Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1054 insertions, 0 deletions

diff --git a/fs/afs/write.c b/fs/afs/write.c
new file mode 100644
index 000000000..e1c453417
--- /dev/null
+++ b/fs/afs/write.c
@@ -0,0 +1,1054 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* handling of writes to regular files and writing back to the server
+ *
+ * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/backing-dev.h>
+#include <linux/slab.h>
+#include <linux/fs.h>
+#include <linux/pagemap.h>
+#include <linux/writeback.h>
+#include <linux/pagevec.h>
+#include <linux/netfs.h>
+#include "internal.h"
+
+static int afs_writepages_region(struct address_space *mapping,
+				 struct writeback_control *wbc,
+				 loff_t start, loff_t end, loff_t *_next,
+				 bool max_one_loop);
+
+static void afs_write_to_cache(struct afs_vnode *vnode, loff_t start, size_t len,
+			       loff_t i_size, bool caching);
+
+#ifdef CONFIG_AFS_FSCACHE
+/*
+ * Mark a page as having been made dirty and thus needing writeback.  We also
+ * need to pin the cache object to write back to.
+ */
+bool afs_dirty_folio(struct address_space *mapping, struct folio *folio)
+{
+	return fscache_dirty_folio(mapping, folio,
+				afs_vnode_cache(AFS_FS_I(mapping->host)));
+}
+static void afs_folio_start_fscache(bool caching, struct folio *folio)
+{
+	if (caching)
+		folio_start_fscache(folio);
+}
+#else
+static void afs_folio_start_fscache(bool caching, struct folio *folio)
+{
+}
+#endif
+
+/*
+ * Flush out a conflicting write.  This may extend the write to the surrounding
+ * pages if also dirty and contiguous to the conflicting region..
+ */
+static int afs_flush_conflicting_write(struct address_space *mapping,
+				       struct folio *folio)
+{
+	struct writeback_control wbc = {
+		.sync_mode	= WB_SYNC_ALL,
+		.nr_to_write	= LONG_MAX,
+		.range_start	= folio_pos(folio),
+		.range_end	= LLONG_MAX,
+	};
+	loff_t next;
+
+	return afs_writepages_region(mapping, &wbc, folio_pos(folio), LLONG_MAX,
+				     &next, true);
+}
+
+/*
+ * prepare to perform part of a write to a page
+ */
+int afs_write_begin(struct file *file, struct address_space *mapping,
+		    loff_t pos, unsigned len,
+		    struct page **_page, void **fsdata)
+{
+	struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
+	struct folio *folio;
+	unsigned long priv;
+	unsigned f, from;
+	unsigned t, to;
+	pgoff_t index;
+	int ret;
+
+	_enter("{%llx:%llu},%llx,%x",
+	       vnode->fid.vid, vnode->fid.vnode, pos, len);
+
+	/* 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.
+	 */
+	ret = netfs_write_begin(&vnode->netfs, file, mapping, pos, len, &folio, fsdata);
+	if (ret < 0)
+		return ret;
+
+	index = folio_index(folio);
+	from = pos - index * PAGE_SIZE;
+	to = from + len;
+
+try_again:
+	/* See if this page is already partially written in a way that we can
+	 * merge the new write with.
+	 */
+	if (folio_test_private(folio)) {
+		priv = (unsigned long)folio_get_private(folio);
+		f = afs_folio_dirty_from(folio, priv);
+		t = afs_folio_dirty_to(folio, priv);
+		ASSERTCMP(f, <=, t);
+
+		if (folio_test_writeback(folio)) {
+			trace_afs_folio_dirty(vnode, tracepoint_string("alrdy"), folio);
+			folio_unlock(folio);
+			goto wait_for_writeback;
+		}
+		/* If the file is being filled locally, allow inter-write
+		 * spaces to be merged into writes.  If it's not, only write
+		 * back what the user gives us.
+		 */
+		if (!test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags) &&
+		    (to < f || from > t))
+			goto flush_conflicting_write;
+	}
+
+	*_page = folio_file_page(folio, pos / PAGE_SIZE);
+	_leave(" = 0");
+	return 0;
+
+	/* The previous write and this write aren't adjacent or overlapping, so
+	 * flush the page out.
+	 */
+flush_conflicting_write:
+	trace_afs_folio_dirty(vnode, tracepoint_string("confl"), folio);
+	folio_unlock(folio);
+
+	ret = afs_flush_conflicting_write(mapping, folio);
+	if (ret < 0)
+		goto error;
+
+wait_for_writeback:
+	ret = folio_wait_writeback_killable(folio);
+	if (ret < 0)
+		goto error;
+
+	ret = folio_lock_killable(folio);
+	if (ret < 0)
+		goto error;
+	goto try_again;
+
+error:
+	folio_put(folio);
+	_leave(" = %d", ret);
+	return ret;
+}
+
+/*
+ * finalise part of a write to a page
+ */
+int afs_write_end(struct file *file, struct address_space *mapping,
+		  loff_t pos, unsigned len, unsigned copied,
+		  struct page *subpage, void *fsdata)
+{
+	struct folio *folio = page_folio(subpage);
+	struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
+	unsigned long priv;
+	unsigned int f, from = offset_in_folio(folio, pos);
+	unsigned int t, to = from + copied;
+	loff_t i_size, write_end_pos;
+
+	_enter("{%llx:%llu},{%lx}",
+	       vnode->fid.vid, vnode->fid.vnode, folio_index(folio));
+
+	if (!folio_test_uptodate(folio)) {
+		if (copied < len) {
+			copied = 0;
+			goto out;
+		}
+
+		folio_mark_uptodate(folio);
+	}
+
+	if (copied == 0)
+		goto out;
+
+	write_end_pos = pos + copied;
+
+	i_size = i_size_read(&vnode->netfs.inode);
+	if (write_end_pos > i_size) {
+		write_seqlock(&vnode->cb_lock);
+		i_size = i_size_read(&vnode->netfs.inode);
+		if (write_end_pos > i_size)
+			afs_set_i_size(vnode, write_end_pos);
+		write_sequnlock(&vnode->cb_lock);
+		fscache_update_cookie(afs_vnode_cache(vnode), NULL, &write_end_pos);
+	}
+
+	if (folio_test_private(folio)) {
+		priv = (unsigned long)folio_get_private(folio);
+		f = afs_folio_dirty_from(folio, priv);
+		t = afs_folio_dirty_to(folio, priv);
+		if (from < f)
+			f = from;
+		if (to > t)
+			t = to;
+		priv = afs_folio_dirty(folio, f, t);
+		folio_change_private(folio, (void *)priv);
+		trace_afs_folio_dirty(vnode, tracepoint_string("dirty+"), folio);
+	} else {
+		priv = afs_folio_dirty(folio, from, to);
+		folio_attach_private(folio, (void *)priv);
+		trace_afs_folio_dirty(vnode, tracepoint_string("dirty"), folio);
+	}
+
+	if (folio_mark_dirty(folio))
+		_debug("dirtied %lx", folio_index(folio));
+
+out:
+	folio_unlock(folio);
+	folio_put(folio);
+	return copied;
+}
+
+/*
+ * kill all the pages in the given range
+ */
+static void afs_kill_pages(struct address_space *mapping,
+			   loff_t start, loff_t len)
+{
+	struct afs_vnode *vnode = AFS_FS_I(mapping->host);
+	struct folio *folio;
+	pgoff_t index = start / PAGE_SIZE;
+	pgoff_t last = (start + len - 1) / PAGE_SIZE, next;
+
+	_enter("{%llx:%llu},%llx @%llx",
+	       vnode->fid.vid, vnode->fid.vnode, len, start);
+
+	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);
+
+		folio_clear_uptodate(folio);
+		folio_end_writeback(folio);
+		folio_lock(folio);
+		generic_error_remove_page(mapping, &folio->page);
+		folio_unlock(folio);
+		folio_put(folio);
+
+	} while (index = next, index <= last);
+
+	_leave("");
+}
+
+/*
+ * Redirty all the pages in a given range.
+ */
+static void afs_redirty_pages(struct writeback_control *wbc,
+			      struct address_space *mapping,
+			      loff_t start, loff_t len)
+{
+	struct afs_vnode *vnode = AFS_FS_I(mapping->host);
+	struct folio *folio;
+	pgoff_t index = start / PAGE_SIZE;
+	pgoff_t last = (start + len - 1) / PAGE_SIZE, next;
+
+	_enter("{%llx:%llu},%llx @%llx",
+	       vnode->fid.vid, vnode->fid.vnode, len, start);
+
+	do {
+		_debug("redirty %llx @%llx", len, start);
+
+		folio = filemap_get_folio(mapping, index);
+		if (IS_ERR(folio)) {
+			next = index + 1;
+			continue;
+		}
+
+		next = index + folio_nr_pages(folio);
+		folio_redirty_for_writepage(wbc, folio);
+		folio_end_writeback(folio);
+		folio_put(folio);
+	} while (index = next, index <= last);
+
+	_leave("");
+}
+
+/*
+ * completion of write to server
+ */
+static void afs_pages_written_back(struct afs_vnode *vnode, loff_t start, unsigned int len)
+{
+	struct address_space *mapping = vnode->netfs.inode.i_mapping;
+	struct folio *folio;
+	pgoff_t end;
+
+	XA_STATE(xas, &mapping->i_pages, start / PAGE_SIZE);
+
+	_enter("{%llx:%llu},{%x @%llx}",
+	       vnode->fid.vid, vnode->fid.vnode, len, start);
+
+	rcu_read_lock();
+
+	end = (start + len - 1) / PAGE_SIZE;
+	xas_for_each(&xas, folio, end) {
+		if (!folio_test_writeback(folio)) {
+			kdebug("bad %x @%llx page %lx %lx",
+			       len, start, folio_index(folio), end);
+			ASSERT(folio_test_writeback(folio));
+		}
+
+		trace_afs_folio_dirty(vnode, tracepoint_string("clear"), folio);
+		folio_detach_private(folio);
+		folio_end_writeback(folio);
+	}
+
+	rcu_read_unlock();
+
+	afs_prune_wb_keys(vnode);
+	_leave("");
+}
+
+/*
+ * Find a key to use for the writeback.  We cached the keys used to author the
+ * writes on the vnode.  *_wbk will contain the last writeback key used or NULL
+ * and we need to start from there if it's set.
+ */
+static int afs_get_writeback_key(struct afs_vnode *vnode,
+				 struct afs_wb_key **_wbk)
+{
+	struct afs_wb_key *wbk = NULL;
+	struct list_head *p;
+	int ret = -ENOKEY, ret2;
+
+	spin_lock(&vnode->wb_lock);
+	if (*_wbk)
+		p = (*_wbk)->vnode_link.next;
+	else
+		p = vnode->wb_keys.next;
+
+	while (p != &vnode->wb_keys) {
+		wbk = list_entry(p, struct afs_wb_key, vnode_link);
+		_debug("wbk %u", key_serial(wbk->key));
+		ret2 = key_validate(wbk->key);
+		if (ret2 == 0) {
+			refcount_inc(&wbk->usage);
+			_debug("USE WB KEY %u", key_serial(wbk->key));
+			break;
+		}
+
+		wbk = NULL;
+		if (ret == -ENOKEY)
+			ret = ret2;
+		p = p->next;
+	}
+
+	spin_unlock(&vnode->wb_lock);
+	if (*_wbk)
+		afs_put_wb_key(*_wbk);
+	*_wbk = wbk;
+	return 0;
+}
+
+static void afs_store_data_success(struct afs_operation *op)
+{
+	struct afs_vnode *vnode = op->file[0].vnode;
+
+	op->ctime = op->file[0].scb.status.mtime_client;
+	afs_vnode_commit_status(op, &op->file[0]);
+	if (op->error == 0) {
+		if (!op->store.laundering)
+			afs_pages_written_back(vnode, op->store.pos, op->store.size);
+		afs_stat_v(vnode, n_stores);
+		atomic_long_add(op->store.size, &afs_v2net(vnode)->n_store_bytes);
+	}
+}
+
+static const struct afs_operation_ops afs_store_data_operation = {
+	.issue_afs_rpc	= afs_fs_store_data,
+	.issue_yfs_rpc	= yfs_fs_store_data,
+	.success	= afs_store_data_success,
+};
+
+/*
+ * write to a file
+ */
+static int afs_store_data(struct afs_vnode *vnode, struct iov_iter *iter, loff_t pos,
+			  bool laundering)
+{
+	struct afs_operation *op;
+	struct afs_wb_key *wbk = NULL;
+	loff_t size = iov_iter_count(iter);
+	int ret = -ENOKEY;
+
+	_enter("%s{%llx:%llu.%u},%llx,%llx",
+	       vnode->volume->name,
+	       vnode->fid.vid,
+	       vnode->fid.vnode,
+	       vnode->fid.unique,
+	       size, pos);
+
+	ret = afs_get_writeback_key(vnode, &wbk);
+	if (ret) {
+		_leave(" = %d [no keys]", ret);
+		return ret;
+	}
+
+	op = afs_alloc_operation(wbk->key, vnode->volume);
+	if (IS_ERR(op)) {
+		afs_put_wb_key(wbk);
+		return -ENOMEM;
+	}
+
+	afs_op_set_vnode(op, 0, vnode);
+	op->file[0].dv_delta = 1;
+	op->file[0].modification = true;
+	op->store.pos = pos;
+	op->store.size = size;
+	op->store.laundering = laundering;
+	op->flags |= AFS_OPERATION_UNINTR;
+	op->ops = &afs_store_data_operation;
+
+try_next_key:
+	afs_begin_vnode_operation(op);
+
+	op->store.write_iter = iter;
+	op->store.i_size = max(pos + size, vnode->netfs.remote_i_size);
+	op->mtime = vnode->netfs.inode.i_mtime;
+
+	afs_wait_for_operation(op);
+
+	switch (op->error) {
+	case -EACCES:
+	case -EPERM:
+	case -ENOKEY:
+	case -EKEYEXPIRED:
+	case -EKEYREJECTED:
+	case -EKEYREVOKED:
+		_debug("next");
+
+		ret = afs_get_writeback_key(vnode, &wbk);
+		if (ret == 0) {
+			key_put(op->key);
+			op->key = key_get(wbk->key);
+			goto try_next_key;
+		}
+		break;
+	}
+
+	afs_put_wb_key(wbk);
+	_leave(" = %d", op->error);
+	return afs_put_operation(op);
+}
+
+/*
+ * 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 afs_extend_writeback(struct address_space *mapping,
+				 struct afs_vnode *vnode,
+				 long *_count,
+				 loff_t start,
+				 loff_t max_len,
+				 bool new_content,
+				 bool caching,
+				 unsigned int *_len)
+{
+	struct folio_batch fbatch;
+	struct folio *folio;
+	unsigned long priv;
+	unsigned int psize, filler = 0;
+	unsigned int f, t;
+	loff_t len = *_len;
+	pgoff_t index = (start + len) / PAGE_SIZE;
+	bool stop = true;
+	unsigned int i;
+
+	XA_STATE(xas, &mapping->i_pages, index);
+	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(folio) != index)
+				break;
+
+			if (!folio_try_get_rcu(folio)) {
+				xas_reset(&xas);
+				continue;
+			}
+
+			/* Has the page moved or been split? */
+			if (unlikely(folio != xas_reload(&xas))) {
+				folio_put(folio);
+				break;
+			}
+
+			if (!folio_trylock(folio)) {
+				folio_put(folio);
+				break;
+			}
+			if (!folio_test_dirty(folio) ||
+			    folio_test_writeback(folio) ||
+			    folio_test_fscache(folio)) {
+				folio_unlock(folio);
+				folio_put(folio);
+				break;
+			}
+
+			psize = folio_size(folio);
+			priv = (unsigned long)folio_get_private(folio);
+			f = afs_folio_dirty_from(folio, priv);
+			t = afs_folio_dirty_to(folio, priv);
+			if (f != 0 && !new_content) {
+				folio_unlock(folio);
+				folio_put(folio);
+				break;
+			}
+
+			len += filler + t;
+			filler = psize - t;
+			if (len >= max_len || *_count <= 0)
+				stop = true;
+			else if (t == psize || new_content)
+				stop = false;
+
+			index += folio_nr_pages(folio);
+			if (!folio_batch_add(&fbatch, folio))
+				break;
+			if (stop)
+				break;
+		}
+
+		if (!stop)
+			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_afs_folio_dirty(vnode, tracepoint_string("store+"), folio);
+
+			if (!folio_clear_dirty_for_io(folio))
+				BUG();
+			if (folio_start_writeback(folio))
+				BUG();
+			afs_folio_start_fscache(caching, folio);
+
+			*_count -= folio_nr_pages(folio);
+			folio_unlock(folio);
+		}
+
+		folio_batch_release(&fbatch);
+		cond_resched();
+	} while (!stop);
+
+	*_len = len;
+}
+
+/*
+ * Synchronously write back the locked page and any subsequent non-locked dirty
+ * pages.
+ */
+static ssize_t afs_write_back_from_locked_folio(struct address_space *mapping,
+						struct writeback_control *wbc,
+						struct folio *folio,
+						loff_t start, loff_t end)
+{
+	struct afs_vnode *vnode = AFS_FS_I(mapping->host);
+	struct iov_iter iter;
+	unsigned long priv;
+	unsigned int offset, to, len, max_len;
+	loff_t i_size = i_size_read(&vnode->netfs.inode);
+	bool new_content = test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags);
+	bool caching = fscache_cookie_enabled(afs_vnode_cache(vnode));
+	long count = wbc->nr_to_write;
+	int ret;
+
+	_enter(",%lx,%llx-%llx", folio_index(folio), start, end);
+
+	if (folio_start_writeback(folio))
+		BUG();
+	afs_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.
+	 */
+	priv = (unsigned long)folio_get_private(folio);
+	offset = afs_folio_dirty_from(folio, priv);
+	to = afs_folio_dirty_to(folio, priv);
+	trace_afs_folio_dirty(vnode, tracepoint_string("store"), folio);
+
+	len = to - offset;
+	start += offset;
+	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 &&
+		    (to == folio_size(folio) || new_content))
+			afs_extend_writeback(mapping, vnode, &count,
+					     start, max_len, new_content,
+					     caching, &len);
+		len = min_t(loff_t, len, max_len);
+	}
+
+	/* 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);
+
+	if (start < i_size) {
+		_debug("write back %x @%llx [%llx]", len, start, i_size);
+
+		/* Speculatively write to the cache.  We have to fix this up
+		 * later if the store fails.
+		 */
+		afs_write_to_cache(vnode, start, len, i_size, caching);
+
+		iov_iter_xarray(&iter, ITER_SOURCE, &mapping->i_pages, start, len);
+		ret = afs_store_data(vnode, &iter, start, false);
+	} else {
+		_debug("write discard %x @%llx [%llx]", len, start, i_size);
+
+		/* The dirty region was entirely beyond the EOF. */
+		fscache_clear_page_bits(mapping, start, len, caching);
+		afs_pages_written_back(vnode, start, len);
+		ret = 0;
+	}
+
+	switch (ret) {
+	case 0:
+		wbc->nr_to_write = count;
+		ret = len;
+		break;
+
+	default:
+		pr_notice("kAFS: Unexpected error from FS.StoreData %d\n", ret);
+		fallthrough;
+	case -EACCES:
+	case -EPERM:
+	case -ENOKEY:
+	case -EKEYEXPIRED:
+	case -EKEYREJECTED:
+	case -EKEYREVOKED:
+	case -ENETRESET:
+		afs_redirty_pages(wbc, mapping, start, len);
+		mapping_set_error(mapping, ret);
+		break;
+
+	case -EDQUOT:
+	case -ENOSPC:
+		afs_redirty_pages(wbc, mapping, start, len);
+		mapping_set_error(mapping, -ENOSPC);
+		break;
+
+	case -EROFS:
+	case -EIO:
+	case -EREMOTEIO:
+	case -EFBIG:
+	case -ENOENT:
+	case -ENOMEDIUM:
+	case -ENXIO:
+		trace_afs_file_error(vnode, ret, afs_file_error_writeback_fail);
+		afs_kill_pages(mapping, start, len);
+		mapping_set_error(mapping, ret);
+		break;
+	}
+
+	_leave(" = %d", ret);
+	return ret;
+}
+
+/*
+ * write a region of pages back to the server
+ */
+static int afs_writepages_region(struct address_space *mapping,
+				 struct writeback_control *wbc,
+				 loff_t start, loff_t end, loff_t *_next,
+				 bool max_one_loop)
+{
+	struct folio *folio;
+	struct folio_batch fbatch;
+	ssize_t ret;
+	unsigned int i;
+	int n, skips = 0;
+
+	_enter("%llx,%llx,", start, end);
+	folio_batch_init(&fbatch);
+
+	do {
+		pgoff_t index = start / PAGE_SIZE;
+
+		n = filemap_get_folios_tag(mapping, &index, end / PAGE_SIZE,
+					PAGECACHE_TAG_DIRTY, &fbatch);
+
+		if (!n)
+			break;
+		for (i = 0; i < n; i++) {
+			folio = fbatch.folios[i];
+			start = folio_pos(folio); /* May regress with THPs */
+
+			_debug("wback %lx", folio_index(folio));
+
+			/* 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
+			 */
+try_again:
+			if (wbc->sync_mode != WB_SYNC_NONE) {
+				ret = folio_lock_killable(folio);
+				if (ret < 0) {
+					folio_batch_release(&fbatch);
+					return ret;
+				}
+			} else {
+				if (!folio_trylock(folio))
+					continue;
+			}
+
+			if (folio->mapping != mapping ||
+			    !folio_test_dirty(folio)) {
+				start += folio_size(folio);
+				folio_unlock(folio);
+				continue;
+			}
+
+			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_AFS_FSCACHE
+					folio_wait_fscache(folio);
+#endif
+					goto try_again;
+				}
+
+				start += folio_size(folio);
+				if (wbc->sync_mode == WB_SYNC_NONE) {
+					if (skips >= 5 || need_resched()) {
+						*_next = start;
+						folio_batch_release(&fbatch);
+						_leave(" = 0 [%llx]", *_next);
+						return 0;
+					}
+					skips++;
+				}
+				continue;
+			}
+
+			if (!folio_clear_dirty_for_io(folio))
+				BUG();
+			ret = afs_write_back_from_locked_folio(mapping, wbc,
+					folio, start, end);
+			if (ret < 0) {
+				_leave(" = %zd", ret);
+				folio_batch_release(&fbatch);
+				return ret;
+			}
+
+			start += ret;
+		}
+
+		folio_batch_release(&fbatch);
+		cond_resched();
+	} while (wbc->nr_to_write > 0);
+
+	*_next = start;
+	_leave(" = 0 [%llx]", *_next);
+	return 0;
+}
+
+/*
+ * write some of the pending data back to the server
+ */
+int afs_writepages(struct address_space *mapping,
+		   struct writeback_control *wbc)
+{
+	struct afs_vnode *vnode = AFS_FS_I(mapping->host);
+	loff_t start, next;
+	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->sync_mode == WB_SYNC_ALL)
+		down_read(&vnode->validate_lock);
+	else if (!down_read_trylock(&vnode->validate_lock))
+		return 0;
+
+	if (wbc->range_cyclic) {
+		start = mapping->writeback_index * PAGE_SIZE;
+		ret = afs_writepages_region(mapping, wbc, start, LLONG_MAX,
+					    &next, false);
+		if (ret == 0) {
+			mapping->writeback_index = next / PAGE_SIZE;
+			if (start > 0 && wbc->nr_to_write > 0) {
+				ret = afs_writepages_region(mapping, wbc, 0,
+							    start, &next, false);
+				if (ret == 0)
+					mapping->writeback_index =
+						next / PAGE_SIZE;
+			}
+		}
+	} else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
+		ret = afs_writepages_region(mapping, wbc, 0, LLONG_MAX,
+					    &next, false);
+		if (wbc->nr_to_write > 0 && ret == 0)
+			mapping->writeback_index = next / PAGE_SIZE;
+	} else {
+		ret = afs_writepages_region(mapping, wbc,
+					    wbc->range_start, wbc->range_end,
+					    &next, false);
+	}
+
+	up_read(&vnode->validate_lock);
+	_leave(" = %d", ret);
+	return ret;
+}
+
+/*
+ * write to an AFS file
+ */
+ssize_t afs_file_write(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct afs_vnode *vnode = AFS_FS_I(file_inode(iocb->ki_filp));
+	struct afs_file *af = iocb->ki_filp->private_data;
+	ssize_t result;
+	size_t count = iov_iter_count(from);
+
+	_enter("{%llx:%llu},{%zu},",
+	       vnode->fid.vid, vnode->fid.vnode, count);
+
+	if (IS_SWAPFILE(&vnode->netfs.inode)) {
+		printk(KERN_INFO
+		       "AFS: Attempt to write to active swap file!\n");
+		return -EBUSY;
+	}
+
+	if (!count)
+		return 0;
+
+	result = afs_validate(vnode, af->key);
+	if (result < 0)
+		return result;
+
+	result = generic_file_write_iter(iocb, from);
+
+	_leave(" = %zd", result);
+	return result;
+}
+
+/*
+ * flush any dirty pages for this process, and check for write errors.
+ * - the return status from this call provides a reliable indication of
+ *   whether any write errors occurred for this process.
+ */
+int afs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
+{
+	struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
+	struct afs_file *af = file->private_data;
+	int ret;
+
+	_enter("{%llx:%llu},{n=%pD},%d",
+	       vnode->fid.vid, vnode->fid.vnode, file,
+	       datasync);
+
+	ret = afs_validate(vnode, af->key);
+	if (ret < 0)
+		return ret;
+
+	return file_write_and_wait_range(file, start, end);
+}
+
+/*
+ * notification that a previously read-only page is about to become writable
+ * - if it returns an error, the caller will deliver a bus error signal
+ */
+vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
+{
+	struct folio *folio = page_folio(vmf->page);
+	struct file *file = vmf->vma->vm_file;
+	struct inode *inode = file_inode(file);
+	struct afs_vnode *vnode = AFS_FS_I(inode);
+	struct afs_file *af = file->private_data;
+	unsigned long priv;
+	vm_fault_t ret = VM_FAULT_RETRY;
+
+	_enter("{{%llx:%llu}},{%lx}", vnode->fid.vid, vnode->fid.vnode, folio_index(folio));
+
+	afs_validate(vnode, af->key);
+
+	sb_start_pagefault(inode->i_sb);
+
+	/* 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_AFS_FSCACHE
+	if (folio_test_fscache(folio) &&
+	    folio_wait_fscache_killable(folio) < 0)
+		goto out;
+#endif
+
+	if (folio_wait_writeback_killable(folio))
+		goto out;
+
+	if (folio_lock_killable(folio) < 0)
+		goto out;
+
+	/* We mustn't change folio->private until writeback is complete as that
+	 * details the portion of the page we need to write back and we might
+	 * need to redirty the page if there's a problem.
+	 */
+	if (folio_wait_writeback_killable(folio) < 0) {
+		folio_unlock(folio);
+		goto out;
+	}
+
+	priv = afs_folio_dirty(folio, 0, folio_size(folio));
+	priv = afs_folio_dirty_mmapped(priv);
+	if (folio_test_private(folio)) {
+		folio_change_private(folio, (void *)priv);
+		trace_afs_folio_dirty(vnode, tracepoint_string("mkwrite+"), folio);
+	} else {
+		folio_attach_private(folio, (void *)priv);
+		trace_afs_folio_dirty(vnode, tracepoint_string("mkwrite"), folio);
+	}
+	file_update_time(file);
+
+	ret = VM_FAULT_LOCKED;
+out:
+	sb_end_pagefault(inode->i_sb);
+	return ret;
+}
+
+/*
+ * Prune the keys cached for writeback.  The caller must hold vnode->wb_lock.
+ */
+void afs_prune_wb_keys(struct afs_vnode *vnode)
+{
+	LIST_HEAD(graveyard);
+	struct afs_wb_key *wbk, *tmp;
+
+	/* Discard unused keys */
+	spin_lock(&vnode->wb_lock);
+
+	if (!mapping_tagged(&vnode->netfs.inode.i_data, PAGECACHE_TAG_WRITEBACK) &&
+	    !mapping_tagged(&vnode->netfs.inode.i_data, PAGECACHE_TAG_DIRTY)) {
+		list_for_each_entry_safe(wbk, tmp, &vnode->wb_keys, vnode_link) {
+			if (refcount_read(&wbk->usage) == 1)
+				list_move(&wbk->vnode_link, &graveyard);
+		}
+	}
+
+	spin_unlock(&vnode->wb_lock);
+
+	while (!list_empty(&graveyard)) {
+		wbk = list_entry(graveyard.next, struct afs_wb_key, vnode_link);
+		list_del(&wbk->vnode_link);
+		afs_put_wb_key(wbk);
+	}
+}
+
+/*
+ * Clean up a page during invalidation.
+ */
+int afs_launder_folio(struct folio *folio)
+{
+	struct afs_vnode *vnode = AFS_FS_I(folio_inode(folio));
+	struct iov_iter iter;
+	struct bio_vec bv;
+	unsigned long priv;
+	unsigned int f, t;
+	int ret = 0;
+
+	_enter("{%lx}", folio->index);
+
+	priv = (unsigned long)folio_get_private(folio);
+	if (folio_clear_dirty_for_io(folio)) {
+		f = 0;
+		t = folio_size(folio);
+		if (folio_test_private(folio)) {
+			f = afs_folio_dirty_from(folio, priv);
+			t = afs_folio_dirty_to(folio, priv);
+		}
+
+		bvec_set_folio(&bv, folio, t - f, f);
+		iov_iter_bvec(&iter, ITER_SOURCE, &bv, 1, bv.bv_len);
+
+		trace_afs_folio_dirty(vnode, tracepoint_string("launder"), folio);
+		ret = afs_store_data(vnode, &iter, folio_pos(folio) + f, true);
+	}
+
+	trace_afs_folio_dirty(vnode, tracepoint_string("laundered"), folio);
+	folio_detach_private(folio);
+	folio_wait_fscache(folio);
+	return ret;
+}
+
+/*
+ * Deal with the completion of writing the data to the cache.
+ */
+static void afs_write_to_cache_done(void *priv, ssize_t transferred_or_error,
+				    bool was_async)
+{
+	struct afs_vnode *vnode = priv;
+
+	if (IS_ERR_VALUE(transferred_or_error) &&
+	    transferred_or_error != -ENOBUFS)
+		afs_invalidate_cache(vnode, 0);
+}
+
+/*
+ * Save the write to the cache also.
+ */
+static void afs_write_to_cache(struct afs_vnode *vnode,
+			       loff_t start, size_t len, loff_t i_size,
+			       bool caching)
+{
+	fscache_write_to_cache(afs_vnode_cache(vnode),
+			       vnode->netfs.inode.i_mapping, start, len, i_size,
+			       afs_write_to_cache_done, vnode, caching);
+}