1// SPDX-License-Identifier: GPL-2.0-or-later
  2/* Cache data I/O routines
  3 *
  4 * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
  5 * Written by David Howells (dhowells@redhat.com)
  6 */
  7#define FSCACHE_DEBUG_LEVEL OPERATION
  8#include <linux/fscache-cache.h>
  9#include <linux/uio.h>
 10#include <linux/bvec.h>
 11#include <linux/slab.h>
 12#include <linux/uio.h>
 13#include "internal.h"
 14
 15/**
 16 * fscache_wait_for_operation - Wait for an object become accessible
 17 * @cres: The cache resources for the operation being performed
 18 * @want_state: The minimum state the object must be at
 19 *
 20 * See if the target cache object is at the specified minimum state of
 21 * accessibility yet, and if not, wait for it.
 22 */
 23bool fscache_wait_for_operation(struct netfs_cache_resources *cres,
 24				enum fscache_want_state want_state)
 25{
 26	struct fscache_cookie *cookie = fscache_cres_cookie(cres);
 27	enum fscache_cookie_state state;
 28
 29again:
 30	if (!fscache_cache_is_live(cookie->volume->cache)) {
 31		_leave(" [broken]");
 32		return false;
 33	}
 34
 35	state = fscache_cookie_state(cookie);
 36	_enter("c=%08x{%u},%x", cookie->debug_id, state, want_state);
 37
 38	switch (state) {
 39	case FSCACHE_COOKIE_STATE_CREATING:
 40	case FSCACHE_COOKIE_STATE_INVALIDATING:
 41		if (want_state == FSCACHE_WANT_PARAMS)
 42			goto ready; /* There can be no content */
 43		fallthrough;
 44	case FSCACHE_COOKIE_STATE_LOOKING_UP:
 45	case FSCACHE_COOKIE_STATE_LRU_DISCARDING:
 46		wait_var_event(&cookie->state,
 47			       fscache_cookie_state(cookie) != state);
 48		goto again;
 49
 50	case FSCACHE_COOKIE_STATE_ACTIVE:
 51		goto ready;
 52	case FSCACHE_COOKIE_STATE_DROPPED:
 53	case FSCACHE_COOKIE_STATE_RELINQUISHING:
 54	default:
 55		_leave(" [not live]");
 56		return false;
 57	}
 58
 59ready:
 60	if (!cres->cache_priv2)
 61		return cookie->volume->cache->ops->begin_operation(cres, want_state);
 62	return true;
 63}
 64EXPORT_SYMBOL(fscache_wait_for_operation);
 65
 66/*
 67 * Begin an I/O operation on the cache, waiting till we reach the right state.
 68 *
 69 * Attaches the resources required to the operation resources record.
 70 */
 71static int fscache_begin_operation(struct netfs_cache_resources *cres,
 72				   struct fscache_cookie *cookie,
 73				   enum fscache_want_state want_state,
 74				   enum fscache_access_trace why)
 75{
 76	enum fscache_cookie_state state;
 77	long timeo;
 78	bool once_only = false;
 79
 80	cres->ops		= NULL;
 81	cres->cache_priv	= cookie;
 82	cres->cache_priv2	= NULL;
 83	cres->debug_id		= cookie->debug_id;
 84	cres->inval_counter	= cookie->inval_counter;
 85
 86	if (!fscache_begin_cookie_access(cookie, why))
 87		return -ENOBUFS;
 88
 89again:
 90	spin_lock(&cookie->lock);
 91
 92	state = fscache_cookie_state(cookie);
 93	_enter("c=%08x{%u},%x", cookie->debug_id, state, want_state);
 94
 95	switch (state) {
 96	case FSCACHE_COOKIE_STATE_LOOKING_UP:
 97	case FSCACHE_COOKIE_STATE_LRU_DISCARDING:
 98	case FSCACHE_COOKIE_STATE_INVALIDATING:
 99		goto wait_for_file_wrangling;
100	case FSCACHE_COOKIE_STATE_CREATING:
101		if (want_state == FSCACHE_WANT_PARAMS)
102			goto ready; /* There can be no content */
103		goto wait_for_file_wrangling;
104	case FSCACHE_COOKIE_STATE_ACTIVE:
105		goto ready;
106	case FSCACHE_COOKIE_STATE_DROPPED:
107	case FSCACHE_COOKIE_STATE_RELINQUISHING:
108		WARN(1, "Can't use cookie in state %u\n", cookie->state);
109		goto not_live;
110	default:
111		goto not_live;
112	}
113
114ready:
115	spin_unlock(&cookie->lock);
116	if (!cookie->volume->cache->ops->begin_operation(cres, want_state))
117		goto failed;
118	return 0;
119
120wait_for_file_wrangling:
121	spin_unlock(&cookie->lock);
122	trace_fscache_access(cookie->debug_id, refcount_read(&cookie->ref),
123			     atomic_read(&cookie->n_accesses),
124			     fscache_access_io_wait);
125	timeo = wait_var_event_timeout(&cookie->state,
126				       fscache_cookie_state(cookie) != state, 20 * HZ);
127	if (timeo <= 1 && !once_only) {
128		pr_warn("%s: cookie state change wait timed out: cookie->state=%u state=%u",
129			__func__, fscache_cookie_state(cookie), state);
130		fscache_print_cookie(cookie, 'O');
131		once_only = true;
132	}
133	goto again;
134
135not_live:
136	spin_unlock(&cookie->lock);
137failed:
138	cres->cache_priv = NULL;
139	cres->ops = NULL;
140	fscache_end_cookie_access(cookie, fscache_access_io_not_live);
141	_leave(" = -ENOBUFS");
142	return -ENOBUFS;
143}
144
145int __fscache_begin_read_operation(struct netfs_cache_resources *cres,
146				   struct fscache_cookie *cookie)
147{
148	return fscache_begin_operation(cres, cookie, FSCACHE_WANT_PARAMS,
149				       fscache_access_io_read);
150}
151EXPORT_SYMBOL(__fscache_begin_read_operation);
152
153int __fscache_begin_write_operation(struct netfs_cache_resources *cres,
154				    struct fscache_cookie *cookie)
155{
156	return fscache_begin_operation(cres, cookie, FSCACHE_WANT_PARAMS,
157				       fscache_access_io_write);
158}
159EXPORT_SYMBOL(__fscache_begin_write_operation);
160
161struct fscache_write_request {
162	struct netfs_cache_resources cache_resources;
163	struct address_space	*mapping;
164	loff_t			start;
165	size_t			len;
166	bool			set_bits;
167	netfs_io_terminated_t	term_func;
168	void			*term_func_priv;
169};
170
171void __fscache_clear_page_bits(struct address_space *mapping,
172			       loff_t start, size_t len)
173{
174	pgoff_t first = start / PAGE_SIZE;
175	pgoff_t last = (start + len - 1) / PAGE_SIZE;
176	struct page *page;
177
178	if (len) {
179		XA_STATE(xas, &mapping->i_pages, first);
180
181		rcu_read_lock();
182		xas_for_each(&xas, page, last) {
183			end_page_fscache(page);
184		}
185		rcu_read_unlock();
186	}
187}
188EXPORT_SYMBOL(__fscache_clear_page_bits);
189
190/*
191 * Deal with the completion of writing the data to the cache.
192 */
193static void fscache_wreq_done(void *priv, ssize_t transferred_or_error,
194			      bool was_async)
195{
196	struct fscache_write_request *wreq = priv;
197
198	fscache_clear_page_bits(wreq->mapping, wreq->start, wreq->len,
199				wreq->set_bits);
200
201	if (wreq->term_func)
202		wreq->term_func(wreq->term_func_priv, transferred_or_error,
203				was_async);
204	fscache_end_operation(&wreq->cache_resources);
205	kfree(wreq);
206}
207
208void __fscache_write_to_cache(struct fscache_cookie *cookie,
209			      struct address_space *mapping,
210			      loff_t start, size_t len, loff_t i_size,
211			      netfs_io_terminated_t term_func,
212			      void *term_func_priv,
213			      bool cond)
214{
215	struct fscache_write_request *wreq;
216	struct netfs_cache_resources *cres;
217	struct iov_iter iter;
218	int ret = -ENOBUFS;
219
220	if (len == 0)
221		goto abandon;
222
223	_enter("%llx,%zx", start, len);
224
225	wreq = kzalloc(sizeof(struct fscache_write_request), GFP_NOFS);
226	if (!wreq)
227		goto abandon;
228	wreq->mapping		= mapping;
229	wreq->start		= start;
230	wreq->len		= len;
231	wreq->set_bits		= cond;
232	wreq->term_func		= term_func;
233	wreq->term_func_priv	= term_func_priv;
234
235	cres = &wreq->cache_resources;
236	if (fscache_begin_operation(cres, cookie, FSCACHE_WANT_WRITE,
237				    fscache_access_io_write) < 0)
238		goto abandon_free;
239
240	ret = cres->ops->prepare_write(cres, &start, &len, len, i_size, false);
241	if (ret < 0)
242		goto abandon_end;
243
244	/* TODO: Consider clearing page bits now for space the write isn't
245	 * covering.  This is more complicated than it appears when THPs are
246	 * taken into account.
247	 */
248
249	iov_iter_xarray(&iter, ITER_SOURCE, &mapping->i_pages, start, len);
250	fscache_write(cres, start, &iter, fscache_wreq_done, wreq);
251	return;
252
253abandon_end:
254	return fscache_wreq_done(wreq, ret, false);
255abandon_free:
256	kfree(wreq);
257abandon:
258	fscache_clear_page_bits(mapping, start, len, cond);
259	if (term_func)
260		term_func(term_func_priv, ret, false);
261}
262EXPORT_SYMBOL(__fscache_write_to_cache);
263
264/*
265 * Change the size of a backing object.
266 */
267void __fscache_resize_cookie(struct fscache_cookie *cookie, loff_t new_size)
268{
269	struct netfs_cache_resources cres;
270
271	trace_fscache_resize(cookie, new_size);
272	if (fscache_begin_operation(&cres, cookie, FSCACHE_WANT_WRITE,
273				    fscache_access_io_resize) == 0) {
274		fscache_stat(&fscache_n_resizes);
275		set_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &cookie->flags);
276
277		/* We cannot defer a resize as we need to do it inside the
278		 * netfs's inode lock so that we're serialised with respect to
279		 * writes.
280		 */
281		cookie->volume->cache->ops->resize_cookie(&cres, new_size);
282		fscache_end_operation(&cres);
283	} else {
284		fscache_stat(&fscache_n_resizes_null);
285	}
286}
287EXPORT_SYMBOL(__fscache_resize_cookie);