivers:
+      'file': 'ImageInfoSpecificFile'
   } }

 ##
diff --git a/block/file-posix.c b/block/file-posix.c
index 8aee7a3fb8b..d4ce0e9116c 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -1079,6 +1079,23 @@ static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
     bs->bl.opt_mem_alignment = MAX(s->buf_align, getpagesize());
 }

+static ImageInfoSpecific *raw_get_specific_info(BlockDriverState *bs)
+{
+    BDRVRawState *s = bs->opaque;
+    ImageInfoSpecific *info = g_new0(ImageInfoSpecific, 1);
+    ImageInfoSpecificFile *infofile = g_new0(ImageInfoSpecificFile, 1);
+
+    info->type = IMAGE_INFO_SPECIFIC_KIND_FILE;
+    info->u.file.data = infofile;
+    infofile->align = s->buf_align;
+    infofile->discard = s->has_discard;
+    infofile->write_zero = s->has_write_zeroes;
+    infofile->has_discard_zero = s->has_discard;
+    infofile->discard_zero = s->discard_zeroes;
+
+    return info;
+}
+
 static int check_for_dasd(int fd)
 {
 #ifdef BIODASDINFO2
@@ -2765,6 +2782,7 @@ BlockDriver bdrv_file = {
     .bdrv_co_copy_range_from = raw_co_copy_range_from,
     .bdrv_co_copy_range_to  = raw_co_copy_range_to,
     .bdrv_refresh_limits = raw_refresh_limits,
+    .bdrv_get_specific_info = raw_get_specific_info,
     .bdrv_io_plug = raw_aio_plug,
     .bdrv_io_unplug = raw_aio_unplug,
     .bdrv_attach_aio_context = raw_aio_attach_aio_context,
@@ -3240,6 +3258,7 @@ static BlockDriver bdrv_host_device = {
     .bdrv_co_copy_range_from = raw_co_copy_range_from,
     .bdrv_co_copy_range_to  = raw_co_copy_range_to,
     .bdrv_refresh_limits = raw_refresh_limits,
+    .bdrv_get_specific_info = raw_get_specific_info,
     .bdrv_io_plug = raw_aio_plug,
     .bdrv_io_unplug = raw_aio_unplug,
     .bdrv_attach_aio_context = raw_aio_attach_aio_context,
@@ -3363,6 +3382,7 @@ static BlockDriver bdrv_host_cdrom = {
     .bdrv_co_pwritev        = raw_co_pwritev,
     .bdrv_co_flush_to_disk  = raw_co_flush_to_disk,
     .bdrv_refresh_limits = raw_refresh_limits,
+    .bdrv_get_specific_info = raw_get_specific_info,
     .bdrv_io_plug = raw_aio_plug,
     .bdrv_io_unplug = raw_aio_unplug,
     .bdrv_attach_aio_context = raw_aio_attach_aio_context,
@@ -3494,6 +3514,7 @@ static BlockDriver bdrv_host_cdrom = {
     .bdrv_co_pwritev        = raw_co_pwritev,
     .bdrv_co_flush_to_disk  = raw_co_flush_to_disk,
     .bdrv_refresh_limits = raw_refresh_limits,
+    .bdrv_get_specific_info = raw_get_specific_info,
     .bdrv_io_plug = raw_aio_plug,
     .bdrv_io_unplug = raw_aio_unplug,
     .bdrv_attach_aio_context = raw_aio_attach_aio_context,
-- 
2.20.1