1 files changed, 87 insertions, 763 deletions

diff --git a/fs/netfs/buffered_write.c b/fs/netfs/buffered_write.c
index 9a0d32e4b422ad..1121601536d184 100644
--- a/fs/netfs/buffered_write.c
+++ b/fs/netfs/buffered_write.c
@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0-only
-/* Network filesystem high-level write support.
+/* Network filesystem high-level buffered write support.
  *
  * Copyright (C) 2023 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
@@ -26,25 +26,15 @@ enum netfs_how_to_modify {
 	NETFS_FLUSH_CONTENT,		/* Flush incompatible content. */
 };
 
-static void netfs_cleanup_buffered_write(struct netfs_io_request *wreq);
-
 static void netfs_set_group(struct folio *folio, struct netfs_group *netfs_group)
 {
-	if (netfs_group && !folio_get_private(folio))
-		folio_attach_private(folio, netfs_get_group(netfs_group));
-}
+	void *priv = folio_get_private(folio);
 
-#if IS_ENABLED(CONFIG_FSCACHE)
-static void netfs_folio_start_fscache(bool caching, struct folio *folio)
-{
-	if (caching)
-		folio_start_fscache(folio);
-}
-#else
-static void netfs_folio_start_fscache(bool caching, struct folio *folio)
-{
+	if (netfs_group && (!priv || priv == NETFS_FOLIO_COPY_TO_CACHE))
+		folio_attach_private(folio, netfs_get_group(netfs_group));
+	else if (!netfs_group && priv == NETFS_FOLIO_COPY_TO_CACHE)
+		folio_detach_private(folio);
 }
-#endif
 
 /*
  * Decide how we should modify a folio.  We might be attempting to do
@@ -63,11 +53,12 @@ static enum netfs_how_to_modify netfs_how_to_modify(struct netfs_inode *ctx,
 						    bool maybe_trouble)
 {
 	struct netfs_folio *finfo = netfs_folio_info(folio);
+	struct netfs_group *group = netfs_folio_group(folio);
 	loff_t pos = folio_file_pos(folio);
 
 	_enter("");
 
-	if (netfs_folio_group(folio) != netfs_group)
+	if (group != netfs_group && group != NETFS_FOLIO_COPY_TO_CACHE)
 		return NETFS_FLUSH_CONTENT;
 
 	if (folio_test_uptodate(folio))
@@ -81,16 +72,12 @@ static enum netfs_how_to_modify netfs_how_to_modify(struct netfs_inode *ctx,
 
 	if (file->f_mode & FMODE_READ)
 		goto no_write_streaming;
-	if (test_bit(NETFS_ICTX_NO_WRITE_STREAMING, &ctx->flags))
-		goto no_write_streaming;
 
 	if (netfs_is_cache_enabled(ctx)) {
 		/* We don't want to get a streaming write on a file that loses
 		 * caching service temporarily because the backing store got
 		 * culled.
 		 */
-		if (!test_bit(NETFS_ICTX_NO_WRITE_STREAMING, &ctx->flags))
-			set_bit(NETFS_ICTX_NO_WRITE_STREAMING, &ctx->flags);
 		goto no_write_streaming;
 	}
 
@@ -130,6 +117,37 @@ static struct folio *netfs_grab_folio_for_write(struct address_space *mapping,
 				   mapping_gfp_mask(mapping));
 }
 
+/*
+ * Update i_size and estimate the update to i_blocks to reflect the additional
+ * data written into the pagecache until we can find out from the server what
+ * the values actually are.
+ */
+static void netfs_update_i_size(struct netfs_inode *ctx, struct inode *inode,
+				loff_t i_size, loff_t pos, size_t copied)
+{
+	blkcnt_t add;
+	size_t gap;
+
+	if (ctx->ops->update_i_size) {
+		ctx->ops->update_i_size(inode, pos);
+		return;
+	}
+
+	i_size_write(inode, pos);
+#if IS_ENABLED(CONFIG_FSCACHE)
+	fscache_update_cookie(ctx->cache, NULL, &pos);
+#endif
+
+	gap = SECTOR_SIZE - (i_size & (SECTOR_SIZE - 1));
+	if (copied > gap) {
+		add = DIV_ROUND_UP(copied - gap, SECTOR_SIZE);
+
+		inode->i_blocks = min_t(blkcnt_t,
+					DIV_ROUND_UP(pos, SECTOR_SIZE),
+					inode->i_blocks + add);
+	}
+}
+
 /**
  * netfs_perform_write - Copy data into the pagecache.
  * @iocb: The operation parameters
@@ -160,11 +178,11 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 	};
 	struct netfs_io_request *wreq = NULL;
 	struct netfs_folio *finfo;
-	struct folio *folio;
+	struct folio *folio, *writethrough = NULL;
 	enum netfs_how_to_modify howto;
 	enum netfs_folio_trace trace;
 	unsigned int bdp_flags = (iocb->ki_flags & IOCB_SYNC) ? 0: BDP_ASYNC;
-	ssize_t written = 0, ret;
+	ssize_t written = 0, ret, ret2;
 	loff_t i_size, pos = iocb->ki_pos, from, to;
 	size_t max_chunk = PAGE_SIZE << MAX_PAGECACHE_ORDER;
 	bool maybe_trouble = false;
@@ -172,15 +190,14 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 	if (unlikely(test_bit(NETFS_ICTX_WRITETHROUGH, &ctx->flags) ||
 		     iocb->ki_flags & (IOCB_DSYNC | IOCB_SYNC))
 	    ) {
-		if (pos < i_size_read(inode)) {
-			ret = filemap_write_and_wait_range(mapping, pos, pos + iter->count);
-			if (ret < 0) {
-				goto out;
-			}
-		}
-
 		wbc_attach_fdatawrite_inode(&wbc, mapping->host);
 
+		ret = filemap_write_and_wait_range(mapping, pos, pos + iter->count);
+		if (ret < 0) {
+			wbc_detach_inode(&wbc);
+			goto out;
+		}
+
 		wreq = netfs_begin_writethrough(iocb, iter->count);
 		if (IS_ERR(wreq)) {
 			wbc_detach_inode(&wbc);
@@ -190,7 +207,9 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 		}
 		if (!is_sync_kiocb(iocb))
 			wreq->iocb = iocb;
-		wreq->cleanup = netfs_cleanup_buffered_write;
+		netfs_stat(&netfs_n_wh_writethrough);
+	} else {
+		netfs_stat(&netfs_n_wh_buffered_write);
 	}
 
 	do {
@@ -231,6 +250,16 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 		offset = pos & (flen - 1);
 		part = min_t(size_t, flen - offset, part);
 
+		/* Wait for writeback to complete.  The writeback engine owns
+		 * the info in folio->private and may change it until it
+		 * removes the WB mark.
+		 */
+		if (folio_get_private(folio) &&
+		    folio_wait_writeback_killable(folio)) {
+			ret = written ? -EINTR : -ERESTARTSYS;
+			goto error_folio_unlock;
+		}
+
 		if (signal_pending(current)) {
 			ret = written ? -EINTR : -ERESTARTSYS;
 			goto error_folio_unlock;
@@ -305,6 +334,7 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 				maybe_trouble = true;
 				iov_iter_revert(iter, copied);
 				copied = 0;
+				folio_unlock(folio);
 				goto retry;
 			}
 			netfs_set_group(folio, netfs_group);
@@ -352,41 +382,22 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 		trace_netfs_folio(folio, trace);
 
 		/* Update the inode size if we moved the EOF marker */
-		i_size = i_size_read(inode);
 		pos += copied;
-		if (pos > i_size) {
-			if (ctx->ops->update_i_size) {
-				ctx->ops->update_i_size(inode, pos);
-			} else {
-				i_size_write(inode, pos);
-#if IS_ENABLED(CONFIG_FSCACHE)
-				fscache_update_cookie(ctx->cache, NULL, &pos);
-#endif
-			}
-		}
+		i_size = i_size_read(inode);
+		if (pos > i_size)
+			netfs_update_i_size(ctx, inode, i_size, pos, copied);
 		written += copied;
 
 		if (likely(!wreq)) {
 			folio_mark_dirty(folio);
+			folio_unlock(folio);
 		} else {
-			if (folio_test_dirty(folio))
-				/* Sigh.  mmap. */
-				folio_clear_dirty_for_io(folio);
-			/* We make multiple writes to the folio... */
-			if (!folio_test_writeback(folio)) {
-				folio_wait_fscache(folio);
-				folio_start_writeback(folio);
-				folio_start_fscache(folio);
-				if (wreq->iter.count == 0)
-					trace_netfs_folio(folio, netfs_folio_trace_wthru);
-				else
-					trace_netfs_folio(folio, netfs_folio_trace_wthru_plus);
-			}
-			netfs_advance_writethrough(wreq, copied,
-						   offset + copied == flen);
+			netfs_advance_writethrough(wreq, &wbc, folio, copied,
+						   offset + copied == flen,
+						   &writethrough);
+			/* Folio unlocked */
 		}
 	retry:
-		folio_unlock(folio);
 		folio_put(folio);
 		folio = NULL;
 
@@ -394,11 +405,16 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
 	} while (iov_iter_count(iter));
 
 out:
+	if (likely(written) && ctx->ops->post_modify)
+		ctx->ops->post_modify(inode);
+
 	if (unlikely(wreq)) {
-		ret = netfs_end_writethrough(wreq, iocb);
+		ret2 = netfs_end_writethrough(wreq, &wbc, writethrough);
 		wbc_detach_inode(&wbc);
-		if (ret == -EIOCBQUEUED)
-			return ret;
+		if (ret2 == -EIOCBQUEUED)
+			return ret2;
+		if (ret == 0)
+			ret = ret2;
 	}
 
 	iocb->ki_pos += written;
@@ -504,9 +520,11 @@ EXPORT_SYMBOL(netfs_file_write_iter);
  */
 vm_fault_t netfs_page_mkwrite(struct vm_fault *vmf, struct netfs_group *netfs_group)
 {
+	struct netfs_group *group;
 	struct folio *folio = page_folio(vmf->page);
 	struct file *file = vmf->vma->vm_file;
 	struct inode *inode = file_inode(file);
+	struct netfs_inode *ictx = netfs_inode(inode);
 	vm_fault_t ret = VM_FAULT_RETRY;
 	int err;
 
@@ -514,11 +532,13 @@ vm_fault_t netfs_page_mkwrite(struct vm_fault *vmf, struct netfs_group *netfs_gr
 
 	sb_start_pagefault(inode->i_sb);
 
-	if (folio_wait_writeback_killable(folio))
+	if (folio_lock_killable(folio) < 0)
 		goto out;
 
-	if (folio_lock_killable(folio) < 0)
+	if (folio_wait_writeback_killable(folio)) {
+		ret = VM_FAULT_LOCKED;
 		goto out;
+	}
 
 	/* Can we see a streaming write here? */
 	if (WARN_ON(!folio_test_uptodate(folio))) {
@@ -526,7 +546,8 @@ vm_fault_t netfs_page_mkwrite(struct vm_fault *vmf, struct netfs_group *netfs_gr
 		goto out;
 	}
 
-	if (netfs_folio_group(folio) != netfs_group) {
+	group = netfs_folio_group(folio);
+	if (group != netfs_group && group != NETFS_FOLIO_COPY_TO_CACHE) {
 		folio_unlock(folio);
 		err = filemap_fdatawait_range(inode->i_mapping,
 					      folio_pos(folio),
@@ -550,708 +571,11 @@ vm_fault_t netfs_page_mkwrite(struct vm_fault *vmf, struct netfs_group *netfs_gr
 		trace_netfs_folio(folio, netfs_folio_trace_mkwrite);
 	netfs_set_group(folio, netfs_group);
 	file_update_time(file);
+	if (ictx->ops->post_modify)
+		ictx->ops->post_modify(inode);
 	ret = VM_FAULT_LOCKED;
 out:
 	sb_end_pagefault(inode->i_sb);
 	return ret;
 }
 EXPORT_SYMBOL(netfs_page_mkwrite);
-
-/*
- * Kill all the pages in the given range
- */
-static void netfs_kill_pages(struct address_space *mapping,
-			     loff_t start, loff_t len)
-{
-	struct folio *folio;
-	pgoff_t index = start / PAGE_SIZE;
-	pgoff_t last = (start + len - 1) / PAGE_SIZE, next;
-
-	_enter("%llx-%llx", start, start + len - 1);
-
-	do {
-		_debug("kill %lx (to %lx)", index, last);
-
-		folio = filemap_get_folio(mapping, index);
-		if (IS_ERR(folio)) {
-			next = index + 1;
-			continue;
-		}
-
-		next = folio_next_index(folio);
-
-		trace_netfs_folio(folio, netfs_folio_trace_kill);
-		folio_clear_uptodate(folio);
-		if (folio_test_fscache(folio))
-			folio_end_fscache(folio);
-		folio_end_writeback(folio);
-		folio_lock(folio);
-		generic_error_remove_folio(mapping, folio);
-		folio_unlock(folio);
-		folio_put(folio);
-
-	} while (index = next, index <= last);
-
-	_leave("");
-}
-
-/*
- * Redirty all the pages in a given range.
- */
-static void netfs_redirty_pages(struct address_space *mapping,
-				loff_t start, loff_t len)
-{
-	struct folio *folio;
-	pgoff_t index = start / PAGE_SIZE;
-	pgoff_t last = (start + len - 1) / PAGE_SIZE, next;
-
-	_enter("%llx-%llx", start, start + len - 1);
-
-	do {
-		_debug("redirty %llx @%llx", len, start);
-
-		folio = filemap_get_folio(mapping, index);
-		if (IS_ERR(folio)) {
-			next = index + 1;
-			continue;
-		}
-
-		next = folio_next_index(folio);
-		trace_netfs_folio(folio, netfs_folio_trace_redirty);
-		filemap_dirty_folio(mapping, folio);
-		if (folio_test_fscache(folio))
-			folio_end_fscache(folio);
-		folio_end_writeback(folio);
-		folio_put(folio);
-	} while (index = next, index <= last);
-
-	balance_dirty_pages_ratelimited(mapping);
-
-	_leave("");
-}
-
-/*
- * Completion of write to server
- */
-static void netfs_pages_written_back(struct netfs_io_request *wreq)
-{
-	struct address_space *mapping = wreq->mapping;
-	struct netfs_folio *finfo;
-	struct netfs_group *group = NULL;
-	struct folio *folio;
-	pgoff_t last;
-	int gcount = 0;
-
-	XA_STATE(xas, &mapping->i_pages, wreq->start / PAGE_SIZE);
-
-	_enter("%llx-%llx", wreq->start, wreq->start + wreq->len);
-
-	rcu_read_lock();
-
-	last = (wreq->start + wreq->len - 1) / PAGE_SIZE;
-	xas_for_each(&xas, folio, last) {
-		WARN(!folio_test_writeback(folio),
-		     "bad %zx @%llx page %lx %lx\n",
-		     wreq->len, wreq->start, folio->index, last);
-
-		if ((finfo = netfs_folio_info(folio))) {
-			/* Streaming writes cannot be redirtied whilst under
-			 * writeback, so discard the streaming record.
-			 */
-			folio_detach_private(folio);
-			group = finfo->netfs_group;
-			gcount++;
-			trace_netfs_folio(folio, netfs_folio_trace_clear_s);
-			kfree(finfo);
-		} else if ((group = netfs_folio_group(folio))) {
-			/* Need to detach the group pointer if the page didn't
-			 * get redirtied.  If it has been redirtied, then it
-			 * must be within the same group.
-			 */
-			if (folio_test_dirty(folio)) {
-				trace_netfs_folio(folio, netfs_folio_trace_redirtied);
-				goto end_wb;
-			}
-			if (folio_trylock(folio)) {
-				if (!folio_test_dirty(folio)) {
-					folio_detach_private(folio);
-					gcount++;
-					trace_netfs_folio(folio, netfs_folio_trace_clear_g);
-				} else {
-					trace_netfs_folio(folio, netfs_folio_trace_redirtied);
-				}
-				folio_unlock(folio);
-				goto end_wb;
-			}
-
-			xas_pause(&xas);
-			rcu_read_unlock();
-			folio_lock(folio);
-			if (!folio_test_dirty(folio)) {
-				folio_detach_private(folio);
-				gcount++;
-				trace_netfs_folio(folio, netfs_folio_trace_clear_g);
-			} else {
-				trace_netfs_folio(folio, netfs_folio_trace_redirtied);
-			}
-			folio_unlock(folio);
-			rcu_read_lock();
-		} else {
-			trace_netfs_folio(folio, netfs_folio_trace_clear);
-		}
-	end_wb:
-		if (folio_test_fscache(folio))
-			folio_end_fscache(folio);
-		xas_advance(&xas, folio_next_index(folio) - 1);
-		folio_end_writeback(folio);
-	}
-
-	rcu_read_unlock();
-	netfs_put_group_many(group, gcount);
-	_leave("");
-}
-
-/*
- * Deal with the disposition of the folios that are under writeback to close
- * out the operation.
- */
-static void netfs_cleanup_buffered_write(struct netfs_io_request *wreq)
-{
-	struct address_space *mapping = wreq->mapping;
-
-	_enter("");
-
-	switch (wreq->error) {
-	case 0:
-		netfs_pages_written_back(wreq);
-		break;
-
-	default:
-		pr_notice("R=%08x Unexpected error %d\n", wreq->debug_id, wreq->error);
-		fallthrough;
-	case -EACCES:
-	case -EPERM:
-	case -ENOKEY:
-	case -EKEYEXPIRED:
-	case -EKEYREJECTED:
-	case -EKEYREVOKED:
-	case -ENETRESET:
-	case -EDQUOT:
-	case -ENOSPC:
-		netfs_redirty_pages(mapping, wreq->start, wreq->len);
-		break;
-
-	case -EROFS:
-	case -EIO:
-	case -EREMOTEIO:
-	case -EFBIG:
-	case -ENOENT:
-	case -ENOMEDIUM:
-	case -ENXIO:
-		netfs_kill_pages(mapping, wreq->start, wreq->len);
-		break;
-	}
-
-	if (wreq->error)
-		mapping_set_error(mapping, wreq->error);
-	if (wreq->netfs_ops->done)
-		wreq->netfs_ops->done(wreq);
-}
-
-/*
- * Extend the region to be written back to include subsequent contiguously
- * dirty pages if possible, but don't sleep while doing so.
- *
- * If this page holds new content, then we can include filler zeros in the
- * writeback.
- */
-static void netfs_extend_writeback(struct address_space *mapping,
-				   struct netfs_group *group,
-				   struct xa_state *xas,
-				   long *_count,
-				   loff_t start,
-				   loff_t max_len,
-				   bool caching,
-				   size_t *_len,
-				   size_t *_top)
-{
-	struct netfs_folio *finfo;
-	struct folio_batch fbatch;
-	struct folio *folio;
-	unsigned int i;
-	pgoff_t index = (start + *_len) / PAGE_SIZE;
-	size_t len;
-	void *priv;
-	bool stop = true;
-
-	folio_batch_init(&fbatch);
-
-	do {
-		/* Firstly, we gather up a batch of contiguous dirty pages
-		 * under the RCU read lock - but we can't clear the dirty flags
-		 * there if any of those pages are mapped.
-		 */
-		rcu_read_lock();
-
-		xas_for_each(xas, folio, ULONG_MAX) {
-			stop = true;
-			if (xas_retry(xas, folio))
-				continue;
-			if (xa_is_value(folio))
-				break;
-			if (folio->index != index) {
-				xas_reset(xas);
-				break;
-			}
-
-			if (!folio_try_get_rcu(folio)) {
-				xas_reset(xas);
-				continue;
-			}
-
-			/* Has the folio moved or been split? */
-			if (unlikely(folio != xas_reload(xas))) {
-				folio_put(folio);
-				xas_reset(xas);
-				break;
-			}
-
-			if (!folio_trylock(folio)) {
-				folio_put(folio);
-				xas_reset(xas);
-				break;
-			}
-			if (!folio_test_dirty(folio) ||
-			    folio_test_writeback(folio) ||
-			    folio_test_fscache(folio)) {
-				folio_unlock(folio);
-				folio_put(folio);
-				xas_reset(xas);
-				break;
-			}
-
-			stop = false;
-			len = folio_size(folio);
-			priv = folio_get_private(folio);
-			if ((const struct netfs_group *)priv != group) {
-				stop = true;
-				finfo = netfs_folio_info(folio);
-				if (finfo->netfs_group != group ||
-				    finfo->dirty_offset > 0) {
-					folio_unlock(folio);
-					folio_put(folio);
-					xas_reset(xas);
-					break;
-				}
-				len = finfo->dirty_len;
-			}
-
-			*_top += folio_size(folio);
-			index += folio_nr_pages(folio);
-			*_count -= folio_nr_pages(folio);
-			*_len += len;
-			if (*_len >= max_len || *_count <= 0)
-				stop = true;
-
-			if (!folio_batch_add(&fbatch, folio))
-				break;
-			if (stop)
-				break;
-		}
-
-		xas_pause(xas);
-		rcu_read_unlock();
-
-		/* Now, if we obtained any folios, we can shift them to being
-		 * writable and mark them for caching.
-		 */
-		if (!folio_batch_count(&fbatch))
-			break;
-
-		for (i = 0; i < folio_batch_count(&fbatch); i++) {
-			folio = fbatch.folios[i];
-			trace_netfs_folio(folio, netfs_folio_trace_store_plus);
-
-			if (!folio_clear_dirty_for_io(folio))
-				BUG();
-			folio_start_writeback(folio);
-			netfs_folio_start_fscache(caching, folio);
-			folio_unlock(folio);
-		}
-
-		folio_batch_release(&fbatch);
-		cond_resched();
-	} while (!stop);
-}
-
-/*
- * Synchronously write back the locked page and any subsequent non-locked dirty
- * pages.
- */
-static ssize_t netfs_write_back_from_locked_folio(struct address_space *mapping,
-						  struct writeback_control *wbc,
-						  struct netfs_group *group,
-						  struct xa_state *xas,
-						  struct folio *folio,
-						  unsigned long long start,
-						  unsigned long long end)
-{
-	struct netfs_io_request *wreq;
-	struct netfs_folio *finfo;
-	struct netfs_inode *ctx = netfs_inode(mapping->host);
-	unsigned long long i_size = i_size_read(&ctx->inode);
-	size_t len, max_len;
-	bool caching = netfs_is_cache_enabled(ctx);
-	long count = wbc->nr_to_write;
-	int ret;
-
-	_enter(",%lx,%llx-%llx,%u", folio->index, start, end, caching);
-
-	wreq = netfs_alloc_request(mapping, NULL, start, folio_size(folio),
-				   NETFS_WRITEBACK);
-	if (IS_ERR(wreq)) {
-		folio_unlock(folio);
-		return PTR_ERR(wreq);
-	}
-
-	if (!folio_clear_dirty_for_io(folio))
-		BUG();
-	folio_start_writeback(folio);
-	netfs_folio_start_fscache(caching, folio);
-
-	count -= folio_nr_pages(folio);
-
-	/* Find all consecutive lockable dirty pages that have contiguous
-	 * written regions, stopping when we find a page that is not
-	 * immediately lockable, is not dirty or is missing, or we reach the
-	 * end of the range.
-	 */
-	trace_netfs_folio(folio, netfs_folio_trace_store);
-
-	len = wreq->len;
-	finfo = netfs_folio_info(folio);
-	if (finfo) {
-		start += finfo->dirty_offset;
-		if (finfo->dirty_offset + finfo->dirty_len != len) {
-			len = finfo->dirty_len;
-			goto cant_expand;
-		}
-		len = finfo->dirty_len;
-	}
-
-	if (start < i_size) {
-		/* Trim the write to the EOF; the extra data is ignored.  Also
-		 * put an upper limit on the size of a single storedata op.
-		 */
-		max_len = 65536 * 4096;
-		max_len = min_t(unsigned long long, max_len, end - start + 1);
-		max_len = min_t(unsigned long long, max_len, i_size - start);
-
-		if (len < max_len)
-			netfs_extend_writeback(mapping, group, xas, &count, start,
-					       max_len, caching, &len, &wreq->upper_len);
-	}
-
-cant_expand:
-	len = min_t(unsigned long long, len, i_size - start);
-
-	/* We now have a contiguous set of dirty pages, each with writeback
-	 * set; the first page is still locked at this point, but all the rest
-	 * have been unlocked.
-	 */
-	folio_unlock(folio);
-	wreq->start = start;
-	wreq->len = len;
-
-	if (start < i_size) {
-		_debug("write back %zx @%llx [%llx]", len, start, i_size);
-
-		/* Speculatively write to the cache.  We have to fix this up
-		 * later if the store fails.
-		 */
-		wreq->cleanup = netfs_cleanup_buffered_write;
-
-		iov_iter_xarray(&wreq->iter, ITER_SOURCE, &mapping->i_pages, start,
-				wreq->upper_len);
-		__set_bit(NETFS_RREQ_UPLOAD_TO_SERVER, &wreq->flags);
-		ret = netfs_begin_write(wreq, true, netfs_write_trace_writeback);
-		if (ret == 0 || ret == -EIOCBQUEUED)
-			wbc->nr_to_write -= len / PAGE_SIZE;
-	} else {
-		_debug("write discard %zx @%llx [%llx]", len, start, i_size);
-
-		/* The dirty region was entirely beyond the EOF. */
-		fscache_clear_page_bits(mapping, start, len, caching);
-		netfs_pages_written_back(wreq);
-		ret = 0;
-	}
-
-	netfs_put_request(wreq, false, netfs_rreq_trace_put_return);
-	_leave(" = 1");
-	return 1;
-}
-
-/*
- * Write a region of pages back to the server
- */
-static ssize_t netfs_writepages_begin(struct address_space *mapping,
-				      struct writeback_control *wbc,
-				      struct netfs_group *group,
-				      struct xa_state *xas,
-				      unsigned long long *_start,
-				      unsigned long long end)
-{
-	const struct netfs_folio *finfo;
-	struct folio *folio;
-	unsigned long long start = *_start;
-	ssize_t ret;
-	void *priv;
-	int skips = 0;
-
-	_enter("%llx,%llx,", start, end);
-
-search_again:
-	/* Find the first dirty page in the group. */
-	rcu_read_lock();
-
-	for (;;) {
-		folio = xas_find_marked(xas, end / PAGE_SIZE, PAGECACHE_TAG_DIRTY);
-		if (xas_retry(xas, folio) || xa_is_value(folio))
-			continue;
-		if (!folio)
-			break;
-
-		if (!folio_try_get_rcu(folio)) {
-			xas_reset(xas);
-			continue;
-		}
-
-		if (unlikely(folio != xas_reload(xas))) {
-			folio_put(folio);
-			xas_reset(xas);
-			continue;
-		}
-
-		/* Skip any dirty folio that's not in the group of interest. */
-		priv = folio_get_private(folio);
-		if ((const struct netfs_group *)priv != group) {
-			finfo = netfs_folio_info(folio);
-			if (finfo->netfs_group != group) {
-				folio_put(folio);
-				continue;
-			}
-		}
-
-		xas_pause(xas);
-		break;
-	}
-	rcu_read_unlock();
-	if (!folio)
-		return 0;
-
-	start = folio_pos(folio); /* May regress with THPs */
-
-	_debug("wback %lx", folio->index);
-
-	/* At this point we hold neither the i_pages lock nor the page lock:
-	 * the page may be truncated or invalidated (changing page->mapping to
-	 * NULL), or even swizzled back from swapper_space to tmpfs file
-	 * mapping
-	 */
-lock_again:
-	if (wbc->sync_mode != WB_SYNC_NONE) {
-		ret = folio_lock_killable(folio);
-		if (ret < 0)
-			return ret;
-	} else {
-		if (!folio_trylock(folio))
-			goto search_again;
-	}
-
-	if (folio->mapping != mapping ||
-	    !folio_test_dirty(folio)) {
-		start += folio_size(folio);
-		folio_unlock(folio);
-		goto search_again;
-	}
-
-	if (folio_test_writeback(folio) ||
-	    folio_test_fscache(folio)) {
-		folio_unlock(folio);
-		if (wbc->sync_mode != WB_SYNC_NONE) {
-			folio_wait_writeback(folio);
-#ifdef CONFIG_FSCACHE
-			folio_wait_fscache(folio);
-#endif
-			goto lock_again;
-		}
-
-		start += folio_size(folio);
-		if (wbc->sync_mode == WB_SYNC_NONE) {
-			if (skips >= 5 || need_resched()) {
-				ret = 0;
-				goto out;
-			}
-			skips++;
-		}
-		goto search_again;
-	}
-
-	ret = netfs_write_back_from_locked_folio(mapping, wbc, group, xas,
-						 folio, start, end);
-out:
-	if (ret > 0)
-		*_start = start + ret;
-	_leave(" = %zd [%llx]", ret, *_start);
-	return ret;
-}
-
-/*
- * Write a region of pages back to the server
- */
-static int netfs_writepages_region(struct address_space *mapping,
-				   struct writeback_control *wbc,
-				   struct netfs_group *group,
-				   unsigned long long *_start,
-				   unsigned long long end)
-{
-	ssize_t ret;
-
-	XA_STATE(xas, &mapping->i_pages, *_start / PAGE_SIZE);
-
-	do {
-		ret = netfs_writepages_begin(mapping, wbc, group, &xas,
-					     _start, end);
-		if (ret > 0 && wbc->nr_to_write > 0)
-			cond_resched();
-	} while (ret > 0 && wbc->nr_to_write > 0);
-
-	return ret > 0 ? 0 : ret;
-}
-
-/*
- * write some of the pending data back to the server
- */
-int netfs_writepages(struct address_space *mapping,
-		     struct writeback_control *wbc)
-{
-	struct netfs_group *group = NULL;
-	loff_t start, end;
-	int ret;
-
-	_enter("");
-
-	/* We have to be careful as we can end up racing with setattr()
-	 * truncating the pagecache since the caller doesn't take a lock here
-	 * to prevent it.
-	 */
-
-	if (wbc->range_cyclic && mapping->writeback_index) {
-		start = mapping->writeback_index * PAGE_SIZE;
-		ret = netfs_writepages_region(mapping, wbc, group,
-					      &start, LLONG_MAX);
-		if (ret < 0)
-			goto out;
-
-		if (wbc->nr_to_write <= 0) {
-			mapping->writeback_index = start / PAGE_SIZE;
-			goto out;
-		}
-
-		start = 0;
-		end = mapping->writeback_index * PAGE_SIZE;
-		mapping->writeback_index = 0;
-		ret = netfs_writepages_region(mapping, wbc, group, &start, end);
-		if (ret == 0)
-			mapping->writeback_index = start / PAGE_SIZE;
-	} else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
-		start = 0;
-		ret = netfs_writepages_region(mapping, wbc, group,
-					      &start, LLONG_MAX);
-		if (wbc->nr_to_write > 0 && ret == 0)
-			mapping->writeback_index = start / PAGE_SIZE;
-	} else {
-		start = wbc->range_start;
-		ret = netfs_writepages_region(mapping, wbc, group,
-					      &start, wbc->range_end);
-	}
-
-out:
-	_leave(" = %d", ret);
-	return ret;
-}
-EXPORT_SYMBOL(netfs_writepages);
-
-/*
- * Deal with the disposition of a laundered folio.
- */
-static void netfs_cleanup_launder_folio(struct netfs_io_request *wreq)
-{
-	if (wreq->error) {
-		pr_notice("R=%08x Laundering error %d\n", wreq->debug_id, wreq->error);
-		mapping_set_error(wreq->mapping, wreq->error);
-	}
-}
-
-/**
- * netfs_launder_folio - Clean up a dirty folio that's being invalidated
- * @folio: The folio to clean
- *
- * This is called to write back a folio that's being invalidated when an inode
- * is getting torn down.  Ideally, writepages would be used instead.
- */
-int netfs_launder_folio(struct folio *folio)
-{
-	struct netfs_io_request *wreq;
-	struct address_space *mapping = folio->mapping;
-	struct netfs_folio *finfo = netfs_folio_info(folio);
-	struct netfs_group *group = netfs_folio_group(folio);
-	struct bio_vec bvec;
-	unsigned long long i_size = i_size_read(mapping->host);
-	unsigned long long start = folio_pos(folio);
-	size_t offset = 0, len;
-	int ret = 0;
-
-	if (finfo) {
-		offset = finfo->dirty_offset;
-		start += offset;
-		len = finfo->dirty_len;
-	} else {
-		len = folio_size(folio);
-	}
-	len = min_t(unsigned long long, len, i_size - start);
-
-	wreq = netfs_alloc_request(mapping, NULL, start, len, NETFS_LAUNDER_WRITE);
-	if (IS_ERR(wreq)) {
-		ret = PTR_ERR(wreq);
-		goto out;
-	}
-
-	if (!folio_clear_dirty_for_io(folio))
-		goto out_put;
-
-	trace_netfs_folio(folio, netfs_folio_trace_launder);
-
-	_debug("launder %llx-%llx", start, start + len - 1);
-
-	/* Speculatively write to the cache.  We have to fix this up later if
-	 * the store fails.
-	 */
-	wreq->cleanup = netfs_cleanup_launder_folio;
-
-	bvec_set_folio(&bvec, folio, len, offset);
-	iov_iter_bvec(&wreq->iter, ITER_SOURCE, &bvec, 1, len);
-	__set_bit(NETFS_RREQ_UPLOAD_TO_SERVER, &wreq->flags);
-	ret = netfs_begin_write(wreq, true, netfs_write_trace_launder);
-
-out_put:
-	folio_detach_private(folio);
-	netfs_put_group(group);
-	kfree(finfo);
-	netfs_put_request(wreq, false, netfs_rreq_trace_put_return);
-out:
-	folio_wait_fscache(folio);
-	_leave(" = %d", ret);
-	return ret;
-}
-EXPORT_SYMBOL(netfs_launder_folio);