linux/fs/fscache/page.c
David Howells 102f4d900c FS-Cache: Handle a write to the page immediately beyond the EOF marker
Handle a write being requested to the page immediately beyond the EOF
marker on a cache object.  Currently this gets an assertion failure in
CacheFiles because the EOF marker is used there to encode information about
a partial page at the EOF - which could lead to an unknown blank spot in
the file if we extend the file over it.

The problem is actually in fscache where we check the index of the page
being written against store_limit.  store_limit is set to the number of
pages that we're allowed to store by fscache_set_store_limit() - which
means it's one more than the index of the last page we're allowed to store.
The problem is that we permit writing to a page with an index _equal_ to
the store limit - when we should reject that case.

Whilst we're at it, change the triggered assertion in CacheFiles to just
return -ENOBUFS instead.

The assertion failure looks something like this:

CacheFiles: Assertion failed
1000 < 7b1 is false
------------[ cut here ]------------
kernel BUG at fs/cachefiles/rdwr.c:962!
...
RIP: 0010:[<ffffffffa02c9e83>]  [<ffffffffa02c9e83>] cachefiles_write_page+0x273/0x2d0 [cachefiles]

Cc: stable@vger.kernel.org # v2.6.31+; earlier - that + backport of a17754f (at least)
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-11-11 02:11:02 -05:00

1196 lines
31 KiB
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;
}
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));
}
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);
}
/*
* 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)
page_cache_release(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;
}
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)
page_cache_release(xpage);
}
/*
* 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("");
}
/*
* 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;
}
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);
}
/*
* 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("");
}
/*
* 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;
}
/*
* 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;
}
/*
* 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;
}
/*
* 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;
}
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;
}
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(&cookie->lock);
fscache_stat(&fscache_n_alloc_ops);
ret = fscache_wait_for_operation_activation(
object, &op->op,
__fscache_stat(&fscache_n_alloc_op_waits),
__fscache_stat(&fscache_n_allocs_object_dead));
if (ret < 0)
goto error;
/* ask the cache to honour the operation */
fscache_stat(&fscache_n_cop_allocate_page);
ret = object->cache->ops->allocate_page(op, page, gfp);
fscache_stat_d(&fscache_n_cop_allocate_page);
error:
if (ret == -ERESTARTSYS)
fscache_stat(&fscache_n_allocs_intr);
else if (ret < 0)
fscache_stat(&fscache_n_allocs_nobufs);
else
fscache_stat(&fscache_n_allocs_ok);
fscache_put_retrieval(op);
_leave(" = %d", ret);
return ret;
nobufs_unlock_dec:
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_allocs_nobufs);
_leave(" = -ENOBUFS");
return -ENOBUFS;
}
EXPORT_SYMBOL(__fscache_alloc_page);
/*
* Unmark pages allocate in the readahead code path (via:
* fscache_readpages_or_alloc) after delegating to the base filesystem
*/
void __fscache_readpages_cancel(struct fscache_cookie *cookie,
struct list_head *pages)
{
struct page *page;
list_for_each_entry(page, pages, lru) {
if (PageFsCache(page))
__fscache_uncache_page(cookie, page);
}
}
EXPORT_SYMBOL(__fscache_readpages_cancel);
/*
* release a write op reference
*/
static void fscache_release_write_op(struct fscache_operation *_op)
{
_enter("{OP%x}", _op->debug_id);
}
/*
* perform the background storage of a page into the cache
*/
static void fscache_write_op(struct fscache_operation *_op)
{
struct fscache_storage *op =
container_of(_op, struct fscache_storage, op);
struct fscache_object *object = op->op.object;
struct fscache_cookie *cookie;
struct page *page;
unsigned n;
void *results[1];
int ret;
_enter("{OP%x,%d}", op->op.debug_id, atomic_read(&op->op.usage));
spin_lock(&object->lock);
cookie = object->cookie;
if (!fscache_object_is_active(object)) {
/* If we get here, then the on-disk cache object likely longer
* exists, so we should just cancel this write operation.
*/
spin_unlock(&object->lock);
fscache_op_complete(&op->op, false);
_leave(" [inactive]");
return;
}
if (!cookie) {
/* If we get here, then the cookie belonging to the object was
* detached, probably by the cookie being withdrawn due to
* memory pressure, which means that the pages we might write
* to the cache from no longer exist - therefore, we can just
* cancel this write operation.
*/
spin_unlock(&object->lock);
fscache_op_complete(&op->op, false);
_leave(" [cancel] op{f=%lx s=%u} obj{s=%s f=%lx}",
_op->flags, _op->state, object->state->short_name,
object->flags);
return;
}
spin_lock(&cookie->stores_lock);
fscache_stat(&fscache_n_store_calls);
/* find a page to store */
page = NULL;
n = radix_tree_gang_lookup_tag(&cookie->stores, results, 0, 1,
FSCACHE_COOKIE_PENDING_TAG);
if (n != 1)
goto superseded;
page = results[0];
_debug("gang %d [%lx]", n, page->index);
if (page->index >= op->store_limit) {
fscache_stat(&fscache_n_store_pages_over_limit);
goto superseded;
}
radix_tree_tag_set(&cookie->stores, page->index,
FSCACHE_COOKIE_STORING_TAG);
radix_tree_tag_clear(&cookie->stores, page->index,
FSCACHE_COOKIE_PENDING_TAG);
spin_unlock(&cookie->stores_lock);
spin_unlock(&object->lock);
fscache_stat(&fscache_n_store_pages);
fscache_stat(&fscache_n_cop_write_page);
ret = object->cache->ops->write_page(op, page);
fscache_stat_d(&fscache_n_cop_write_page);
fscache_end_page_write(object, page);
if (ret < 0) {
fscache_abort_object(object);
fscache_op_complete(&op->op, true);
} else {
fscache_enqueue_operation(&op->op);
}
_leave("");
return;
superseded:
/* this writer is going away and there aren't any more things to
* write */
_debug("cease");
spin_unlock(&cookie->stores_lock);
clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
spin_unlock(&object->lock);
fscache_op_complete(&op->op, true);
_leave("");
}
/*
* Clear the pages pending writing for invalidation
*/
void fscache_invalidate_writes(struct fscache_cookie *cookie)
{
struct page *page;
void *results[16];
int n, i;
_enter("");
for (;;) {
spin_lock(&cookie->stores_lock);
n = radix_tree_gang_lookup_tag(&cookie->stores, results, 0,
ARRAY_SIZE(results),
FSCACHE_COOKIE_PENDING_TAG);
if (n == 0) {
spin_unlock(&cookie->stores_lock);
break;
}
for (i = n - 1; i >= 0; i--) {
page = results[i];
radix_tree_delete(&cookie->stores, page->index);
}
spin_unlock(&cookie->stores_lock);
for (i = n - 1; i >= 0; i--)
page_cache_release(results[i]);
}
_leave("");
}
/*
* request a page be stored in the cache
* - returns:
* -ENOMEM - out of memory, nothing done
* -ENOBUFS - no backing object available in which to cache the page
* 0 - dispatched a write - it'll call end_io_func() when finished
*
* if the cookie still has a backing object at this point, that object can be
* in one of a few states with respect to storage processing:
*
* (1) negative lookup, object not yet created (FSCACHE_COOKIE_CREATING is
* set)
*
* (a) no writes yet
*
* (b) writes deferred till post-creation (mark page for writing and
* return immediately)
*
* (2) negative lookup, object created, initial fill being made from netfs
*
* (a) fill point not yet reached this page (mark page for writing and
* return)
*
* (b) fill point passed this page (queue op to store this page)
*
* (3) object extant (queue op to store this page)
*
* any other state is invalid
*/
int __fscache_write_page(struct fscache_cookie *cookie,
struct page *page,
gfp_t gfp)
{
struct fscache_storage *op;
struct fscache_object *object;
bool wake_cookie = false;
int ret;
_enter("%p,%x,", cookie, (u32) page->flags);
ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
ASSERT(PageFsCache(page));
fscache_stat(&fscache_n_stores);
if (test_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags)) {
_leave(" = -ENOBUFS [invalidating]");
return -ENOBUFS;
}
op = kzalloc(sizeof(*op), GFP_NOIO | __GFP_NOMEMALLOC | __GFP_NORETRY);
if (!op)
goto nomem;
fscache_operation_init(&op->op, fscache_write_op, NULL,
fscache_release_write_op);
op->op.flags = FSCACHE_OP_ASYNC |
(1 << FSCACHE_OP_WAITING) |
(1 << FSCACHE_OP_UNUSE_COOKIE);
ret = radix_tree_maybe_preload(gfp & ~__GFP_HIGHMEM);
if (ret < 0)
goto nomem_free;
ret = -ENOBUFS;
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);
if (test_bit(FSCACHE_IOERROR, &object->cache->flags))
goto nobufs;
/* add the page to the pending-storage radix tree on the backing
* object */
spin_lock(&object->lock);
spin_lock(&cookie->stores_lock);
_debug("store limit %llx", (unsigned long long) object->store_limit);
ret = radix_tree_insert(&cookie->stores, page->index, page);
if (ret < 0) {
if (ret == -EEXIST)
goto already_queued;
_debug("insert failed %d", ret);
goto nobufs_unlock_obj;
}
radix_tree_tag_set(&cookie->stores, page->index,
FSCACHE_COOKIE_PENDING_TAG);
page_cache_get(page);
/* we only want one writer at a time, but we do need to queue new
* writers after exclusive ops */
if (test_and_set_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags))
goto already_pending;
spin_unlock(&cookie->stores_lock);
spin_unlock(&object->lock);
op->op.debug_id = atomic_inc_return(&fscache_op_debug_id);
op->store_limit = object->store_limit;
__fscache_use_cookie(cookie);
if (fscache_submit_op(object, &op->op) < 0)
goto submit_failed;
spin_unlock(&cookie->lock);
radix_tree_preload_end();
fscache_stat(&fscache_n_store_ops);
fscache_stat(&fscache_n_stores_ok);
/* the work queue now carries its own ref on the object */
fscache_put_operation(&op->op);
_leave(" = 0");
return 0;
already_queued:
fscache_stat(&fscache_n_stores_again);
already_pending:
spin_unlock(&cookie->stores_lock);
spin_unlock(&object->lock);
spin_unlock(&cookie->lock);
radix_tree_preload_end();
fscache_put_operation(&op->op);
fscache_stat(&fscache_n_stores_ok);
_leave(" = 0");
return 0;
submit_failed:
spin_lock(&cookie->stores_lock);
radix_tree_delete(&cookie->stores, page->index);
spin_unlock(&cookie->stores_lock);
wake_cookie = __fscache_unuse_cookie(cookie);
page_cache_release(page);
ret = -ENOBUFS;
goto nobufs;
nobufs_unlock_obj:
spin_unlock(&cookie->stores_lock);
spin_unlock(&object->lock);
nobufs:
spin_unlock(&cookie->lock);
radix_tree_preload_end();
fscache_put_operation(&op->op);
if (wake_cookie)
__fscache_wake_unused_cookie(cookie);
fscache_stat(&fscache_n_stores_nobufs);
_leave(" = -ENOBUFS");
return -ENOBUFS;
nomem_free:
fscache_put_operation(&op->op);
nomem:
fscache_stat(&fscache_n_stores_oom);
_leave(" = -ENOMEM");
return -ENOMEM;
}
EXPORT_SYMBOL(__fscache_write_page);
/*
* remove a page from the cache
*/
void __fscache_uncache_page(struct fscache_cookie *cookie, struct page *page)
{
struct fscache_object *object;
_enter(",%p", page);
ASSERTCMP(cookie->def->type, !=, FSCACHE_COOKIE_TYPE_INDEX);
ASSERTCMP(page, !=, NULL);
fscache_stat(&fscache_n_uncaches);
/* cache withdrawal may beat us to it */
if (!PageFsCache(page))
goto done;
/* get the object */
spin_lock(&cookie->lock);
if (hlist_empty(&cookie->backing_objects)) {
ClearPageFsCache(page);
goto done_unlock;
}
object = hlist_entry(cookie->backing_objects.first,
struct fscache_object, cookie_link);
/* there might now be stuff on disk we could read */
clear_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
/* only invoke the cache backend if we managed to mark the page
* uncached here; this deals with synchronisation vs withdrawal */
if (TestClearPageFsCache(page) &&
object->cache->ops->uncache_page) {
/* the cache backend releases the cookie lock */
fscache_stat(&fscache_n_cop_uncache_page);
object->cache->ops->uncache_page(object, page);
fscache_stat_d(&fscache_n_cop_uncache_page);
goto done;
}
done_unlock:
spin_unlock(&cookie->lock);
done:
_leave("");
}
EXPORT_SYMBOL(__fscache_uncache_page);
/**
* fscache_mark_page_cached - Mark a page as being cached
* @op: The retrieval op pages are being marked for
* @page: The page to be marked
*
* Mark a netfs page as being cached. After this is called, the netfs
* must call fscache_uncache_page() to remove the mark.
*/
void fscache_mark_page_cached(struct fscache_retrieval *op, struct page *page)
{
struct fscache_cookie *cookie = op->op.object->cookie;
#ifdef CONFIG_FSCACHE_STATS
atomic_inc(&fscache_n_marks);
#endif
_debug("- mark %p{%lx}", page, page->index);
if (TestSetPageFsCache(page)) {
static bool once_only;
if (!once_only) {
once_only = true;
pr_warn("Cookie type %s marked page %lx multiple times\n",
cookie->def->name, page->index);
}
}
if (cookie->def->mark_page_cached)
cookie->def->mark_page_cached(cookie->netfs_data,
op->mapping, page);
}
EXPORT_SYMBOL(fscache_mark_page_cached);
/**
* fscache_mark_pages_cached - Mark pages as being cached
* @op: The retrieval op pages are being marked for
* @pagevec: The pages to be marked
*
* Mark a bunch of netfs pages as being cached. After this is called,
* the netfs must call fscache_uncache_page() to remove the mark.
*/
void fscache_mark_pages_cached(struct fscache_retrieval *op,
struct pagevec *pagevec)
{
unsigned long loop;
for (loop = 0; loop < pagevec->nr; loop++)
fscache_mark_page_cached(op, pagevec->pages[loop]);
pagevec_reinit(pagevec);
}
EXPORT_SYMBOL(fscache_mark_pages_cached);
/*
* Uncache all the pages in an inode that are marked PG_fscache, assuming them
* to be associated with the given cookie.
*/
void __fscache_uncache_all_inode_pages(struct fscache_cookie *cookie,
struct inode *inode)
{
struct address_space *mapping = inode->i_mapping;
struct pagevec pvec;
pgoff_t next;
int i;
_enter("%p,%p", cookie, inode);
if (!mapping || mapping->nrpages == 0) {
_leave(" [no pages]");
return;
}
pagevec_init(&pvec, 0);
next = 0;
do {
if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE))
break;
for (i = 0; i < pagevec_count(&pvec); i++) {
struct page *page = pvec.pages[i];
next = page->index;
if (PageFsCache(page)) {
__fscache_wait_on_page_write(cookie, page);
__fscache_uncache_page(cookie, page);
}
}
pagevec_release(&pvec);
cond_resched();
} while (++next);
_leave("");
}
EXPORT_SYMBOL(__fscache_uncache_all_inode_pages);