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![Vladimir Davydov](/assets/img/avatar_default.png)
The limit equals 32 and is imposed by the number of entries in the
fs_poolid_map and shared_fs_poolid_map. Nowadays it is insufficient,
because with containers on board a Linux host can have hundreds of
active fs mounts.
These maps were introduced by commit 49a9ab815a
("mm: cleancache:
lazy initialization to allow tmem backends to build/run as modules") in
order to allow compiling cleancache drivers as modules. Real pool ids
are stored in these maps while super_block->cleancache_poolid points to
an entry in the map, so that on cleancache registration we can walk over
all (if there are <= 32 of them, of course) cleancache-enabled super
blocks and assign real pool ids.
Actually, there is absolutely no need in these maps, because we can
iterate over all super blocks immediately using iterate_supers. This is
not racy, because cleancache_init_ops is called from mount_fs with
super_block->s_umount held for writing, while iterate_supers takes this
semaphore for reading, so if we call iterate_supers after setting
cleancache_ops, all super blocks that had been created before
cleancache_register_ops was called will be assigned pool ids by the
action function of iterate_supers while all newer super blocks will
receive it in cleancache_init_fs.
This patch therefore removes the maps and hence the artificial limit on
the number of cleancache enabled filesystems.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Stefan Hengelein <ilendir@googlemail.com>
Cc: Florian Schmaus <fschmaus@gmail.com>
Cc: Andor Daam <andor.daam@googlemail.com>
Cc: Dan Magenheimer <dan.magenheimer@oracle.com>
Cc: Bob Liu <lliubbo@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
319 lines
9.9 KiB
C
319 lines
9.9 KiB
C
/*
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* Cleancache frontend
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*
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* This code provides the generic "frontend" layer to call a matching
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* "backend" driver implementation of cleancache. See
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* Documentation/vm/cleancache.txt for more information.
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*
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* Copyright (C) 2009-2010 Oracle Corp. All rights reserved.
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* Author: Dan Magenheimer
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*
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* This work is licensed under the terms of the GNU GPL, version 2.
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*/
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#include <linux/module.h>
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#include <linux/fs.h>
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#include <linux/exportfs.h>
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#include <linux/mm.h>
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#include <linux/debugfs.h>
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#include <linux/cleancache.h>
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/*
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* cleancache_ops is set by cleancache_register_ops to contain the pointers
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* to the cleancache "backend" implementation functions.
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*/
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static struct cleancache_ops *cleancache_ops __read_mostly;
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/*
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* Counters available via /sys/kernel/debug/cleancache (if debugfs is
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* properly configured. These are for information only so are not protected
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* against increment races.
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*/
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static u64 cleancache_succ_gets;
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static u64 cleancache_failed_gets;
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static u64 cleancache_puts;
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static u64 cleancache_invalidates;
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static void cleancache_register_ops_sb(struct super_block *sb, void *unused)
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{
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switch (sb->cleancache_poolid) {
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case CLEANCACHE_NO_BACKEND:
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__cleancache_init_fs(sb);
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break;
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case CLEANCACHE_NO_BACKEND_SHARED:
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__cleancache_init_shared_fs(sb);
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break;
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}
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}
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/*
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* Register operations for cleancache. Returns 0 on success.
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*/
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int cleancache_register_ops(struct cleancache_ops *ops)
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{
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if (cmpxchg(&cleancache_ops, NULL, ops))
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return -EBUSY;
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/*
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* A cleancache backend can be built as a module and hence loaded after
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* a cleancache enabled filesystem has called cleancache_init_fs. To
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* handle such a scenario, here we call ->init_fs or ->init_shared_fs
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* for each active super block. To differentiate between local and
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* shared filesystems, we temporarily initialize sb->cleancache_poolid
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* to CLEANCACHE_NO_BACKEND or CLEANCACHE_NO_BACKEND_SHARED
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* respectively in case there is no backend registered at the time
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* cleancache_init_fs or cleancache_init_shared_fs is called.
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*
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* Since filesystems can be mounted concurrently with cleancache
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* backend registration, we have to be careful to guarantee that all
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* cleancache enabled filesystems that has been mounted by the time
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* cleancache_register_ops is called has got and all mounted later will
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* get cleancache_poolid. This is assured by the following statements
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* tied together:
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*
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* a) iterate_supers skips only those super blocks that has started
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* ->kill_sb
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*
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* b) if iterate_supers encounters a super block that has not finished
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* ->mount yet, it waits until it is finished
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*
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* c) cleancache_init_fs is called from ->mount and
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* cleancache_invalidate_fs is called from ->kill_sb
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*
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* d) we call iterate_supers after cleancache_ops has been set
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*
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* From a) it follows that if iterate_supers skips a super block, then
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* either the super block is already dead, in which case we do not need
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* to bother initializing cleancache for it, or it was mounted after we
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* initiated iterate_supers. In the latter case, it must have seen
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* cleancache_ops set according to d) and initialized cleancache from
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* ->mount by itself according to c). This proves that we call
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* ->init_fs at least once for each active super block.
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*
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* From b) and c) it follows that if iterate_supers encounters a super
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* block that has already started ->init_fs, it will wait until ->mount
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* and hence ->init_fs has finished, then check cleancache_poolid, see
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* that it has already been set and therefore do nothing. This proves
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* that we call ->init_fs no more than once for each super block.
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*
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* Combined together, the last two paragraphs prove the function
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* correctness.
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*
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* Note that various cleancache callbacks may proceed before this
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* function is called or even concurrently with it, but since
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* CLEANCACHE_NO_BACKEND is negative, they will all result in a noop
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* until the corresponding ->init_fs has been actually called and
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* cleancache_ops has been set.
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*/
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iterate_supers(cleancache_register_ops_sb, NULL);
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return 0;
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}
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EXPORT_SYMBOL(cleancache_register_ops);
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/* Called by a cleancache-enabled filesystem at time of mount */
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void __cleancache_init_fs(struct super_block *sb)
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{
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int pool_id = CLEANCACHE_NO_BACKEND;
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if (cleancache_ops) {
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pool_id = cleancache_ops->init_fs(PAGE_SIZE);
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if (pool_id < 0)
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pool_id = CLEANCACHE_NO_POOL;
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}
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sb->cleancache_poolid = pool_id;
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}
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EXPORT_SYMBOL(__cleancache_init_fs);
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/* Called by a cleancache-enabled clustered filesystem at time of mount */
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void __cleancache_init_shared_fs(struct super_block *sb)
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{
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int pool_id = CLEANCACHE_NO_BACKEND_SHARED;
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if (cleancache_ops) {
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pool_id = cleancache_ops->init_shared_fs(sb->s_uuid, PAGE_SIZE);
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if (pool_id < 0)
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pool_id = CLEANCACHE_NO_POOL;
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}
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sb->cleancache_poolid = pool_id;
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}
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EXPORT_SYMBOL(__cleancache_init_shared_fs);
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/*
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* If the filesystem uses exportable filehandles, use the filehandle as
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* the key, else use the inode number.
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*/
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static int cleancache_get_key(struct inode *inode,
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struct cleancache_filekey *key)
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{
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int (*fhfn)(struct inode *, __u32 *fh, int *, struct inode *);
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int len = 0, maxlen = CLEANCACHE_KEY_MAX;
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struct super_block *sb = inode->i_sb;
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key->u.ino = inode->i_ino;
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if (sb->s_export_op != NULL) {
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fhfn = sb->s_export_op->encode_fh;
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if (fhfn) {
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len = (*fhfn)(inode, &key->u.fh[0], &maxlen, NULL);
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if (len <= FILEID_ROOT || len == FILEID_INVALID)
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return -1;
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if (maxlen > CLEANCACHE_KEY_MAX)
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return -1;
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}
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}
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return 0;
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}
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/*
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* "Get" data from cleancache associated with the poolid/inode/index
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* that were specified when the data was put to cleanache and, if
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* successful, use it to fill the specified page with data and return 0.
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* The pageframe is unchanged and returns -1 if the get fails.
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* Page must be locked by caller.
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*
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* The function has two checks before any action is taken - whether
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* a backend is registered and whether the sb->cleancache_poolid
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* is correct.
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*/
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int __cleancache_get_page(struct page *page)
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{
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int ret = -1;
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int pool_id;
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struct cleancache_filekey key = { .u.key = { 0 } };
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if (!cleancache_ops) {
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cleancache_failed_gets++;
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goto out;
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}
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VM_BUG_ON_PAGE(!PageLocked(page), page);
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pool_id = page->mapping->host->i_sb->cleancache_poolid;
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if (pool_id < 0)
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goto out;
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if (cleancache_get_key(page->mapping->host, &key) < 0)
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goto out;
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ret = cleancache_ops->get_page(pool_id, key, page->index, page);
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if (ret == 0)
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cleancache_succ_gets++;
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else
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cleancache_failed_gets++;
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out:
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return ret;
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}
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EXPORT_SYMBOL(__cleancache_get_page);
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/*
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* "Put" data from a page to cleancache and associate it with the
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* (previously-obtained per-filesystem) poolid and the page's,
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* inode and page index. Page must be locked. Note that a put_page
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* always "succeeds", though a subsequent get_page may succeed or fail.
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*
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* The function has two checks before any action is taken - whether
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* a backend is registered and whether the sb->cleancache_poolid
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* is correct.
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*/
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void __cleancache_put_page(struct page *page)
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{
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int pool_id;
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struct cleancache_filekey key = { .u.key = { 0 } };
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if (!cleancache_ops) {
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cleancache_puts++;
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return;
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}
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VM_BUG_ON_PAGE(!PageLocked(page), page);
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pool_id = page->mapping->host->i_sb->cleancache_poolid;
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if (pool_id >= 0 &&
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cleancache_get_key(page->mapping->host, &key) >= 0) {
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cleancache_ops->put_page(pool_id, key, page->index, page);
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cleancache_puts++;
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}
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}
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EXPORT_SYMBOL(__cleancache_put_page);
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/*
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* Invalidate any data from cleancache associated with the poolid and the
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* page's inode and page index so that a subsequent "get" will fail.
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*
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* The function has two checks before any action is taken - whether
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* a backend is registered and whether the sb->cleancache_poolid
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* is correct.
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*/
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void __cleancache_invalidate_page(struct address_space *mapping,
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struct page *page)
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{
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/* careful... page->mapping is NULL sometimes when this is called */
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int pool_id = mapping->host->i_sb->cleancache_poolid;
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struct cleancache_filekey key = { .u.key = { 0 } };
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if (!cleancache_ops)
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return;
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if (pool_id >= 0) {
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VM_BUG_ON_PAGE(!PageLocked(page), page);
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if (cleancache_get_key(mapping->host, &key) >= 0) {
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cleancache_ops->invalidate_page(pool_id,
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key, page->index);
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cleancache_invalidates++;
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}
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}
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}
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EXPORT_SYMBOL(__cleancache_invalidate_page);
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/*
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* Invalidate all data from cleancache associated with the poolid and the
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* mappings's inode so that all subsequent gets to this poolid/inode
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* will fail.
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*
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* The function has two checks before any action is taken - whether
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* a backend is registered and whether the sb->cleancache_poolid
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* is correct.
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*/
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void __cleancache_invalidate_inode(struct address_space *mapping)
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{
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int pool_id = mapping->host->i_sb->cleancache_poolid;
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struct cleancache_filekey key = { .u.key = { 0 } };
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if (!cleancache_ops)
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return;
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if (pool_id >= 0 && cleancache_get_key(mapping->host, &key) >= 0)
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cleancache_ops->invalidate_inode(pool_id, key);
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}
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EXPORT_SYMBOL(__cleancache_invalidate_inode);
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/*
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* Called by any cleancache-enabled filesystem at time of unmount;
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* note that pool_id is surrendered and may be returned by a subsequent
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* cleancache_init_fs or cleancache_init_shared_fs.
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*/
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void __cleancache_invalidate_fs(struct super_block *sb)
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{
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int pool_id;
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pool_id = sb->cleancache_poolid;
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sb->cleancache_poolid = CLEANCACHE_NO_POOL;
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if (cleancache_ops && pool_id >= 0)
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cleancache_ops->invalidate_fs(pool_id);
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}
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EXPORT_SYMBOL(__cleancache_invalidate_fs);
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static int __init init_cleancache(void)
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{
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#ifdef CONFIG_DEBUG_FS
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struct dentry *root = debugfs_create_dir("cleancache", NULL);
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if (root == NULL)
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return -ENXIO;
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debugfs_create_u64("succ_gets", S_IRUGO, root, &cleancache_succ_gets);
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debugfs_create_u64("failed_gets", S_IRUGO,
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root, &cleancache_failed_gets);
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debugfs_create_u64("puts", S_IRUGO, root, &cleancache_puts);
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debugfs_create_u64("invalidates", S_IRUGO,
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root, &cleancache_invalidates);
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#endif
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return 0;
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}
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module_init(init_cleancache)
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