cifs: Implement netfslib hooks

Provide implementation of the netfslib hooks that will be used by netfslib
to ask cifs to set up and perform operations.  Of particular note are

 (*) cifs_clamp_length() - This is used to negotiate the size of the next
     subrequest in a read request, taking into account the credit available
     and the rsize.  The credits are attached to the subrequest.

 (*) cifs_req_issue_read() - This is used to issue a subrequest that has
     been set up and clamped.

 (*) cifs_prepare_write() - This prepares to fill a subrequest by picking a
     channel, reopening the file and requesting credits so that we can set
     the maximum size of the subrequest and also sets the maximum number of
     segments if we're doing RDMA.

 (*) cifs_issue_write() - This releases any unneeded credits and issues an
     asynchronous data write for the contiguous slice of file covered by
     the subrequest.  This should possibly be folded in to all
     ->async_writev() ops and that called directly.

 (*) cifs_begin_writeback() - This gets the cached writable handle through
     which we do writeback (this does not affect writethrough, unbuffered
     or direct writes).

At this point, cifs is not wired up to actually *use* netfslib; that will
be done in a subsequent patch.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Steve French <sfrench@samba.org>
cc: Shyam Prasad N <nspmangalore@gmail.com>
cc: Rohith Surabattula <rohiths.msft@gmail.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: linux-cifs@vger.kernel.org
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org

1 files changed, 19 insertions, 9 deletions

diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h
index 611f59c6d2c0..4e9033b2f191 100644
--- a/fs/smb/client/cifsglob.h
+++ b/fs/smb/client/cifsglob.h
@@ -1491,15 +1491,24 @@ struct cifs_aio_ctx {
 	bool			direct_io;
 };
 
+struct cifs_io_request {
+	struct netfs_io_request		rreq;
+	struct cifsFileInfo		*cfile;
+};
+
 /* asynchronous read support */
 struct cifs_io_subrequest {
-	struct netfs_io_subrequest	subreq;
-	struct cifsFileInfo		*cfile;
-	struct address_space		*mapping;
-	struct cifs_aio_ctx		*ctx;
+	union {
+		struct netfs_io_subrequest subreq;
+		struct netfs_io_request *rreq;
+		struct cifs_io_request *req;
+	};
 	ssize_t				got_bytes;
 	pid_t				pid;
+	unsigned int			xid;
 	int				result;
+	bool				have_xid;
+	bool				replay;
 	struct kvec			iov[2];
 	struct TCP_Server_Info		*server;
 #ifdef CONFIG_CIFS_SMB_DIRECT
@@ -1507,15 +1516,16 @@ struct cifs_io_subrequest {
 #endif
 	struct cifs_credits		credits;
 
-	enum writeback_sync_modes	sync_mode;
-	bool				uncached;
-	bool				replay;
-	struct bio_vec			*bv;
-
 	// TODO: Remove following elements
 	struct list_head		list;
 	struct completion		done;
 	struct work_struct		work;
+	struct cifsFileInfo		*cfile;
+	struct address_space		*mapping;
+	struct cifs_aio_ctx		*ctx;
+	enum writeback_sync_modes	sync_mode;
+	bool				uncached;
+	struct bio_vec			*bv;
 };
 
 /*