Release 4.10 fs/fscache/page.c

/* Cache page management and data I/O routines
 *
 * Copyright (C) 2004-2008 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */


#define FSCACHE_DEBUG_LEVEL PAGE
#include <linux/module.h>
#include <linux/fscache-cache.h>
#include <linux/buffer_head.h>
#include <linux/pagevec.h>
#include <linux/slab.h>
#include "internal.h"

/*
 * check to see if a page is being written to the cache
 */


bool __fscache_check_page_write(struct fscache_cookie *cookie, struct page *page)
{
	void *val;

	rcu_read_lock();
	val = radix_tree_lookup(&cookie->stores, page->index);
	rcu_read_unlock();

	return val != NULL;
}
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EXPORT_SYMBOL(__fscache_check_page_write);

/*
 * wait for a page to finish being written to the cache
 */


void __fscache_wait_on_page_write(struct fscache_cookie *cookie, struct page *page)
{
	wait_queue_head_t *wq = bit_waitqueue(&cookie->flags, 0);

	wait_event(*wq, !__fscache_check_page_write(cookie, page));
}
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EXPORT_SYMBOL(__fscache_wait_on_page_write);

/*
 * wait for a page to finish being written to the cache. Put a timeout here
 * since we might be called recursively via parent fs.
 */

static

bool release_page_wait_timeout(struct fscache_cookie *cookie, struct page *page)
{
	wait_queue_head_t *wq = bit_waitqueue(&cookie->flags, 0);

	return wait_event_timeout(*wq, !__fscache_check_page_write(cookie, page),
				  HZ);
}

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/*
 * decide whether a page can be released, possibly by cancelling a store to it
 * - we're allowed to sleep if __GFP_DIRECT_RECLAIM is flagged
 */


bool __fscache_maybe_release_page(struct fscache_cookie *cookie,
				  struct page *page,
				  gfp_t gfp)
{
	struct page *xpage;
	void *val;

	_enter("%p,%p,%x", cookie, page, gfp);

try_again:
	rcu_read_lock();
	val = radix_tree_lookup(&cookie->stores, page->index);
	if (!val) {
		rcu_read_unlock();
		fscache_stat(&fscache_n_store_vmscan_not_storing);
		__fscache_uncache_page(cookie, page);
		return true;
	}

	/* see if the page is actually undergoing storage - if so we can't get
         * rid of it till the cache has finished with it */
	if (radix_tree_tag_get(&cookie->stores, page->index,
			       FSCACHE_COOKIE_STORING_TAG)) {
		rcu_read_unlock();
		goto page_busy;
	}

	/* the page is pending storage, so we attempt to cancel the store and
         * discard the store request so that the page can be reclaimed */
	spin_lock(&cookie->stores_lock);
	rcu_read_unlock();

	if (radix_tree_tag_get(&cookie->stores, page->index,
			       FSCACHE_COOKIE_STORING_TAG)) {
		/* the page started to undergo storage whilst we were looking,
                 * so now we can only wait or return */
		spin_unlock(&cookie->stores_lock);
		goto page_busy;
	}

	xpage = radix_tree_delete(&cookie->stores, page->index);
	spin_unlock(&cookie->stores_lock);

	if (xpage) {
		fscache_stat(&fscache_n_store_vmscan_cancelled);
		fscache_stat(&fscache_n_store_radix_deletes);
		ASSERTCMP(xpage, ==, page);
	} else {
		fscache_stat(&fscache_n_store_vmscan_gone);
	}

	wake_up_bit(&cookie->flags, 0);
	if (xpage)
		put_page(xpage);
	__fscache_uncache_page(cookie, page);
	return true;

page_busy:
	/* We will wait here if we're allowed to, but that could deadlock the
         * allocator as the work threads writing to the cache may all end up
         * sleeping on memory allocation, so we may need to impose a timeout
         * too. */
	if (!(gfp & __GFP_DIRECT_RECLAIM) || !(gfp & __GFP_FS)) {
		fscache_stat(&fscache_n_store_vmscan_busy);
		return false;
	}

	fscache_stat(&fscache_n_store_vmscan_wait);
	if (!release_page_wait_timeout(cookie, page))
		_debug("fscache writeout timeout page: %p{%lx}",
			page, page->index);

	gfp &= ~__GFP_DIRECT_RECLAIM;
	goto try_again;
}
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EXPORT_SYMBOL(__fscache_maybe_release_page);

/*
 * note that a page has finished being written to the cache
 */


static void fscache_end_page_write(struct fscache_object *object,
				   struct page *page)
{
	struct fscache_cookie *cookie;
	struct page *xpage = NULL;

	spin_lock(&object->lock);
	cookie = object->cookie;
	if (cookie) {
		/* delete the page from the tree if it is now no longer
                 * pending */
		spin_lock(&cookie->stores_lock);
		radix_tree_tag_clear(&cookie->stores, page->index,
				     FSCACHE_COOKIE_STORING_TAG);
		if (!radix_tree_tag_get(&cookie->stores, page->index,
					FSCACHE_COOKIE_PENDING_TAG)) {
			fscache_stat(&fscache_n_store_radix_deletes);
			xpage = radix_tree_delete(&cookie->stores, page->index);
		}
		spin_unlock(&cookie->stores_lock);
		wake_up_bit(&cookie->flags, 0);
	}
	spin_unlock(&object->lock);
	if (xpage)
		put_page(xpage);
}

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/*
 * actually apply the changed attributes to a cache object
 */


static void fscache_attr_changed_op(struct fscache_operation *op)
{
	struct fscache_object *object = op->object;
	int ret;

	_enter("{OBJ%x OP%x}", object->debug_id, op->debug_id);

	fscache_stat(&fscache_n_attr_changed_calls);

	if (fscache_object_is_active(object)) {
		fscache_stat(&fscache_n_cop_attr_changed);
		ret = object->cache->ops->attr_changed(object);
		fscache_stat_d(&fscache_n_cop_attr_changed);
		if (ret < 0)
			fscache_abort_object(object);
	}

	fscache_op_complete(op, true);
	_leave("");
}

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/*
 * notification that the attributes on an object have changed
 */


int __fscache_attr_changed(struct fscache_cookie *cookie)
{
	struct fscache_operation *op;
	struct fscache_object *object;
	bool wake_cookie = false;

	_enter("%p", cookie);

	ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);

	fscache_stat(&fscache_n_attr_changed);

	op = kzalloc(sizeof(*op), GFP_KERNEL);
	if (!op) {
		fscache_stat(&fscache_n_attr_changed_nomem);
		_leave(" = -ENOMEM");
		return -ENOMEM;
	}

	fscache_operation_init(op, fscache_attr_changed_op, NULL, NULL);
	op->flags = FSCACHE_OP_ASYNC |
		(1 << FSCACHE_OP_EXCLUSIVE) |
		(1 << FSCACHE_OP_UNUSE_COOKIE);

	spin_lock(&cookie->lock);

	if (!fscache_cookie_enabled(cookie) ||
	    hlist_empty(&cookie->backing_objects))
		goto nobufs;
	object = hlist_entry(cookie->backing_objects.first,
			     struct fscache_object, cookie_link);

	__fscache_use_cookie(cookie);
	if (fscache_submit_exclusive_op(object, op) < 0)
		goto nobufs_dec;
	spin_unlock(&cookie->lock);
	fscache_stat(&fscache_n_attr_changed_ok);
	fscache_put_operation(op);
	_leave(" = 0");
	return 0;

nobufs_dec:
	wake_cookie = __fscache_unuse_cookie(cookie);
nobufs:
	spin_unlock(&cookie->lock);
	fscache_put_operation(op);
	if (wake_cookie)
		__fscache_wake_unused_cookie(cookie);
	fscache_stat(&fscache_n_attr_changed_nobufs);
	_leave(" = %d", -ENOBUFS);
	return -ENOBUFS;
}
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EXPORT_SYMBOL(__fscache_attr_changed);

/*
 * Handle cancellation of a pending retrieval op
 */


static void fscache_do_cancel_retrieval(struct fscache_operation *_op)
{
	struct fscache_retrieval *op =
		container_of(_op, struct fscache_retrieval, op);

	atomic_set(&op->n_pages, 0);
}

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/*
 * release a retrieval op reference
 */


static void fscache_release_retrieval_op(struct fscache_operation *_op)
{
	struct fscache_retrieval *op =
		container_of(_op, struct fscache_retrieval, op);

	_enter("{OP%x}", op->op.debug_id);

	ASSERTIFCMP(op->op.state != FSCACHE_OP_ST_INITIALISED,
		    atomic_read(&op->n_pages), ==, 0);

	fscache_hist(fscache_retrieval_histogram, op->start_time);
	if (op->context)
		fscache_put_context(op->cookie, op->context);

	_leave("");
}

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/*
 * allocate a retrieval op
 */


static struct fscache_retrieval *fscache_alloc_retrieval(
	struct fscache_cookie *cookie,
	struct address_space *mapping,
	fscache_rw_complete_t end_io_func,
	void *context)
{
	struct fscache_retrieval *op;

	/* allocate a retrieval operation and attempt to submit it */
	op = kzalloc(sizeof(*op), GFP_NOIO);
	if (!op) {
		fscache_stat(&fscache_n_retrievals_nomem);
		return NULL;
	}

	fscache_operation_init(&op->op, NULL,
			       fscache_do_cancel_retrieval,
			       fscache_release_retrieval_op);
	op->op.flags	= FSCACHE_OP_MYTHREAD |
		(1UL << FSCACHE_OP_WAITING) |
		(1UL << FSCACHE_OP_UNUSE_COOKIE);
	op->cookie	= cookie;
	op->mapping	= mapping;
	op->end_io_func	= end_io_func;
	op->context	= context;
	op->start_time	= jiffies;
	INIT_LIST_HEAD(&op->to_do);

	/* Pin the netfs read context in case we need to do the actual netfs
         * read because we've encountered a cache read failure.
         */
	if (context)
		fscache_get_context(op->cookie, context);
	return op;
}

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/*
 * wait for a deferred lookup to complete
 */


int fscache_wait_for_deferred_lookup(struct fscache_cookie *cookie)
{
	unsigned long jif;

	_enter("");

	if (!test_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags)) {
		_leave(" = 0 [imm]");
		return 0;
	}

	fscache_stat(&fscache_n_retrievals_wait);

	jif = jiffies;
	if (wait_on_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP,
			TASK_INTERRUPTIBLE) != 0) {
		fscache_stat(&fscache_n_retrievals_intr);
		_leave(" = -ERESTARTSYS");
		return -ERESTARTSYS;
	}

	ASSERT(!test_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags));

	smp_rmb();
	fscache_hist(fscache_retrieval_delay_histogram, jif);
	_leave(" = 0 [dly]");
	return 0;
}

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/*
 * wait for an object to become active (or dead)
 */


int fscache_wait_for_operation_activation(struct fscache_object *object,
					  struct fscache_operation *op,
					  atomic_t *stat_op_waits,
					  atomic_t *stat_object_dead)
{
	int ret;

	if (!test_bit(FSCACHE_OP_WAITING, &op->flags))
		goto check_if_dead;

	_debug(">>> WT");
	if (stat_op_waits)
		fscache_stat(stat_op_waits);
	if (wait_on_bit(&op->flags, FSCACHE_OP_WAITING,
			TASK_INTERRUPTIBLE) != 0) {
		ret = fscache_cancel_op(op, false);
		if (ret == 0)
			return -ERESTARTSYS;

		/* it's been removed from the pending queue by another party,
                 * so we should get to run shortly */
		wait_on_bit(&op->flags, FSCACHE_OP_WAITING,
			    TASK_UNINTERRUPTIBLE);
	}
	_debug("<<< GO");

check_if_dead:
	if (op->state == FSCACHE_OP_ST_CANCELLED) {
		if (stat_object_dead)
			fscache_stat(stat_object_dead);
		_leave(" = -ENOBUFS [cancelled]");
		return -ENOBUFS;
	}
	if (unlikely(fscache_object_is_dying(object) ||
		     fscache_cache_is_broken(object))) {
		enum fscache_operation_state state = op->state;
		fscache_cancel_op(op, true);
		if (stat_object_dead)
			fscache_stat(stat_object_dead);
		_leave(" = -ENOBUFS [obj dead %d]", state);
		return -ENOBUFS;
	}
	return 0;
}

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/*
 * read a page from the cache or allocate a block in which to store it
 * - we return:
 *   -ENOMEM    - out of memory, nothing done
 *   -ERESTARTSYS - interrupted
 *   -ENOBUFS   - no backing object available in which to cache the block
 *   -ENODATA   - no data available in the backing object for this block
 *   0          - dispatched a read - it'll call end_io_func() when finished
 */


int __fscache_read_or_alloc_page(struct fscache_cookie *cookie,
				 struct page *page,
				 fscache_rw_complete_t end_io_func,
				 void *context,
				 gfp_t gfp)
{
	struct fscache_retrieval *op;
	struct fscache_object *object;
	bool wake_cookie = false;
	int ret;

	_enter("%p,%p,,,", cookie, page);

	fscache_stat(&fscache_n_retrievals);

	if (hlist_empty(&cookie->backing_objects))
		goto nobufs;

	if (test_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags)) {
		_leave(" = -ENOBUFS [invalidating]");
		return -ENOBUFS;
	}

	ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
	ASSERTCMP(page, !=, NULL);

	if (fscache_wait_for_deferred_lookup(cookie) < 0)
		return -ERESTARTSYS;

	op = fscache_alloc_retrieval(cookie, page->mapping,
				     end_io_func, context);
	if (!op) {
		_leave(" = -ENOMEM");
		return -ENOMEM;
	}
	atomic_set(&op->n_pages, 1);

	spin_lock(&cookie->lock);

	if (!fscache_cookie_enabled(cookie) ||
	    hlist_empty(&cookie->backing_objects))
		goto nobufs_unlock;
	object = hlist_entry(cookie->backing_objects.first,
			     struct fscache_object, cookie_link);

	ASSERT(test_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags));

	__fscache_use_cookie(cookie);
	atomic_inc(&object->n_reads);
	__set_bit(FSCACHE_OP_DEC_READ_CNT, &op->op.flags);

	if (fscache_submit_op(object, &op->op) < 0)
		goto nobufs_unlock_dec;
	spin_unlock(&cookie->lock);

	fscache_stat(&fscache_n_retrieval_ops);

	/* we wait for the operation to become active, and then process it
         * *here*, in this thread, and not in the thread pool */
	ret = fscache_wait_for_operation_activation(
		object, &op->op,
		__fscache_stat(&fscache_n_retrieval_op_waits),
		__fscache_stat(&fscache_n_retrievals_object_dead));
	if (ret < 0)
		goto error;

	/* ask the cache to honour the operation */
	if (test_bit(FSCACHE_COOKIE_NO_DATA_YET, &object->cookie->flags)) {
		fscache_stat(&fscache_n_cop_allocate_page);
		ret = object->cache->ops->allocate_page(op, page, gfp);
		fscache_stat_d(&fscache_n_cop_allocate_page);
		if (ret == 0)
			ret = -ENODATA;
	} else {
		fscache_stat(&fscache_n_cop_read_or_alloc_page);
		ret = object->cache->ops->read_or_alloc_page(op, page, gfp);
		fscache_stat_d(&fscache_n_cop_read_or_alloc_page);
	}

error:
	if (ret == -ENOMEM)
		fscache_stat(&fscache_n_retrievals_nomem);
	else if (ret == -ERESTARTSYS)
		fscache_stat(&fscache_n_retrievals_intr);
	else if (ret == -ENODATA)
		fscache_stat(&fscache_n_retrievals_nodata);
	else if (ret < 0)
		fscache_stat(&fscache_n_retrievals_nobufs);
	else
		fscache_stat(&fscache_n_retrievals_ok);

	fscache_put_retrieval(op);
	_leave(" = %d", ret);
	return ret;

nobufs_unlock_dec:
	atomic_dec(&object->n_reads);
	wake_cookie = __fscache_unuse_cookie(cookie);
nobufs_unlock:
	spin_unlock(&cookie->lock);
	if (wake_cookie)
		__fscache_wake_unused_cookie(cookie);
	fscache_put_retrieval(op);
nobufs:
	fscache_stat(&fscache_n_retrievals_nobufs);
	_leave(" = -ENOBUFS");
	return -ENOBUFS;
}
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EXPORT_SYMBOL(__fscache_read_or_alloc_page);

/*
 * read a list of page from the cache or allocate a block in which to store
 * them
 * - we return:
 *   -ENOMEM    - out of memory, some pages may be being read
 *   -ERESTARTSYS - interrupted, some pages may be being read
 *   -ENOBUFS   - no backing object or space available in which to cache any
 *                pages not being read
 *   -ENODATA   - no data available in the backing object for some or all of
 *                the pages
 *   0          - dispatched a read on all pages
 *
 * end_io_func() will be called for each page read from the cache as it is
 * finishes being read
 *
 * any pages for which a read is dispatched will be removed from pages and
 * nr_pages
 */


int __fscache_read_or_alloc_pages(struct fscache_cookie *cookie,
				  struct address_space *mapping,
				  struct list_head *pages,
				  unsigned *nr_pages,
				  fscache_rw_complete_t end_io_func,
				  void *context,
				  gfp_t gfp)
{
	struct fscache_retrieval *op;
	struct fscache_object *object;
	bool wake_cookie = false;
	int ret;

	_enter("%p,,%d,,,", cookie, *nr_pages);

	fscache_stat(&fscache_n_retrievals);

	if (hlist_empty(&cookie->backing_objects))
		goto nobufs;

	if (test_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags)) {
		_leave(" = -ENOBUFS [invalidating]");
		return -ENOBUFS;
	}

	ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
	ASSERTCMP(*nr_pages, >, 0);
	ASSERT(!list_empty(pages));

	if (fscache_wait_for_deferred_lookup(cookie) < 0)
		return -ERESTARTSYS;

	op = fscache_alloc_retrieval(cookie, mapping, end_io_func, context);
	if (!op)
		return -ENOMEM;
	atomic_set(&op->n_pages, *nr_pages);

	spin_lock(&cookie->lock);

	if (!fscache_cookie_enabled(cookie) ||
	    hlist_empty(&cookie->backing_objects))
		goto nobufs_unlock;
	object = hlist_entry(cookie->backing_objects.first,
			     struct fscache_object, cookie_link);

	__fscache_use_cookie(cookie);
	atomic_inc(&object->n_reads);
	__set_bit(FSCACHE_OP_DEC_READ_CNT, &op->op.flags);

	if (fscache_submit_op(object, &op->op) < 0)
		goto nobufs_unlock_dec;
	spin_unlock(&cookie->lock);

	fscache_stat(&fscache_n_retrieval_ops);

	/* we wait for the operation to become active, and then process it
         * *here*, in this thread, and not in the thread pool */
	ret = fscache_wait_for_operation_activation(
		object, &op->op,
		__fscache_stat(&fscache_n_retrieval_op_waits),
		__fscache_stat(&fscache_n_retrievals_object_dead));
	if (ret < 0)
		goto error;

	/* ask the cache to honour the operation */
	if (test_bit(FSCACHE_COOKIE_NO_DATA_YET, &object->cookie->flags)) {
		fscache_stat(&fscache_n_cop_allocate_pages);
		ret = object->cache->ops->allocate_pages(
			op, pages, nr_pages, gfp);
		fscache_stat_d(&fscache_n_cop_allocate_pages);
	} else {
		fscache_stat(&fscache_n_cop_read_or_alloc_pages);
		ret = object->cache->ops->read_or_alloc_pages(
			op, pages, nr_pages, gfp);
		fscache_stat_d(&fscache_n_cop_read_or_alloc_pages);
	}

error:
	if (ret == -ENOMEM)
		fscache_stat(&fscache_n_retrievals_nomem);
	else if (ret == -ERESTARTSYS)
		fscache_stat(&fscache_n_retrievals_intr);
	else if (ret == -ENODATA)
		fscache_stat(&fscache_n_retrievals_nodata);
	else if (ret < 0)
		fscache_stat(&fscache_n_retrievals_nobufs);
	else
		fscache_stat(&fscache_n_retrievals_ok);

	fscache_put_retrieval(op);
	_leave(" = %d", ret);
	return ret;

nobufs_unlock_dec:
	atomic_dec(&object->n_reads);
	wake_cookie = __fscache_unuse_cookie(cookie);
nobufs_unlock:
	spin_unlock(&cookie->lock);
	fscache_put_retrieval(op);
	if (wake_cookie)
		__fscache_wake_unused_cookie(cookie);
nobufs:
	fscache_stat(&fscache_n_retrievals_nobufs);
	_leave(" = -ENOBUFS");
	return -ENOBUFS;
}
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david howells
david howells
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EXPORT_SYMBOL(__fscache_read_or_alloc_pages);

/*
 * allocate a block in the cache on which to store a page
 * - we return:
 *   -ENOMEM    - out of memory, nothing done
 *   -ERESTARTSYS - interrupted
 *   -ENOBUFS   - no backing object available in which to cache the block
 *   0          - block allocated
 */


int __fscache_alloc_page(struct fscache_cookie *cookie,
			 struct page *page,
			 gfp_t gfp)
{
	struct fscache_retrieval *op;
	struct fscache_object *object;
	bool wake_cookie = false;
	int ret;

	_enter("%p,%p,,,", cookie, page);

	fscache_stat(&fscache_n_allocs);

	if (hlist_empty(&cookie->backing_objects))
		goto nobufs;

	ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
	ASSERTCMP(page, !=, NULL);

	if (test_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags)) {
		_leave(" = -ENOBUFS [invalidating]");
		return -ENOBUFS;
	}

	if (fscache_wait_for_deferred_lookup(cookie) < 0)
		return -ERESTARTSYS;

	op = fscache_alloc_retrieval(cookie, page->mapping, NULL, NULL);
	if (!op)
		return -ENOMEM;
	atomic_set(&op->n_pages, 1);

	spin_lock(&cookie->lock);

	if (!fscache_cookie_enabled(cookie) ||
	    hlist_empty(&cookie->backing_objects))
		goto nobufs_unlock;
	object = hlist_entry(cookie->backing_objects.first,
			     struct fscache_object, cookie_link);

	__fscache_use_cookie(cookie);
	if (fscache_submit_op(object, &op->op) < 0)
		goto nobufs_unlock_dec;
	spin_unlock(