cleancache: Make cleancache_init use a pointer for the ops
Instead of using a backend_registered to determine whether a backend is
enabled. This allows us to remove the backend_register check and just
do 'if (cleancache_ops)'
[v1: Rebase on top of b97c4b430b0a (ramster->zcache move]
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: Andor Daam <andor.daam@googlemail.com>
Cc: Dan Magenheimer <dan.magenheimer@oracle.com>
Cc: Florian Schmaus <fschmaus@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Stefan Hengelein <ilendir@googlemail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/cleancache.c b/mm/cleancache.c
index 0cecdbb..b3ae19b 100644
--- a/mm/cleancache.c
+++ b/mm/cleancache.c
@@ -32,7 +32,7 @@
* cleancache_ops is set by cleancache_ops_register to contain the pointers
* to the cleancache "backend" implementation functions.
*/
-static struct cleancache_ops cleancache_ops __read_mostly;
+static struct cleancache_ops *cleancache_ops __read_mostly;
/*
* Counters available via /sys/kernel/debug/frontswap (if debugfs is
@@ -72,15 +72,14 @@
/*
* 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
+ * by the if (!cleancache_ops) return. This means multiple threads (from
+ * different filesystems) will be checking cleancache_ops. 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
+ * cleancache_ops has been set to not NULL) 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
@@ -90,13 +89,13 @@
* [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.
+ * which return immediately as cleancache_ops is false.
*
* c). modprobe zcache -> cleancache_register_ops. We init the backend
- * and set backend_registered to true, and for any fs_poolid_map
+ * and set cleancache_ops 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
+ * d). user does I/Os -> now that cleancache_ops 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.
*
@@ -120,23 +119,26 @@
* 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 *cleancache_register_ops(struct cleancache_ops *ops)
{
- struct cleancache_ops old = cleancache_ops;
+ struct cleancache_ops *old = cleancache_ops;
int i;
mutex_lock(&poolid_mutex);
- cleancache_ops = *ops;
-
- 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);
+ fs_poolid_map[i] = ops->init_fs(PAGE_SIZE);
if (shared_fs_poolid_map[i] == FS_NO_BACKEND)
- shared_fs_poolid_map[i] = (*cleancache_ops.init_shared_fs)
+ shared_fs_poolid_map[i] = ops->init_shared_fs
(uuids[i], PAGE_SIZE);
}
-out:
+ /*
+ * We MUST set cleancache_ops _after_ we have called the backends
+ * init_fs or init_shared_fs functions. Otherwise the compiler might
+ * re-order where cleancache_ops is set in this function.
+ */
+ barrier();
+ cleancache_ops = ops;
mutex_unlock(&poolid_mutex);
return old;
}
@@ -151,8 +153,8 @@
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);
+ if (cleancache_ops)
+ fs_poolid_map[i] = cleancache_ops->init_fs(PAGE_SIZE);
else
fs_poolid_map[i] = FS_NO_BACKEND;
break;
@@ -172,8 +174,8 @@
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)
+ if (cleancache_ops)
+ shared_fs_poolid_map[i] = cleancache_ops->init_shared_fs
(uuid, PAGE_SIZE);
else
shared_fs_poolid_map[i] = FS_NO_BACKEND;
@@ -240,7 +242,7 @@
int fake_pool_id;
struct cleancache_filekey key = { .u.key = { 0 } };
- if (!backend_registered) {
+ if (!cleancache_ops) {
cleancache_failed_gets++;
goto out;
}
@@ -255,7 +257,7 @@
goto out;
if (pool_id >= 0)
- ret = (*cleancache_ops.get_page)(pool_id,
+ ret = cleancache_ops->get_page(pool_id,
key, page->index, page);
if (ret == 0)
cleancache_succ_gets++;
@@ -282,7 +284,7 @@
int fake_pool_id;
struct cleancache_filekey key = { .u.key = { 0 } };
- if (!backend_registered) {
+ if (!cleancache_ops) {
cleancache_puts++;
return;
}
@@ -296,7 +298,7 @@
if (pool_id >= 0 &&
cleancache_get_key(page->mapping->host, &key) >= 0) {
- (*cleancache_ops.put_page)(pool_id, key, page->index, page);
+ cleancache_ops->put_page(pool_id, key, page->index, page);
cleancache_puts++;
}
}
@@ -318,7 +320,7 @@
int fake_pool_id = mapping->host->i_sb->cleancache_poolid;
struct cleancache_filekey key = { .u.key = { 0 } };
- if (!backend_registered)
+ if (!cleancache_ops)
return;
if (fake_pool_id >= 0) {
@@ -328,7 +330,7 @@
VM_BUG_ON(!PageLocked(page));
if (cleancache_get_key(mapping->host, &key) >= 0) {
- (*cleancache_ops.invalidate_page)(pool_id,
+ cleancache_ops->invalidate_page(pool_id,
key, page->index);
cleancache_invalidates++;
}
@@ -351,7 +353,7 @@
int fake_pool_id = mapping->host->i_sb->cleancache_poolid;
struct cleancache_filekey key = { .u.key = { 0 } };
- if (!backend_registered)
+ if (!cleancache_ops)
return;
if (fake_pool_id < 0)
@@ -360,7 +362,7 @@
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);
+ cleancache_ops->invalidate_inode(pool_id, key);
}
EXPORT_SYMBOL(__cleancache_invalidate_inode);
@@ -387,8 +389,8 @@
fs_poolid_map[index] = FS_UNKNOWN;
}
sb->cleancache_poolid = -1;
- if (backend_registered)
- (*cleancache_ops.invalidate_fs)(old_poolid);
+ if (cleancache_ops)
+ cleancache_ops->invalidate_fs(old_poolid);
mutex_unlock(&poolid_mutex);
}
EXPORT_SYMBOL(__cleancache_invalidate_fs);