From e0c9143ea1ec510a41b347be043e98034eedf5c8 Mon Sep 17 00:00:00 2001 From: SecureCRT Date: Mon, 20 Aug 2012 00:49:43 +0800 Subject: [PATCH] mm: cleancache core ops functions and config --- Documentation/vm/cleancache.txt | 279 ++++++++++++++++++++++++++++++++ include/linux/cleancache.h | 122 ++++++++++++++ mm/Kconfig | 22 +++ mm/Makefile | 1 + mm/cleancache.c | 244 ++++++++++++++++++++++++++++ 5 files changed, 668 insertions(+) create mode 100755 Documentation/vm/cleancache.txt create mode 100755 include/linux/cleancache.h mode change 100644 => 100755 mm/Kconfig mode change 100644 => 100755 mm/Makefile create mode 100755 mm/cleancache.c diff --git a/Documentation/vm/cleancache.txt b/Documentation/vm/cleancache.txt new file mode 100755 index 00000000..e0a53567 --- /dev/null +++ b/Documentation/vm/cleancache.txt @@ -0,0 +1,279 @@ +MOTIVATION + +Cleancache is a new optional feature provided by the VFS layer that +potentially dramatically increases page cache effectiveness for +many workloads in many environments at a negligible cost. + +Cleancache can be thought of as a page-granularity victim cache for clean +pages that the kernel's pageframe replacement algorithm (PFRA) would like +to keep around, but can't since there isn't enough memory. So when the +PFRA "evicts" a page, it first attempts to use cleancache code to +put the data contained in that page into "transcendent memory", memory +that is not directly accessible or addressable by the kernel and is +of unknown and possibly time-varying size. + +Later, when a cleancache-enabled filesystem wishes to access a page +in a file on disk, it first checks cleancache to see if it already +contains it; if it does, the page of data is copied into the kernel +and a disk access is avoided. + +Transcendent memory "drivers" for cleancache are currently implemented +in Xen (using hypervisor memory) and zcache (using in-kernel compressed +memory) and other implementations are in development. + +FAQs are included below. + +IMPLEMENTATION OVERVIEW + +A cleancache "backend" that provides transcendent memory registers itself +to the kernel's cleancache "frontend" by calling cleancache_register_ops, +passing a pointer to a cleancache_ops structure with funcs set appropriately. +Note that cleancache_register_ops returns the previous settings so that +chaining can be performed if desired. The functions provided must conform to +certain semantics as follows: + +Most important, cleancache is "ephemeral". Pages which are copied into +cleancache have an indefinite lifetime which is completely unknowable +by the kernel and so may or may not still be in cleancache at any later time. +Thus, as its name implies, cleancache is not suitable for dirty pages. +Cleancache has complete discretion over what pages to preserve and what +pages to discard and when. + +Mounting a cleancache-enabled filesystem should call "init_fs" to obtain a +pool id which, if positive, must be saved in the filesystem's superblock; +a negative return value indicates failure. A "put_page" will copy a +(presumably about-to-be-evicted) page into cleancache and associate it with +the pool id, a file key, and a page index into the file. (The combination +of a pool id, a file key, and an index is sometimes called a "handle".) +A "get_page" will copy the page, if found, from cleancache into kernel memory. +An "invalidate_page" will ensure the page no longer is present in cleancache; +an "invalidate_inode" will invalidate all pages associated with the specified +file; and, when a filesystem is unmounted, an "invalidate_fs" will invalidate +all pages in all files specified by the given pool id and also surrender +the pool id. + +An "init_shared_fs", like init_fs, obtains a pool id but tells cleancache +to treat the pool as shared using a 128-bit UUID as a key. On systems +that may run multiple kernels (such as hard partitioned or virtualized +systems) that may share a clustered filesystem, and where cleancache +may be shared among those kernels, calls to init_shared_fs that specify the +same UUID will receive the same pool id, thus allowing the pages to +be shared. Note that any security requirements must be imposed outside +of the kernel (e.g. by "tools" that control cleancache). Or a +cleancache implementation can simply disable shared_init by always +returning a negative value. + +If a get_page is successful on a non-shared pool, the page is invalidated +(thus making cleancache an "exclusive" cache). On a shared pool, the page +is NOT invalidated on a successful get_page so that it remains accessible to +other sharers. The kernel is responsible for ensuring coherency between +cleancache (shared or not), the page cache, and the filesystem, using +cleancache invalidate operations as required. + +Note that cleancache must enforce put-put-get coherency and get-get +coherency. For the former, if two puts are made to the same handle but +with different data, say AAA by the first put and BBB by the second, a +subsequent get can never return the stale data (AAA). For get-get coherency, +if a get for a given handle fails, subsequent gets for that handle will +never succeed unless preceded by a successful put with that handle. + +Last, cleancache provides no SMP serialization guarantees; if two +different Linux threads are simultaneously putting and invalidating a page +with the same handle, the results are indeterminate. Callers must +lock the page to ensure serial behavior. + +CLEANCACHE PERFORMANCE METRICS + +Cleancache monitoring is done by sysfs files in the +/sys/kernel/mm/cleancache directory. The effectiveness of cleancache +can be measured (across all filesystems) with: + +succ_gets - number of gets that were successful +failed_gets - number of gets that failed +puts - number of puts attempted (all "succeed") +invalidates - number of invalidates attempted + +A backend implementatation may provide additional metrics. + +FAQ + +1) Where's the value? (Andrew Morton) + +Cleancache provides a significant performance benefit to many workloads +in many environments with negligible overhead by improving the +effectiveness of the pagecache. Clean pagecache pages are +saved in transcendent memory (RAM that is otherwise not directly +addressable to the kernel); fetching those pages later avoids "refaults" +and thus disk reads. + +Cleancache (and its sister code "frontswap") provide interfaces for +this transcendent memory (aka "tmem"), which conceptually lies between +fast kernel-directly-addressable RAM and slower DMA/asynchronous devices. +Disallowing direct kernel or userland reads/writes to tmem +is ideal when data is transformed to a different form and size (such +as with compression) or secretly moved (as might be useful for write- +balancing for some RAM-like devices). Evicted page-cache pages (and +swap pages) are a great use for this kind of slower-than-RAM-but-much- +faster-than-disk transcendent memory, and the cleancache (and frontswap) +"page-object-oriented" specification provides a nice way to read and +write -- and indirectly "name" -- the pages. + +In the virtual case, the whole point of virtualization is to statistically +multiplex physical resources across the varying demands of multiple +virtual machines. This is really hard to do with RAM and efforts to +do it well with no kernel change have essentially failed (except in some +well-publicized special-case workloads). Cleancache -- and frontswap -- +with a fairly small impact on the kernel, provide a huge amount +of flexibility for more dynamic, flexible RAM multiplexing. +Specifically, the Xen Transcendent Memory backend allows otherwise +"fallow" hypervisor-owned RAM to not only be "time-shared" between multiple +virtual machines, but the pages can be compressed and deduplicated to +optimize RAM utilization. And when guest OS's are induced to surrender +underutilized RAM (e.g. with "self-ballooning"), page cache pages +are the first to go, and cleancache allows those pages to be +saved and reclaimed if overall host system memory conditions allow. + +And the identical interface used for cleancache can be used in +physical systems as well. The zcache driver acts as a memory-hungry +device that stores pages of data in a compressed state. And +the proposed "RAMster" driver shares RAM across multiple physical +systems. + +2) Why does cleancache have its sticky fingers so deep inside the + filesystems and VFS? (Andrew Morton and Christoph Hellwig) + +The core hooks for cleancache in VFS are in most cases a single line +and the minimum set are placed precisely where needed to maintain +coherency (via cleancache_invalidate operations) between cleancache, +the page cache, and disk. All hooks compile into nothingness if +cleancache is config'ed off and turn into a function-pointer- +compare-to-NULL if config'ed on but no backend claims the ops +functions, or to a compare-struct-element-to-negative if a +backend claims the ops functions but a filesystem doesn't enable +cleancache. + +Some filesystems are built entirely on top of VFS and the hooks +in VFS are sufficient, so don't require an "init_fs" hook; the +initial implementation of cleancache didn't provide this hook. +But for some filesystems (such as btrfs), the VFS hooks are +incomplete and one or more hooks in fs-specific code are required. +And for some other filesystems, such as tmpfs, cleancache may +be counterproductive. So it seemed prudent to require a filesystem +to "opt in" to use cleancache, which requires adding a hook in +each filesystem. Not all filesystems are supported by cleancache +only because they haven't been tested. The existing set should +be sufficient to validate the concept, the opt-in approach means +that untested filesystems are not affected, and the hooks in the +existing filesystems should make it very easy to add more +filesystems in the future. + +The total impact of the hooks to existing fs and mm files is only +about 40 lines added (not counting comments and blank lines). + +3) Why not make cleancache asynchronous and batched so it can + more easily interface with real devices with DMA instead + of copying each individual page? (Minchan Kim) + +The one-page-at-a-time copy semantics simplifies the implementation +on both the frontend and backend and also allows the backend to +do fancy things on-the-fly like page compression and +page deduplication. And since the data is "gone" (copied into/out +of the pageframe) before the cleancache get/put call returns, +a great deal of race conditions and potential coherency issues +are avoided. While the interface seems odd for a "real device" +or for real kernel-addressable RAM, it makes perfect sense for +transcendent memory. + +4) Why is non-shared cleancache "exclusive"? And where is the + page "invalidated" after a "get"? (Minchan Kim) + +The main reason is to free up space in transcendent memory and +to avoid unnecessary cleancache_invalidate calls. If you want inclusive, +the page can be "put" immediately following the "get". If +put-after-get for inclusive becomes common, the interface could +be easily extended to add a "get_no_invalidate" call. + +The invalidate is done by the cleancache backend implementation. + +5) What's the performance impact? + +Performance analysis has been presented at OLS'09 and LCA'10. +Briefly, performance gains can be significant on most workloads, +especially when memory pressure is high (e.g. when RAM is +overcommitted in a virtual workload); and because the hooks are +invoked primarily in place of or in addition to a disk read/write, +overhead is negligible even in worst case workloads. Basically +cleancache replaces I/O with memory-copy-CPU-overhead; on older +single-core systems with slow memory-copy speeds, cleancache +has little value, but in newer multicore machines, especially +consolidated/virtualized machines, it has great value. + +6) How do I add cleancache support for filesystem X? (Boaz Harrash) + +Filesystems that are well-behaved and conform to certain +restrictions can utilize cleancache simply by making a call to +cleancache_init_fs at mount time. Unusual, misbehaving, or +poorly layered filesystems must either add additional hooks +and/or undergo extensive additional testing... or should just +not enable the optional cleancache. + +Some points for a filesystem to consider: + +- The FS should be block-device-based (e.g. a ram-based FS such + as tmpfs should not enable cleancache) +- To ensure coherency/correctness, the FS must ensure that all + file removal or truncation operations either go through VFS or + add hooks to do the equivalent cleancache "invalidate" operations +- To ensure coherency/correctness, either inode numbers must + be unique across the lifetime of the on-disk file OR the + FS must provide an "encode_fh" function. +- The FS must call the VFS superblock alloc and deactivate routines + or add hooks to do the equivalent cleancache calls done there. +- To maximize performance, all pages fetched from the FS should + go through the do_mpag_readpage routine or the FS should add + hooks to do the equivalent (cf. btrfs) +- Currently, the FS blocksize must be the same as PAGESIZE. This + is not an architectural restriction, but no backends currently + support anything different. +- A clustered FS should invoke the "shared_init_fs" cleancache + hook to get best performance for some backends. + +7) Why not use the KVA of the inode as the key? (Christoph Hellwig) + +If cleancache would use the inode virtual address instead of +inode/filehandle, the pool id could be eliminated. But, this +won't work because cleancache retains pagecache data pages +persistently even when the inode has been pruned from the +inode unused list, and only invalidates the data page if the file +gets removed/truncated. So if cleancache used the inode kva, +there would be potential coherency issues if/when the inode +kva is reused for a different file. Alternately, if cleancache +invalidated the pages when the inode kva was freed, much of the value +of cleancache would be lost because the cache of pages in cleanache +is potentially much larger than the kernel pagecache and is most +useful if the pages survive inode cache removal. + +8) Why is a global variable required? + +The cleancache_enabled flag is checked in all of the frequently-used +cleancache hooks. The alternative is a function call to check a static +variable. Since cleancache is enabled dynamically at runtime, systems +that don't enable cleancache would suffer thousands (possibly +tens-of-thousands) of unnecessary function calls per second. So the +global variable allows cleancache to be enabled by default at compile +time, but have insignificant performance impact when cleancache remains +disabled at runtime. + +9) Does cleanache work with KVM? + +The memory model of KVM is sufficiently different that a cleancache +backend may have less value for KVM. This remains to be tested, +especially in an overcommitted system. + +10) Does cleancache work in userspace? It sounds useful for + memory hungry caches like web browsers. (Jamie Lokier) + +No plans yet, though we agree it sounds useful, at least for +apps that bypass the page cache (e.g. O_DIRECT). + +Last updated: Dan Magenheimer, April 13 2011 diff --git a/include/linux/cleancache.h b/include/linux/cleancache.h new file mode 100755 index 00000000..04ffb2e6 --- /dev/null +++ b/include/linux/cleancache.h @@ -0,0 +1,122 @@ +#ifndef _LINUX_CLEANCACHE_H +#define _LINUX_CLEANCACHE_H + +#include +#include +#include + +#define CLEANCACHE_KEY_MAX 6 + +/* + * cleancache requires every file with a page in cleancache to have a + * unique key unless/until the file is removed/truncated. For some + * filesystems, the inode number is unique, but for "modern" filesystems + * an exportable filehandle is required (see exportfs.h) + */ +struct cleancache_filekey { + union { + ino_t ino; + __u32 fh[CLEANCACHE_KEY_MAX]; + u32 key[CLEANCACHE_KEY_MAX]; + } u; +}; + +struct cleancache_ops { + int (*init_fs)(size_t); + int (*init_shared_fs)(char *uuid, size_t); + int (*get_page)(int, struct cleancache_filekey, + pgoff_t, struct page *); + void (*put_page)(int, struct cleancache_filekey, + pgoff_t, struct page *); + void (*flush_page)(int, struct cleancache_filekey, pgoff_t); + void (*flush_inode)(int, struct cleancache_filekey); + void (*flush_fs)(int); +}; + +extern struct cleancache_ops + cleancache_register_ops(struct cleancache_ops *ops); +extern void __cleancache_init_fs(struct super_block *); +extern void __cleancache_init_shared_fs(char *, struct super_block *); +extern int __cleancache_get_page(struct page *); +extern void __cleancache_put_page(struct page *); +extern void __cleancache_flush_page(struct address_space *, struct page *); +extern void __cleancache_flush_inode(struct address_space *); +extern void __cleancache_flush_fs(struct super_block *); +extern int cleancache_enabled; + +#ifdef CONFIG_CLEANCACHE +static inline bool cleancache_fs_enabled(struct page *page) +{ + return page->mapping->host->i_sb->cleancache_poolid >= 0; +} +static inline bool cleancache_fs_enabled_mapping(struct address_space *mapping) +{ + return mapping->host->i_sb->cleancache_poolid >= 0; +} +#else +#define cleancache_enabled (0) +#define cleancache_fs_enabled(_page) (0) +#define cleancache_fs_enabled_mapping(_page) (0) +#endif + +/* + * The shim layer provided by these inline functions allows the compiler + * to reduce all cleancache hooks to nothingness if CONFIG_CLEANCACHE + * is disabled, to a single global variable check if CONFIG_CLEANCACHE + * is enabled but no cleancache "backend" has dynamically enabled it, + * and, for the most frequent cleancache ops, to a single global variable + * check plus a superblock element comparison if CONFIG_CLEANCACHE is enabled + * and a cleancache backend has dynamically enabled cleancache, but the + * filesystem referenced by that cleancache op has not enabled cleancache. + * As a result, CONFIG_CLEANCACHE can be enabled by default with essentially + * no measurable performance impact. + */ + +static inline void cleancache_init_fs(struct super_block *sb) +{ + if (cleancache_enabled) + __cleancache_init_fs(sb); +} + +static inline void cleancache_init_shared_fs(char *uuid, struct super_block *sb) +{ + if (cleancache_enabled) + __cleancache_init_shared_fs(uuid, sb); +} + +static inline int cleancache_get_page(struct page *page) +{ + int ret = -1; + + if (cleancache_enabled && cleancache_fs_enabled(page)) + ret = __cleancache_get_page(page); + return ret; +} + +static inline void cleancache_put_page(struct page *page) +{ + if (cleancache_enabled && cleancache_fs_enabled(page)) + __cleancache_put_page(page); +} + +static inline void cleancache_flush_page(struct address_space *mapping, + struct page *page) +{ + /* careful... page->mapping is NULL sometimes when this is called */ + if (cleancache_enabled && cleancache_fs_enabled_mapping(mapping)) + __cleancache_flush_page(mapping, page); +} + +static inline void cleancache_flush_inode(struct address_space *mapping) +{ + if (cleancache_enabled && cleancache_fs_enabled_mapping(mapping)) + __cleancache_flush_inode(mapping); +} + +static inline void cleancache_flush_fs(struct super_block *sb) +{ + if (cleancache_enabled) + __cleancache_flush_fs(sb); +} + +#endif /* _LINUX_CLEANCACHE_H */ diff --git a/mm/Kconfig b/mm/Kconfig old mode 100644 new mode 100755 index 2c19c0ba..f86e0d29 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -288,3 +288,25 @@ config NOMMU_INITIAL_TRIM_EXCESS of 1 says that all excess pages should be trimmed. See Documentation/nommu-mmap.txt for more information. +config CLEANCACHE + bool "Enable cleancache driver to cache clean pages if tmem is present" + default n + help + Cleancache can be thought of as a page-granularity victim cache + for clean pages that the kernel's pageframe replacement algorithm + (PFRA) would like to keep around, but can't since there isn't enough + memory. So when the PFRA "evicts" a page, it first attempts to use + cleancacne code to put the data contained in that page into + "transcendent memory", memory that is not directly accessible or + addressable by the kernel and is of unknown and possibly + time-varying size. And when a cleancache-enabled + filesystem wishes to access a page in a file on disk, it first + checks cleancache to see if it already contains it; if it does, + the page is copied into the kernel and a disk access is avoided. + When a transcendent memory driver is available (such as zcache or + Xen transcendent memory), a significant I/O reduction + may be achieved. When none is available, all cleancache calls + are reduced to a single pointer-compare-against-NULL resulting + in a negligible performance hit. + + If unsure, say Y to enable cleancache \ No newline at end of file diff --git a/mm/Makefile b/mm/Makefile old mode 100644 new mode 100755 index 66f54865..82a734fd --- a/mm/Makefile +++ b/mm/Makefile @@ -46,3 +46,4 @@ obj-$(CONFIG_MEMORY_FAILURE) += memory-failure.o obj-$(CONFIG_HWPOISON_INJECT) += hwpoison-inject.o obj-$(CONFIG_DEBUG_KMEMLEAK) += kmemleak.o obj-$(CONFIG_DEBUG_KMEMLEAK_TEST) += kmemleak-test.o +obj-$(CONFIG_CLEANCACHE) += cleancache.o diff --git a/mm/cleancache.c b/mm/cleancache.c new file mode 100755 index 00000000..bcaae4c2 --- /dev/null +++ b/mm/cleancache.c @@ -0,0 +1,244 @@ +/* + * Cleancache frontend + * + * This code provides the generic "frontend" layer to call a matching + * "backend" driver implementation of cleancache. See + * Documentation/vm/cleancache.txt for more information. + * + * Copyright (C) 2009-2010 Oracle Corp. All rights reserved. + * Author: Dan Magenheimer + * + * This work is licensed under the terms of the GNU GPL, version 2. + */ + +#include +#include +#include +#include +#include + +/* + * This global enablement flag may be read thousands of times per second + * by cleancache_get/put/flush even on systems where cleancache_ops + * is not claimed (e.g. cleancache is config'ed on but remains + * disabled), so is preferred to the slower alternative: a function + * call that checks a non-global. + */ +int cleancache_enabled; +EXPORT_SYMBOL(cleancache_enabled); + +/* + * cleancache_ops is set by cleancache_ops_register to contain the pointers + * to the cleancache "backend" implementation functions. + */ +static struct cleancache_ops cleancache_ops; + +/* useful stats available in /sys/kernel/mm/cleancache */ +static unsigned long cleancache_succ_gets; +static unsigned long cleancache_failed_gets; +static unsigned long cleancache_puts; +static unsigned long cleancache_flushes; + +/* + * register operations for cleancache, returning previous thus allowing + * detection of multiple backends and possible nesting + */ +struct cleancache_ops cleancache_register_ops(struct cleancache_ops *ops) +{ + struct cleancache_ops old = cleancache_ops; + + cleancache_ops = *ops; + cleancache_enabled = 1; + return old; +} +EXPORT_SYMBOL(cleancache_register_ops); + +/* Called by a cleancache-enabled filesystem at time of mount */ +void __cleancache_init_fs(struct super_block *sb) +{ + sb->cleancache_poolid = (*cleancache_ops.init_fs)(PAGE_SIZE); +} +EXPORT_SYMBOL(__cleancache_init_fs); + +/* Called by a cleancache-enabled clustered filesystem at time of mount */ +void __cleancache_init_shared_fs(char *uuid, struct super_block *sb) +{ + sb->cleancache_poolid = + (*cleancache_ops.init_shared_fs)(uuid, PAGE_SIZE); +} +EXPORT_SYMBOL(__cleancache_init_shared_fs); + +/* + * If the filesystem uses exportable filehandles, use the filehandle as + * the key, else use the inode number. + */ +static int cleancache_get_key(struct inode *inode, + struct cleancache_filekey *key) +{ + int (*fhfn)(struct dentry *, __u32 *fh, int *, int); + int len = 0, maxlen = CLEANCACHE_KEY_MAX; + struct super_block *sb = inode->i_sb; + + key->u.ino = inode->i_ino; + if (sb->s_export_op != NULL) { + fhfn = sb->s_export_op->encode_fh; + if (fhfn) { + struct dentry d; + d.d_inode = inode; + len = (*fhfn)(&d, &key->u.fh[0], &maxlen, 0); + if (len <= 0 || len == 255) + return -1; + if (maxlen > CLEANCACHE_KEY_MAX) + return -1; + } + } + return 0; +} + +/* + * "Get" data from cleancache associated with the poolid/inode/index + * that were specified when the data was put to cleanache and, if + * successful, use it to fill the specified page with data and return 0. + * The pageframe is unchanged and returns -1 if the get fails. + * Page must be locked by caller. + */ +int __cleancache_get_page(struct page *page) +{ + int ret = -1; + int pool_id; + struct cleancache_filekey key = { .u.key = { 0 } }; + + VM_BUG_ON(!PageLocked(page)); + pool_id = page->mapping->host->i_sb->cleancache_poolid; + if (pool_id < 0) + goto out; + + if (cleancache_get_key(page->mapping->host, &key) < 0) + goto out; + + ret = (*cleancache_ops.get_page)(pool_id, key, page->index, page); + if (ret == 0) + cleancache_succ_gets++; + else + cleancache_failed_gets++; +out: + return ret; +} +EXPORT_SYMBOL(__cleancache_get_page); + +/* + * "Put" data from a page to cleancache and associate it with the + * (previously-obtained per-filesystem) poolid and the page's, + * inode and page index. Page must be locked. Note that a put_page + * always "succeeds", though a subsequent get_page may succeed or fail. + */ +void __cleancache_put_page(struct page *page) +{ + int pool_id; + struct cleancache_filekey key = { .u.key = { 0 } }; + + VM_BUG_ON(!PageLocked(page)); + pool_id = page->mapping->host->i_sb->cleancache_poolid; + if (pool_id >= 0 && + cleancache_get_key(page->mapping->host, &key) >= 0) { + (*cleancache_ops.put_page)(pool_id, key, page->index, page); + cleancache_puts++; + } +} +EXPORT_SYMBOL(__cleancache_put_page); + +/* + * Flush any data from cleancache associated with the poolid and the + * page's inode and page index so that a subsequent "get" will fail. + */ +void __cleancache_flush_page(struct address_space *mapping, struct page *page) +{ + /* careful... page->mapping is NULL sometimes when this is called */ + int pool_id = mapping->host->i_sb->cleancache_poolid; + struct cleancache_filekey key = { .u.key = { 0 } }; + + if (pool_id >= 0) { + VM_BUG_ON(!PageLocked(page)); + if (cleancache_get_key(mapping->host, &key) >= 0) { + (*cleancache_ops.flush_page)(pool_id, key, page->index); + cleancache_flushes++; + } + } +} +EXPORT_SYMBOL(__cleancache_flush_page); + +/* + * Flush all data from cleancache associated with the poolid and the + * mappings's inode so that all subsequent gets to this poolid/inode + * will fail. + */ +void __cleancache_flush_inode(struct address_space *mapping) +{ + int pool_id = mapping->host->i_sb->cleancache_poolid; + struct cleancache_filekey key = { .u.key = { 0 } }; + + if (pool_id >= 0 && cleancache_get_key(mapping->host, &key) >= 0) + (*cleancache_ops.flush_inode)(pool_id, key); +} +EXPORT_SYMBOL(__cleancache_flush_inode); + +/* + * Called by any cleancache-enabled filesystem at time of unmount; + * note that pool_id is surrendered and may be reutrned by a subsequent + * cleancache_init_fs or cleancache_init_shared_fs + */ +void __cleancache_flush_fs(struct super_block *sb) +{ + if (sb->cleancache_poolid >= 0) { + int old_poolid = sb->cleancache_poolid; + sb->cleancache_poolid = -1; + (*cleancache_ops.flush_fs)(old_poolid); + } +} +EXPORT_SYMBOL(__cleancache_flush_fs); + +#ifdef CONFIG_SYSFS + +/* see Documentation/ABI/xxx/sysfs-kernel-mm-cleancache */ + +#define CLEANCACHE_SYSFS_RO(_name) \ + static ssize_t cleancache_##_name##_show(struct kobject *kobj, \ + struct kobj_attribute *attr, char *buf) \ + { \ + return sprintf(buf, "%lu\n", cleancache_##_name); \ + } \ + static struct kobj_attribute cleancache_##_name##_attr = { \ + .attr = { .name = __stringify(_name), .mode = 0444 }, \ + .show = cleancache_##_name##_show, \ + } + +CLEANCACHE_SYSFS_RO(succ_gets); +CLEANCACHE_SYSFS_RO(failed_gets); +CLEANCACHE_SYSFS_RO(puts); +CLEANCACHE_SYSFS_RO(flushes); + +static struct attribute *cleancache_attrs[] = { + &cleancache_succ_gets_attr.attr, + &cleancache_failed_gets_attr.attr, + &cleancache_puts_attr.attr, + &cleancache_flushes_attr.attr, + NULL, +}; + +static struct attribute_group cleancache_attr_group = { + .attrs = cleancache_attrs, + .name = "cleancache", +}; + +#endif /* CONFIG_SYSFS */ + +static int __init init_cleancache(void) +{ +#ifdef CONFIG_SYSFS + int err; + + err = sysfs_create_group(mm_kobj, &cleancache_attr_group); +#endif /* CONFIG_SYSFS */ + return 0; +} +module_init(init_cleancache)