2021-10-20 21:06:34 +08:00
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// SPDX-License-Identifier: GPL-2.0-or-later
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/* Cache data I/O routines
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*
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* Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*/
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#define FSCACHE_DEBUG_LEVEL OPERATION
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#include <linux/fscache-cache.h>
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#include <linux/uio.h>
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#include <linux/bvec.h>
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#include <linux/slab.h>
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#include <linux/uio.h>
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#include "internal.h"
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/**
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* fscache_wait_for_operation - Wait for an object become accessible
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* @cres: The cache resources for the operation being performed
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* @want_state: The minimum state the object must be at
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*
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* See if the target cache object is at the specified minimum state of
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* accessibility yet, and if not, wait for it.
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*/
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bool fscache_wait_for_operation(struct netfs_cache_resources *cres,
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enum fscache_want_state want_state)
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{
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struct fscache_cookie *cookie = fscache_cres_cookie(cres);
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enum fscache_cookie_state state;
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again:
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if (!fscache_cache_is_live(cookie->volume->cache)) {
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_leave(" [broken]");
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return false;
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}
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state = fscache_cookie_state(cookie);
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_enter("c=%08x{%u},%x", cookie->debug_id, state, want_state);
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switch (state) {
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case FSCACHE_COOKIE_STATE_CREATING:
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case FSCACHE_COOKIE_STATE_INVALIDATING:
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if (want_state == FSCACHE_WANT_PARAMS)
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goto ready; /* There can be no content */
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fallthrough;
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case FSCACHE_COOKIE_STATE_LOOKING_UP:
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case FSCACHE_COOKIE_STATE_LRU_DISCARDING:
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wait_var_event(&cookie->state,
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fscache_cookie_state(cookie) != state);
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goto again;
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case FSCACHE_COOKIE_STATE_ACTIVE:
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goto ready;
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case FSCACHE_COOKIE_STATE_DROPPED:
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case FSCACHE_COOKIE_STATE_RELINQUISHING:
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default:
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_leave(" [not live]");
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return false;
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}
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ready:
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if (!cres->cache_priv2)
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return cookie->volume->cache->ops->begin_operation(cres, want_state);
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return true;
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}
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EXPORT_SYMBOL(fscache_wait_for_operation);
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/*
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* Begin an I/O operation on the cache, waiting till we reach the right state.
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*
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* Attaches the resources required to the operation resources record.
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*/
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static int fscache_begin_operation(struct netfs_cache_resources *cres,
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struct fscache_cookie *cookie,
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enum fscache_want_state want_state,
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enum fscache_access_trace why)
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{
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enum fscache_cookie_state state;
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long timeo;
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bool once_only = false;
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cres->ops = NULL;
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cres->cache_priv = cookie;
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cres->cache_priv2 = NULL;
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cres->debug_id = cookie->debug_id;
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cres->inval_counter = cookie->inval_counter;
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if (!fscache_begin_cookie_access(cookie, why))
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return -ENOBUFS;
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again:
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spin_lock(&cookie->lock);
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state = fscache_cookie_state(cookie);
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_enter("c=%08x{%u},%x", cookie->debug_id, state, want_state);
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switch (state) {
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case FSCACHE_COOKIE_STATE_LOOKING_UP:
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case FSCACHE_COOKIE_STATE_LRU_DISCARDING:
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case FSCACHE_COOKIE_STATE_INVALIDATING:
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goto wait_for_file_wrangling;
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case FSCACHE_COOKIE_STATE_CREATING:
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if (want_state == FSCACHE_WANT_PARAMS)
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goto ready; /* There can be no content */
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goto wait_for_file_wrangling;
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case FSCACHE_COOKIE_STATE_ACTIVE:
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goto ready;
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case FSCACHE_COOKIE_STATE_DROPPED:
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case FSCACHE_COOKIE_STATE_RELINQUISHING:
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WARN(1, "Can't use cookie in state %u\n", cookie->state);
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goto not_live;
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default:
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goto not_live;
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}
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ready:
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spin_unlock(&cookie->lock);
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if (!cookie->volume->cache->ops->begin_operation(cres, want_state))
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goto failed;
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return 0;
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wait_for_file_wrangling:
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spin_unlock(&cookie->lock);
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trace_fscache_access(cookie->debug_id, refcount_read(&cookie->ref),
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atomic_read(&cookie->n_accesses),
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fscache_access_io_wait);
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timeo = wait_var_event_timeout(&cookie->state,
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fscache_cookie_state(cookie) != state, 20 * HZ);
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if (timeo <= 1 && !once_only) {
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pr_warn("%s: cookie state change wait timed out: cookie->state=%u state=%u",
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__func__, fscache_cookie_state(cookie), state);
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fscache_print_cookie(cookie, 'O');
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once_only = true;
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}
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goto again;
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not_live:
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spin_unlock(&cookie->lock);
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failed:
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cres->cache_priv = NULL;
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cres->ops = NULL;
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fscache_end_cookie_access(cookie, fscache_access_io_not_live);
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_leave(" = -ENOBUFS");
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return -ENOBUFS;
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}
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int __fscache_begin_read_operation(struct netfs_cache_resources *cres,
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struct fscache_cookie *cookie)
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{
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return fscache_begin_operation(cres, cookie, FSCACHE_WANT_PARAMS,
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fscache_access_io_read);
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}
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EXPORT_SYMBOL(__fscache_begin_read_operation);
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fscache: Implement higher-level write I/O interface
Provide a higher-level function than fscache_write() to perform a write
from an inode's pagecache to the cache, whilst fending off concurrent
writes by means of the PG_fscache mark on a page:
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 caching);
If caching is false, this function does nothing except call (*term_func)()
if given. It assumes that, in such a case, PG_fscache will not have been
set on the pages.
Otherwise, if caching is true, this function requires the source pages to
have had PG_fscache set on them before calling. start and len define the
region of the file to be modified and i_size indicates the new file size.
The source pages are extracted from the mapping.
term_func and term_func_priv work as for fscache_write(). The PG_fscache
marks will be cleared at the end of the operation, before term_func is
called or the function otherwise returns.
There is an additonal helper function to clear the PG_fscache bits from a
range of pages:
void fscache_clear_page_bits(struct fscache_cookie *cookie,
struct address_space *mapping,
loff_t start, size_t len,
bool caching);
If caching is true, the pages to be managed are expected to be located on
mapping in the range defined by start and len. If caching is false, it
does nothing.
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819614155.215744.5528123235123721230.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906916346.143852.15632773570362489926.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967123599.1823006.12946816026724657428.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021522672.640689.4381958316198807813.stgit@warthog.procyon.org.uk/ # v4
2021-10-20 21:06:34 +08:00
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2021-08-27 22:19:34 +08:00
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int __fscache_begin_write_operation(struct netfs_cache_resources *cres,
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struct fscache_cookie *cookie)
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{
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return fscache_begin_operation(cres, cookie, FSCACHE_WANT_PARAMS,
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fscache_access_io_write);
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}
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EXPORT_SYMBOL(__fscache_begin_write_operation);
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vfs, fscache: Implement pinning of cache usage for writeback
Cachefiles has a problem in that it needs to keep the backing file for a
cookie open whilst there are local modifications pending that need to be
written to it. However, we don't want to keep the file open indefinitely,
as that causes EMFILE/ENFILE/ENOMEM problems.
Reopening the cache file, however, is a problem if this is being done due
to writeback triggered by exit(). Some filesystems will oops if we try to
open a file in that context because they want to access current->fs or
other resources that have already been dismantled.
To get around this, I added the following:
(1) An inode flag, I_PINNING_FSCACHE_WB, to be set on a network filesystem
inode to indicate that we have a usage count on the cookie caching
that inode.
(2) A flag in struct writeback_control, unpinned_fscache_wb, that is set
when __writeback_single_inode() clears the last dirty page from
i_pages - at which point it clears I_PINNING_FSCACHE_WB and sets this
flag.
This has to be done here so that clearing I_PINNING_FSCACHE_WB can be
done atomically with the check of PAGECACHE_TAG_DIRTY that clears
I_DIRTY_PAGES.
(3) A function, fscache_set_page_dirty(), which if it is not set, sets
I_PINNING_FSCACHE_WB and calls fscache_use_cookie() to pin the cache
resources.
(4) A function, fscache_unpin_writeback(), to be called by ->write_inode()
to unuse the cookie.
(5) A function, fscache_clear_inode_writeback(), to be called when the
inode is evicted, before clear_inode() is called. This cleans up any
lingering I_PINNING_FSCACHE_WB.
The network filesystem can then use these tools to make sure that
fscache_write_to_cache() can write locally modified data to the cache as
well as to the server.
For the future, I'm working on write helpers for netfs lib that should
allow this facility to be removed by keeping track of the dirty regions
separately - but that's incomplete at the moment and is also going to be
affected by folios, one way or another, since it deals with pages
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819615157.215744.17623791756928043114.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906917856.143852.8224898306177154573.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967124567.1823006.14188359004568060298.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021524705.640689.17824932021727663017.stgit@warthog.procyon.org.uk/ # v4
2021-10-21 06:50:01 +08:00
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/**
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2022-02-10 04:22:01 +08:00
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* fscache_dirty_folio - Mark folio dirty and pin a cache object for writeback
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* @mapping: The mapping the folio belongs to.
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* @folio: The folio being dirtied.
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vfs, fscache: Implement pinning of cache usage for writeback
Cachefiles has a problem in that it needs to keep the backing file for a
cookie open whilst there are local modifications pending that need to be
written to it. However, we don't want to keep the file open indefinitely,
as that causes EMFILE/ENFILE/ENOMEM problems.
Reopening the cache file, however, is a problem if this is being done due
to writeback triggered by exit(). Some filesystems will oops if we try to
open a file in that context because they want to access current->fs or
other resources that have already been dismantled.
To get around this, I added the following:
(1) An inode flag, I_PINNING_FSCACHE_WB, to be set on a network filesystem
inode to indicate that we have a usage count on the cookie caching
that inode.
(2) A flag in struct writeback_control, unpinned_fscache_wb, that is set
when __writeback_single_inode() clears the last dirty page from
i_pages - at which point it clears I_PINNING_FSCACHE_WB and sets this
flag.
This has to be done here so that clearing I_PINNING_FSCACHE_WB can be
done atomically with the check of PAGECACHE_TAG_DIRTY that clears
I_DIRTY_PAGES.
(3) A function, fscache_set_page_dirty(), which if it is not set, sets
I_PINNING_FSCACHE_WB and calls fscache_use_cookie() to pin the cache
resources.
(4) A function, fscache_unpin_writeback(), to be called by ->write_inode()
to unuse the cookie.
(5) A function, fscache_clear_inode_writeback(), to be called when the
inode is evicted, before clear_inode() is called. This cleans up any
lingering I_PINNING_FSCACHE_WB.
The network filesystem can then use these tools to make sure that
fscache_write_to_cache() can write locally modified data to the cache as
well as to the server.
For the future, I'm working on write helpers for netfs lib that should
allow this facility to be removed by keeping track of the dirty regions
separately - but that's incomplete at the moment and is also going to be
affected by folios, one way or another, since it deals with pages
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819615157.215744.17623791756928043114.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906917856.143852.8224898306177154573.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967124567.1823006.14188359004568060298.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021524705.640689.17824932021727663017.stgit@warthog.procyon.org.uk/ # v4
2021-10-21 06:50:01 +08:00
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* @cookie: The cookie referring to the cache object
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*
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2022-02-10 04:22:01 +08:00
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* Set the dirty flag on a folio and pin an in-use cache object in memory
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* so that writeback can later write to it. This is intended
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* to be called from the filesystem's ->dirty_folio() method.
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vfs, fscache: Implement pinning of cache usage for writeback
Cachefiles has a problem in that it needs to keep the backing file for a
cookie open whilst there are local modifications pending that need to be
written to it. However, we don't want to keep the file open indefinitely,
as that causes EMFILE/ENFILE/ENOMEM problems.
Reopening the cache file, however, is a problem if this is being done due
to writeback triggered by exit(). Some filesystems will oops if we try to
open a file in that context because they want to access current->fs or
other resources that have already been dismantled.
To get around this, I added the following:
(1) An inode flag, I_PINNING_FSCACHE_WB, to be set on a network filesystem
inode to indicate that we have a usage count on the cookie caching
that inode.
(2) A flag in struct writeback_control, unpinned_fscache_wb, that is set
when __writeback_single_inode() clears the last dirty page from
i_pages - at which point it clears I_PINNING_FSCACHE_WB and sets this
flag.
This has to be done here so that clearing I_PINNING_FSCACHE_WB can be
done atomically with the check of PAGECACHE_TAG_DIRTY that clears
I_DIRTY_PAGES.
(3) A function, fscache_set_page_dirty(), which if it is not set, sets
I_PINNING_FSCACHE_WB and calls fscache_use_cookie() to pin the cache
resources.
(4) A function, fscache_unpin_writeback(), to be called by ->write_inode()
to unuse the cookie.
(5) A function, fscache_clear_inode_writeback(), to be called when the
inode is evicted, before clear_inode() is called. This cleans up any
lingering I_PINNING_FSCACHE_WB.
The network filesystem can then use these tools to make sure that
fscache_write_to_cache() can write locally modified data to the cache as
well as to the server.
For the future, I'm working on write helpers for netfs lib that should
allow this facility to be removed by keeping track of the dirty regions
separately - but that's incomplete at the moment and is also going to be
affected by folios, one way or another, since it deals with pages
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819615157.215744.17623791756928043114.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906917856.143852.8224898306177154573.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967124567.1823006.14188359004568060298.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021524705.640689.17824932021727663017.stgit@warthog.procyon.org.uk/ # v4
2021-10-21 06:50:01 +08:00
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*
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2022-02-10 04:22:01 +08:00
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* Return: true if the dirty flag was set on the folio, false otherwise.
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vfs, fscache: Implement pinning of cache usage for writeback
Cachefiles has a problem in that it needs to keep the backing file for a
cookie open whilst there are local modifications pending that need to be
written to it. However, we don't want to keep the file open indefinitely,
as that causes EMFILE/ENFILE/ENOMEM problems.
Reopening the cache file, however, is a problem if this is being done due
to writeback triggered by exit(). Some filesystems will oops if we try to
open a file in that context because they want to access current->fs or
other resources that have already been dismantled.
To get around this, I added the following:
(1) An inode flag, I_PINNING_FSCACHE_WB, to be set on a network filesystem
inode to indicate that we have a usage count on the cookie caching
that inode.
(2) A flag in struct writeback_control, unpinned_fscache_wb, that is set
when __writeback_single_inode() clears the last dirty page from
i_pages - at which point it clears I_PINNING_FSCACHE_WB and sets this
flag.
This has to be done here so that clearing I_PINNING_FSCACHE_WB can be
done atomically with the check of PAGECACHE_TAG_DIRTY that clears
I_DIRTY_PAGES.
(3) A function, fscache_set_page_dirty(), which if it is not set, sets
I_PINNING_FSCACHE_WB and calls fscache_use_cookie() to pin the cache
resources.
(4) A function, fscache_unpin_writeback(), to be called by ->write_inode()
to unuse the cookie.
(5) A function, fscache_clear_inode_writeback(), to be called when the
inode is evicted, before clear_inode() is called. This cleans up any
lingering I_PINNING_FSCACHE_WB.
The network filesystem can then use these tools to make sure that
fscache_write_to_cache() can write locally modified data to the cache as
well as to the server.
For the future, I'm working on write helpers for netfs lib that should
allow this facility to be removed by keeping track of the dirty regions
separately - but that's incomplete at the moment and is also going to be
affected by folios, one way or another, since it deals with pages
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819615157.215744.17623791756928043114.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906917856.143852.8224898306177154573.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967124567.1823006.14188359004568060298.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021524705.640689.17824932021727663017.stgit@warthog.procyon.org.uk/ # v4
2021-10-21 06:50:01 +08:00
|
|
|
*/
|
2022-02-10 04:22:01 +08:00
|
|
|
bool fscache_dirty_folio(struct address_space *mapping, struct folio *folio,
|
|
|
|
struct fscache_cookie *cookie)
|
vfs, fscache: Implement pinning of cache usage for writeback
Cachefiles has a problem in that it needs to keep the backing file for a
cookie open whilst there are local modifications pending that need to be
written to it. However, we don't want to keep the file open indefinitely,
as that causes EMFILE/ENFILE/ENOMEM problems.
Reopening the cache file, however, is a problem if this is being done due
to writeback triggered by exit(). Some filesystems will oops if we try to
open a file in that context because they want to access current->fs or
other resources that have already been dismantled.
To get around this, I added the following:
(1) An inode flag, I_PINNING_FSCACHE_WB, to be set on a network filesystem
inode to indicate that we have a usage count on the cookie caching
that inode.
(2) A flag in struct writeback_control, unpinned_fscache_wb, that is set
when __writeback_single_inode() clears the last dirty page from
i_pages - at which point it clears I_PINNING_FSCACHE_WB and sets this
flag.
This has to be done here so that clearing I_PINNING_FSCACHE_WB can be
done atomically with the check of PAGECACHE_TAG_DIRTY that clears
I_DIRTY_PAGES.
(3) A function, fscache_set_page_dirty(), which if it is not set, sets
I_PINNING_FSCACHE_WB and calls fscache_use_cookie() to pin the cache
resources.
(4) A function, fscache_unpin_writeback(), to be called by ->write_inode()
to unuse the cookie.
(5) A function, fscache_clear_inode_writeback(), to be called when the
inode is evicted, before clear_inode() is called. This cleans up any
lingering I_PINNING_FSCACHE_WB.
The network filesystem can then use these tools to make sure that
fscache_write_to_cache() can write locally modified data to the cache as
well as to the server.
For the future, I'm working on write helpers for netfs lib that should
allow this facility to be removed by keeping track of the dirty regions
separately - but that's incomplete at the moment and is also going to be
affected by folios, one way or another, since it deals with pages
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819615157.215744.17623791756928043114.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906917856.143852.8224898306177154573.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967124567.1823006.14188359004568060298.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021524705.640689.17824932021727663017.stgit@warthog.procyon.org.uk/ # v4
2021-10-21 06:50:01 +08:00
|
|
|
{
|
2022-02-10 04:22:01 +08:00
|
|
|
struct inode *inode = mapping->host;
|
vfs, fscache: Implement pinning of cache usage for writeback
Cachefiles has a problem in that it needs to keep the backing file for a
cookie open whilst there are local modifications pending that need to be
written to it. However, we don't want to keep the file open indefinitely,
as that causes EMFILE/ENFILE/ENOMEM problems.
Reopening the cache file, however, is a problem if this is being done due
to writeback triggered by exit(). Some filesystems will oops if we try to
open a file in that context because they want to access current->fs or
other resources that have already been dismantled.
To get around this, I added the following:
(1) An inode flag, I_PINNING_FSCACHE_WB, to be set on a network filesystem
inode to indicate that we have a usage count on the cookie caching
that inode.
(2) A flag in struct writeback_control, unpinned_fscache_wb, that is set
when __writeback_single_inode() clears the last dirty page from
i_pages - at which point it clears I_PINNING_FSCACHE_WB and sets this
flag.
This has to be done here so that clearing I_PINNING_FSCACHE_WB can be
done atomically with the check of PAGECACHE_TAG_DIRTY that clears
I_DIRTY_PAGES.
(3) A function, fscache_set_page_dirty(), which if it is not set, sets
I_PINNING_FSCACHE_WB and calls fscache_use_cookie() to pin the cache
resources.
(4) A function, fscache_unpin_writeback(), to be called by ->write_inode()
to unuse the cookie.
(5) A function, fscache_clear_inode_writeback(), to be called when the
inode is evicted, before clear_inode() is called. This cleans up any
lingering I_PINNING_FSCACHE_WB.
The network filesystem can then use these tools to make sure that
fscache_write_to_cache() can write locally modified data to the cache as
well as to the server.
For the future, I'm working on write helpers for netfs lib that should
allow this facility to be removed by keeping track of the dirty regions
separately - but that's incomplete at the moment and is also going to be
affected by folios, one way or another, since it deals with pages
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819615157.215744.17623791756928043114.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906917856.143852.8224898306177154573.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967124567.1823006.14188359004568060298.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021524705.640689.17824932021727663017.stgit@warthog.procyon.org.uk/ # v4
2021-10-21 06:50:01 +08:00
|
|
|
bool need_use = false;
|
|
|
|
|
|
|
|
_enter("");
|
|
|
|
|
2022-02-10 04:22:01 +08:00
|
|
|
if (!filemap_dirty_folio(mapping, folio))
|
|
|
|
return false;
|
vfs, fscache: Implement pinning of cache usage for writeback
Cachefiles has a problem in that it needs to keep the backing file for a
cookie open whilst there are local modifications pending that need to be
written to it. However, we don't want to keep the file open indefinitely,
as that causes EMFILE/ENFILE/ENOMEM problems.
Reopening the cache file, however, is a problem if this is being done due
to writeback triggered by exit(). Some filesystems will oops if we try to
open a file in that context because they want to access current->fs or
other resources that have already been dismantled.
To get around this, I added the following:
(1) An inode flag, I_PINNING_FSCACHE_WB, to be set on a network filesystem
inode to indicate that we have a usage count on the cookie caching
that inode.
(2) A flag in struct writeback_control, unpinned_fscache_wb, that is set
when __writeback_single_inode() clears the last dirty page from
i_pages - at which point it clears I_PINNING_FSCACHE_WB and sets this
flag.
This has to be done here so that clearing I_PINNING_FSCACHE_WB can be
done atomically with the check of PAGECACHE_TAG_DIRTY that clears
I_DIRTY_PAGES.
(3) A function, fscache_set_page_dirty(), which if it is not set, sets
I_PINNING_FSCACHE_WB and calls fscache_use_cookie() to pin the cache
resources.
(4) A function, fscache_unpin_writeback(), to be called by ->write_inode()
to unuse the cookie.
(5) A function, fscache_clear_inode_writeback(), to be called when the
inode is evicted, before clear_inode() is called. This cleans up any
lingering I_PINNING_FSCACHE_WB.
The network filesystem can then use these tools to make sure that
fscache_write_to_cache() can write locally modified data to the cache as
well as to the server.
For the future, I'm working on write helpers for netfs lib that should
allow this facility to be removed by keeping track of the dirty regions
separately - but that's incomplete at the moment and is also going to be
affected by folios, one way or another, since it deals with pages
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819615157.215744.17623791756928043114.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906917856.143852.8224898306177154573.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967124567.1823006.14188359004568060298.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021524705.640689.17824932021727663017.stgit@warthog.procyon.org.uk/ # v4
2021-10-21 06:50:01 +08:00
|
|
|
if (!fscache_cookie_valid(cookie))
|
2022-02-10 04:22:01 +08:00
|
|
|
return true;
|
vfs, fscache: Implement pinning of cache usage for writeback
Cachefiles has a problem in that it needs to keep the backing file for a
cookie open whilst there are local modifications pending that need to be
written to it. However, we don't want to keep the file open indefinitely,
as that causes EMFILE/ENFILE/ENOMEM problems.
Reopening the cache file, however, is a problem if this is being done due
to writeback triggered by exit(). Some filesystems will oops if we try to
open a file in that context because they want to access current->fs or
other resources that have already been dismantled.
To get around this, I added the following:
(1) An inode flag, I_PINNING_FSCACHE_WB, to be set on a network filesystem
inode to indicate that we have a usage count on the cookie caching
that inode.
(2) A flag in struct writeback_control, unpinned_fscache_wb, that is set
when __writeback_single_inode() clears the last dirty page from
i_pages - at which point it clears I_PINNING_FSCACHE_WB and sets this
flag.
This has to be done here so that clearing I_PINNING_FSCACHE_WB can be
done atomically with the check of PAGECACHE_TAG_DIRTY that clears
I_DIRTY_PAGES.
(3) A function, fscache_set_page_dirty(), which if it is not set, sets
I_PINNING_FSCACHE_WB and calls fscache_use_cookie() to pin the cache
resources.
(4) A function, fscache_unpin_writeback(), to be called by ->write_inode()
to unuse the cookie.
(5) A function, fscache_clear_inode_writeback(), to be called when the
inode is evicted, before clear_inode() is called. This cleans up any
lingering I_PINNING_FSCACHE_WB.
The network filesystem can then use these tools to make sure that
fscache_write_to_cache() can write locally modified data to the cache as
well as to the server.
For the future, I'm working on write helpers for netfs lib that should
allow this facility to be removed by keeping track of the dirty regions
separately - but that's incomplete at the moment and is also going to be
affected by folios, one way or another, since it deals with pages
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819615157.215744.17623791756928043114.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906917856.143852.8224898306177154573.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967124567.1823006.14188359004568060298.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021524705.640689.17824932021727663017.stgit@warthog.procyon.org.uk/ # v4
2021-10-21 06:50:01 +08:00
|
|
|
|
|
|
|
if (!(inode->i_state & I_PINNING_FSCACHE_WB)) {
|
|
|
|
spin_lock(&inode->i_lock);
|
|
|
|
if (!(inode->i_state & I_PINNING_FSCACHE_WB)) {
|
|
|
|
inode->i_state |= I_PINNING_FSCACHE_WB;
|
|
|
|
need_use = true;
|
|
|
|
}
|
|
|
|
spin_unlock(&inode->i_lock);
|
|
|
|
|
|
|
|
if (need_use)
|
|
|
|
fscache_use_cookie(cookie, true);
|
|
|
|
}
|
2022-02-10 04:22:01 +08:00
|
|
|
return true;
|
vfs, fscache: Implement pinning of cache usage for writeback
Cachefiles has a problem in that it needs to keep the backing file for a
cookie open whilst there are local modifications pending that need to be
written to it. However, we don't want to keep the file open indefinitely,
as that causes EMFILE/ENFILE/ENOMEM problems.
Reopening the cache file, however, is a problem if this is being done due
to writeback triggered by exit(). Some filesystems will oops if we try to
open a file in that context because they want to access current->fs or
other resources that have already been dismantled.
To get around this, I added the following:
(1) An inode flag, I_PINNING_FSCACHE_WB, to be set on a network filesystem
inode to indicate that we have a usage count on the cookie caching
that inode.
(2) A flag in struct writeback_control, unpinned_fscache_wb, that is set
when __writeback_single_inode() clears the last dirty page from
i_pages - at which point it clears I_PINNING_FSCACHE_WB and sets this
flag.
This has to be done here so that clearing I_PINNING_FSCACHE_WB can be
done atomically with the check of PAGECACHE_TAG_DIRTY that clears
I_DIRTY_PAGES.
(3) A function, fscache_set_page_dirty(), which if it is not set, sets
I_PINNING_FSCACHE_WB and calls fscache_use_cookie() to pin the cache
resources.
(4) A function, fscache_unpin_writeback(), to be called by ->write_inode()
to unuse the cookie.
(5) A function, fscache_clear_inode_writeback(), to be called when the
inode is evicted, before clear_inode() is called. This cleans up any
lingering I_PINNING_FSCACHE_WB.
The network filesystem can then use these tools to make sure that
fscache_write_to_cache() can write locally modified data to the cache as
well as to the server.
For the future, I'm working on write helpers for netfs lib that should
allow this facility to be removed by keeping track of the dirty regions
separately - but that's incomplete at the moment and is also going to be
affected by folios, one way or another, since it deals with pages
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819615157.215744.17623791756928043114.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906917856.143852.8224898306177154573.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967124567.1823006.14188359004568060298.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021524705.640689.17824932021727663017.stgit@warthog.procyon.org.uk/ # v4
2021-10-21 06:50:01 +08:00
|
|
|
}
|
2022-02-10 04:22:01 +08:00
|
|
|
EXPORT_SYMBOL(fscache_dirty_folio);
|
vfs, fscache: Implement pinning of cache usage for writeback
Cachefiles has a problem in that it needs to keep the backing file for a
cookie open whilst there are local modifications pending that need to be
written to it. However, we don't want to keep the file open indefinitely,
as that causes EMFILE/ENFILE/ENOMEM problems.
Reopening the cache file, however, is a problem if this is being done due
to writeback triggered by exit(). Some filesystems will oops if we try to
open a file in that context because they want to access current->fs or
other resources that have already been dismantled.
To get around this, I added the following:
(1) An inode flag, I_PINNING_FSCACHE_WB, to be set on a network filesystem
inode to indicate that we have a usage count on the cookie caching
that inode.
(2) A flag in struct writeback_control, unpinned_fscache_wb, that is set
when __writeback_single_inode() clears the last dirty page from
i_pages - at which point it clears I_PINNING_FSCACHE_WB and sets this
flag.
This has to be done here so that clearing I_PINNING_FSCACHE_WB can be
done atomically with the check of PAGECACHE_TAG_DIRTY that clears
I_DIRTY_PAGES.
(3) A function, fscache_set_page_dirty(), which if it is not set, sets
I_PINNING_FSCACHE_WB and calls fscache_use_cookie() to pin the cache
resources.
(4) A function, fscache_unpin_writeback(), to be called by ->write_inode()
to unuse the cookie.
(5) A function, fscache_clear_inode_writeback(), to be called when the
inode is evicted, before clear_inode() is called. This cleans up any
lingering I_PINNING_FSCACHE_WB.
The network filesystem can then use these tools to make sure that
fscache_write_to_cache() can write locally modified data to the cache as
well as to the server.
For the future, I'm working on write helpers for netfs lib that should
allow this facility to be removed by keeping track of the dirty regions
separately - but that's incomplete at the moment and is also going to be
affected by folios, one way or another, since it deals with pages
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819615157.215744.17623791756928043114.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906917856.143852.8224898306177154573.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967124567.1823006.14188359004568060298.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021524705.640689.17824932021727663017.stgit@warthog.procyon.org.uk/ # v4
2021-10-21 06:50:01 +08:00
|
|
|
|
fscache: Implement higher-level write I/O interface
Provide a higher-level function than fscache_write() to perform a write
from an inode's pagecache to the cache, whilst fending off concurrent
writes by means of the PG_fscache mark on a page:
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 caching);
If caching is false, this function does nothing except call (*term_func)()
if given. It assumes that, in such a case, PG_fscache will not have been
set on the pages.
Otherwise, if caching is true, this function requires the source pages to
have had PG_fscache set on them before calling. start and len define the
region of the file to be modified and i_size indicates the new file size.
The source pages are extracted from the mapping.
term_func and term_func_priv work as for fscache_write(). The PG_fscache
marks will be cleared at the end of the operation, before term_func is
called or the function otherwise returns.
There is an additonal helper function to clear the PG_fscache bits from a
range of pages:
void fscache_clear_page_bits(struct fscache_cookie *cookie,
struct address_space *mapping,
loff_t start, size_t len,
bool caching);
If caching is true, the pages to be managed are expected to be located on
mapping in the range defined by start and len. If caching is false, it
does nothing.
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819614155.215744.5528123235123721230.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906916346.143852.15632773570362489926.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967123599.1823006.12946816026724657428.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021522672.640689.4381958316198807813.stgit@warthog.procyon.org.uk/ # v4
2021-10-20 21:06:34 +08:00
|
|
|
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;
|
|
|
|
|
2022-04-06 11:50:17 +08:00
|
|
|
fscache_clear_page_bits(wreq->mapping, wreq->start, wreq->len,
|
fscache: Implement higher-level write I/O interface
Provide a higher-level function than fscache_write() to perform a write
from an inode's pagecache to the cache, whilst fending off concurrent
writes by means of the PG_fscache mark on a page:
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 caching);
If caching is false, this function does nothing except call (*term_func)()
if given. It assumes that, in such a case, PG_fscache will not have been
set on the pages.
Otherwise, if caching is true, this function requires the source pages to
have had PG_fscache set on them before calling. start and len define the
region of the file to be modified and i_size indicates the new file size.
The source pages are extracted from the mapping.
term_func and term_func_priv work as for fscache_write(). The PG_fscache
marks will be cleared at the end of the operation, before term_func is
called or the function otherwise returns.
There is an additonal helper function to clear the PG_fscache bits from a
range of pages:
void fscache_clear_page_bits(struct fscache_cookie *cookie,
struct address_space *mapping,
loff_t start, size_t len,
bool caching);
If caching is true, the pages to be managed are expected to be located on
mapping in the range defined by start and len. If caching is false, it
does nothing.
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819614155.215744.5528123235123721230.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906916346.143852.15632773570362489926.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967123599.1823006.12946816026724657428.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021522672.640689.4381958316198807813.stgit@warthog.procyon.org.uk/ # v4
2021-10-20 21:06:34 +08:00
|
|
|
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, 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.
|
|
|
|
*/
|
|
|
|
|
2022-09-16 08:25:47 +08:00
|
|
|
iov_iter_xarray(&iter, ITER_SOURCE, &mapping->i_pages, start, len);
|
fscache: Implement higher-level write I/O interface
Provide a higher-level function than fscache_write() to perform a write
from an inode's pagecache to the cache, whilst fending off concurrent
writes by means of the PG_fscache mark on a page:
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 caching);
If caching is false, this function does nothing except call (*term_func)()
if given. It assumes that, in such a case, PG_fscache will not have been
set on the pages.
Otherwise, if caching is true, this function requires the source pages to
have had PG_fscache set on them before calling. start and len define the
region of the file to be modified and i_size indicates the new file size.
The source pages are extracted from the mapping.
term_func and term_func_priv work as for fscache_write(). The PG_fscache
marks will be cleared at the end of the operation, before term_func is
called or the function otherwise returns.
There is an additonal helper function to clear the PG_fscache bits from a
range of pages:
void fscache_clear_page_bits(struct fscache_cookie *cookie,
struct address_space *mapping,
loff_t start, size_t len,
bool caching);
If caching is true, the pages to be managed are expected to be located on
mapping in the range defined by start and len. If caching is false, it
does nothing.
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819614155.215744.5528123235123721230.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906916346.143852.15632773570362489926.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967123599.1823006.12946816026724657428.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021522672.640689.4381958316198807813.stgit@warthog.procyon.org.uk/ # v4
2021-10-20 21:06:34 +08:00
|
|
|
fscache_write(cres, start, &iter, fscache_wreq_done, wreq);
|
|
|
|
return;
|
|
|
|
|
|
|
|
abandon_end:
|
|
|
|
return fscache_wreq_done(wreq, ret, false);
|
|
|
|
abandon_free:
|
|
|
|
kfree(wreq);
|
|
|
|
abandon:
|
2022-04-06 11:50:17 +08:00
|
|
|
fscache_clear_page_bits(mapping, start, len, cond);
|
fscache: Implement higher-level write I/O interface
Provide a higher-level function than fscache_write() to perform a write
from an inode's pagecache to the cache, whilst fending off concurrent
writes by means of the PG_fscache mark on a page:
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 caching);
If caching is false, this function does nothing except call (*term_func)()
if given. It assumes that, in such a case, PG_fscache will not have been
set on the pages.
Otherwise, if caching is true, this function requires the source pages to
have had PG_fscache set on them before calling. start and len define the
region of the file to be modified and i_size indicates the new file size.
The source pages are extracted from the mapping.
term_func and term_func_priv work as for fscache_write(). The PG_fscache
marks will be cleared at the end of the operation, before term_func is
called or the function otherwise returns.
There is an additonal helper function to clear the PG_fscache bits from a
range of pages:
void fscache_clear_page_bits(struct fscache_cookie *cookie,
struct address_space *mapping,
loff_t start, size_t len,
bool caching);
If caching is true, the pages to be managed are expected to be located on
mapping in the range defined by start and len. If caching is false, it
does nothing.
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819614155.215744.5528123235123721230.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906916346.143852.15632773570362489926.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967123599.1823006.12946816026724657428.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021522672.640689.4381958316198807813.stgit@warthog.procyon.org.uk/ # v4
2021-10-20 21:06:34 +08:00
|
|
|
if (term_func)
|
|
|
|
term_func(term_func_priv, ret, false);
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL(__fscache_write_to_cache);
|
2021-10-20 21:06:34 +08:00
|
|
|
|
|
|
|
/*
|
|
|
|
* 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);
|