[Qemu-devel] [PATCH 3/8] block: Support to keep track of I/O status

[Luiz Capitulino]

This commit adds support to the BlockDriverState type to keep track
of the last I/O status. That is, at every I/O operation we update
a status field in the BlockDriverState instance. Valid statuses are:
OK, FAILED and ENOSPC.

ENOSPC is distinguished from FAILED because an management application
can use it to implement thin-provisioning.

This feature has to be explicit enabled by buses/devices supporting it.

Signed-off-by: Luiz Capitulino <lcapitul...@redhat.com>
---
 block.c     |   18 ++++++++++++++++++
 block.h     |    7 +++++++
 block_int.h |    2 ++
 3 files changed, 27 insertions(+), 0 deletions(-)

diff --git a/block.c b/block.c
index 24a25d5..cc0a34e 100644
--- a/block.c
+++ b/block.c
@@ -195,6 +195,7 @@ BlockDriverState *bdrv_new(const char *device_name)
     if (device_name[0] != '\0') {
         QTAILQ_INSERT_TAIL(&bdrv_states, bs, list);
     }
+    bs->iostatus_enabled = false;
     return bs;
 }
 
@@ -2876,6 +2877,23 @@ int bdrv_in_use(BlockDriverState *bs)
     return bs->in_use;
 }
 
+void bdrv_enable_iostatus(BlockDriverState *bs)
+{
+    bs->iostatus_enabled = true;
+}
+
+void bdrv_iostatus_update(BlockDriverState *bs, int error)
+{
+    error = abs(error);
+
+    if (!error) {
+        bs->iostatus = BDRV_IOS_OK;
+    } else {
+        bs->iostatus = (error == ENOSPC) ? BDRV_IOS_ENOSPC :
+                                           BDRV_IOS_FAILED;
+    }
+}
+
 int bdrv_img_create(const char *filename, const char *fmt,
                     const char *base_filename, const char *base_fmt,
                     char *options, uint64_t img_size, int flags)
diff --git a/block.h b/block.h
index 859d1d9..0dca1bb 100644
--- a/block.h
+++ b/block.h
@@ -50,6 +50,13 @@ typedef enum {
     BDRV_ACTION_REPORT, BDRV_ACTION_IGNORE, BDRV_ACTION_STOP
 } BlockMonEventAction;
 
+typedef enum {
+    BDRV_IOS_OK, BDRV_IOS_FAILED, BDRV_IOS_ENOSPC
+} BlockIOStatus;
+
+void bdrv_iostatus_update(BlockDriverState *bs, int error);
+void bdrv_enable_iostatus(BlockDriverState *bs);
+void bdrv_enable_io_status(BlockDriverState *bs);
 void bdrv_mon_event(const BlockDriverState *bdrv,
                     BlockMonEventAction action, int is_read);
 void bdrv_info_print(Monitor *mon, const QObject *data);
diff --git a/block_int.h b/block_int.h
index 1e265d2..09f038d 100644
--- a/block_int.h
+++ b/block_int.h
@@ -195,6 +195,8 @@ struct BlockDriverState {
        drivers. They are not used by the block driver */
     int cyls, heads, secs, translation;
     BlockErrorAction on_read_error, on_write_error;
+    bool iostatus_enabled;
+    BlockIOStatus iostatus;
     char device_name[32];
     unsigned long *dirty_bitmap;
     int64_t dirty_count;
-- 
1.7.6.131.g99019