cifs: Cut over to using netfslib

Make the cifs filesystem use netfslib to handle reading and writing on
behalf of cifs.  The changes include:

 (1) Various read_iter/write_iter type functions are turned into wrappers
     around netfslib API functions or are pointed directly at those
     functions:

	cifs_file_direct{,_nobrl}_ops switch to use
	netfs_unbuffered_read_iter and netfs_unbuffered_write_iter.

Large pieces of code that will be removed are #if'd out and will be removed
in subsequent patches.

[?] Why does cifs mark the page dirty in the destination buffer of a DIO
    read?  Should that happen automatically?  Does netfs need to do that?

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

fs/netfs/io.c

@@ -213,8 +213,13 @@ static void netfs_rreq_assess_dio(struct netfs_io_request *rreq)
 	unsigned int i;
 	size_t transferred = 0;
 
-	for (i = 0; i < rreq->direct_bv_count; i++)
+	for (i = 0; i < rreq->direct_bv_count; i++) {
 		flush_dcache_page(rreq->direct_bv[i].bv_page);
+		// TODO: cifs marks pages in the destination buffer
+		// dirty under some circumstances after a read.  Do we
+		// need to do that too?
+		set_page_dirty(rreq->direct_bv[i].bv_page);
+	}
 
 	list_for_each_entry(subreq, &rreq->subrequests, rreq_link) {
 		if (subreq->error || subreq->transferred == 0)

fs/smb/client/cifsfs.c

@@ -1522,8 +1522,8 @@ const struct file_operations cifs_file_strict_ops = {
 };
 
 const struct file_operations cifs_file_direct_ops = {
-	.read_iter = cifs_direct_readv,
-	.write_iter = cifs_direct_writev,
+	.read_iter = netfs_unbuffered_read_iter,
+	.write_iter = netfs_file_write_iter,
 	.open = cifs_open,
 	.release = cifs_close,
 	.lock = cifs_lock,
@@ -1578,8 +1578,8 @@ const struct file_operations cifs_file_strict_nobrl_ops = {
 };
 
 const struct file_operations cifs_file_direct_nobrl_ops = {
-	.read_iter = cifs_direct_readv,
-	.write_iter = cifs_direct_writev,
+	.read_iter = netfs_unbuffered_read_iter,
+	.write_iter = netfs_file_write_iter,
 	.open = cifs_open,
 	.release = cifs_close,
 	.fsync = cifs_fsync,

fs/smb/client/cifsfs.h

@@ -94,11 +94,7 @@ extern const struct file_operations cifs_file_strict_nobrl_ops;
 extern int cifs_open(struct inode *inode, struct file *file);
 extern int cifs_close(struct inode *inode, struct file *file);
 extern int cifs_closedir(struct inode *inode, struct file *file);
-extern ssize_t cifs_user_readv(struct kiocb *iocb, struct iov_iter *to);
-extern ssize_t cifs_direct_readv(struct kiocb *iocb, struct iov_iter *to);
 extern ssize_t cifs_strict_readv(struct kiocb *iocb, struct iov_iter *to);
-extern ssize_t cifs_user_writev(struct kiocb *iocb, struct iov_iter *from);
-extern ssize_t cifs_direct_writev(struct kiocb *iocb, struct iov_iter *from);
 extern ssize_t cifs_strict_writev(struct kiocb *iocb, struct iov_iter *from);
 ssize_t cifs_file_write_iter(struct kiocb *iocb, struct iov_iter *from);
 ssize_t cifs_loose_read_iter(struct kiocb *iocb, struct iov_iter *iter);
@@ -112,9 +108,6 @@ extern int cifs_file_strict_mmap(struct file *file, struct vm_area_struct *vma);
 extern const struct file_operations cifs_dir_ops;
 extern int cifs_dir_open(struct inode *inode, struct file *file);
 extern int cifs_readdir(struct file *file, struct dir_context *ctx);
-extern void cifs_pages_written_back(struct inode *inode, loff_t start, unsigned int len);
-extern void cifs_pages_write_failed(struct inode *inode, loff_t start, unsigned int len);
-extern void cifs_pages_write_redirty(struct inode *inode, loff_t start, unsigned int len);
 
 /* Functions related to dir entries */
 extern const struct dentry_operations cifs_dentry_ops;

fs/smb/client/cifsglob.h

@@ -451,7 +451,7 @@ struct smb_version_operations {
 	/* async read from the server */
 	int (*async_readv)(struct cifs_io_subrequest *);
 	/* async write to the server */
-	int (*async_writev)(struct cifs_io_subrequest *);
+	void (*async_writev)(struct cifs_io_subrequest *);
 	/* sync read from the server */
 	int (*sync_read)(const unsigned int, struct cifs_fid *,
 			 struct cifs_io_parms *, unsigned int *, char **,
@@ -1516,7 +1516,7 @@ struct cifs_io_subrequest {
 #endif
 	struct cifs_credits		credits;
 
-	// TODO: Remove following elements
+#if 0 // TODO: Remove following elements
 	struct list_head		list;
 	struct completion		done;
 	struct work_struct		work;
@@ -1526,6 +1526,7 @@ struct cifs_io_subrequest {
 	enum writeback_sync_modes	sync_mode;
 	bool				uncached;
 	struct bio_vec			*bv;
+#endif
 };
 
 /*

fs/smb/client/cifsproto.h

@@ -148,6 +148,8 @@ extern bool is_size_safe_to_change(struct cifsInodeInfo *cifsInode, __u64 eof,
 				   bool from_readdir);
 extern void cifs_update_eof(struct cifsInodeInfo *cifsi, loff_t offset,
 			    unsigned int bytes_written);
+void cifs_write_subrequest_terminated(struct cifs_io_subrequest *wdata, ssize_t result,
+				      bool was_async);
 extern struct cifsFileInfo *find_writable_file(struct cifsInodeInfo *, int);
 extern int cifs_get_writable_file(struct cifsInodeInfo *cifs_inode,
 				  int flags,
@@ -599,6 +601,7 @@ void __cifs_put_smb_ses(struct cifs_ses *ses);
 extern struct cifs_ses *
 cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb3_fs_context *ctx);
 
+#if 0 // TODO Remove
 void cifs_readdata_release(struct cifs_io_subrequest *rdata);
 static inline void cifs_get_readdata(struct cifs_io_subrequest *rdata)
 {
@@ -609,11 +612,13 @@ static inline void cifs_put_readdata(struct cifs_io_subrequest *rdata)
 	if (refcount_dec_and_test(&rdata->subreq.ref))
 		cifs_readdata_release(rdata);
 }
+#endif
 int cifs_async_readv(struct cifs_io_subrequest *rdata);
 int cifs_readv_receive(struct TCP_Server_Info *server, struct mid_q_entry *mid);
 
-int cifs_async_writev(struct cifs_io_subrequest *wdata);
+void cifs_async_writev(struct cifs_io_subrequest *wdata);
 void cifs_writev_complete(struct work_struct *work);
+#if 0 // TODO Remove
 struct cifs_io_subrequest *cifs_writedata_alloc(work_func_t complete);
 void cifs_writedata_release(struct cifs_io_subrequest *rdata);
 static inline void cifs_get_writedata(struct cifs_io_subrequest *wdata)
@@ -625,6 +630,7 @@ static inline void cifs_put_writedata(struct cifs_io_subrequest *wdata)
 	if (refcount_dec_and_test(&wdata->subreq.ref))
 		cifs_writedata_release(wdata);
 }
+#endif
 int cifs_query_mf_symlink(unsigned int xid, struct cifs_tcon *tcon,
 			  struct cifs_sb_info *cifs_sb,
 			  const unsigned char *path, char *pbuf,

fs/smb/client/cifssmb.c

@@ -1265,7 +1265,7 @@ static void
 cifs_readv_callback(struct mid_q_entry *mid)
 {
 	struct cifs_io_subrequest *rdata = mid->callback_data;
-	struct cifs_tcon *tcon = tlink_tcon(rdata->cfile->tlink);
+	struct cifs_tcon *tcon = tlink_tcon(rdata->req->cfile->tlink);
 	struct TCP_Server_Info *server = tcon->ses->server;
 	struct smb_rqst rqst = { .rq_iov = rdata->iov,
 				 .rq_nvec = 2,
@@ -1306,7 +1306,13 @@ cifs_readv_callback(struct mid_q_entry *mid)
 		rdata->result = -EIO;
 	}
 
-	queue_work(cifsiod_wq, &rdata->work);
+	if (rdata->result == 0 || rdata->result == -EAGAIN)
+		iov_iter_advance(&rdata->subreq.io_iter, rdata->got_bytes);
+	rdata->credits.value = 0;
+	netfs_subreq_terminated(&rdata->subreq,
+				(rdata->result == 0 || rdata->result == -EAGAIN) ?
+				rdata->got_bytes : rdata->result,
+				false);
 	release_mid(mid);
 	add_credits(server, &credits, 0);
 }
@@ -1318,7 +1324,7 @@ cifs_async_readv(struct cifs_io_subrequest *rdata)
 	int rc;
 	READ_REQ *smb = NULL;
 	int wct;
-	struct cifs_tcon *tcon = tlink_tcon(rdata->cfile->tlink);
+	struct cifs_tcon *tcon = tlink_tcon(rdata->req->cfile->tlink);
 	struct smb_rqst rqst = { .rq_iov = rdata->iov,
 				 .rq_nvec = 2 };
 
@@ -1343,7 +1349,7 @@ cifs_async_readv(struct cifs_io_subrequest *rdata)
 	smb->hdr.PidHigh = cpu_to_le16((__u16)(rdata->pid >> 16));
 
 	smb->AndXCommand = 0xFF;	/* none */
-	smb->Fid = rdata->cfile->fid.netfid;
+	smb->Fid = rdata->req->cfile->fid.netfid;
 	smb->OffsetLow = cpu_to_le32(rdata->subreq.start & 0xFFFFFFFF);
 	if (wct == 12)
 		smb->OffsetHigh = cpu_to_le32(rdata->subreq.start >> 32);
@@ -1613,15 +1619,16 @@ static void
 cifs_writev_callback(struct mid_q_entry *mid)
 {
 	struct cifs_io_subrequest *wdata = mid->callback_data;
-	struct cifs_tcon *tcon = tlink_tcon(wdata->cfile->tlink);
-	unsigned int written;
+	struct cifs_tcon *tcon = tlink_tcon(wdata->req->cfile->tlink);
 	WRITE_RSP *smb = (WRITE_RSP *)mid->resp_buf;
 	struct cifs_credits credits = { .value = 1, .instance = 0 };
+	ssize_t result;
+	size_t written;
 
 	switch (mid->mid_state) {
 	case MID_RESPONSE_RECEIVED:
-		wdata->result = cifs_check_receive(mid, tcon->ses->server, 0);
-		if (wdata->result != 0)
+		result = cifs_check_receive(mid, tcon->ses->server, 0);
+		if (result != 0)
 			break;
 
 		written = le16_to_cpu(smb->CountHigh);
@@ -1637,32 +1644,33 @@ cifs_writev_callback(struct mid_q_entry *mid)
 			written &= 0xFFFF;
 
 		if (written < wdata->subreq.len)
-			wdata->result = -ENOSPC;
+			result = -ENOSPC;
 		else
-			wdata->subreq.len = written;
+			result = written;
 		break;
 	case MID_REQUEST_SUBMITTED:
 	case MID_RETRY_NEEDED:
-		wdata->result = -EAGAIN;
+		result = -EAGAIN;
 		break;
 	default:
-		wdata->result = -EIO;
+		result = -EIO;
 		break;
 	}
 
-	queue_work(cifsiod_wq, &wdata->work);
+	wdata->credits.value = 0;
+	cifs_write_subrequest_terminated(wdata, result, true);
 	release_mid(mid);
 	add_credits(tcon->ses->server, &credits, 0);
 }
 
 /* cifs_async_writev - send an async write, and set up mid to handle result */
-int
+void
 cifs_async_writev(struct cifs_io_subrequest *wdata)
 {
 	int rc = -EACCES;
 	WRITE_REQ *smb = NULL;
 	int wct;
-	struct cifs_tcon *tcon = tlink_tcon(wdata->cfile->tlink);
+	struct cifs_tcon *tcon = tlink_tcon(wdata->req->cfile->tlink);
 	struct kvec iov[2];
 	struct smb_rqst rqst = { };
 
@@ -1672,7 +1680,8 @@ cifs_async_writev(struct cifs_io_subrequest *wdata)
 		wct = 12;
 		if (wdata->subreq.start >> 32 > 0) {
 			/* can not handle big offset for old srv */
-			return -EIO;
+			rc = -EIO;
+			goto out;
 		}
 	}
 
@@ -1684,7 +1693,7 @@ cifs_async_writev(struct cifs_io_subrequest *wdata)
 	smb->hdr.PidHigh = cpu_to_le16((__u16)(wdata->pid >> 16));
 
 	smb->AndXCommand = 0xFF;	/* none */
-	smb->Fid = wdata->cfile->fid.netfid;
+	smb->Fid = wdata->req->cfile->fid.netfid;
 	smb->OffsetLow = cpu_to_le32(wdata->subreq.start & 0xFFFFFFFF);
 	if (wct == 14)
 		smb->OffsetHigh = cpu_to_le32(wdata->subreq.start >> 32);
@@ -1724,18 +1733,19 @@ cifs_async_writev(struct cifs_io_subrequest *wdata)
 		iov[1].iov_len += 4; /* pad bigger by four bytes */
 	}
 
-	cifs_get_writedata(wdata);
 	rc = cifs_call_async(tcon->ses->server, &rqst, NULL,
 			     cifs_writev_callback, NULL, wdata, 0, NULL);
-
+	/* Can't touch wdata if rc == 0 */
 	if (rc == 0)
 		cifs_stats_inc(&tcon->stats.cifs_stats.num_writes);
-	else
-		cifs_put_writedata(wdata);
 
 async_writev_out:
 	cifs_small_buf_release(smb);
-	return rc;
+out:
+	if (rc) {
+		add_credits_and_wake_if(wdata->server, &wdata->credits, 0);
+		cifs_write_subrequest_terminated(wdata, rc, false);
+	}
 }
 
 int