[Qemu-devel] [PATCH RFC 04/14] Revert "raw-posix: drop raw_get_aio_fd() since it is no longer used"

[Ming Lei <ming.lei@canonical.com>]

This reverts commit 76ef2cf5493a215efc351f48ae7094d6c183fcac.

Reintroduce the helper of raw_get_aio_fd() for enabling
coroutinue bypass mode in case of raw image.

Signed-off-by: Ming Lei <ming.lei@canonical.com>
---
 block/raw-posix.c     |   34 ++++++++++++++++++++++++++++++++++
 include/block/block.h |    9 +++++++++
 2 files changed, 43 insertions(+)

diff --git a/block/raw-posix.c b/block/raw-posix.c
index 2bcc73d..98b9626 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -2419,6 +2419,40 @@ static BlockDriver bdrv_host_cdrom = {
 };
 #endif /* __FreeBSD__ */
 
+#ifdef CONFIG_LINUX_AIO
+/**
+ * Return the file descriptor for Linux AIO
+ *
+ * This function is a layering violation and should be removed when it becomes
+ * possible to call the block layer outside the global mutex.  It allows the
+ * caller to hijack the file descriptor so I/O can be performed outside the
+ * block layer.
+ */
+int raw_get_aio_fd(BlockDriverState *bs)
+{
+    BDRVRawState *s;
+
+    if (!bs->drv) {
+        return -ENOMEDIUM;
+    }
+
+    if (bs->drv == bdrv_find_format("raw")) {
+        bs = bs->file;
+    }
+
+    /* raw-posix has several protocols so just check for raw_aio_readv */
+    if (bs->drv->bdrv_aio_readv != raw_aio_readv) {
+        return -ENOTSUP;
+    }
+
+    s = bs->opaque;
+    if (!s->use_aio) {
+        return -ENOTSUP;
+    }
+    return s->fd;
+}
+#endif /* CONFIG_LINUX_AIO */
+
 static void bdrv_file_init(void)
 {
     /*
diff --git a/include/block/block.h b/include/block/block.h
index 32d3676..8d15693 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -482,6 +482,15 @@ void bdrv_op_block_all(BlockDriverState *bs, Error *reason);
 void bdrv_op_unblock_all(BlockDriverState *bs, Error *reason);
 bool bdrv_op_blocker_is_empty(BlockDriverState *bs);
 
+#ifdef CONFIG_LINUX_AIO
+int raw_get_aio_fd(BlockDriverState *bs);
+#else
+static inline int raw_get_aio_fd(BlockDriverState *bs)
+{
+    return -ENOTSUP;
+}
+#endif
+
 enum BlockAcctType {
     BDRV_ACCT_READ,
     BDRV_ACCT_WRITE,
-- 
1.7.9.5