linux/fs/mbcache.c

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/*
* linux/fs/mbcache.c
* (C) 2001-2002 Andreas Gruenbacher, <a.gruenbacher@computer.org>
*/
/*
* Filesystem Meta Information Block Cache (mbcache)
*
* The mbcache caches blocks of block devices that need to be located
* by their device/block number, as well as by other criteria (such
* as the block's contents).
*
* There can only be one cache entry in a cache per device and block number.
* Additional indexes need not be unique in this sense. The number of
* additional indexes (=other criteria) can be hardwired at compile time
* or specified at cache create time.
*
* Each cache entry is of fixed size. An entry may be `valid' or `invalid'
* in the cache. A valid entry is in the main hash tables of the cache,
* and may also be in the lru list. An invalid entry is not in any hashes
* or lists.
*
* A valid cache entry is only in the lru list if no handles refer to it.
* Invalid cache entries will be freed when the last handle to the cache
* entry is released. Entries that cannot be freed immediately are put
* back on the lru list.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/hash.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/mbcache.h>
#ifdef MB_CACHE_DEBUG
# define mb_debug(f...) do { \
printk(KERN_DEBUG f); \
printk("\n"); \
} while (0)
#define mb_assert(c) do { if (!(c)) \
printk(KERN_ERR "assertion " #c " failed\n"); \
} while(0)
#else
# define mb_debug(f...) do { } while(0)
# define mb_assert(c) do { } while(0)
#endif
#define mb_error(f...) do { \
printk(KERN_ERR f); \
printk("\n"); \
} while(0)
#define MB_CACHE_WRITER ((unsigned short)~0U >> 1)
static DECLARE_WAIT_QUEUE_HEAD(mb_cache_queue);
MODULE_AUTHOR("Andreas Gruenbacher <a.gruenbacher@computer.org>");
MODULE_DESCRIPTION("Meta block cache (for extended attributes)");
MODULE_LICENSE("GPL");
EXPORT_SYMBOL(mb_cache_create);
EXPORT_SYMBOL(mb_cache_shrink);
EXPORT_SYMBOL(mb_cache_destroy);
EXPORT_SYMBOL(mb_cache_entry_alloc);
EXPORT_SYMBOL(mb_cache_entry_insert);
EXPORT_SYMBOL(mb_cache_entry_release);
EXPORT_SYMBOL(mb_cache_entry_free);
EXPORT_SYMBOL(mb_cache_entry_get);
#if !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0)
EXPORT_SYMBOL(mb_cache_entry_find_first);
EXPORT_SYMBOL(mb_cache_entry_find_next);
#endif
struct mb_cache {
struct list_head c_cache_list;
const char *c_name;
struct mb_cache_op c_op;
atomic_t c_entry_count;
int c_bucket_bits;
#ifndef MB_CACHE_INDEXES_COUNT
int c_indexes_count;
#endif
struct kmem_cache *c_entry_cache;
struct list_head *c_block_hash;
struct list_head *c_indexes_hash[0];
};
/*
* Global data: list of all mbcache's, lru list, and a spinlock for
* accessing cache data structures on SMP machines. The lru list is
* global across all mbcaches.
*/
static LIST_HEAD(mb_cache_list);
static LIST_HEAD(mb_cache_lru_list);
static DEFINE_SPINLOCK(mb_cache_spinlock);
static struct shrinker *mb_shrinker;
static inline int
mb_cache_indexes(struct mb_cache *cache)
{
#ifdef MB_CACHE_INDEXES_COUNT
return MB_CACHE_INDEXES_COUNT;
#else
return cache->c_indexes_count;
#endif
}
/*
* What the mbcache registers as to get shrunk dynamically.
*/
static int mb_cache_shrink_fn(int nr_to_scan, gfp_t gfp_mask);
static inline int
__mb_cache_entry_is_hashed(struct mb_cache_entry *ce)
{
return !list_empty(&ce->e_block_list);
}
static void
__mb_cache_entry_unhash(struct mb_cache_entry *ce)
{
int n;
if (__mb_cache_entry_is_hashed(ce)) {
list_del_init(&ce->e_block_list);
for (n=0; n<mb_cache_indexes(ce->e_cache); n++)
list_del(&ce->e_indexes[n].o_list);
}
}
static void
__mb_cache_entry_forget(struct mb_cache_entry *ce, gfp_t gfp_mask)
{
struct mb_cache *cache = ce->e_cache;
mb_assert(!(ce->e_used || ce->e_queued));
if (cache->c_op.free && cache->c_op.free(ce, gfp_mask)) {
/* free failed -- put back on the lru list
for freeing later. */
spin_lock(&mb_cache_spinlock);
list_add(&ce->e_lru_list, &mb_cache_lru_list);
spin_unlock(&mb_cache_spinlock);
} else {
kmem_cache_free(cache->c_entry_cache, ce);
atomic_dec(&cache->c_entry_count);
}
}
static void
__mb_cache_entry_release_unlock(struct mb_cache_entry *ce)
__releases(mb_cache_spinlock)
{
/* Wake up all processes queuing for this cache entry. */
if (ce->e_queued)
wake_up_all(&mb_cache_queue);
if (ce->e_used >= MB_CACHE_WRITER)
ce->e_used -= MB_CACHE_WRITER;
ce->e_used--;
if (!(ce->e_used || ce->e_queued)) {
if (!__mb_cache_entry_is_hashed(ce))
goto forget;
mb_assert(list_empty(&ce->e_lru_list));
list_add_tail(&ce->e_lru_list, &mb_cache_lru_list);
}
spin_unlock(&mb_cache_spinlock);
return;
forget:
spin_unlock(&mb_cache_spinlock);
__mb_cache_entry_forget(ce, GFP_KERNEL);
}
/*
* mb_cache_shrink_fn() memory pressure callback
*
* This function is called by the kernel memory management when memory
* gets low.
*
* @nr_to_scan: Number of objects to scan
* @gfp_mask: (ignored)
*
* Returns the number of objects which are present in the cache.
*/
static int
mb_cache_shrink_fn(int nr_to_scan, gfp_t gfp_mask)
{
LIST_HEAD(free_list);
struct list_head *l, *ltmp;
int count = 0;
spin_lock(&mb_cache_spinlock);
list_for_each(l, &mb_cache_list) {
struct mb_cache *cache =
list_entry(l, struct mb_cache, c_cache_list);
mb_debug("cache %s (%d)", cache->c_name,
atomic_read(&cache->c_entry_count));
count += atomic_read(&cache->c_entry_count);
}
mb_debug("trying to free %d entries", nr_to_scan);
if (nr_to_scan == 0) {
spin_unlock(&mb_cache_spinlock);
goto out;
}
while (nr_to_scan-- && !list_empty(&mb_cache_lru_list)) {
struct mb_cache_entry *ce =
list_entry(mb_cache_lru_list.next,
struct mb_cache_entry, e_lru_list);
list_move_tail(&ce->e_lru_list, &free_list);
__mb_cache_entry_unhash(ce);
}
spin_unlock(&mb_cache_spinlock);
list_for_each_safe(l, ltmp, &free_list) {
__mb_cache_entry_forget(list_entry(l, struct mb_cache_entry,
e_lru_list), gfp_mask);
}
out:
return (count / 100) * sysctl_vfs_cache_pressure;
}
/*
* mb_cache_create() create a new cache
*
* All entries in one cache are equal size. Cache entries may be from
* multiple devices. If this is the first mbcache created, registers
* the cache with kernel memory management. Returns NULL if no more
* memory was available.
*
* @name: name of the cache (informal)
* @cache_op: contains the callback called when freeing a cache entry
* @entry_size: The size of a cache entry, including
* struct mb_cache_entry
* @indexes_count: number of additional indexes in the cache. Must equal
* MB_CACHE_INDEXES_COUNT if the number of indexes is
* hardwired.
* @bucket_bits: log2(number of hash buckets)
*/
struct mb_cache *
mb_cache_create(const char *name, struct mb_cache_op *cache_op,
size_t entry_size, int indexes_count, int bucket_bits)
{
int m=0, n, bucket_count = 1 << bucket_bits;
struct mb_cache *cache = NULL;
if(entry_size < sizeof(struct mb_cache_entry) +
indexes_count * sizeof(((struct mb_cache_entry *) 0)->e_indexes[0]))
return NULL;
cache = kmalloc(sizeof(struct mb_cache) +
indexes_count * sizeof(struct list_head), GFP_KERNEL);
if (!cache)
goto fail;
cache->c_name = name;
cache->c_op.free = NULL;
if (cache_op)
cache->c_op.free = cache_op->free;
atomic_set(&cache->c_entry_count, 0);
cache->c_bucket_bits = bucket_bits;
#ifdef MB_CACHE_INDEXES_COUNT
mb_assert(indexes_count == MB_CACHE_INDEXES_COUNT);
#else
cache->c_indexes_count = indexes_count;
#endif
cache->c_block_hash = kmalloc(bucket_count * sizeof(struct list_head),
GFP_KERNEL);
if (!cache->c_block_hash)
goto fail;
for (n=0; n<bucket_count; n++)
INIT_LIST_HEAD(&cache->c_block_hash[n]);
for (m=0; m<indexes_count; m++) {
cache->c_indexes_hash[m] = kmalloc(bucket_count *
sizeof(struct list_head),
GFP_KERNEL);
if (!cache->c_indexes_hash[m])
goto fail;
for (n=0; n<bucket_count; n++)
INIT_LIST_HEAD(&cache->c_indexes_hash[m][n]);
}
cache->c_entry_cache = kmem_cache_create(name, entry_size, 0,
[PATCH] cpuset memory spread: slab cache filesystems Mark file system inode and similar slab caches subject to SLAB_MEM_SPREAD memory spreading. If a slab cache is marked SLAB_MEM_SPREAD, then anytime that a task that's in a cpuset with the 'memory_spread_slab' option enabled goes to allocate from such a slab cache, the allocations are spread evenly over all the memory nodes (task->mems_allowed) allowed to that task, instead of favoring allocation on the node local to the current cpu. The following inode and similar caches are marked SLAB_MEM_SPREAD: file cache ==== ===== fs/adfs/super.c adfs_inode_cache fs/affs/super.c affs_inode_cache fs/befs/linuxvfs.c befs_inode_cache fs/bfs/inode.c bfs_inode_cache fs/block_dev.c bdev_cache fs/cifs/cifsfs.c cifs_inode_cache fs/coda/inode.c coda_inode_cache fs/dquot.c dquot fs/efs/super.c efs_inode_cache fs/ext2/super.c ext2_inode_cache fs/ext2/xattr.c (fs/mbcache.c) ext2_xattr fs/ext3/super.c ext3_inode_cache fs/ext3/xattr.c (fs/mbcache.c) ext3_xattr fs/fat/cache.c fat_cache fs/fat/inode.c fat_inode_cache fs/freevxfs/vxfs_super.c vxfs_inode fs/hpfs/super.c hpfs_inode_cache fs/isofs/inode.c isofs_inode_cache fs/jffs/inode-v23.c jffs_fm fs/jffs2/super.c jffs2_i fs/jfs/super.c jfs_ip fs/minix/inode.c minix_inode_cache fs/ncpfs/inode.c ncp_inode_cache fs/nfs/direct.c nfs_direct_cache fs/nfs/inode.c nfs_inode_cache fs/ntfs/super.c ntfs_big_inode_cache_name fs/ntfs/super.c ntfs_inode_cache fs/ocfs2/dlm/dlmfs.c dlmfs_inode_cache fs/ocfs2/super.c ocfs2_inode_cache fs/proc/inode.c proc_inode_cache fs/qnx4/inode.c qnx4_inode_cache fs/reiserfs/super.c reiser_inode_cache fs/romfs/inode.c romfs_inode_cache fs/smbfs/inode.c smb_inode_cache fs/sysv/inode.c sysv_inode_cache fs/udf/super.c udf_inode_cache fs/ufs/super.c ufs_inode_cache net/socket.c sock_inode_cache net/sunrpc/rpc_pipe.c rpc_inode_cache The choice of which slab caches to so mark was quite simple. I marked those already marked SLAB_RECLAIM_ACCOUNT, except for fs/xfs, dentry_cache, inode_cache, and buffer_head, which were marked in a previous patch. Even though SLAB_RECLAIM_ACCOUNT is for a different purpose, it marks the same potentially large file system i/o related slab caches as we need for memory spreading. Given that the rule now becomes "wherever you would have used a SLAB_RECLAIM_ACCOUNT slab cache flag before (usually the inode cache), use the SLAB_MEM_SPREAD flag too", this should be easy enough to maintain. Future file system writers will just copy one of the existing file system slab cache setups and tend to get it right without thinking. Signed-off-by: Paul Jackson <pj@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-24 11:16:05 +00:00
SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD, NULL, NULL);
if (!cache->c_entry_cache)
goto fail;
spin_lock(&mb_cache_spinlock);
list_add(&cache->c_cache_list, &mb_cache_list);
spin_unlock(&mb_cache_spinlock);
return cache;
fail:
if (cache) {
while (--m >= 0)
kfree(cache->c_indexes_hash[m]);
kfree(cache->c_block_hash);
kfree(cache);
}
return NULL;
}
/*
* mb_cache_shrink()
*
* Removes all cache entries of a device from the cache. All cache entries
* currently in use cannot be freed, and thus remain in the cache. All others
* are freed.
*
* @bdev: which device's cache entries to shrink
*/
void
mb_cache_shrink(struct block_device *bdev)
{
LIST_HEAD(free_list);
struct list_head *l, *ltmp;
spin_lock(&mb_cache_spinlock);
list_for_each_safe(l, ltmp, &mb_cache_lru_list) {
struct mb_cache_entry *ce =
list_entry(l, struct mb_cache_entry, e_lru_list);
if (ce->e_bdev == bdev) {
list_move_tail(&ce->e_lru_list, &free_list);
__mb_cache_entry_unhash(ce);
}
}
spin_unlock(&mb_cache_spinlock);
list_for_each_safe(l, ltmp, &free_list) {
__mb_cache_entry_forget(list_entry(l, struct mb_cache_entry,
e_lru_list), GFP_KERNEL);
}
}
/*
* mb_cache_destroy()
*
* Shrinks the cache to its minimum possible size (hopefully 0 entries),
* and then destroys it. If this was the last mbcache, un-registers the
* mbcache from kernel memory management.
*/
void
mb_cache_destroy(struct mb_cache *cache)
{
LIST_HEAD(free_list);
struct list_head *l, *ltmp;
int n;
spin_lock(&mb_cache_spinlock);
list_for_each_safe(l, ltmp, &mb_cache_lru_list) {
struct mb_cache_entry *ce =
list_entry(l, struct mb_cache_entry, e_lru_list);
if (ce->e_cache == cache) {
list_move_tail(&ce->e_lru_list, &free_list);
__mb_cache_entry_unhash(ce);
}
}
list_del(&cache->c_cache_list);
spin_unlock(&mb_cache_spinlock);
list_for_each_safe(l, ltmp, &free_list) {
__mb_cache_entry_forget(list_entry(l, struct mb_cache_entry,
e_lru_list), GFP_KERNEL);
}
if (atomic_read(&cache->c_entry_count) > 0) {
mb_error("cache %s: %d orphaned entries",
cache->c_name,
atomic_read(&cache->c_entry_count));
}
kmem_cache_destroy(cache->c_entry_cache);
for (n=0; n < mb_cache_indexes(cache); n++)
kfree(cache->c_indexes_hash[n]);
kfree(cache->c_block_hash);
kfree(cache);
}
/*
* mb_cache_entry_alloc()
*
* Allocates a new cache entry. The new entry will not be valid initially,
* and thus cannot be looked up yet. It should be filled with data, and
* then inserted into the cache using mb_cache_entry_insert(). Returns NULL
* if no more memory was available.
*/
struct mb_cache_entry *
mb_cache_entry_alloc(struct mb_cache *cache)
{
struct mb_cache_entry *ce;
atomic_inc(&cache->c_entry_count);
ce = kmem_cache_alloc(cache->c_entry_cache, GFP_KERNEL);
if (ce) {
INIT_LIST_HEAD(&ce->e_lru_list);
INIT_LIST_HEAD(&ce->e_block_list);
ce->e_cache = cache;
ce->e_used = 1 + MB_CACHE_WRITER;
ce->e_queued = 0;
}
return ce;
}
/*
* mb_cache_entry_insert()
*
* Inserts an entry that was allocated using mb_cache_entry_alloc() into
* the cache. After this, the cache entry can be looked up, but is not yet
* in the lru list as the caller still holds a handle to it. Returns 0 on
* success, or -EBUSY if a cache entry for that device + inode exists
* already (this may happen after a failed lookup, but when another process
* has inserted the same cache entry in the meantime).
*
* @bdev: device the cache entry belongs to
* @block: block number
* @keys: array of additional keys. There must be indexes_count entries
* in the array (as specified when creating the cache).
*/
int
mb_cache_entry_insert(struct mb_cache_entry *ce, struct block_device *bdev,
sector_t block, unsigned int keys[])
{
struct mb_cache *cache = ce->e_cache;
unsigned int bucket;
struct list_head *l;
int error = -EBUSY, n;
bucket = hash_long((unsigned long)bdev + (block & 0xffffffff),
cache->c_bucket_bits);
spin_lock(&mb_cache_spinlock);
list_for_each_prev(l, &cache->c_block_hash[bucket]) {
struct mb_cache_entry *ce =
list_entry(l, struct mb_cache_entry, e_block_list);
if (ce->e_bdev == bdev && ce->e_block == block)
goto out;
}
__mb_cache_entry_unhash(ce);
ce->e_bdev = bdev;
ce->e_block = block;
list_add(&ce->e_block_list, &cache->c_block_hash[bucket]);
for (n=0; n<mb_cache_indexes(cache); n++) {
ce->e_indexes[n].o_key = keys[n];
bucket = hash_long(keys[n], cache->c_bucket_bits);
list_add(&ce->e_indexes[n].o_list,
&cache->c_indexes_hash[n][bucket]);
}
error = 0;
out:
spin_unlock(&mb_cache_spinlock);
return error;
}
/*
* mb_cache_entry_release()
*
* Release a handle to a cache entry. When the last handle to a cache entry
* is released it is either freed (if it is invalid) or otherwise inserted
* in to the lru list.
*/
void
mb_cache_entry_release(struct mb_cache_entry *ce)
{
spin_lock(&mb_cache_spinlock);
__mb_cache_entry_release_unlock(ce);
}
/*
* mb_cache_entry_free()
*
* This is equivalent to the sequence mb_cache_entry_takeout() --
* mb_cache_entry_release().
*/
void
mb_cache_entry_free(struct mb_cache_entry *ce)
{
spin_lock(&mb_cache_spinlock);
mb_assert(list_empty(&ce->e_lru_list));
__mb_cache_entry_unhash(ce);
__mb_cache_entry_release_unlock(ce);
}
/*
* mb_cache_entry_get()
*
* Get a cache entry by device / block number. (There can only be one entry
* in the cache per device and block.) Returns NULL if no such cache entry
* exists. The returned cache entry is locked for exclusive access ("single
* writer").
*/
struct mb_cache_entry *
mb_cache_entry_get(struct mb_cache *cache, struct block_device *bdev,
sector_t block)
{
unsigned int bucket;
struct list_head *l;
struct mb_cache_entry *ce;
bucket = hash_long((unsigned long)bdev + (block & 0xffffffff),
cache->c_bucket_bits);
spin_lock(&mb_cache_spinlock);
list_for_each(l, &cache->c_block_hash[bucket]) {
ce = list_entry(l, struct mb_cache_entry, e_block_list);
if (ce->e_bdev == bdev && ce->e_block == block) {
DEFINE_WAIT(wait);
if (!list_empty(&ce->e_lru_list))
list_del_init(&ce->e_lru_list);
while (ce->e_used > 0) {
ce->e_queued++;
prepare_to_wait(&mb_cache_queue, &wait,
TASK_UNINTERRUPTIBLE);
spin_unlock(&mb_cache_spinlock);
schedule();
spin_lock(&mb_cache_spinlock);
ce->e_queued--;
}
finish_wait(&mb_cache_queue, &wait);
ce->e_used += 1 + MB_CACHE_WRITER;
if (!__mb_cache_entry_is_hashed(ce)) {
__mb_cache_entry_release_unlock(ce);
return NULL;
}
goto cleanup;
}
}
ce = NULL;
cleanup:
spin_unlock(&mb_cache_spinlock);
return ce;
}
#if !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0)
static struct mb_cache_entry *
__mb_cache_entry_find(struct list_head *l, struct list_head *head,
int index, struct block_device *bdev, unsigned int key)
{
while (l != head) {
struct mb_cache_entry *ce =
list_entry(l, struct mb_cache_entry,
e_indexes[index].o_list);
if (ce->e_bdev == bdev && ce->e_indexes[index].o_key == key) {
DEFINE_WAIT(wait);
if (!list_empty(&ce->e_lru_list))
list_del_init(&ce->e_lru_list);
/* Incrementing before holding the lock gives readers
priority over writers. */
ce->e_used++;
while (ce->e_used >= MB_CACHE_WRITER) {
ce->e_queued++;
prepare_to_wait(&mb_cache_queue, &wait,
TASK_UNINTERRUPTIBLE);
spin_unlock(&mb_cache_spinlock);
schedule();
spin_lock(&mb_cache_spinlock);
ce->e_queued--;
}
finish_wait(&mb_cache_queue, &wait);
if (!__mb_cache_entry_is_hashed(ce)) {
__mb_cache_entry_release_unlock(ce);
spin_lock(&mb_cache_spinlock);
return ERR_PTR(-EAGAIN);
}
return ce;
}
l = l->next;
}
return NULL;
}
/*
* mb_cache_entry_find_first()
*
* Find the first cache entry on a given device with a certain key in
* an additional index. Additonal matches can be found with
* mb_cache_entry_find_next(). Returns NULL if no match was found. The
* returned cache entry is locked for shared access ("multiple readers").
*
* @cache: the cache to search
* @index: the number of the additonal index to search (0<=index<indexes_count)
* @bdev: the device the cache entry should belong to
* @key: the key in the index
*/
struct mb_cache_entry *
mb_cache_entry_find_first(struct mb_cache *cache, int index,
struct block_device *bdev, unsigned int key)
{
unsigned int bucket = hash_long(key, cache->c_bucket_bits);
struct list_head *l;
struct mb_cache_entry *ce;
mb_assert(index < mb_cache_indexes(cache));
spin_lock(&mb_cache_spinlock);
l = cache->c_indexes_hash[index][bucket].next;
ce = __mb_cache_entry_find(l, &cache->c_indexes_hash[index][bucket],
index, bdev, key);
spin_unlock(&mb_cache_spinlock);
return ce;
}
/*
* mb_cache_entry_find_next()
*
* Find the next cache entry on a given device with a certain key in an
* additional index. Returns NULL if no match could be found. The previous
* entry is atomatically released, so that mb_cache_entry_find_next() can
* be called like this:
*
* entry = mb_cache_entry_find_first();
* while (entry) {
* ...
* entry = mb_cache_entry_find_next(entry, ...);
* }
*
* @prev: The previous match
* @index: the number of the additonal index to search (0<=index<indexes_count)
* @bdev: the device the cache entry should belong to
* @key: the key in the index
*/
struct mb_cache_entry *
mb_cache_entry_find_next(struct mb_cache_entry *prev, int index,
struct block_device *bdev, unsigned int key)
{
struct mb_cache *cache = prev->e_cache;
unsigned int bucket = hash_long(key, cache->c_bucket_bits);
struct list_head *l;
struct mb_cache_entry *ce;
mb_assert(index < mb_cache_indexes(cache));
spin_lock(&mb_cache_spinlock);
l = prev->e_indexes[index].o_list.next;
ce = __mb_cache_entry_find(l, &cache->c_indexes_hash[index][bucket],
index, bdev, key);
__mb_cache_entry_release_unlock(prev);
return ce;
}
#endif /* !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0) */
static int __init init_mbcache(void)
{
mb_shrinker = set_shrinker(DEFAULT_SEEKS, mb_cache_shrink_fn);
return 0;
}
static void __exit exit_mbcache(void)
{
remove_shrinker(mb_shrinker);
}
module_init(init_mbcache)
module_exit(exit_mbcache)