mm: cleancache: lazy initialization to allow tmem backends to build/run as modules
With the goal of allowing tmem backends (zcache, ramster, Xen tmem) to be built/loaded as modules rather than built-in and enabled by a boot parameter, this patch provides "lazy initialization", allowing backends to register to cleancache even after filesystems were mounted. Calls to init_fs and init_shared_fs are remembered as fake poolids but no real tmem_pools created. On backend registration the fake poolids are mapped to real poolids and respective tmem_pools. Signed-off-by: Stefan Hengelein <ilendir@googlemail.com> Signed-off-by: Florian Schmaus <fschmaus@gmail.com> Signed-off-by: Andor Daam <andor.daam@googlemail.com> Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com> [v1: Minor fixes: used #define for some values and bools] [v2: Removed CLEANCACHE_HAS_LAZY_INIT] [v3: Added more comments, added a lock for [shared_|]fs_poolid_map] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Signed-off-by: Bob Liu <lliubbo@gmail.com> Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com> Cc: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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1 changed files with 220 additions and 22 deletions
242
mm/cleancache.c
242
mm/cleancache.c
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@ -45,15 +45,99 @@ static u64 cleancache_puts;
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static u64 cleancache_invalidates;
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/*
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* register operations for cleancache, returning previous thus allowing
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* detection of multiple backends and possible nesting
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* When no backend is registered all calls to init_fs and init_shared_fs
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* are registered and fake poolids (FAKE_FS_POOLID_OFFSET or
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* FAKE_SHARED_FS_POOLID_OFFSET, plus offset in the respective array
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* [shared_|]fs_poolid_map) are given to the respective super block
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* (sb->cleancache_poolid) and no tmem_pools are created. When a backend
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* registers with cleancache the previous calls to init_fs and init_shared_fs
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* are executed to create tmem_pools and set the respective poolids. While no
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* backend is registered all "puts", "gets" and "flushes" are ignored or failed.
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*/
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#define MAX_INITIALIZABLE_FS 32
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#define FAKE_FS_POOLID_OFFSET 1000
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#define FAKE_SHARED_FS_POOLID_OFFSET 2000
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#define FS_NO_BACKEND (-1)
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#define FS_UNKNOWN (-2)
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static int fs_poolid_map[MAX_INITIALIZABLE_FS];
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static int shared_fs_poolid_map[MAX_INITIALIZABLE_FS];
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static char *uuids[MAX_INITIALIZABLE_FS];
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/*
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* Mutex for the [shared_|]fs_poolid_map to guard against multiple threads
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* invoking umount (and ending in __cleancache_invalidate_fs) and also multiple
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* threads calling mount (and ending up in __cleancache_init_[shared|]fs).
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*/
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static DEFINE_MUTEX(poolid_mutex);
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/*
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* When set to false (default) all calls to the cleancache functions, except
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* the __cleancache_invalidate_fs and __cleancache_init_[shared|]fs are guarded
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* by the if (!backend_registered) return. This means multiple threads (from
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* different filesystems) will be checking backend_registered. The usage of a
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* bool instead of a atomic_t or a bool guarded by a spinlock is OK - we are
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* OK if the time between the backend's have been initialized (and
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* backend_registered has been set to true) and when the filesystems start
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* actually calling the backends. The inverse (when unloading) is obviously
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* not good - but this shim does not do that (yet).
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*/
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static bool backend_registered __read_mostly;
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/*
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* The backends and filesystems work all asynchronously. This is b/c the
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* backends can be built as modules.
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* The usual sequence of events is:
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* a) mount / -> __cleancache_init_fs is called. We set the
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* [shared_|]fs_poolid_map and uuids for.
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*
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* b). user does I/Os -> we call the rest of __cleancache_* functions
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* which return immediately as backend_registered is false.
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*
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* c). modprobe zcache -> cleancache_register_ops. We init the backend
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* and set backend_registered to true, and for any fs_poolid_map
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* (which is set by __cleancache_init_fs) we initialize the poolid.
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*
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* d). user does I/Os -> now that backend_registered is true all the
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* __cleancache_* functions can call the backend. They all check
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* that fs_poolid_map is valid and if so invoke the backend.
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*
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* e). umount / -> __cleancache_invalidate_fs, the fs_poolid_map is
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* reset (which is the second check in the __cleancache_* ops
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* to call the backend).
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*
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* The sequence of event could also be c), followed by a), and d). and e). The
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* c) would not happen anymore. There is also the chance of c), and one thread
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* doing a) + d), and another doing e). For that case we depend on the
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* filesystem calling __cleancache_invalidate_fs in the proper sequence (so
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* that it handles all I/Os before it invalidates the fs (which is last part
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* of unmounting process).
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*
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* Note: The acute reader will notice that there is no "rmmod zcache" case.
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* This is b/c the functionality for that is not yet implemented and when
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* done, will require some extra locking not yet devised.
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*/
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/*
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* Register operations for cleancache, returning previous thus allowing
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* detection of multiple backends and possible nesting.
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*/
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struct cleancache_ops cleancache_register_ops(struct cleancache_ops *ops)
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{
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struct cleancache_ops old = cleancache_ops;
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int i;
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mutex_lock(&poolid_mutex);
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cleancache_ops = *ops;
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cleancache_enabled = 1;
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backend_registered = true;
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for (i = 0; i < MAX_INITIALIZABLE_FS; i++) {
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if (fs_poolid_map[i] == FS_NO_BACKEND)
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fs_poolid_map[i] = (*cleancache_ops.init_fs)(PAGE_SIZE);
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if (shared_fs_poolid_map[i] == FS_NO_BACKEND)
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shared_fs_poolid_map[i] = (*cleancache_ops.init_shared_fs)
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(uuids[i], PAGE_SIZE);
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}
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out:
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mutex_unlock(&poolid_mutex);
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return old;
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}
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EXPORT_SYMBOL(cleancache_register_ops);
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@ -61,15 +145,42 @@ 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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sb->cleancache_poolid = (*cleancache_ops.init_fs)(PAGE_SIZE);
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int i;
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mutex_lock(&poolid_mutex);
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for (i = 0; i < MAX_INITIALIZABLE_FS; i++) {
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if (fs_poolid_map[i] == FS_UNKNOWN) {
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sb->cleancache_poolid = i + FAKE_FS_POOLID_OFFSET;
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if (backend_registered)
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fs_poolid_map[i] = (*cleancache_ops.init_fs)(PAGE_SIZE);
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else
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fs_poolid_map[i] = FS_NO_BACKEND;
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break;
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}
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}
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mutex_unlock(&poolid_mutex);
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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(char *uuid, struct super_block *sb)
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{
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sb->cleancache_poolid =
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(*cleancache_ops.init_shared_fs)(uuid, PAGE_SIZE);
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int i;
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mutex_lock(&poolid_mutex);
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for (i = 0; i < MAX_INITIALIZABLE_FS; i++) {
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if (shared_fs_poolid_map[i] == FS_UNKNOWN) {
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sb->cleancache_poolid = i + FAKE_SHARED_FS_POOLID_OFFSET;
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uuids[i] = uuid;
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if (backend_registered)
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shared_fs_poolid_map[i] = (*cleancache_ops.init_shared_fs)
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(uuid, PAGE_SIZE);
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else
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shared_fs_poolid_map[i] = FS_NO_BACKEND;
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break;
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}
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}
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mutex_unlock(&poolid_mutex);
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}
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EXPORT_SYMBOL(__cleancache_init_shared_fs);
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@ -98,28 +209,54 @@ static int cleancache_get_key(struct inode *inode,
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return 0;
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}
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/*
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* Returns a pool_id that is associated with a given fake poolid.
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*/
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static int get_poolid_from_fake(int fake_pool_id)
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{
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if (fake_pool_id >= FAKE_SHARED_FS_POOLID_OFFSET)
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return shared_fs_poolid_map[fake_pool_id -
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FAKE_SHARED_FS_POOLID_OFFSET];
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else if (fake_pool_id >= FAKE_FS_POOLID_OFFSET)
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return fs_poolid_map[fake_pool_id - FAKE_FS_POOLID_OFFSET];
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return FS_NO_BACKEND;
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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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int fake_pool_id;
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struct cleancache_filekey key = { .u.key = { 0 } };
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VM_BUG_ON(!PageLocked(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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if (!backend_registered) {
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cleancache_failed_gets++;
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goto out;
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}
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VM_BUG_ON(!PageLocked(page));
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fake_pool_id = page->mapping->host->i_sb->cleancache_poolid;
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if (fake_pool_id < 0)
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goto out;
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pool_id = get_poolid_from_fake(fake_pool_id);
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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 (pool_id >= 0)
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ret = (*cleancache_ops.get_page)(pool_id,
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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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* (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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int fake_pool_id;
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struct cleancache_filekey key = { .u.key = { 0 } };
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if (!backend_registered) {
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cleancache_puts++;
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return;
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}
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VM_BUG_ON(!PageLocked(page));
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pool_id = page->mapping->host->i_sb->cleancache_poolid;
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fake_pool_id = page->mapping->host->i_sb->cleancache_poolid;
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if (fake_pool_id < 0)
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return;
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pool_id = get_poolid_from_fake(fake_pool_id);
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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_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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* 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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int pool_id;
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int fake_pool_id = mapping->host->i_sb->cleancache_poolid;
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struct cleancache_filekey key = { .u.key = { 0 } };
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if (pool_id >= 0) {
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if (!backend_registered)
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return;
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if (fake_pool_id >= 0) {
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pool_id = get_poolid_from_fake(fake_pool_id);
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if (pool_id < 0)
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return;
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VM_BUG_ON(!PageLocked(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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key, page->index);
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cleancache_invalidates++;
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}
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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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int pool_id;
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int fake_pool_id = mapping->host->i_sb->cleancache_poolid;
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struct cleancache_filekey key = { .u.key = { 0 } };
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if (!backend_registered)
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return;
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if (fake_pool_id < 0)
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return;
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pool_id = get_poolid_from_fake(fake_pool_id);
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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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/*
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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 reutrned by a subsequent
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* cleancache_init_fs or cleancache_init_shared_fs
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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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if (sb->cleancache_poolid >= 0) {
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int old_poolid = sb->cleancache_poolid;
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sb->cleancache_poolid = -1;
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(*cleancache_ops.invalidate_fs)(old_poolid);
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int index;
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int fake_pool_id = sb->cleancache_poolid;
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int old_poolid = fake_pool_id;
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mutex_lock(&poolid_mutex);
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if (fake_pool_id >= FAKE_SHARED_FS_POOLID_OFFSET) {
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index = fake_pool_id - FAKE_SHARED_FS_POOLID_OFFSET;
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old_poolid = shared_fs_poolid_map[index];
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shared_fs_poolid_map[index] = FS_UNKNOWN;
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uuids[index] = NULL;
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} else if (fake_pool_id >= FAKE_FS_POOLID_OFFSET) {
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index = fake_pool_id - FAKE_FS_POOLID_OFFSET;
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old_poolid = fs_poolid_map[index];
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fs_poolid_map[index] = FS_UNKNOWN;
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}
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sb->cleancache_poolid = -1;
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if (backend_registered)
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(*cleancache_ops.invalidate_fs)(old_poolid);
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mutex_unlock(&poolid_mutex);
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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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int i;
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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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debugfs_create_u64("invalidates", S_IRUGO,
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root, &cleancache_invalidates);
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#endif
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for (i = 0; i < MAX_INITIALIZABLE_FS; i++) {
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fs_poolid_map[i] = FS_UNKNOWN;
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shared_fs_poolid_map[i] = FS_UNKNOWN;
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}
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cleancache_enabled = 1;
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return 0;
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}
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module_init(init_cleancache)
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