1 files changed, 287 insertions, 0 deletions
diff --git a/fs/netfs/fscache_io.c b/fs/netfs/fscache_io.c
new file mode 100644
index 000000000000..ad572f7ee897
--- /dev/null
+++ b/fs/netfs/fscache_io.c
@@ -0,0 +1,287 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Cache data I/O routines
+ *
+ * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+#define FSCACHE_DEBUG_LEVEL OPERATION
+#include <linux/fscache-cache.h>
+#include <linux/uio.h>
+#include <linux/bvec.h>
+#include <linux/slab.h>
+#include <linux/uio.h>
+#include "internal.h"
+
+/**
+ * fscache_wait_for_operation - Wait for an object become accessible
+ * @cres: The cache resources for the operation being performed
+ * @want_state: The minimum state the object must be at
+ *
+ * See if the target cache object is at the specified minimum state of
+ * accessibility yet, and if not, wait for it.
+ */
+bool fscache_wait_for_operation(struct netfs_cache_resources *cres,
+				enum fscache_want_state want_state)
+{
+	struct fscache_cookie *cookie = fscache_cres_cookie(cres);
+	enum fscache_cookie_state state;
+
+again:
+	if (!fscache_cache_is_live(cookie->volume->cache)) {
+		_leave(" [broken]");
+		return false;
+	}
+
+	state = fscache_cookie_state(cookie);
+	_enter("c=%08x{%u},%x", cookie->debug_id, state, want_state);
+
+	switch (state) {
+	case FSCACHE_COOKIE_STATE_CREATING:
+	case FSCACHE_COOKIE_STATE_INVALIDATING:
+		if (want_state == FSCACHE_WANT_PARAMS)
+			goto ready; /* There can be no content */
+		fallthrough;
+	case FSCACHE_COOKIE_STATE_LOOKING_UP:
+	case FSCACHE_COOKIE_STATE_LRU_DISCARDING:
+		wait_var_event(&cookie->state,
+			       fscache_cookie_state(cookie) != state);
+		goto again;
+
+	case FSCACHE_COOKIE_STATE_ACTIVE:
+		goto ready;
+	case FSCACHE_COOKIE_STATE_DROPPED:
+	case FSCACHE_COOKIE_STATE_RELINQUISHING:
+	default:
+		_leave(" [not live]");
+		return false;
+	}
+
+ready:
+	if (!cres->cache_priv2)
+		return cookie->volume->cache->ops->begin_operation(cres, want_state);
+	return true;
+}
+EXPORT_SYMBOL(fscache_wait_for_operation);
+
+/*
+ * Begin an I/O operation on the cache, waiting till we reach the right state.
+ *
+ * Attaches the resources required to the operation resources record.
+ */
+static int fscache_begin_operation(struct netfs_cache_resources *cres,
+				   struct fscache_cookie *cookie,
+				   enum fscache_want_state want_state,
+				   enum fscache_access_trace why)
+{
+	enum fscache_cookie_state state;
+	long timeo;
+	bool once_only = false;
+
+	cres->ops		= NULL;
+	cres->cache_priv	= cookie;
+	cres->cache_priv2	= NULL;
+	cres->debug_id		= cookie->debug_id;
+	cres->inval_counter	= cookie->inval_counter;
+
+	if (!fscache_begin_cookie_access(cookie, why))
+		return -ENOBUFS;
+
+again:
+	spin_lock(&cookie->lock);
+
+	state = fscache_cookie_state(cookie);
+	_enter("c=%08x{%u},%x", cookie->debug_id, state, want_state);
+
+	switch (state) {
+	case FSCACHE_COOKIE_STATE_LOOKING_UP:
+	case FSCACHE_COOKIE_STATE_LRU_DISCARDING:
+	case FSCACHE_COOKIE_STATE_INVALIDATING:
+		goto wait_for_file_wrangling;
+	case FSCACHE_COOKIE_STATE_CREATING:
+		if (want_state == FSCACHE_WANT_PARAMS)
+			goto ready; /* There can be no content */
+		goto wait_for_file_wrangling;
+	case FSCACHE_COOKIE_STATE_ACTIVE:
+		goto ready;
+	case FSCACHE_COOKIE_STATE_DROPPED:
+	case FSCACHE_COOKIE_STATE_RELINQUISHING:
+		WARN(1, "Can't use cookie in state %u\n", cookie->state);
+		goto not_live;
+	default:
+		goto not_live;
+	}
+
+ready:
+	spin_unlock(&cookie->lock);
+	if (!cookie->volume->cache->ops->begin_operation(cres, want_state))
+		goto failed;
+	return 0;
+
+wait_for_file_wrangling:
+	spin_unlock(&cookie->lock);
+	trace_fscache_access(cookie->debug_id, refcount_read(&cookie->ref),
+			     atomic_read(&cookie->n_accesses),
+			     fscache_access_io_wait);
+	timeo = wait_var_event_timeout(&cookie->state,
+				       fscache_cookie_state(cookie) != state, 20 * HZ);
+	if (timeo <= 1 && !once_only) {
+		pr_warn("%s: cookie state change wait timed out: cookie->state=%u state=%u",
+			__func__, fscache_cookie_state(cookie), state);
+		fscache_print_cookie(cookie, 'O');
+		once_only = true;
+	}
+	goto again;
+
+not_live:
+	spin_unlock(&cookie->lock);
+failed:
+	cres->cache_priv = NULL;
+	cres->ops = NULL;
+	fscache_end_cookie_access(cookie, fscache_access_io_not_live);
+	_leave(" = -ENOBUFS");
+	return -ENOBUFS;
+}
+
+int __fscache_begin_read_operation(struct netfs_cache_resources *cres,
+				   struct fscache_cookie *cookie)
+{
+	return fscache_begin_operation(cres, cookie, FSCACHE_WANT_PARAMS,
+				       fscache_access_io_read);
+}
+EXPORT_SYMBOL(__fscache_begin_read_operation);
+
+int __fscache_begin_write_operation(struct netfs_cache_resources *cres,
+				    struct fscache_cookie *cookie)
+{
+	return fscache_begin_operation(cres, cookie, FSCACHE_WANT_PARAMS,
+				       fscache_access_io_write);
+}
+EXPORT_SYMBOL(__fscache_begin_write_operation);
+
+struct fscache_write_request {
+	struct netfs_cache_resources cache_resources;
+	struct address_space	*mapping;
+	loff_t			start;
+	size_t			len;
+	bool			set_bits;
+	netfs_io_terminated_t	term_func;
+	void			*term_func_priv;
+};
+
+void __fscache_clear_page_bits(struct address_space *mapping,
+			       loff_t start, size_t len)
+{
+	pgoff_t first = start / PAGE_SIZE;
+	pgoff_t last = (start + len - 1) / PAGE_SIZE;
+	struct page *page;
+
+	if (len) {
+		XA_STATE(xas, &mapping->i_pages, first);
+
+		rcu_read_lock();
+		xas_for_each(&xas, page, last) {
+			end_page_fscache(page);
+		}
+		rcu_read_unlock();
+	}
+}
+EXPORT_SYMBOL(__fscache_clear_page_bits);
+
+/*
+ * Deal with the completion of writing the data to the cache.
+ */
+static void fscache_wreq_done(void *priv, ssize_t transferred_or_error,
+			      bool was_async)
+{
+	struct fscache_write_request *wreq = priv;
+
+	fscache_clear_page_bits(wreq->mapping, wreq->start, wreq->len,
+				wreq->set_bits);
+
+	if (wreq->term_func)
+		wreq->term_func(wreq->term_func_priv, transferred_or_error,
+				was_async);
+	fscache_end_operation(&wreq->cache_resources);
+	kfree(wreq);
+}
+
+void __fscache_write_to_cache(struct fscache_cookie *cookie,
+			      struct address_space *mapping,
+			      loff_t start, size_t len, loff_t i_size,
+			      netfs_io_terminated_t term_func,
+			      void *term_func_priv,
+			      bool cond)
+{
+	struct fscache_write_request *wreq;
+	struct netfs_cache_resources *cres;
+	struct iov_iter iter;
+	int ret = -ENOBUFS;
+
+	if (len == 0)
+		goto abandon;
+
+	_enter("%llx,%zx", start, len);
+
+	wreq = kzalloc(sizeof(struct fscache_write_request), GFP_NOFS);
+	if (!wreq)
+		goto abandon;
+	wreq->mapping		= mapping;
+	wreq->start		= start;
+	wreq->len		= len;
+	wreq->set_bits		= cond;
+	wreq->term_func		= term_func;
+	wreq->term_func_priv	= term_func_priv;
+
+	cres = &wreq->cache_resources;
+	if (fscache_begin_operation(cres, cookie, FSCACHE_WANT_WRITE,
+				    fscache_access_io_write) < 0)
+		goto abandon_free;
+
+	ret = cres->ops->prepare_write(cres, &start, &len, len, i_size, false);
+	if (ret < 0)
+		goto abandon_end;
+
+	/* TODO: Consider clearing page bits now for space the write isn't
+	 * covering.  This is more complicated than it appears when THPs are
+	 * taken into account.
+	 */
+
+	iov_iter_xarray(&iter, ITER_SOURCE, &mapping->i_pages, start, len);
+	fscache_write(cres, start, &iter, fscache_wreq_done, wreq);
+	return;
+
+abandon_end:
+	return fscache_wreq_done(wreq, ret, false);
+abandon_free:
+	kfree(wreq);
+abandon:
+	fscache_clear_page_bits(mapping, start, len, cond);
+	if (term_func)
+		term_func(term_func_priv, ret, false);
+}
+EXPORT_SYMBOL(__fscache_write_to_cache);
+
+/*
+ * Change the size of a backing object.
+ */
+void __fscache_resize_cookie(struct fscache_cookie *cookie, loff_t new_size)
+{
+	struct netfs_cache_resources cres;
+
+	trace_fscache_resize(cookie, new_size);
+	if (fscache_begin_operation(&cres, cookie, FSCACHE_WANT_WRITE,
+				    fscache_access_io_resize) == 0) {
+		fscache_stat(&fscache_n_resizes);
+		set_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &cookie->flags);
+
+		/* We cannot defer a resize as we need to do it inside the
+		 * netfs's inode lock so that we're serialised with respect to
+		 * writes.
+		 */
+		cookie->volume->cache->ops->resize_cookie(&cres, new_size);
+		fscache_end_operation(&cres);
+	} else {
+		fscache_stat(&fscache_n_resizes_null);
+	}
+}
+EXPORT_SYMBOL(__fscache_resize_cookie);