blob_bdev: add spdk_bdev_create_bs_dev_from_desc

New interface for create spdk_bs_dev from bdev desc.
This change, together with spdk_bdev_open_ext, can
remove the race condition where user gets the bdev
structure, but bdev is removed after getting that
structure and before spdk_bdev_create_bs_dev function
is called.

Change-Id: Ia80c3527ff91b45f97f44d295a5cb6d83f5ee0e4
Signed-off-by: Xiaodong Liu <xiaodong.liu@intel.com>
Reviewed-on: https://review.gerrithub.io/c/spdk/spdk/+/468412
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Changpeng Liu <changpeng.liu@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-by: Paul Luse <paul.e.luse@intel.com>

CHANGELOG.md

@@ -24,6 +24,13 @@ asynchronous event such as bdev removal. spdk_bdev_open_ext function takes bdev
 an argument instead of bdev structure to avoid a race condition that can happen when the bdev
 is being removed between a call to get its structure based on a name and actually openning it.
 
+### blobstore
+
+A new spdk_bdev_create_bs_dev_from_desc function has been added and spdk_bdev_create_bs_dev
+function has been deprecated.
+The new create function can cowork with spdk_bdev_open_ext function, which provides callback
+function that will be called by asynchronous event such as bdev removal.
+
 ### nvme
 
 Added `no_shn_notification` to NVMe controller initialization options, users can enable

include/spdk/blob_bdev.h

@@ -50,7 +50,8 @@ struct spdk_bdev;
 struct spdk_bdev_module;
 
 /**
- * Create a blobstore block device from a bdev.
+ * Create a blobstore block device from a bdev. (deprecated, please use spdk_bdev_create_bs_dev_from_desc,
+ * together with spdk_bdev_open_ext).
  *
  * \param bdev Bdev to use.
  * \param remove_cb Called when the block device is removed.
@@ -61,6 +62,15 @@ struct spdk_bdev_module;
 struct spdk_bs_dev *spdk_bdev_create_bs_dev(struct spdk_bdev *bdev, spdk_bdev_remove_cb_t remove_cb,
 		void *remove_ctx);
 
+/**
+ * Create a blobstore block device from the descriptor of a bdev.
+ *
+ * \param desc Descriptor of a bdev. spdk_bdev_open_ext() is recommended to get the desc.
+ *
+ * \return a pointer to the blobstore block device on success or NULL otherwise.
+ */
+struct spdk_bs_dev *spdk_bdev_create_bs_dev_from_desc(struct spdk_bdev_desc *desc);
+
 /**
  * Claim the bdev module for the given blobstore.
  *

module/blob/bdev/blob_bdev.c

@@ -355,3 +355,36 @@ spdk_bdev_create_bs_dev(struct spdk_bdev *bdev, spdk_bdev_remove_cb_t remove_cb,
 
 	return &b->bs_dev;
 }
+
+struct spdk_bs_dev *
+spdk_bdev_create_bs_dev_from_desc(struct spdk_bdev_desc *desc)
+{
+	struct blob_bdev *b;
+	struct spdk_bdev *bdev;
+
+	b = calloc(1, sizeof(*b));
+
+	if (b == NULL) {
+		SPDK_ERRLOG("could not allocate blob_bdev\n");
+		return NULL;
+	}
+
+	bdev = spdk_bdev_desc_get_bdev(desc);
+	assert(bdev != NULL);
+
+	b->bdev = bdev;
+	b->desc = desc;
+	b->bs_dev.blockcnt = spdk_bdev_get_num_blocks(bdev);
+	b->bs_dev.blocklen = spdk_bdev_get_block_size(bdev);
+	b->bs_dev.create_channel = bdev_blob_create_channel;
+	b->bs_dev.destroy_channel = bdev_blob_destroy_channel;
+	b->bs_dev.destroy = bdev_blob_destroy;
+	b->bs_dev.read = bdev_blob_read;
+	b->bs_dev.write = bdev_blob_write;
+	b->bs_dev.readv = bdev_blob_readv;
+	b->bs_dev.writev = bdev_blob_writev;
+	b->bs_dev.write_zeroes = bdev_blob_write_zeroes;
+	b->bs_dev.unmap = bdev_blob_unmap;
+
+	return &b->bs_dev;
+}