[PATCH] cifs: Rough, incomplete conversion to revised fscache I/O API

[David Howells <dhowells@redhat.com>]

Hi Steve,

Here's a rough, but incomplete, conversion of cifs to use the revised fscache
I/O API and the netfs helper lib, but I've about hit the limit of what I can
manage to do.  It's built on top of my fscache-netfs-lib branch:

	https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=fscache-netfs-lib

Notes:

 (*) I've replaced some code to discard data by reading into a big buffer with
     code that uses the ITER_DISCARD iterator instead.  See
     cifs_discard_from_socket().

 (*) I've tried to make the ordinary read use an ITER_XARRAY iterator and read
     into that directly from the socket, rather than looping through a bunch
     of pages.  This will handle THPs and partial pages for you.  However,
     under some circumstances, readpages_fill_pages() would then be reading
     from an iterator to an iterator, it appears.  Possibly the source
     iterator can be got rid of, but the code is quite complex.

 (*) There's a new function, cifs_req_issue_op(), which the netfs helpers use
     to issue a read on part of a request.  This looks at current->tgid, but
     might be running on a workqueue, so needs to get the tgid from somewhere
     else if not CIFS_MOUNT_RWPIDFORWARD.

 (*) cifs_readpage(), cifs_readahead() and cifs_write_begin() now go through
     the helpers.  cifs_readpages() is obsolete and is removed.

 (*) At the completion of a read, netfs_subreq_terminated() is called.  As a
     future optimisation, we can add a function to do incremental advancement
     of the pages, unlocking them as we go.  The issue is, however, that we
     have to coordinate with writing larger page lumps to the cache.

 (*) The clause in cifs_write_begin() about optimising away a read when we
     have an oplock needs dealing with, but I'm not sure how to fit it in.

David
---
diff --git a/fs/cifs/Kconfig b/fs/cifs/Kconfig
index fe03cbdae959..ad296c3dbd04 100644
--- a/fs/cifs/Kconfig
+++ b/fs/cifs/Kconfig
@@ -2,6 +2,7 @@
 config CIFS
 	tristate "SMB3 and CIFS support (advanced network filesystem)"
 	depends on INET
+	select NETFS_SUPPORT
 	select NLS
 	select CRYPTO
 	select CRYPTO_MD4
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 50fcb65920e8..fe5fd4bcb866 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -1283,6 +1283,7 @@ struct cifs_readdata;
 
 /* asynchronous read support */
 struct cifs_readdata {
+	struct netfs_read_subrequest	*subreq;
 	struct kref			refcount;
 	struct list_head		list;
 	struct completion		done;
@@ -1301,6 +1302,7 @@ struct cifs_readdata {
 	int (*copy_into_pages)(struct TCP_Server_Info *server,
 				struct cifs_readdata *rdata,
 				struct iov_iter *iter);
+	struct iov_iter			iter;
 	struct kvec			iov[2];
 	struct TCP_Server_Info		*server;
 #ifdef CONFIG_CIFS_SMB_DIRECT
diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index 340ff81ee87b..f5ac4a7c1cfc 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -230,11 +230,16 @@ extern unsigned int setup_special_user_owner_ACE(struct cifs_ace *pace);
 extern void dequeue_mid(struct mid_q_entry *mid, bool malformed);
 extern int cifs_read_from_socket(struct TCP_Server_Info *server, char *buf,
 			         unsigned int to_read);
+extern ssize_t cifs_discard_from_socket(struct TCP_Server_Info *server,
+					size_t to_read);
 extern int cifs_read_page_from_socket(struct TCP_Server_Info *server,
 					struct page *page,
 					unsigned int page_offset,
 					unsigned int to_read);
 extern int cifs_setup_cifs_sb(struct cifs_sb_info *cifs_sb);
+extern int cifs_read_iter_from_socket(struct TCP_Server_Info *server,
+				      struct iov_iter *iter,
+				      unsigned int to_read);
 extern int cifs_match_super(struct super_block *, void *);
 extern int cifs_mount(struct cifs_sb_info *cifs_sb, struct smb3_fs_context *ctx);
 extern void cifs_umount(struct cifs_sb_info *);
diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 0496934feecb..671afc822afc 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -36,6 +36,7 @@
 #include <linux/swap.h>
 #include <linux/task_io_accounting_ops.h>
 #include <linux/uaccess.h>
+#include <linux/netfs.h>
 #include "cifspdu.h"
 #include "cifsglob.h"
 #include "cifsacl.h"
@@ -1445,15 +1446,15 @@ int
 cifs_discard_remaining_data(struct TCP_Server_Info *server)
 {
 	unsigned int rfclen = server->pdu_size;
-	int remaining = rfclen + server->vals->header_preamble_size -
+	size_t remaining = rfclen + server->vals->header_preamble_size -
 		server->total_read;
 
 	while (remaining > 0) {
-		int length;
+		ssize_t length;
 
-		length = cifs_read_from_socket(server, server->bigbuf,
-				min_t(unsigned int, remaining,
-				    CIFSMaxBufSize + MAX_HEADER_SIZE(server)));
+		length = cifs_discard_from_socket(server,
+				min_t(size_t, remaining,
+				      CIFSMaxBufSize + MAX_HEADER_SIZE(server)));
 		if (length < 0)
 			return length;
 		server->total_read += length;
@@ -1664,7 +1665,14 @@ cifs_readv_callback(struct mid_q_entry *mid)
 		rdata->result = -EIO;
 	}
 
-	queue_work(cifsiod_wq, &rdata->work);
+	if (rdata->subreq) {
+		netfs_subreq_terminated(rdata->subreq,
+					(rdata->result == 0 || rdata->result == -EAGAIN) ?
+					rdata->got_bytes : rdata->result);
+		kref_put(&rdata->refcount, cifs_readdata_release);
+	} else {
+		queue_work(cifsiod_wq, &rdata->work);
+	}
 	DeleteMidQEntry(mid);
 	add_credits(server, &credits, 0);
 }
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 5d39129406ea..28c13602ed43 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -564,6 +564,15 @@ cifs_read_from_socket(struct TCP_Server_Info *server, char *buf,
 	return cifs_readv_from_socket(server, &smb_msg);
 }
 
+ssize_t
+cifs_discard_from_socket(struct TCP_Server_Info *server, size_t to_read)
+{
+	struct msghdr smb_msg;
+	iov_iter_discard(&smb_msg.msg_iter, READ, to_read);
+
+	return cifs_readv_from_socket(server, &smb_msg);
+}
+
 int
 cifs_read_page_from_socket(struct TCP_Server_Info *server, struct page *page,
 	unsigned int page_offset, unsigned int to_read)
@@ -575,6 +584,22 @@ cifs_read_page_from_socket(struct TCP_Server_Info *server, struct page *page,
 	return cifs_readv_from_socket(server, &smb_msg);
 }
 
+int
+cifs_read_iter_from_socket(struct TCP_Server_Info *server, struct iov_iter *iter,
+			   unsigned int to_read)
+{
+	struct msghdr smb_msg;
+	int ret;
+
+	smb_msg.msg_iter = *iter;
+	if (smb_msg.msg_iter.count > to_read)
+		smb_msg.msg_iter.count = to_read;
+	ret = cifs_readv_from_socket(server, &smb_msg);
+	if (ret > 0)
+		iov_iter_advance(iter, ret);
+	return ret;
+}
+
 static bool
 is_smb_response(struct TCP_Server_Info *server, unsigned char type)
 {
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 6d001905c8e5..c1f7ad4dbcb9 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -34,6 +34,7 @@
 #include <linux/slab.h>
 #include <linux/swap.h>
 #include <linux/mm.h>
+#include <linux/netfs.h>
 #include <asm/div64.h>
 #include "cifsfs.h"
 #include "cifspdu.h"
@@ -4006,98 +4007,6 @@ cifs_strict_readv(struct kiocb *iocb, struct iov_iter *to)
 	return rc;
 }
 
-static ssize_t
-cifs_read(struct file *file, char *read_data, size_t read_size, loff_t *offset)
-{
-	int rc = -EACCES;
-	unsigned int bytes_read = 0;
-	unsigned int total_read;
-	unsigned int current_read_size;
-	unsigned int rsize;
-	struct cifs_sb_info *cifs_sb;
-	struct cifs_tcon *tcon;
-	struct TCP_Server_Info *server;
-	unsigned int xid;
-	char *cur_offset;
-	struct cifsFileInfo *open_file;
-	struct cifs_io_parms io_parms = {0};
-	int buf_type = CIFS_NO_BUFFER;
-	__u32 pid;
-
-	xid = get_xid();
-	cifs_sb = CIFS_FILE_SB(file);
-
-	/* FIXME: set up handlers for larger reads and/or convert to async */
-	rsize = min_t(unsigned int, cifs_sb->ctx->rsize, CIFSMaxBufSize);
-
-	if (file->private_data == NULL) {
-		rc = -EBADF;
-		free_xid(xid);
-		return rc;
-	}
-	open_file = file->private_data;
-	tcon = tlink_tcon(open_file->tlink);
-	server = cifs_pick_channel(tcon->ses);
-
-	if (!server->ops->sync_read) {
-		free_xid(xid);
-		return -ENOSYS;
-	}
-
-	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_RWPIDFORWARD)
-		pid = open_file->pid;
-	else
-		pid = current->tgid;
-
-	if ((file->f_flags & O_ACCMODE) == O_WRONLY)
-		cifs_dbg(FYI, "attempting read on write only file instance\n");
-
-	for (total_read = 0, cur_offset = read_data; read_size > total_read;
-	     total_read += bytes_read, cur_offset += bytes_read) {
-		do {
-			current_read_size = min_t(uint, read_size - total_read,
-						  rsize);
-			/*
-			 * For windows me and 9x we do not want to request more
-			 * than it negotiated since it will refuse the read
-			 * then.
-			 */
-			if (!(tcon->ses->capabilities &
-				tcon->ses->server->vals->cap_large_files)) {
-				current_read_size = min_t(uint,
-					current_read_size, CIFSMaxBufSize);
-			}
-			if (open_file->invalidHandle) {
-				rc = cifs_reopen_file(open_file, true);
-				if (rc != 0)
-					break;
-			}
-			io_parms.pid = pid;
-			io_parms.tcon = tcon;
-			io_parms.offset = *offset;
-			io_parms.length = current_read_size;
-			io_parms.server = server;
-			rc = server->ops->sync_read(xid, &open_file->fid, &io_parms,
-						    &bytes_read, &cur_offset,
-						    &buf_type);
-		} while (rc == -EAGAIN);
-
-		if (rc || (bytes_read == 0)) {
-			if (total_read) {
-				break;
-			} else {
-				free_xid(xid);
-				return rc;
-			}
-		} else {
-			cifs_stats_bytes_read(tcon, total_read);
-			*offset += bytes_read;
-		}
-	}
-	free_xid(xid);
-	return total_read;
-}
-
 /*
  * If the page is mmap'ed into a process' page tables, then we need to make
  * sure that it doesn't change while being written back.
@@ -4107,7 +4016,21 @@ cifs_page_mkwrite(struct vm_fault *vmf)
 {
 	struct page *page = vmf->page;
 
-	lock_page(page);
+	/* Wait for the page to be written to the cache before we allow it to
+	 * be modified.  We then assume the entire page will need writing back.
+	 */
+#ifdef CONFIG_CIFS_FSCACHE
+	if (PageFsCache(page) &&
+	    wait_on_page_bit_killable(page, PG_fscache) < 0)
+		return VM_FAULT_RETRY;
+#endif
+
+	if (PageWriteback(page) &&
+	    wait_on_page_bit_killable(page, PG_writeback) < 0)
+		return VM_FAULT_RETRY;
+
+	if (lock_page_killable(page) < 0)
+		return VM_FAULT_RETRY;
 	return VM_FAULT_LOCKED;
 }
 
@@ -4154,39 +4077,6 @@ int cifs_file_mmap(struct file *file, struct vm_area_struct *vma)
 	return rc;
 }
 
-static void
-cifs_readv_complete(struct work_struct *work)
-{
-	unsigned int i, got_bytes;
-	struct cifs_readdata *rdata = container_of(work,
-						struct cifs_readdata, work);
-
-	got_bytes = rdata->got_bytes;
-	for (i = 0; i < rdata->nr_pages; i++) {
-		struct page *page = rdata->pages[i];
-
-		lru_cache_add(page);
-
-		if (rdata->result == 0 ||
-		    (rdata->result == -EAGAIN && got_bytes)) {
-			flush_dcache_page(page);
-			SetPageUptodate(page);
-		}
-
-		unlock_page(page);
-
-		if (rdata->result == 0 ||
-		    (rdata->result == -EAGAIN && got_bytes))
-			cifs_readpage_to_fscache(rdata->mapping->host, page);
-
-		got_bytes -= min_t(unsigned int, PAGE_SIZE, got_bytes);
-
-		put_page(page);
-		rdata->pages[i] = NULL;
-	}
-	kref_put(&rdata->refcount, cifs_readdata_release);
-}
-
 static int
 readpages_fill_pages(struct TCP_Server_Info *server,
 		     struct cifs_readdata *rdata, struct iov_iter *iter,
@@ -4261,8 +4151,7 @@ readpages_fill_pages(struct TCP_Server_Info *server,
 			result = n;
 #endif
 		else
-			result = cifs_read_page_from_socket(
-					server, page, page_offset, n);
+			result = cifs_read_iter_from_socket(server, &rdata->iter, n);
 		if (result < 0)
 			break;
 
@@ -4288,292 +4177,179 @@ cifs_readpages_copy_into_pages(struct TCP_Server_Info *server,
 	return readpages_fill_pages(server, rdata, iter, iter->count);
 }
 
-static int
-readpages_get_pages(struct address_space *mapping, struct list_head *page_list,
-		    unsigned int rsize, struct list_head *tmplist,
-		    unsigned int *nr_pages, loff_t *offset, unsigned int *bytes)
-{
-	struct page *page, *tpage;
-	unsigned int expected_index;
-	int rc;
-	gfp_t gfp = readahead_gfp_mask(mapping);
-
-	INIT_LIST_HEAD(tmplist);
-
-	page = lru_to_page(page_list);
-
-	/*
-	 * Lock the page and put it in the cache. Since no one else
-	 * should have access to this page, we're safe to simply set
-	 * PG_locked without checking it first.
-	 */
-	__SetPageLocked(page);
-	rc = add_to_page_cache_locked(page, mapping,
-				      page->index, gfp);
-
-	/* give up if we can't stick it in the cache */
-	if (rc) {
-		__ClearPageLocked(page);
-		return rc;
-	}
-
-	/* move first page to the tmplist */
-	*offset = (loff_t)page->index << PAGE_SHIFT;
-	*bytes = PAGE_SIZE;
-	*nr_pages = 1;
-	list_move_tail(&page->lru, tmplist);
-
-	/* now try and add more pages onto the request */
-	expected_index = page->index + 1;
-	list_for_each_entry_safe_reverse(page, tpage, page_list, lru) {
-		/* discontinuity ? */
-		if (page->index != expected_index)
-			break;
-
-		/* would this page push the read over the rsize? */
-		if (*bytes + PAGE_SIZE > rsize)
-			break;
-
-		__SetPageLocked(page);
-		rc = add_to_page_cache_locked(page, mapping, page->index, gfp);
-		if (rc) {
-			__ClearPageLocked(page);
-			break;
-		}
-		list_move_tail(&page->lru, tmplist);
-		(*bytes) += PAGE_SIZE;
-		expected_index++;
-		(*nr_pages)++;
-	}
-	return rc;
-}
-
-static int cifs_readpages(struct file *file, struct address_space *mapping,
-	struct list_head *page_list, unsigned num_pages)
+/*
+ * Issue a read operation on behalf of the netfs helper functions.  We're asked
+ * to make a read of a certain size at a point in the file.  We are permitted
+ * to only read a portion of that, but as long as we read something, the netfs
+ * helper will call us again so that we can issue another read.
+ */
+static void cifs_req_issue_op(struct netfs_read_subrequest *subreq)
 {
-	int rc;
-	int err = 0;
-	struct list_head tmplist;
-	struct cifsFileInfo *open_file = file->private_data;
-	struct cifs_sb_info *cifs_sb = CIFS_FILE_SB(file);
+	struct netfs_read_request *rreq = subreq->rreq;
 	struct TCP_Server_Info *server;
-	pid_t pid;
+	struct cifs_readdata *rdata;
+	struct cifsFileInfo *open_file = rreq->netfs_priv;
+	struct cifs_sb_info *cifs_sb = CIFS_SB(rreq->inode->i_sb);
+	struct cifs_credits credits_on_stack, *credits = &credits_on_stack;
 	unsigned int xid;
+	pid_t pid;
+	int rc;
+	unsigned int rsize;
 
 	xid = get_xid();
-	/*
-	 * Reads as many pages as possible from fscache. Returns -ENOBUFS
-	 * immediately if the cookie is negative
-	 *
-	 * After this point, every page in the list might have PG_fscache set,
-	 * so we will need to clean that up off of every page we don't use.
-	 */
-	rc = cifs_readpages_from_fscache(mapping->host, mapping, page_list,
-					 &num_pages);
-	if (rc == 0) {
-		free_xid(xid);
-		return rc;
-	}
 
 	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_RWPIDFORWARD)
 		pid = open_file->pid;
 	else
 		pid = current->tgid;
+#warning current might be a workqueue
 
 	rc = 0;
 	server = cifs_pick_channel(tlink_tcon(open_file->tlink)->ses);
 
-	cifs_dbg(FYI, "%s: file=%p mapping=%p num_pages=%u\n",
-		 __func__, file, mapping, num_pages);
-
-	/*
-	 * Start with the page at end of list and move it to private
-	 * list. Do the same with any following pages until we hit
-	 * the rsize limit, hit an index discontinuity, or run out of
-	 * pages. Issue the async read and then start the loop again
-	 * until the list is empty.
-	 *
-	 * Note that list order is important. The page_list is in
-	 * the order of declining indexes. When we put the pages in
-	 * the rdata->pages, then we want them in increasing order.
-	 */
-	while (!list_empty(page_list) && !err) {
-		unsigned int i, nr_pages, bytes, rsize;
-		loff_t offset;
-		struct page *page, *tpage;
-		struct cifs_readdata *rdata;
-		struct cifs_credits credits_on_stack;
-		struct cifs_credits *credits = &credits_on_stack;
+	cifs_dbg(FYI, "%s: op=%08x[%x] mapping=%p len=%zu/%zu\n",
+		 __func__, rreq->debug_id, subreq->debug_index, rreq->mapping,
+		 subreq->transferred, subreq->len);
 
-		if (open_file->invalidHandle) {
+	if (open_file->invalidHandle) {
+		do {
 			rc = cifs_reopen_file(open_file, true);
-			if (rc == -EAGAIN)
-				continue;
-			else if (rc)
-				break;
-		}
-
-		rc = server->ops->wait_mtu_credits(server, cifs_sb->ctx->rsize,
-						   &rsize, credits);
+		} while (rc == -EAGAIN);
 		if (rc)
-			break;
-
-		/*
-		 * Give up immediately if rsize is too small to read an entire
-		 * page. The VFS will fall back to readpage. We should never
-		 * reach this point however since we set ra_pages to 0 when the
-		 * rsize is smaller than a cache page.
-		 */
-		if (unlikely(rsize < PAGE_SIZE)) {
-			add_credits_and_wake_if(server, credits, 0);
-			free_xid(xid);
-			return 0;
-		}
-
-		nr_pages = 0;
-		err = readpages_get_pages(mapping, page_list, rsize, &tmplist,
-					 &nr_pages, &offset, &bytes);
-		if (!nr_pages) {
-			add_credits_and_wake_if(server, credits, 0);
-			break;
-		}
-
-		rdata = cifs_readdata_alloc(nr_pages, cifs_readv_complete);
-		if (!rdata) {
-			/* best to give up if we're out of mem */
-			list_for_each_entry_safe(page, tpage, &tmplist, lru) {
-				list_del(&page->lru);
-				lru_cache_add(page);
-				unlock_page(page);
-				put_page(page);
-			}
-			rc = -ENOMEM;
-			add_credits_and_wake_if(server, credits, 0);
-			break;
-		}
+			goto out;
+	}
 
-		rdata->cfile = cifsFileInfo_get(open_file);
-		rdata->server = server;
-		rdata->mapping = mapping;
-		rdata->offset = offset;
-		rdata->bytes = bytes;
-		rdata->pid = pid;
-		rdata->pagesz = PAGE_SIZE;
-		rdata->tailsz = PAGE_SIZE;
-		rdata->read_into_pages = cifs_readpages_read_into_pages;
-		rdata->copy_into_pages = cifs_readpages_copy_into_pages;
-		rdata->credits = credits_on_stack;
+	rc = server->ops->wait_mtu_credits(server, cifs_sb->ctx->rsize, &rsize, credits);
+	if (rc)
+		goto out;
 
-		list_for_each_entry_safe(page, tpage, &tmplist, lru) {
-			list_del(&page->lru);
-			rdata->pages[rdata->nr_pages++] = page;
-		}
+	rdata = cifs_readdata_alloc(0, NULL);
+	if (!rdata) {
+		rc = -ENOMEM;
+		add_credits_and_wake_if(server, credits, 0);
+		goto out;
+	}
 
-		rc = adjust_credits(server, &rdata->credits, rdata->bytes);
+	rdata->subreq = subreq;
+	rdata->cfile = cifsFileInfo_get(open_file);
+	rdata->server = server;
+	rdata->mapping = rreq->mapping;
+	rdata->offset = subreq->start + subreq->transferred;
+	rdata->bytes = subreq->len   - subreq->transferred;
+	rdata->pid = pid;
+	rdata->pagesz = PAGE_SIZE;
+	rdata->tailsz = PAGE_SIZE;
+	rdata->read_into_pages = cifs_readpages_read_into_pages;
+	rdata->copy_into_pages = cifs_readpages_copy_into_pages;
+	rdata->credits = credits_on_stack;
 
-		if (!rc) {
-			if (rdata->cfile->invalidHandle)
-				rc = -EAGAIN;
-			else
-				rc = server->ops->async_readv(rdata);
-		}
+	iov_iter_xarray(&rdata->iter, READ, &rreq->mapping->i_pages,
+			rdata->offset, rdata->bytes);
 
-		if (rc) {
-			add_credits_and_wake_if(server, &rdata->credits, 0);
-			for (i = 0; i < rdata->nr_pages; i++) {
-				page = rdata->pages[i];
-				lru_cache_add(page);
-				unlock_page(page);
-				put_page(page);
-			}
-			/* Fallback to the readpage in error/reconnect cases */
-			kref_put(&rdata->refcount, cifs_readdata_release);
-			break;
-		}
+	rc = adjust_credits(server, &rdata->credits, rdata->bytes);
+	if (!rc) {
+		if (rdata->cfile->invalidHandle)
+			rc = -EAGAIN;
+		else
+			rc = server->ops->async_readv(rdata);
+	}
 
+	if (rc) {
+		add_credits_and_wake_if(server, &rdata->credits, 0);
+		/* Fallback to the readpage in error/reconnect cases */
 		kref_put(&rdata->refcount, cifs_readdata_release);
 	}
 
-	/* Any pages that have been shown to fscache but didn't get added to
-	 * the pagecache must be uncached before they get returned to the
-	 * allocator.
-	 */
-	cifs_fscache_readpages_cancel(mapping->host, page_list);
+	kref_put(&rdata->refcount, cifs_readdata_release);
+
+out:
 	free_xid(xid);
-	return rc;
+	if (rc < 0)
+		netfs_subreq_terminated(subreq, rc);
 }
 
-/*
- * cifs_readpage_worker must be called with the page pinned
- */
-static int cifs_readpage_worker(struct file *file, struct page *page,
-	loff_t *poffset)
+static void cifs_init_rreq(struct netfs_read_request *rreq, struct file *file)
 {
-	char *read_data;
-	int rc;
-
-	/* Is the page cached? */
-	rc = cifs_readpage_from_fscache(file_inode(file), page);
-	if (rc == 0)
-		goto read_complete;
+	rreq->netfs_priv = file->private_data;
+}
 
-	read_data = kmap(page);
-	/* for reads over a certain size could initiate async read ahead */
+static bool cifs_is_cache_enabled(struct inode *inode)
+{
+	struct fscache_cookie *cookie = cifs_inode_cookie(inode);
 
-	rc = cifs_read(file, read_data, PAGE_SIZE, poffset);
+	return fscache_cookie_enabled(cookie) && !hlist_empty(&cookie->backing_objects);
+}
 
-	if (rc < 0)
-		goto io_error;
-	else
-		cifs_dbg(FYI, "Bytes read %d\n", rc);
+static int cifs_begin_cache_operation(struct netfs_read_request *rreq)
+{
+	return fscache_begin_read_operation(rreq, cifs_inode_cookie(rreq->inode));
+}
 
-	/* we do not want atime to be less than mtime, it broke some apps */
-	file_inode(file)->i_atime = current_time(file_inode(file));
-	if (timespec64_compare(&(file_inode(file)->i_atime), &(file_inode(file)->i_mtime)))
-		file_inode(file)->i_atime = file_inode(file)->i_mtime;
-	else
-		file_inode(file)->i_atime = current_time(file_inode(file));
+/*
+ * Expand the size of a readahead to the size of the rsize, if at least as
+ * large as a page, allowing for the possibility that rsize is not pow-2
+ * aligned.  The caller will then clamp it to i_size.
+ */
+static void cifs_expand_readahead(struct netfs_read_request *rreq)
+{
+	struct cifs_sb_info *cifs_sb = CIFS_SB(rreq->inode->i_sb);
+	unsigned int rsize = cifs_sb->ctx->rsize;
+	loff_t misalignment;
 
-	if (PAGE_SIZE > rc)
-		memset(read_data + rc, 0, PAGE_SIZE - rc);
+	if (rsize < PAGE_SIZE)
+		return;
 
-	flush_dcache_page(page);
-	SetPageUptodate(page);
+	if (rsize < INT_MAX)
+		rsize = roundup_pow_of_two(rsize);
+	else
+		rsize = ((unsigned int)INT_MAX + 1) / 2;
 
-	/* send this page to the cache */
-	cifs_readpage_to_fscache(file_inode(file), page);
+	misalignment = rreq->start & (rsize - 1);
+	if (misalignment) {
+		rreq->start -= misalignment;
+		rreq->len += misalignment;
+	}
 
-	rc = 0;
+	rreq->len = round_up(rreq->len, rsize);
+}
 
-io_error:
-	kunmap(page);
-	unlock_page(page);
+static void cifs_rreq_done(struct netfs_read_request *rreq)
+{
+	struct inode *inode = rreq->inode;
 
-read_complete:
-	return rc;
+	/* we do not want atime to be less than mtime, it broke some apps */
+	inode->i_atime = current_time(inode);
+	if (timespec64_compare(&inode->i_atime, &inode->i_mtime))
+		inode->i_atime = inode->i_mtime;
+	else
+		inode->i_atime = current_time(inode);
 }
 
+const struct netfs_read_request_ops cifs_req_ops = {
+	.init_rreq		= cifs_init_rreq,
+	.is_cache_enabled	= cifs_is_cache_enabled,
+	.begin_cache_operation	= cifs_begin_cache_operation,
+	.expand_readahead	= cifs_expand_readahead,
+	.issue_op		= cifs_req_issue_op,
+	.done			= cifs_rreq_done,
+};
+
 static int cifs_readpage(struct file *file, struct page *page)
 {
 	loff_t offset = (loff_t)page->index << PAGE_SHIFT;
-	int rc = -EACCES;
-	unsigned int xid;
-
-	xid = get_xid();
 
-	if (file->private_data == NULL) {
-		rc = -EBADF;
-		free_xid(xid);
-		return rc;
-	}
+	if (!file->private_data)
+		return -EBADF;
 
-	cifs_dbg(FYI, "readpage %p at offset %d 0x%x\n",
-		 page, (int)offset, (int)offset);
+	cifs_dbg(FYI, "readpage %p at offset %u 0x%x\n",
+		 page, (unsigned int)offset, (int)offset);
 
-	rc = cifs_readpage_worker(file, page, &offset);
+	return netfs_readpage(file, page, &cifs_req_ops, NULL);
+}
 
-	free_xid(xid);
-	return rc;
+static void cifs_readahead(struct readahead_control *ractl)
+{
+	netfs_readahead(ractl, &cifs_req_ops, NULL);
 }
 
 static int is_inode_writable(struct cifsInodeInfo *cifs_inode)
@@ -4625,34 +4401,21 @@ static int cifs_write_begin(struct file *file, struct address_space *mapping,
 			loff_t pos, unsigned len, unsigned flags,
 			struct page **pagep, void **fsdata)
 {
-	int oncethru = 0;
-	pgoff_t index = pos >> PAGE_SHIFT;
-	loff_t offset = pos & (PAGE_SIZE - 1);
-	loff_t page_start = pos & PAGE_MASK;
-	loff_t i_size;
 	struct page *page;
-	int rc = 0;
+	int rc;
 
 	cifs_dbg(FYI, "write_begin from %lld len %d\n", (long long)pos, len);
 
-start:
-	page = grab_cache_page_write_begin(mapping, index, flags);
-	if (!page) {
-		rc = -ENOMEM;
-		goto out;
-	}
-
-	if (PageUptodate(page))
-		goto out;
-
-	/*
-	 * If we write a full page it will be up to date, no need to read from
-	 * the server. If the write is short, we'll end up doing a sync write
-	 * instead.
+	/* Prefetch area to be written into the cache if we're caching this
+	 * file.  We need to do this before we get a lock on the page in case
+	 * there's more than one writer competing for the same cache block.
 	 */
-	if (len == PAGE_SIZE)
-		goto out;
+	rc = netfs_write_begin(file, mapping, pos, len, flags, &page, fsdata,
+			       &cifs_req_ops, NULL);
+	if (rc < 0)
+		return rc;
 
+#if 0
 	/*
 	 * optimize away the read when we have an oplock, and we're not
 	 * expecting to use any of the data we'd be reading in. That
@@ -4676,25 +4439,8 @@ static int cifs_write_begin(struct file *file, struct address_space *mapping,
 			goto out;
 		}
 	}
-
-	if ((file->f_flags & O_ACCMODE) != O_WRONLY && !oncethru) {
-		/*
-		 * might as well read a page, it is fast enough. If we get
-		 * an error, we don't need to return it. cifs_write_end will
-		 * do a sync write instead since PG_uptodate isn't set.
-		 */
-		cifs_readpage_worker(file, page, &page_start);
-		put_page(page);
-		oncethru = 1;
-		goto start;
-	} else {
-		/* we could try using another file handle if there is one -
-		   but how would we lock it to prevent close of that handle
-		   racing with this read? In any case
-		   this will be written out by write_end so is fine */
-	}
-out:
-	*pagep = page;
+#endif
+	*pagep = find_subpage(page, pos / PAGE_SIZE);
 	return rc;
 }
 
@@ -4703,16 +4449,23 @@ static int cifs_release_page(struct page *page, gfp_t gfp)
 	if (PagePrivate(page))
 		return 0;
 
-	return cifs_fscache_release_page(page, gfp);
+	/* deny if page is being written to the cache and the caller hasn't
+	 * elected to wait */
+#ifdef CONFIG_CIFS_FSCACHE
+	if (PageFsCache(page)) {
+		if (!(gfp & __GFP_DIRECT_RECLAIM) || !(gfp & __GFP_FS))
+			return 0;
+		wait_on_page_fscache(page);
+	}
+#endif
+
+	return 1;
 }
 
 static void cifs_invalidate_page(struct page *page, unsigned int offset,
 				 unsigned int length)
 {
-	struct cifsInodeInfo *cifsi = CIFS_I(page->mapping->host);
-
-	if (offset == 0 && length == PAGE_SIZE)
-		cifs_fscache_invalidate_page(page, &cifsi->vfs_inode);
+	wait_on_page_fscache(page);
 }
 
 static int cifs_launder_page(struct page *page)
@@ -4732,7 +4485,7 @@ static int cifs_launder_page(struct page *page)
 	if (clear_page_dirty_for_io(page))
 		rc = cifs_writepage_locked(page, &wbc);
 
-	cifs_fscache_invalidate_page(page, page->mapping->host);
+	wait_on_page_fscache(page);
 	return rc;
 }
 
@@ -4872,7 +4625,7 @@ static void cifs_swap_deactivate(struct file *file)
 
 const struct address_space_operations cifs_addr_ops = {
 	.readpage = cifs_readpage,
-	.readpages = cifs_readpages,
+	.readahead = cifs_readahead,
 	.writepage = cifs_writepage,
 	.writepages = cifs_writepages,
 	.write_begin = cifs_write_begin,
diff --git a/fs/cifs/fscache.c b/fs/cifs/fscache.c
index 20d24af33ee2..4acd599d91d9 100644
--- a/fs/cifs/fscache.c
+++ b/fs/cifs/fscache.c
@@ -199,7 +199,6 @@ static void cifs_fscache_disable_inode_cookie(struct inode *inode)
 
 	if (cifsi->fscache) {
 		cifs_dbg(FYI, "%s: (0x%p)\n", __func__, cifsi->fscache);
-		fscache_uncache_all_inode_pages(cifsi->fscache, inode);
 		fscache_relinquish_cookie(cifsi->fscache, NULL, true);
 		cifsi->fscache = NULL;
 	}
@@ -229,120 +228,3 @@ void cifs_fscache_reset_inode_cookie(struct inode *inode)
 			 __func__, cifsi->fscache, old);
 	}
 }
-
-int cifs_fscache_release_page(struct page *page, gfp_t gfp)
-{
-	if (PageFsCache(page)) {
-		struct inode *inode = page->mapping->host;
-		struct cifsInodeInfo *cifsi = CIFS_I(inode);
-
-		cifs_dbg(FYI, "%s: (0x%p/0x%p)\n",
-			 __func__, page, cifsi->fscache);
-		if (!fscache_maybe_release_page(cifsi->fscache, page, gfp))
-			return 0;
-	}
-
-	return 1;
-}
-
-static void cifs_readpage_from_fscache_complete(struct page *page, void *ctx,
-						int error)
-{
-	cifs_dbg(FYI, "%s: (0x%p/%d)\n", __func__, page, error);
-	if (!error)
-		SetPageUptodate(page);
-	unlock_page(page);
-}
-
-/*
- * Retrieve a page from FS-Cache
- */
-int __cifs_readpage_from_fscache(struct inode *inode, struct page *page)
-{
-	int ret;
-
-	cifs_dbg(FYI, "%s: (fsc:%p, p:%p, i:0x%p\n",
-		 __func__, CIFS_I(inode)->fscache, page, inode);
-	ret = fscache_read_or_alloc_page(CIFS_I(inode)->fscache, page,
-					 cifs_readpage_from_fscache_complete,
-					 NULL,
-					 GFP_KERNEL);
-	switch (ret) {
-
-	case 0: /* page found in fscache, read submitted */
-		cifs_dbg(FYI, "%s: submitted\n", __func__);
-		return ret;
-	case -ENOBUFS:	/* page won't be cached */
-	case -ENODATA:	/* page not in cache */
-		cifs_dbg(FYI, "%s: %d\n", __func__, ret);
-		return 1;
-
-	default:
-		cifs_dbg(VFS, "unknown error ret = %d\n", ret);
-	}
-	return ret;
-}
-
-/*
- * Retrieve a set of pages from FS-Cache
- */
-int __cifs_readpages_from_fscache(struct inode *inode,
-				struct address_space *mapping,
-				struct list_head *pages,
-				unsigned *nr_pages)
-{
-	int ret;
-
-	cifs_dbg(FYI, "%s: (0x%p/%u/0x%p)\n",
-		 __func__, CIFS_I(inode)->fscache, *nr_pages, inode);
-	ret = fscache_read_or_alloc_pages(CIFS_I(inode)->fscache, mapping,
-					  pages, nr_pages,
-					  cifs_readpage_from_fscache_complete,
-					  NULL,
-					  mapping_gfp_mask(mapping));
-	switch (ret) {
-	case 0:	/* read submitted to the cache for all pages */
-		cifs_dbg(FYI, "%s: submitted\n", __func__);
-		return ret;
-
-	case -ENOBUFS:	/* some pages are not cached and can't be */
-	case -ENODATA:	/* some pages are not cached */
-		cifs_dbg(FYI, "%s: no page\n", __func__);
-		return 1;
-
-	default:
-		cifs_dbg(FYI, "unknown error ret = %d\n", ret);
-	}
-
-	return ret;
-}
-
-void __cifs_readpage_to_fscache(struct inode *inode, struct page *page)
-{
-	struct cifsInodeInfo *cifsi = CIFS_I(inode);
-	int ret;
-
-	cifs_dbg(FYI, "%s: (fsc: %p, p: %p, i: %p)\n",
-		 __func__, cifsi->fscache, page, inode);
-	ret = fscache_write_page(cifsi->fscache, page,
-				 cifsi->vfs_inode.i_size, GFP_KERNEL);
-	if (ret != 0)
-		fscache_uncache_page(cifsi->fscache, page);
-}
-
-void __cifs_fscache_readpages_cancel(struct inode *inode, struct list_head *pages)
-{
-	cifs_dbg(FYI, "%s: (fsc: %p, i: %p)\n",
-		 __func__, CIFS_I(inode)->fscache, inode);
-	fscache_readpages_cancel(CIFS_I(inode)->fscache, pages);
-}
-
-void __cifs_fscache_invalidate_page(struct page *page, struct inode *inode)
-{
-	struct cifsInodeInfo *cifsi = CIFS_I(inode);
-	struct fscache_cookie *cookie = cifsi->fscache;
-
-	cifs_dbg(FYI, "%s: (0x%p/0x%p)\n", __func__, page, cookie);
-	fscache_wait_on_page_write(cookie, page);
-	fscache_uncache_page(cookie, page);
-}
diff --git a/fs/cifs/fscache.h b/fs/cifs/fscache.h
index e811f2dd7619..b86ef0fcf676 100644
--- a/fs/cifs/fscache.h
+++ b/fs/cifs/fscache.h
@@ -21,6 +21,7 @@
 #ifndef _CIFS_FSCACHE_H
 #define _CIFS_FSCACHE_H
 
+#define FSCACHE_USE_NEW_IO_API
 #include <linux/fscache.h>
 
 #include "cifsglob.h"
@@ -70,56 +71,9 @@ extern void cifs_fscache_release_inode_cookie(struct inode *);
 extern void cifs_fscache_set_inode_cookie(struct inode *, struct file *);
 extern void cifs_fscache_reset_inode_cookie(struct inode *);
 
-extern void __cifs_fscache_invalidate_page(struct page *, struct inode *);
-extern int cifs_fscache_release_page(struct page *page, gfp_t gfp);
-extern int __cifs_readpage_from_fscache(struct inode *, struct page *);
-extern int __cifs_readpages_from_fscache(struct inode *,
-					 struct address_space *,
-					 struct list_head *,
-					 unsigned *);
-extern void __cifs_fscache_readpages_cancel(struct inode *, struct list_head *);
-
-extern void __cifs_readpage_to_fscache(struct inode *, struct page *);
-
-static inline void cifs_fscache_invalidate_page(struct page *page,
-					       struct inode *inode)
-{
-	if (PageFsCache(page))
-		__cifs_fscache_invalidate_page(page, inode);
-}
-
-static inline int cifs_readpage_from_fscache(struct inode *inode,
-					     struct page *page)
-{
-	if (CIFS_I(inode)->fscache)
-		return __cifs_readpage_from_fscache(inode, page);
-
-	return -ENOBUFS;
-}
-
-static inline int cifs_readpages_from_fscache(struct inode *inode,
-					      struct address_space *mapping,
-					      struct list_head *pages,
-					      unsigned *nr_pages)
-{
-	if (CIFS_I(inode)->fscache)
-		return __cifs_readpages_from_fscache(inode, mapping, pages,
-						     nr_pages);
-	return -ENOBUFS;
-}
-
-static inline void cifs_readpage_to_fscache(struct inode *inode,
-					    struct page *page)
-{
-	if (PageFsCache(page))
-		__cifs_readpage_to_fscache(inode, page);
-}
-
-static inline void cifs_fscache_readpages_cancel(struct inode *inode,
-						 struct list_head *pages)
+static inline struct fscache_cookie *cifs_inode_cookie(struct inode *inode)
 {
-	if (CIFS_I(inode)->fscache)
-		return __cifs_fscache_readpages_cancel(inode, pages);
+	return CIFS_I(inode)->fscache;
 }
 
 #else /* CONFIG_CIFS_FSCACHE */
@@ -138,34 +92,8 @@ static inline void cifs_fscache_release_inode_cookie(struct inode *inode) {}
 static inline void cifs_fscache_set_inode_cookie(struct inode *inode,
 						 struct file *filp) {}
 static inline void cifs_fscache_reset_inode_cookie(struct inode *inode) {}
-static inline int cifs_fscache_release_page(struct page *page, gfp_t gfp)
-{
-	return 1; /* May release page */
-}
-
-static inline void cifs_fscache_invalidate_page(struct page *page,
-			struct inode *inode) {}
-static inline int
-cifs_readpage_from_fscache(struct inode *inode, struct page *page)
-{
-	return -ENOBUFS;
-}
 
-static inline int cifs_readpages_from_fscache(struct inode *inode,
-					      struct address_space *mapping,
-					      struct list_head *pages,
-					      unsigned *nr_pages)
-{
-	return -ENOBUFS;
-}
-
-static inline void cifs_readpage_to_fscache(struct inode *inode,
-			struct page *page) {}
-
-static inline void cifs_fscache_readpages_cancel(struct inode *inode,
-						 struct list_head *pages)
-{
-}
+static inline struct fscache_cookie *cifs_inode_cookie(struct inode *inode) { return NULL; }
 
 #endif /* CONFIG_CIFS_FSCACHE */
 
diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 794fc3b68b4f..788b5a364365 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -36,6 +36,7 @@
 #include <linux/uuid.h>
 #include <linux/pagemap.h>
 #include <linux/xattr.h>
+#include <linux/netfs.h>
 #include "smb2pdu.h"
 #include "cifsglob.h"
 #include "cifsacl.h"
@@ -3984,7 +3985,14 @@ smb2_readv_callback(struct mid_q_entry *mid)
 				     tcon->tid, tcon->ses->Suid,
 				     rdata->offset, rdata->got_bytes);
 
-	queue_work(cifsiod_wq, &rdata->work);
+	if (rdata->subreq) {
+		netfs_subreq_terminated(rdata->subreq,
+					(rdata->result == 0 || rdata->result == -EAGAIN) ?
+					rdata->got_bytes : rdata->result);
+		kref_put(&rdata->refcount, cifs_readdata_release);
+	} else {
+		queue_work(cifsiod_wq, &rdata->work);
+	}
 	DeleteMidQEntry(mid);
 	add_credits(server, &credits, 0);
 }