Merge tag 'fuse-fixes-5.8-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse into master

Pull fuse fixes from Miklos Szeredi:

- two regressions in this cycle caused by the conversion of writepage
list to an rb_tree

- two regressions in v5.4 cause by the conversion to the new mount API

- saner behavior of fsconfig(2) for the reconfigure case

- an ancient issue with FS_IOC_{GET,SET}FLAGS ioctls

* tag 'fuse-fixes-5.8-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
fuse: Fix parameter for FS_IOC_{GET,SET}FLAGS
fuse: don't ignore errors from fuse_writepages_fill()
fuse: clean up condition for writepage sending
fuse: reject options on reconfigure via fsconfig(2)
fuse: ignore 'data' argument of mount(..., MS_REMOUNT)
fuse: use ->reconfigure() instead of ->remount_fs()
fuse: fix warning in tree_insert() and clean up writepage insertion
fuse: move rb_erase() before tree_insert()

fs/fuse/file.c

···
 #include <linux/swap.h>
 #include <linux/falloc.h>
 #include <linux/uio.h>
+#include <linux/fs.h>
 
 static struct page **fuse_pages_alloc(unsigned int npages, gfp_t flags,
 				      struct fuse_page_desc **desc)
···
 	struct backing_dev_info *bdi = inode_to_bdi(inode);
 	int i;
 
-	rb_erase(&wpa->writepages_entry, &fi->writepages);
 	for (i = 0; i < ap->num_pages; i++) {
 		dec_wb_stat(&bdi->wb, WB_WRITEBACK);
 		dec_node_page_state(ap->pages[i], NR_WRITEBACK_TEMP);
···
 
  out_free:
 	fi->writectr--;
+	rb_erase(&wpa->writepages_entry, &fi->writepages);
 	fuse_writepage_finish(fc, wpa);
 	spin_unlock(&fi->lock);
 
···
 	}
 }
 
-static void tree_insert(struct rb_root *root, struct fuse_writepage_args *wpa)
+static struct fuse_writepage_args *fuse_insert_writeback(struct rb_root *root,
+						struct fuse_writepage_args *wpa)
 {
 	pgoff_t idx_from = wpa->ia.write.in.offset >> PAGE_SHIFT;
 	pgoff_t idx_to = idx_from + wpa->ia.ap.num_pages - 1;
···
 		else if (idx_to < curr_index)
 			p = &(*p)->rb_left;
 		else
-			return (void) WARN_ON(true);
+			return curr;
 	}
 
 	rb_link_node(&wpa->writepages_entry, parent, p);
 	rb_insert_color(&wpa->writepages_entry, root);
+	return NULL;
+}
+
+static void tree_insert(struct rb_root *root, struct fuse_writepage_args *wpa)
+{
+	WARN_ON(fuse_insert_writeback(root, wpa));
 }
 
 static void fuse_writepage_end(struct fuse_conn *fc, struct fuse_args *args,
···
 
 	mapping_set_error(inode->i_mapping, error);
 	spin_lock(&fi->lock);
+	rb_erase(&wpa->writepages_entry, &fi->writepages);
 	while (wpa->next) {
 		struct fuse_conn *fc = get_fuse_conn(inode);
 		struct fuse_write_in *inarg = &wpa->ia.write.in;
···
 }
 
 /*
- * First recheck under fi->lock if the offending offset is still under
- * writeback.  If yes, then iterate auxiliary write requests, to see if there's
+ * Check under fi->lock if the page is under writeback, and insert it onto the
+ * rb_tree if not. Otherwise iterate auxiliary write requests, to see if there's
  * one already added for a page at this offset.  If there's none, then insert
  * this new request onto the auxiliary list, otherwise reuse the existing one by
- * copying the new page contents over to the old temporary page.
+ * swapping the new temp page with the old one.
  */
-static bool fuse_writepage_in_flight(struct fuse_writepage_args *new_wpa,
-				     struct page *page)
+static bool fuse_writepage_add(struct fuse_writepage_args *new_wpa,
+			       struct page *page)
 {
 	struct fuse_inode *fi = get_fuse_inode(new_wpa->inode);
 	struct fuse_writepage_args *tmp;
···
 	struct fuse_args_pages *new_ap = &new_wpa->ia.ap;
 
 	WARN_ON(new_ap->num_pages != 0);
+	new_ap->num_pages = 1;
 
 	spin_lock(&fi->lock);
-	rb_erase(&new_wpa->writepages_entry, &fi->writepages);
-	old_wpa = fuse_find_writeback(fi, page->index, page->index);
+	old_wpa = fuse_insert_writeback(&fi->writepages, new_wpa);
 	if (!old_wpa) {
-		tree_insert(&fi->writepages, new_wpa);
 		spin_unlock(&fi->lock);
-		return false;
+		return true;
 	}
 
-	new_ap->num_pages = 1;
 	for (tmp = old_wpa->next; tmp; tmp = tmp->next) {
 		pgoff_t curr_index;
 
···
 		fuse_writepage_free(new_wpa);
 	}
 
-	return true;
+	return false;
+}
+
+static bool fuse_writepage_need_send(struct fuse_conn *fc, struct page *page,
+				     struct fuse_args_pages *ap,
+				     struct fuse_fill_wb_data *data)
+{
+	WARN_ON(!ap->num_pages);
+
+	/*
+	 * Being under writeback is unlikely but possible.  For example direct
+	 * read to an mmaped fuse file will set the page dirty twice; once when
+	 * the pages are faulted with get_user_pages(), and then after the read
+	 * completed.
+	 */
+	if (fuse_page_is_writeback(data->inode, page->index))
+		return true;
+
+	/* Reached max pages */
+	if (ap->num_pages == fc->max_pages)
+		return true;
+
+	/* Reached max write bytes */
+	if ((ap->num_pages + 1) * PAGE_SIZE > fc->max_write)
+		return true;
+
+	/* Discontinuity */
+	if (data->orig_pages[ap->num_pages - 1]->index + 1 != page->index)
+		return true;
+
+	/* Need to grow the pages array?  If so, did the expansion fail? */
+	if (ap->num_pages == data->max_pages && !fuse_pages_realloc(data))
+		return true;
+
+	return false;
 }
 
 static int fuse_writepages_fill(struct page *page,
···
 	struct fuse_inode *fi = get_fuse_inode(inode);
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	struct page *tmp_page;
-	bool is_writeback;
 	int err;
 
 	if (!data->ff) {
···
 			goto out_unlock;
 	}
 
-	/*
-	 * Being under writeback is unlikely but possible.  For example direct
-	 * read to an mmaped fuse file will set the page dirty twice; once when
-	 * the pages are faulted with get_user_pages(), and then after the read
-	 * completed.
-	 */
-	is_writeback = fuse_page_is_writeback(inode, 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)) {
+	if (wpa && fuse_writepage_need_send(fc, page, ap, data)) {
 		fuse_writepages_send(data);
 		data->wpa = NULL;
-	} else if (wpa && ap->num_pages == data->max_pages) {
-		if (!fuse_pages_realloc(data)) {
-			fuse_writepages_send(data);
-			data->wpa = NULL;
-		}
 	}
 
 	err = -ENOMEM;
···
 		ap->args.end = fuse_writepage_end;
 		ap->num_pages = 0;
 		wpa->inode = inode;
-
-		spin_lock(&fi->lock);
-		tree_insert(&fi->writepages, wpa);
-		spin_unlock(&fi->lock);
-
-		data->wpa = wpa;
 	}
 	set_page_writeback(page);
 
···
 	ap->pages[ap->num_pages] = tmp_page;
 	ap->descs[ap->num_pages].offset = 0;
 	ap->descs[ap->num_pages].length = PAGE_SIZE;
+	data->orig_pages[ap->num_pages] = page;
 
 	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(wpa, page)) {
+	if (data->wpa) {
+		/*
+		 * Protected by fi->lock against concurrent access by
+		 * fuse_page_is_writeback().
+		 */
+		spin_lock(&fi->lock);
+		ap->num_pages++;
+		spin_unlock(&fi->lock);
+	} else if (fuse_writepage_add(wpa, page)) {
+		data->wpa = wpa;
+	} else {
 		end_page_writeback(page);
-		data->wpa = NULL;
-		goto out_unlock;
 	}
-	data->orig_pages[ap->num_pages] = page;
-
-	/*
-	 * Protected by fi->lock against concurrent access by
-	 * fuse_page_is_writeback().
-	 */
-	spin_lock(&fi->lock);
-	ap->num_pages++;
-	spin_unlock(&fi->lock);
-
 out_unlock:
 	unlock_page(page);
 
···
 
 	err = write_cache_pages(mapping, wbc, fuse_writepages_fill, &data);
 	if (data.wpa) {
-		/* Ignore errors if we can write at least one page */
 		WARN_ON(!data.wpa->ia.ap.num_pages);
 		fuse_writepages_send(&data);
-		err = 0;
 	}
 	if (data.ff)
 		fuse_file_put(data.ff, false, false);
···
 		struct iovec *iov = iov_page;
 
 		iov->iov_base = (void __user *)arg;
-		iov->iov_len = _IOC_SIZE(cmd);
+
+		switch (cmd) {
+		case FS_IOC_GETFLAGS:
+		case FS_IOC_SETFLAGS:
+			iov->iov_len = sizeof(int);
+			break;
+		default:
+			iov->iov_len = _IOC_SIZE(cmd);
+			break;
+		}
 
 		if (_IOC_DIR(cmd) & _IOC_WRITE) {
 			in_iov = iov;

fs/fuse/inode.c

···
 	}
 }
 
-static int fuse_remount_fs(struct super_block *sb, int *flags, char *data)
+static int fuse_reconfigure(struct fs_context *fc)
 {
+	struct super_block *sb = fc->root->d_sb;
+
 	sync_filesystem(sb);
-	if (*flags & SB_MANDLOCK)
+	if (fc->sb_flags & SB_MANDLOCK)
 		return -EINVAL;
 
 	return 0;
···
 	struct fuse_fs_context *ctx = fc->fs_private;
 	int opt;
 
+	if (fc->purpose == FS_CONTEXT_FOR_RECONFIGURE) {
+		/*
+		 * Ignore options coming from mount(MS_REMOUNT) for backward
+		 * compatibility.
+		 */
+		if (fc->oldapi)
+			return 0;
+
+		return invalfc(fc, "No changes allowed in reconfigure");
+	}
+
 	opt = fs_parse(fc, fuse_fs_parameters, param, &result);
 	if (opt < 0)
 		return opt;
···
 	.evict_inode	= fuse_evict_inode,
 	.write_inode	= fuse_write_inode,
 	.drop_inode	= generic_delete_inode,
-	.remount_fs	= fuse_remount_fs,
 	.put_super	= fuse_put_super,
 	.umount_begin	= fuse_umount_begin,
 	.statfs		= fuse_statfs,
···
 static const struct fs_context_operations fuse_context_ops = {
 	.free		= fuse_free_fc,
 	.parse_param	= fuse_parse_param,
+	.reconfigure	= fuse_reconfigure,
 	.get_tree	= fuse_get_tree,
 };
 

fs/namespace.c

···
 	if (IS_ERR(fc))
 		return PTR_ERR(fc);
 
+	fc->oldapi = true;
 	err = parse_monolithic_mount_data(fc, data);
 	if (!err) {
 		down_write(&sb->s_umount);

include/linux/fs_context.h

···
 	enum fs_context_phase	phase:8;	/* The phase the context is in */
 	bool			need_free:1;	/* Need to call ops->free() */
 	bool			global:1;	/* Goes into &init_user_ns */
+	bool			oldapi:1;	/* Coming from mount(2) */
 };
 
 struct fs_context_operations {