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3cb29d1117
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>
125 lines
3.9 KiB
C
125 lines
3.9 KiB
C
#ifndef _LINUX_CLEANCACHE_H
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#define _LINUX_CLEANCACHE_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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#define CLEANCACHE_NO_POOL -1
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#define CLEANCACHE_NO_BACKEND -2
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#define CLEANCACHE_NO_BACKEND_SHARED -3
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#define CLEANCACHE_KEY_MAX 6
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/*
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* cleancache requires every file with a page in cleancache to have a
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* unique key unless/until the file is removed/truncated. For some
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* filesystems, the inode number is unique, but for "modern" filesystems
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* an exportable filehandle is required (see exportfs.h)
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*/
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struct cleancache_filekey {
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union {
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ino_t ino;
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__u32 fh[CLEANCACHE_KEY_MAX];
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u32 key[CLEANCACHE_KEY_MAX];
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} u;
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};
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struct cleancache_ops {
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int (*init_fs)(size_t);
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int (*init_shared_fs)(char *uuid, size_t);
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int (*get_page)(int, struct cleancache_filekey,
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pgoff_t, struct page *);
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void (*put_page)(int, struct cleancache_filekey,
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pgoff_t, struct page *);
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void (*invalidate_page)(int, struct cleancache_filekey, pgoff_t);
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void (*invalidate_inode)(int, struct cleancache_filekey);
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void (*invalidate_fs)(int);
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};
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extern int cleancache_register_ops(struct cleancache_ops *ops);
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extern void __cleancache_init_fs(struct super_block *);
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extern void __cleancache_init_shared_fs(struct super_block *);
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extern int __cleancache_get_page(struct page *);
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extern void __cleancache_put_page(struct page *);
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extern void __cleancache_invalidate_page(struct address_space *, struct page *);
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extern void __cleancache_invalidate_inode(struct address_space *);
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extern void __cleancache_invalidate_fs(struct super_block *);
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#ifdef CONFIG_CLEANCACHE
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#define cleancache_enabled (1)
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static inline bool cleancache_fs_enabled(struct page *page)
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{
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return page->mapping->host->i_sb->cleancache_poolid >= 0;
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}
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static inline bool cleancache_fs_enabled_mapping(struct address_space *mapping)
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{
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return mapping->host->i_sb->cleancache_poolid >= 0;
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}
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#else
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#define cleancache_enabled (0)
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#define cleancache_fs_enabled(_page) (0)
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#define cleancache_fs_enabled_mapping(_page) (0)
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#endif
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/*
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* The shim layer provided by these inline functions allows the compiler
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* to reduce all cleancache hooks to nothingness if CONFIG_CLEANCACHE
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* is disabled, to a single global variable check if CONFIG_CLEANCACHE
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* is enabled but no cleancache "backend" has dynamically enabled it,
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* and, for the most frequent cleancache ops, to a single global variable
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* check plus a superblock element comparison if CONFIG_CLEANCACHE is enabled
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* and a cleancache backend has dynamically enabled cleancache, but the
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* filesystem referenced by that cleancache op has not enabled cleancache.
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* As a result, CONFIG_CLEANCACHE can be enabled by default with essentially
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* no measurable performance impact.
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*/
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static inline void cleancache_init_fs(struct super_block *sb)
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{
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if (cleancache_enabled)
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__cleancache_init_fs(sb);
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}
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static inline void cleancache_init_shared_fs(struct super_block *sb)
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{
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if (cleancache_enabled)
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__cleancache_init_shared_fs(sb);
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}
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static inline int cleancache_get_page(struct page *page)
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{
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int ret = -1;
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if (cleancache_enabled && cleancache_fs_enabled(page))
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ret = __cleancache_get_page(page);
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return ret;
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}
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static inline void cleancache_put_page(struct page *page)
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{
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if (cleancache_enabled && cleancache_fs_enabled(page))
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__cleancache_put_page(page);
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}
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static inline 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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if (cleancache_enabled && cleancache_fs_enabled_mapping(mapping))
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__cleancache_invalidate_page(mapping, page);
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}
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static inline void cleancache_invalidate_inode(struct address_space *mapping)
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{
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if (cleancache_enabled && cleancache_fs_enabled_mapping(mapping))
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__cleancache_invalidate_inode(mapping);
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}
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static inline void cleancache_invalidate_fs(struct super_block *sb)
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{
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if (cleancache_enabled)
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__cleancache_invalidate_fs(sb);
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}
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#endif /* _LINUX_CLEANCACHE_H */
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