fuse: convert writepages to simple api

Derive fuse_writepage_args from fuse_io_args.

Sending the request is tricky since it was done with fi->lock held, hence
we must either use atomic allocation or release the lock.  Both are
possible so try atomic first and if it fails, release the lock and do the
regular allocation with GFP_NOFS and __GFP_NOFAIL.  Both flags are
necessary for correct operation.

Move the page realloc function from dev.c to file.c and convert to using
fuse_writepage_args.

The last caller of fuse_write_fill() is gone, so get rid of it.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

1 files changed, 206 insertions, 155 deletions

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 3cb98ff267cf..399b89b29bb4 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -347,19 +347,27 @@ u64 fuse_lock_owner_id(struct fuse_conn *fc, fl_owner_t id)
 	return (u64) v0 + ((u64) v1 << 32);
 }
 
-static struct fuse_req *fuse_find_writeback(struct fuse_inode *fi,
+struct fuse_writepage_args {
+	struct fuse_io_args ia;
+	struct list_head writepages_entry;
+	struct list_head queue_entry;
+	struct fuse_writepage_args *next;
+	struct inode *inode;
+};
+
+static struct fuse_writepage_args *fuse_find_writeback(struct fuse_inode *fi,
 					    pgoff_t idx_from, pgoff_t idx_to)
 {
-	struct fuse_req *req;
+	struct fuse_writepage_args *wpa;
 
-	list_for_each_entry(req, &fi->writepages, writepages_entry) {
+	list_for_each_entry(wpa, &fi->writepages, writepages_entry) {
 		pgoff_t curr_index;
 
-		WARN_ON(get_fuse_inode(req->inode) != fi);
-		curr_index = req->misc.write.in.offset >> PAGE_SHIFT;
-		if (idx_from < curr_index + req->num_pages &&
+		WARN_ON(get_fuse_inode(wpa->inode) != fi);
+		curr_index = wpa->ia.write.in.offset >> PAGE_SHIFT;
+		if (idx_from < curr_index + wpa->ia.ap.num_pages &&
 		    curr_index <= idx_to) {
-			return req;
+			return wpa;
 		}
 	}
 	return NULL;
@@ -984,29 +992,6 @@ static ssize_t fuse_cache_read_iter(struct kiocb *iocb, struct iov_iter *to)
 	return generic_file_read_iter(iocb, to);
 }
 
-static void fuse_write_fill(struct fuse_req *req, struct fuse_file *ff,
-			    loff_t pos, size_t count)
-{
-	struct fuse_write_in *inarg = &req->misc.write.in;
-	struct fuse_write_out *outarg = &req->misc.write.out;
-
-	inarg->fh = ff->fh;
-	inarg->offset = pos;
-	inarg->size = count;
-	req->in.h.opcode = FUSE_WRITE;
-	req->in.h.nodeid = ff->nodeid;
-	req->in.numargs = 2;
-	if (ff->fc->minor < 9)
-		req->in.args[0].size = FUSE_COMPAT_WRITE_IN_SIZE;
-	else
-		req->in.args[0].size = sizeof(struct fuse_write_in);
-	req->in.args[0].value = inarg;
-	req->in.args[1].size = count;
-	req->out.numargs = 1;
-	req->out.args[0].size = sizeof(struct fuse_write_out);
-	req->out.args[0].value = outarg;
-}
-
 static void fuse_write_args_fill(struct fuse_io_args *ia, struct fuse_file *ff,
 				 loff_t pos, size_t count)
 {
@@ -1576,45 +1561,53 @@ static ssize_t fuse_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 		return fuse_direct_write_iter(iocb, from);
 }
 
-static void fuse_writepage_free(struct fuse_conn *fc, struct fuse_req *req)
+static void fuse_writepage_free(struct fuse_writepage_args *wpa)
 {
+	struct fuse_args_pages *ap = &wpa->ia.ap;
 	int i;
 
-	for (i = 0; i < req->num_pages; i++)
-		__free_page(req->pages[i]);
+	for (i = 0; i < ap->num_pages; i++)
+		__free_page(ap->pages[i]);
+
+	if (wpa->ia.ff)
+		fuse_file_put(wpa->ia.ff, false, false);
 
-	if (req->ff)
-		fuse_file_put(req->ff, false, false);
+	kfree(ap->pages);
+	kfree(wpa);
 }
 
-static void fuse_writepage_finish(struct fuse_conn *fc, struct fuse_req *req)
+static void fuse_writepage_finish(struct fuse_conn *fc,
+				  struct fuse_writepage_args *wpa)
 {
-	struct inode *inode = req->inode;
+	struct fuse_args_pages *ap = &wpa->ia.ap;
+	struct inode *inode = wpa->inode;
 	struct fuse_inode *fi = get_fuse_inode(inode);
 	struct backing_dev_info *bdi = inode_to_bdi(inode);
 	int i;
 
-	list_del(&req->writepages_entry);
-	for (i = 0; i < req->num_pages; i++) {
+	list_del(&wpa->writepages_entry);
+	for (i = 0; i < ap->num_pages; i++) {
 		dec_wb_stat(&bdi->wb, WB_WRITEBACK);
-		dec_node_page_state(req->pages[i], NR_WRITEBACK_TEMP);
+		dec_node_page_state(ap->pages[i], NR_WRITEBACK_TEMP);
 		wb_writeout_inc(&bdi->wb);
 	}
 	wake_up(&fi->page_waitq);
 }
 
 /* Called under fi->lock, may release and reacquire it */
-static void fuse_send_writepage(struct fuse_conn *fc, struct fuse_req *req,
-				loff_t size)
+static void fuse_send_writepage(struct fuse_conn *fc,
+				struct fuse_writepage_args *wpa, loff_t size)
 __releases(fi->lock)
 __acquires(fi->lock)
 {
-	struct fuse_req *aux, *next;
-	struct fuse_inode *fi = get_fuse_inode(req->inode);
-	struct fuse_write_in *inarg = &req->misc.write.in;
-	__u64 data_size = req->num_pages * PAGE_SIZE;
-	bool queued;
+	struct fuse_writepage_args *aux, *next;
+	struct fuse_inode *fi = get_fuse_inode(wpa->inode);
+	struct fuse_write_in *inarg = &wpa->ia.write.in;
+	struct fuse_args *args = &wpa->ia.ap.args;
+	__u64 data_size = wpa->ia.ap.num_pages * PAGE_SIZE;
+	int err;
 
+	fi->writectr++;
 	if (inarg->offset + data_size <= size) {
 		inarg->size = data_size;
 	} else if (inarg->offset < size) {
@@ -1624,29 +1617,36 @@ __acquires(fi->lock)
 		goto out_free;
 	}
 
-	req->in.args[1].size = inarg->size;
-	queued = fuse_request_queue_background(fc, req);
+	args->in_args[1].size = inarg->size;
+	args->force = true;
+	args->nocreds = true;
+
+	err = fuse_simple_background(fc, args, GFP_ATOMIC);
+	if (err == -ENOMEM) {
+		spin_unlock(&fi->lock);
+		err = fuse_simple_background(fc, args, GFP_NOFS | __GFP_NOFAIL);
+		spin_lock(&fi->lock);
+	}
+
 	/* Fails on broken connection only */
-	if (unlikely(!queued))
+	if (unlikely(err))
 		goto out_free;
 
-	fi->writectr++;
 	return;
 
  out_free:
-	fuse_writepage_finish(fc, req);
+	fi->writectr--;
+	fuse_writepage_finish(fc, wpa);
 	spin_unlock(&fi->lock);
 
 	/* After fuse_writepage_finish() aux request list is private */
-	for (aux = req->misc.write.next; aux; aux = next) {
-		next = aux->misc.write.next;
-		aux->misc.write.next = NULL;
-		fuse_writepage_free(fc, aux);
-		fuse_put_request(fc, aux);
+	for (aux = wpa->next; aux; aux = next) {
+		next = aux->next;
+		aux->next = NULL;
+		fuse_writepage_free(aux);
 	}
 
-	fuse_writepage_free(fc, req);
-	fuse_put_request(fc, req);
+	fuse_writepage_free(wpa);
 	spin_lock(&fi->lock);
 }
 
@@ -1663,29 +1663,34 @@ __acquires(fi->lock)
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	struct fuse_inode *fi = get_fuse_inode(inode);
 	loff_t crop = i_size_read(inode);
-	struct fuse_req *req;
+	struct fuse_writepage_args *wpa;
 
 	while (fi->writectr >= 0 && !list_empty(&fi->queued_writes)) {
-		req = list_entry(fi->queued_writes.next, struct fuse_req, list);
-		list_del_init(&req->list);
-		fuse_send_writepage(fc, req, crop);
+		wpa = list_entry(fi->queued_writes.next,
+				 struct fuse_writepage_args, queue_entry);
+		list_del_init(&wpa->queue_entry);
+		fuse_send_writepage(fc, wpa, crop);
 	}
 }
 
-static void fuse_writepage_end(struct fuse_conn *fc, struct fuse_req *req)
+static void fuse_writepage_end(struct fuse_conn *fc, struct fuse_args *args,
+			       int error)
 {
-	struct inode *inode = req->inode;
+	struct fuse_writepage_args *wpa =
+		container_of(args, typeof(*wpa), ia.ap.args);
+	struct inode *inode = wpa->inode;
 	struct fuse_inode *fi = get_fuse_inode(inode);
 
-	mapping_set_error(inode->i_mapping, req->out.h.error);
+	mapping_set_error(inode->i_mapping, error);
 	spin_lock(&fi->lock);
-	while (req->misc.write.next) {
+	while (wpa->next) {
 		struct fuse_conn *fc = get_fuse_conn(inode);
-		struct fuse_write_in *inarg = &req->misc.write.in;
-		struct fuse_req *next = req->misc.write.next;
-		req->misc.write.next = next->misc.write.next;
-		next->misc.write.next = NULL;
-		next->ff = fuse_file_get(req->ff);
+		struct fuse_write_in *inarg = &wpa->ia.write.in;
+		struct fuse_writepage_args *next = wpa->next;
+
+		wpa->next = next->next;
+		next->next = NULL;
+		next->ia.ff = fuse_file_get(wpa->ia.ff);
 		list_add(&next->writepages_entry, &fi->writepages);
 
 		/*
@@ -1714,9 +1719,9 @@ static void fuse_writepage_end(struct fuse_conn *fc, struct fuse_req *req)
 		fuse_send_writepage(fc, next, inarg->offset + inarg->size);
 	}
 	fi->writectr--;
-	fuse_writepage_finish(fc, req);
+	fuse_writepage_finish(fc, wpa);
 	spin_unlock(&fi->lock);
-	fuse_writepage_free(fc, req);
+	fuse_writepage_free(wpa);
 }
 
 static struct fuse_file *__fuse_write_file_get(struct fuse_conn *fc,
@@ -1758,52 +1763,71 @@ int fuse_write_inode(struct inode *inode, struct writeback_control *wbc)
 	return err;
 }
 
+static struct fuse_writepage_args *fuse_writepage_args_alloc(void)
+{
+	struct fuse_writepage_args *wpa;
+	struct fuse_args_pages *ap;
+
+	wpa = kzalloc(sizeof(*wpa), GFP_NOFS);
+	if (wpa) {
+		ap = &wpa->ia.ap;
+		ap->num_pages = 0;
+		ap->pages = fuse_pages_alloc(1, GFP_NOFS, &ap->descs);
+		if (!ap->pages) {
+			kfree(wpa);
+			wpa = NULL;
+		}
+	}
+	return wpa;
+
+}
+
 static int fuse_writepage_locked(struct page *page)
 {
 	struct address_space *mapping = page->mapping;
 	struct inode *inode = mapping->host;
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	struct fuse_inode *fi = get_fuse_inode(inode);
-	struct fuse_req *req;
+	struct fuse_writepage_args *wpa;
+	struct fuse_args_pages *ap;
 	struct page *tmp_page;
 	int error = -ENOMEM;
 
 	set_page_writeback(page);
 
-	req = fuse_request_alloc_nofs(1);
-	if (!req)
+	wpa = fuse_writepage_args_alloc();
+	if (!wpa)
 		goto err;
+	ap = &wpa->ia.ap;
 
-	/* writeback always goes to bg_queue */
-	__set_bit(FR_BACKGROUND, &req->flags);
 	tmp_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
 	if (!tmp_page)
 		goto err_free;
 
 	error = -EIO;
-	req->ff = fuse_write_file_get(fc, fi);
-	if (!req->ff)
+	wpa->ia.ff = fuse_write_file_get(fc, fi);
+	if (!wpa->ia.ff)
 		goto err_nofile;
 
-	fuse_write_fill(req, req->ff, page_offset(page), 0);
+	fuse_write_args_fill(&wpa->ia, wpa->ia.ff, page_offset(page), 0);
 
 	copy_highpage(tmp_page, page);
-	req->misc.write.in.write_flags |= FUSE_WRITE_CACHE;
-	req->misc.write.next = NULL;
-	req->in.argpages = 1;
-	req->num_pages = 1;
-	req->pages[0] = tmp_page;
-	req->page_descs[0].offset = 0;
-	req->page_descs[0].length = PAGE_SIZE;
-	req->end = fuse_writepage_end;
-	req->inode = inode;
+	wpa->ia.write.in.write_flags |= FUSE_WRITE_CACHE;
+	wpa->next = NULL;
+	ap->args.in_pages = true;
+	ap->num_pages = 1;
+	ap->pages[0] = tmp_page;
+	ap->descs[0].offset = 0;
+	ap->descs[0].length = PAGE_SIZE;
+	ap->args.end = fuse_writepage_end;
+	wpa->inode = inode;
 
 	inc_wb_stat(&inode_to_bdi(inode)->wb, WB_WRITEBACK);
 	inc_node_page_state(tmp_page, NR_WRITEBACK_TEMP);
 
 	spin_lock(&fi->lock);
-	list_add(&req->writepages_entry, &fi->writepages);
-	list_add_tail(&req->list, &fi->queued_writes);
+	list_add(&wpa->writepages_entry, &fi->writepages);
+	list_add_tail(&wpa->queue_entry, &fi->queued_writes);
 	fuse_flush_writepages(inode);
 	spin_unlock(&fi->lock);
 
@@ -1814,7 +1838,7 @@ static int fuse_writepage_locked(struct page *page)
 err_nofile:
 	__free_page(tmp_page);
 err_free:
-	fuse_request_free(req);
+	kfree(wpa);
 err:
 	mapping_set_error(page->mapping, error);
 	end_page_writeback(page);
@@ -1844,23 +1868,50 @@ static int fuse_writepage(struct page *page, struct writeback_control *wbc)
 }
 
 struct fuse_fill_wb_data {
-	struct fuse_req *req;
+	struct fuse_writepage_args *wpa;
 	struct fuse_file *ff;
 	struct inode *inode;
 	struct page **orig_pages;
+	unsigned int max_pages;
 };
 
+static bool fuse_pages_realloc(struct fuse_fill_wb_data *data)
+{
+	struct fuse_args_pages *ap = &data->wpa->ia.ap;
+	struct fuse_conn *fc = get_fuse_conn(data->inode);
+	struct page **pages;
+	struct fuse_page_desc *descs;
+	unsigned int npages = min_t(unsigned int,
+				    max_t(unsigned int, data->max_pages * 2,
+					  FUSE_DEFAULT_MAX_PAGES_PER_REQ),
+				    fc->max_pages);
+	WARN_ON(npages <= data->max_pages);
+
+	pages = fuse_pages_alloc(npages, GFP_NOFS, &descs);
+	if (!pages)
+		return false;
+
+	memcpy(pages, ap->pages, sizeof(struct page *) * ap->num_pages);
+	memcpy(descs, ap->descs, sizeof(struct fuse_page_desc) * ap->num_pages);
+	kfree(ap->pages);
+	ap->pages = pages;
+	ap->descs = descs;
+	data->max_pages = npages;
+
+	return true;
+}
+
 static void fuse_writepages_send(struct fuse_fill_wb_data *data)
 {
-	struct fuse_req *req = data->req;
+	struct fuse_writepage_args *wpa = data->wpa;
 	struct inode *inode = data->inode;
 	struct fuse_inode *fi = get_fuse_inode(inode);
-	int num_pages = req->num_pages;
+	int num_pages = wpa->ia.ap.num_pages;
 	int i;
 
-	req->ff = fuse_file_get(data->ff);
+	wpa->ia.ff = fuse_file_get(data->ff);
 	spin_lock(&fi->lock);
-	list_add_tail(&req->list, &fi->queued_writes);
+	list_add_tail(&wpa->queue_entry, &fi->queued_writes);
 	fuse_flush_writepages(inode);
 	spin_unlock(&fi->lock);
 
@@ -1875,54 +1926,52 @@ static void fuse_writepages_send(struct fuse_fill_wb_data *data)
  * this new request onto the auxiliary list, otherwise reuse the existing one by
  * copying the new page contents over to the old temporary page.
  */
-static bool fuse_writepage_in_flight(struct fuse_req *new_req,
+static bool fuse_writepage_in_flight(struct fuse_writepage_args *new_wpa,
 				     struct page *page)
 {
-	struct fuse_conn *fc = get_fuse_conn(new_req->inode);
-	struct fuse_inode *fi = get_fuse_inode(new_req->inode);
-	struct fuse_req *tmp;
-	struct fuse_req *old_req;
+	struct fuse_inode *fi = get_fuse_inode(new_wpa->inode);
+	struct fuse_writepage_args *tmp;
+	struct fuse_writepage_args *old_wpa;
+	struct fuse_args_pages *new_ap = &new_wpa->ia.ap;
 
-	WARN_ON(new_req->num_pages != 0);
+	WARN_ON(new_ap->num_pages != 0);
 
 	spin_lock(&fi->lock);
-	list_del(&new_req->writepages_entry);
-	old_req = fuse_find_writeback(fi, page->index, page->index);
-	if (!old_req) {
-		list_add(&new_req->writepages_entry, &fi->writepages);
+	list_del(&new_wpa->writepages_entry);
+	old_wpa = fuse_find_writeback(fi, page->index, page->index);
+	if (!old_wpa) {
+		list_add(&new_wpa->writepages_entry, &fi->writepages);
 		spin_unlock(&fi->lock);
 		return false;
 	}
 
-	new_req->num_pages = 1;
-	for (tmp = old_req->misc.write.next; tmp; tmp = tmp->misc.write.next) {
+	new_ap->num_pages = 1;
+	for (tmp = old_wpa->next; tmp; tmp = tmp->next) {
 		pgoff_t curr_index;
 
-		WARN_ON(tmp->inode != new_req->inode);
-		curr_index = tmp->misc.write.in.offset >> PAGE_SHIFT;
+		WARN_ON(tmp->inode != new_wpa->inode);
+		curr_index = tmp->ia.write.in.offset >> PAGE_SHIFT;
 		if (curr_index == page->index) {
-			WARN_ON(tmp->num_pages != 1);
-			WARN_ON(!test_bit(FR_PENDING, &tmp->flags));
-			swap(tmp->pages[0], new_req->pages[0]);
+			WARN_ON(tmp->ia.ap.num_pages != 1);
+			swap(tmp->ia.ap.pages[0], new_ap->pages[0]);
 			break;
 		}
 	}
 
 	if (!tmp) {
-		new_req->misc.write.next = old_req->misc.write.next;
-		old_req->misc.write.next = new_req;
+		new_wpa->next = old_wpa->next;
+		old_wpa->next = new_wpa;
 	}
 
 	spin_unlock(&fi->lock);
 
 	if (tmp) {
-		struct backing_dev_info *bdi = inode_to_bdi(new_req->inode);
+		struct backing_dev_info *bdi = inode_to_bdi(new_wpa->inode);
 
 		dec_wb_stat(&bdi->wb, WB_WRITEBACK);
-		dec_node_page_state(new_req->pages[0], NR_WRITEBACK_TEMP);
+		dec_node_page_state(new_ap->pages[0], NR_WRITEBACK_TEMP);
 		wb_writeout_inc(&bdi->wb);
-		fuse_writepage_free(fc, new_req);
-		fuse_request_free(new_req);
+		fuse_writepage_free(new_wpa);
 	}
 
 	return true;
@@ -1932,7 +1981,8 @@ static int fuse_writepages_fill(struct page *page,
 		struct writeback_control *wbc, void *_data)
 {
 	struct fuse_fill_wb_data *data = _data;
-	struct fuse_req *req = data->req;
+	struct fuse_writepage_args *wpa = data->wpa;
+	struct fuse_args_pages *ap = &wpa->ia.ap;
 	struct inode *inode = data->inode;
 	struct fuse_inode *fi = get_fuse_inode(inode);
 	struct fuse_conn *fc = get_fuse_conn(inode);
@@ -1955,16 +2005,16 @@ static int fuse_writepages_fill(struct page *page,
 	 */
 	is_writeback = fuse_page_is_writeback(inode, page->index);
 
-	if (req && req->num_pages &&
-	    (is_writeback || req->num_pages == fc->max_pages ||
-	     (req->num_pages + 1) * PAGE_SIZE > fc->max_write ||
-	     data->orig_pages[req->num_pages - 1]->index + 1 != page->index)) {
+	if (wpa && ap->num_pages &&
+	    (is_writeback || ap->num_pages == fc->max_pages ||
+	     (ap->num_pages + 1) * PAGE_SIZE > fc->max_write ||
+	     data->orig_pages[ap->num_pages - 1]->index + 1 != page->index)) {
 		fuse_writepages_send(data);
-		data->req = NULL;
-	} else if (req && req->num_pages == req->max_pages) {
-		if (!fuse_req_realloc_pages(fc, req, GFP_NOFS)) {
+		data->wpa = NULL;
+	} else if (wpa && ap->num_pages == data->max_pages) {
+		if (!fuse_pages_realloc(data)) {
 			fuse_writepages_send(data);
-			req = data->req = NULL;
+			data->wpa = NULL;
 		}
 	}
 
@@ -1982,59 +2032,60 @@ static int fuse_writepages_fill(struct page *page,
 	 * This is ensured by holding the page lock in page_mkwrite() while
 	 * checking fuse_page_is_writeback().  We already hold the page lock
 	 * since clear_page_dirty_for_io() and keep it held until we add the
-	 * request to the fi->writepages list and increment req->num_pages.
+	 * request to the fi->writepages list and increment ap->num_pages.
 	 * After this fuse_page_is_writeback() will indicate that the page is
 	 * under writeback, so we can release the page lock.
 	 */
-	if (data->req == NULL) {
+	if (data->wpa == NULL) {
 		struct fuse_inode *fi = get_fuse_inode(inode);
 
 		err = -ENOMEM;
-		req = fuse_request_alloc_nofs(FUSE_REQ_INLINE_PAGES);
-		if (!req) {
+		wpa = fuse_writepage_args_alloc();
+		if (!wpa) {
 			__free_page(tmp_page);
 			goto out_unlock;
 		}
+		data->max_pages = 1;
 
-		fuse_write_fill(req, data->ff, page_offset(page), 0);
-		req->misc.write.in.write_flags |= FUSE_WRITE_CACHE;
-		req->misc.write.next = NULL;
-		req->in.argpages = 1;
-		__set_bit(FR_BACKGROUND, &req->flags);
-		req->num_pages = 0;
-		req->end = fuse_writepage_end;
-		req->inode = inode;
+		ap = &wpa->ia.ap;
+		fuse_write_args_fill(&wpa->ia, data->ff, page_offset(page), 0);
+		wpa->ia.write.in.write_flags |= FUSE_WRITE_CACHE;
+		wpa->next = NULL;
+		ap->args.in_pages = true;
+		ap->args.end = fuse_writepage_end;
+		ap->num_pages = 0;
+		wpa->inode = inode;
 
 		spin_lock(&fi->lock);
-		list_add(&req->writepages_entry, &fi->writepages);
+		list_add(&wpa->writepages_entry, &fi->writepages);
 		spin_unlock(&fi->lock);
 
-		data->req = req;
+		data->wpa = wpa;
 	}
 	set_page_writeback(page);
 
 	copy_highpage(tmp_page, page);
-	req->pages[req->num_pages] = tmp_page;
-	req->page_descs[req->num_pages].offset = 0;
-	req->page_descs[req->num_pages].length = PAGE_SIZE;
+	ap->pages[ap->num_pages] = tmp_page;
+	ap->descs[ap->num_pages].offset = 0;
+	ap->descs[ap->num_pages].length = PAGE_SIZE;
 
 	inc_wb_stat(&inode_to_bdi(inode)->wb, WB_WRITEBACK);
 	inc_node_page_state(tmp_page, NR_WRITEBACK_TEMP);
 
 	err = 0;
-	if (is_writeback && fuse_writepage_in_flight(req, page)) {
+	if (is_writeback && fuse_writepage_in_flight(wpa, page)) {
 		end_page_writeback(page);
-		data->req = NULL;
+		data->wpa = NULL;
 		goto out_unlock;
 	}
-	data->orig_pages[req->num_pages] = page;
+	data->orig_pages[ap->num_pages] = page;
 
 	/*
 	 * Protected by fi->lock against concurrent access by
 	 * fuse_page_is_writeback().
 	 */
 	spin_lock(&fi->lock);
-	req->num_pages++;
+	ap->num_pages++;
 	spin_unlock(&fi->lock);
 
 out_unlock:
@@ -2056,7 +2107,7 @@ static int fuse_writepages(struct address_space *mapping,
 		goto out;
 
 	data.inode = inode;
-	data.req = NULL;
+	data.wpa = NULL;
 	data.ff = NULL;
 
 	err = -ENOMEM;
@@ -2067,9 +2118,9 @@ static int fuse_writepages(struct address_space *mapping,
 		goto out;
 
 	err = write_cache_pages(mapping, wbc, fuse_writepages_fill, &data);
-	if (data.req) {
+	if (data.wpa) {
 		/* Ignore errors if we can write at least one page */
-		BUG_ON(!data.req->num_pages);
+		WARN_ON(!data.wpa->ia.ap.num_pages);
 		fuse_writepages_send(&data);
 		err = 0;
 	}