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mm: cleancache: lazy initialization to allow tmem backends to build/run as modules

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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>
This commit is contained in:
Dan Magenheimer 2013-04-30 15:26:56 -07:00 committed by Linus Torvalds
parent 4f89849da2
commit 49a9ab815a
1 changed files with 220 additions and 22 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

242
mm/cleancache.c
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@ -45,15 +45,99 @@ static u64 cleancache_puts;
static u64 cleancache_invalidates;
/*
* register operations for cleancache, returning previous thus allowing
* detection of multiple backends and possible nesting
* When no backend is registered all calls to init_fs and init_shared_fs
* are registered and fake poolids (FAKE_FS_POOLID_OFFSET or
* FAKE_SHARED_FS_POOLID_OFFSET, plus offset in the respective array
* [shared_|]fs_poolid_map) are given to the respective super block
* (sb->cleancache_poolid) and no tmem_pools are created. When a backend
* registers with cleancache the previous calls to init_fs and init_shared_fs
* are executed to create tmem_pools and set the respective poolids. While no
* backend is registered all "puts", "gets" and "flushes" are ignored or failed.
*/
#define MAX_INITIALIZABLE_FS 32
#define FAKE_FS_POOLID_OFFSET 1000
#define FAKE_SHARED_FS_POOLID_OFFSET 2000
#define FS_NO_BACKEND (-1)
#define FS_UNKNOWN (-2)
static int fs_poolid_map[MAX_INITIALIZABLE_FS];
static int shared_fs_poolid_map[MAX_INITIALIZABLE_FS];
static char *uuids[MAX_INITIALIZABLE_FS];
/*
* Mutex for the [shared_|]fs_poolid_map to guard against multiple threads
* invoking umount (and ending in __cleancache_invalidate_fs) and also multiple
* threads calling mount (and ending up in __cleancache_init_[shared|]fs).
*/
static DEFINE_MUTEX(poolid_mutex);
/*
* When set to false (default) all calls to the cleancache functions, except
* the __cleancache_invalidate_fs and __cleancache_init_[shared|]fs are guarded
* by the if (!backend_registered) return. This means multiple threads (from
* different filesystems) will be checking backend_registered. The usage of a
* bool instead of a atomic_t or a bool guarded by a spinlock is OK - we are
* OK if the time between the backend's have been initialized (and
* backend_registered has been set to true) and when the filesystems start
* actually calling the backends. The inverse (when unloading) is obviously
* not good - but this shim does not do that (yet).
*/
static bool backend_registered __read_mostly;
/*
* The backends and filesystems work all asynchronously. This is b/c the
* backends can be built as modules.
* The usual sequence of events is:
* a) mount / -> __cleancache_init_fs is called. We set the
* [shared_|]fs_poolid_map and uuids for.
*
* b). user does I/Os -> we call the rest of __cleancache_* functions
* which return immediately as backend_registered is false.
*
* c). modprobe zcache -> cleancache_register_ops. We init the backend
* and set backend_registered to true, and for any fs_poolid_map
* (which is set by __cleancache_init_fs) we initialize the poolid.
*
* d). user does I/Os -> now that backend_registered is true all the
* __cleancache_* functions can call the backend. They all check
* that fs_poolid_map is valid and if so invoke the backend.
*
* e). umount / -> __cleancache_invalidate_fs, the fs_poolid_map is
* reset (which is the second check in the __cleancache_* ops
* to call the backend).
*
* The sequence of event could also be c), followed by a), and d). and e). The
* c) would not happen anymore. There is also the chance of c), and one thread
* doing a) + d), and another doing e). For that case we depend on the
* filesystem calling __cleancache_invalidate_fs in the proper sequence (so
* that it handles all I/Os before it invalidates the fs (which is last part
* of unmounting process).
*
* Note: The acute reader will notice that there is no "rmmod zcache" case.
* This is b/c the functionality for that is not yet implemented and when
* done, will require some extra locking not yet devised.
*/
/*
* 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;
int i;
mutex_lock(&poolid_mutex);
cleancache_ops = *ops;
cleancache_enabled = 1;
backend_registered = true;
for (i = 0; i < MAX_INITIALIZABLE_FS; i++) {
if (fs_poolid_map[i] == FS_NO_BACKEND)
fs_poolid_map[i] = (*cleancache_ops.init_fs)(PAGE_SIZE);
if (shared_fs_poolid_map[i] == FS_NO_BACKEND)
shared_fs_poolid_map[i] = (*cleancache_ops.init_shared_fs)
(uuids[i], PAGE_SIZE);
}
out:
mutex_unlock(&poolid_mutex);
return old;
}
EXPORT_SYMBOL(cleancache_register_ops);
@ -61,15 +145,42 @@ 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);
int i;
mutex_lock(&poolid_mutex);
for (i = 0; i < MAX_INITIALIZABLE_FS; i++) {
if (fs_poolid_map[i] == FS_UNKNOWN) {
sb->cleancache_poolid = i + FAKE_FS_POOLID_OFFSET;
if (backend_registered)
fs_poolid_map[i] = (*cleancache_ops.init_fs)(PAGE_SIZE);
else
fs_poolid_map[i] = FS_NO_BACKEND;
break;
}
}
mutex_unlock(&poolid_mutex);
}
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);
int i;
mutex_lock(&poolid_mutex);
for (i = 0; i < MAX_INITIALIZABLE_FS; i++) {
if (shared_fs_poolid_map[i] == FS_UNKNOWN) {
sb->cleancache_poolid = i + FAKE_SHARED_FS_POOLID_OFFSET;
uuids[i] = uuid;
if (backend_registered)
shared_fs_poolid_map[i] = (*cleancache_ops.init_shared_fs)
(uuid, PAGE_SIZE);
else
shared_fs_poolid_map[i] = FS_NO_BACKEND;
break;
}
}
mutex_unlock(&poolid_mutex);
}
EXPORT_SYMBOL(__cleancache_init_shared_fs);
@ -98,28 +209,54 @@ static int cleancache_get_key(struct inode *inode,
return 0;
}
/*
* Returns a pool_id that is associated with a given fake poolid.
*/
static int get_poolid_from_fake(int fake_pool_id)
{
if (fake_pool_id >= FAKE_SHARED_FS_POOLID_OFFSET)
return shared_fs_poolid_map[fake_pool_id -
FAKE_SHARED_FS_POOLID_OFFSET];
else if (fake_pool_id >= FAKE_FS_POOLID_OFFSET)
return fs_poolid_map[fake_pool_id - FAKE_FS_POOLID_OFFSET];
return FS_NO_BACKEND;
}
/*
* "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.
*
* The function has two checks before any action is taken - whether
* a backend is registered and whether the sb->cleancache_poolid
* is correct.
*/
int __cleancache_get_page(struct page *page)
{
int ret = -1;
int pool_id;
int fake_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)
if (!backend_registered) {
cleancache_failed_gets++;
goto out;
}
VM_BUG_ON(!PageLocked(page));
fake_pool_id = page->mapping->host->i_sb->cleancache_poolid;
if (fake_pool_id < 0)
goto out;
pool_id = get_poolid_from_fake(fake_pool_id);
if (cleancache_get_key(page->mapping->host, &key) < 0)
goto out;
ret = (*cleancache_ops.get_page)(pool_id, key, page->index, page);
if (pool_id >= 0)
ret = (*cleancache_ops.get_page)(pool_id,
key, page->index, page);
if (ret == 0)
cleancache_succ_gets++;
else
@ -134,16 +271,31 @@ EXPORT_SYMBOL(__cleancache_get_page);
* (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.
*
* The function has two checks before any action is taken - whether
* a backend is registered and whether the sb->cleancache_poolid
* is correct.
*/
void __cleancache_put_page(struct page *page)
{
int pool_id;
int fake_pool_id;
struct cleancache_filekey key = { .u.key = { 0 } };
if (!backend_registered) {
cleancache_puts++;
return;
}
VM_BUG_ON(!PageLocked(page));
pool_id = page->mapping->host->i_sb->cleancache_poolid;
fake_pool_id = page->mapping->host->i_sb->cleancache_poolid;
if (fake_pool_id < 0)
return;
pool_id = get_poolid_from_fake(fake_pool_id);
if (pool_id >= 0 &&
cleancache_get_key(page->mapping->host, &key) >= 0) {
cleancache_get_key(page->mapping->host, &key) >= 0) {
(*cleancache_ops.put_page)(pool_id, key, page->index, page);
cleancache_puts++;
}
@ -153,19 +305,31 @@ EXPORT_SYMBOL(__cleancache_put_page);
/*
* Invalidate any data from cleancache associated with the poolid and the
* page's inode and page index so that a subsequent "get" will fail.
*
* The function has two checks before any action is taken - whether
* a backend is registered and whether the sb->cleancache_poolid
* is correct.
*/
void __cleancache_invalidate_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;
int pool_id;
int fake_pool_id = mapping->host->i_sb->cleancache_poolid;
struct cleancache_filekey key = { .u.key = { 0 } };
if (pool_id >= 0) {
if (!backend_registered)
return;
if (fake_pool_id >= 0) {
pool_id = get_poolid_from_fake(fake_pool_id);
if (pool_id < 0)
return;
VM_BUG_ON(!PageLocked(page));
if (cleancache_get_key(mapping->host, &key) >= 0) {
(*cleancache_ops.invalidate_page)(pool_id,
key, page->index);
key, page->index);
cleancache_invalidates++;
}
}
@ -176,12 +340,25 @@ EXPORT_SYMBOL(__cleancache_invalidate_page);
* Invalidate all data from cleancache associated with the poolid and the
* mappings's inode so that all subsequent gets to this poolid/inode
* will fail.
*
* The function has two checks before any action is taken - whether
* a backend is registered and whether the sb->cleancache_poolid
* is correct.
*/
void __cleancache_invalidate_inode(struct address_space *mapping)
{
int pool_id = mapping->host->i_sb->cleancache_poolid;
int pool_id;
int fake_pool_id = mapping->host->i_sb->cleancache_poolid;
struct cleancache_filekey key = { .u.key = { 0 } };
if (!backend_registered)
return;
if (fake_pool_id < 0)
return;
pool_id = get_poolid_from_fake(fake_pool_id);
if (pool_id >= 0 && cleancache_get_key(mapping->host, &key) >= 0)
(*cleancache_ops.invalidate_inode)(pool_id, key);
}
@ -189,21 +366,37 @@ EXPORT_SYMBOL(__cleancache_invalidate_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
* note that pool_id is surrendered and may be returned by a subsequent
* cleancache_init_fs or cleancache_init_shared_fs.
*/
void __cleancache_invalidate_fs(struct super_block *sb)
{
if (sb->cleancache_poolid >= 0) {
int old_poolid = sb->cleancache_poolid;
sb->cleancache_poolid = -1;
(*cleancache_ops.invalidate_fs)(old_poolid);
int index;
int fake_pool_id = sb->cleancache_poolid;
int old_poolid = fake_pool_id;
mutex_lock(&poolid_mutex);
if (fake_pool_id >= FAKE_SHARED_FS_POOLID_OFFSET) {
index = fake_pool_id - FAKE_SHARED_FS_POOLID_OFFSET;
old_poolid = shared_fs_poolid_map[index];
shared_fs_poolid_map[index] = FS_UNKNOWN;
uuids[index] = NULL;
} else if (fake_pool_id >= FAKE_FS_POOLID_OFFSET) {
index = fake_pool_id - FAKE_FS_POOLID_OFFSET;
old_poolid = fs_poolid_map[index];
fs_poolid_map[index] = FS_UNKNOWN;
}
sb->cleancache_poolid = -1;
if (backend_registered)
(*cleancache_ops.invalidate_fs)(old_poolid);
mutex_unlock(&poolid_mutex);
}
EXPORT_SYMBOL(__cleancache_invalidate_fs);
static int __init init_cleancache(void)
{
int i;
#ifdef CONFIG_DEBUG_FS
struct dentry *root = debugfs_create_dir("cleancache", NULL);
if (root == NULL)
@ -215,6 +408,11 @@ static int __init init_cleancache(void)
debugfs_create_u64("invalidates", S_IRUGO,
root, &cleancache_invalidates);
#endif
for (i = 0; i < MAX_INITIALIZABLE_FS; i++) {
fs_poolid_map[i] = FS_UNKNOWN;
shared_fs_poolid_map[i] = FS_UNKNOWN;
}
cleancache_enabled = 1;
return 0;
}
module_init(init_cleancache)