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![T Makphaibulchoke](/assets/img/avatar_default.png)
Fix compiler error with some gcc version(s) that do not support __builtin_log2() by replacing __builtin_log2() with ilog2(). Signed-off-by: T. Makphaibulchoke <tmac@hp.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Reviewed-by: Maciej W. Rozycki <macro@linux-mips.org>
858 lines
24 KiB
C
858 lines
24 KiB
C
/*
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* linux/fs/mbcache.c
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* (C) 2001-2002 Andreas Gruenbacher, <a.gruenbacher@computer.org>
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*/
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/*
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* Filesystem Meta Information Block Cache (mbcache)
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*
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* The mbcache caches blocks of block devices that need to be located
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* by their device/block number, as well as by other criteria (such
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* as the block's contents).
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*
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* There can only be one cache entry in a cache per device and block number.
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* Additional indexes need not be unique in this sense. The number of
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* additional indexes (=other criteria) can be hardwired at compile time
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* or specified at cache create time.
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*
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* Each cache entry is of fixed size. An entry may be `valid' or `invalid'
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* in the cache. A valid entry is in the main hash tables of the cache,
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* and may also be in the lru list. An invalid entry is not in any hashes
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* or lists.
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*
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* A valid cache entry is only in the lru list if no handles refer to it.
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* Invalid cache entries will be freed when the last handle to the cache
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* entry is released. Entries that cannot be freed immediately are put
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* back on the lru list.
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*/
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/*
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* Lock descriptions and usage:
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*
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* Each hash chain of both the block and index hash tables now contains
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* a built-in lock used to serialize accesses to the hash chain.
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*
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* Accesses to global data structures mb_cache_list and mb_cache_lru_list
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* are serialized via the global spinlock mb_cache_spinlock.
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*
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* Each mb_cache_entry contains a spinlock, e_entry_lock, to serialize
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* accesses to its local data, such as e_used and e_queued.
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*
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* Lock ordering:
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*
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* Each block hash chain's lock has the highest lock order, followed by an
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* index hash chain's lock, mb_cache_bg_lock (used to implement mb_cache_entry's
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* lock), and mb_cach_spinlock, with the lowest order. While holding
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* either a block or index hash chain lock, a thread can acquire an
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* mc_cache_bg_lock, which in turn can also acquire mb_cache_spinlock.
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*
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* Synchronization:
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*
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* Since both mb_cache_entry_get and mb_cache_entry_find scan the block and
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* index hash chian, it needs to lock the corresponding hash chain. For each
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* mb_cache_entry within the chain, it needs to lock the mb_cache_entry to
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* prevent either any simultaneous release or free on the entry and also
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* to serialize accesses to either the e_used or e_queued member of the entry.
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*
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* To avoid having a dangling reference to an already freed
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* mb_cache_entry, an mb_cache_entry is only freed when it is not on a
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* block hash chain and also no longer being referenced, both e_used,
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* and e_queued are 0's. When an mb_cache_entry is explicitly freed it is
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* first removed from a block hash chain.
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/hash.h>
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#include <linux/fs.h>
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#include <linux/mm.h>
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#include <linux/slab.h>
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#include <linux/sched.h>
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#include <linux/list_bl.h>
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#include <linux/mbcache.h>
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#include <linux/init.h>
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#include <linux/blockgroup_lock.h>
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#include <linux/log2.h>
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#ifdef MB_CACHE_DEBUG
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# define mb_debug(f...) do { \
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printk(KERN_DEBUG f); \
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printk("\n"); \
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} while (0)
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#define mb_assert(c) do { if (!(c)) \
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printk(KERN_ERR "assertion " #c " failed\n"); \
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} while(0)
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#else
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# define mb_debug(f...) do { } while(0)
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# define mb_assert(c) do { } while(0)
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#endif
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#define mb_error(f...) do { \
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printk(KERN_ERR f); \
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printk("\n"); \
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} while(0)
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#define MB_CACHE_WRITER ((unsigned short)~0U >> 1)
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#define MB_CACHE_ENTRY_LOCK_BITS ilog2(NR_BG_LOCKS)
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#define MB_CACHE_ENTRY_LOCK_INDEX(ce) \
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(hash_long((unsigned long)ce, MB_CACHE_ENTRY_LOCK_BITS))
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static DECLARE_WAIT_QUEUE_HEAD(mb_cache_queue);
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static struct blockgroup_lock *mb_cache_bg_lock;
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static struct kmem_cache *mb_cache_kmem_cache;
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MODULE_AUTHOR("Andreas Gruenbacher <a.gruenbacher@computer.org>");
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MODULE_DESCRIPTION("Meta block cache (for extended attributes)");
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MODULE_LICENSE("GPL");
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EXPORT_SYMBOL(mb_cache_create);
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EXPORT_SYMBOL(mb_cache_shrink);
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EXPORT_SYMBOL(mb_cache_destroy);
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EXPORT_SYMBOL(mb_cache_entry_alloc);
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EXPORT_SYMBOL(mb_cache_entry_insert);
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EXPORT_SYMBOL(mb_cache_entry_release);
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EXPORT_SYMBOL(mb_cache_entry_free);
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EXPORT_SYMBOL(mb_cache_entry_get);
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#if !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0)
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EXPORT_SYMBOL(mb_cache_entry_find_first);
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EXPORT_SYMBOL(mb_cache_entry_find_next);
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#endif
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/*
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* Global data: list of all mbcache's, lru list, and a spinlock for
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* accessing cache data structures on SMP machines. The lru list is
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* global across all mbcaches.
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*/
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static LIST_HEAD(mb_cache_list);
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static LIST_HEAD(mb_cache_lru_list);
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static DEFINE_SPINLOCK(mb_cache_spinlock);
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static inline void
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__spin_lock_mb_cache_entry(struct mb_cache_entry *ce)
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{
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spin_lock(bgl_lock_ptr(mb_cache_bg_lock,
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MB_CACHE_ENTRY_LOCK_INDEX(ce)));
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}
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static inline void
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__spin_unlock_mb_cache_entry(struct mb_cache_entry *ce)
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{
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spin_unlock(bgl_lock_ptr(mb_cache_bg_lock,
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MB_CACHE_ENTRY_LOCK_INDEX(ce)));
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}
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static inline int
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__mb_cache_entry_is_block_hashed(struct mb_cache_entry *ce)
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{
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return !hlist_bl_unhashed(&ce->e_block_list);
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}
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static inline void
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__mb_cache_entry_unhash_block(struct mb_cache_entry *ce)
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{
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if (__mb_cache_entry_is_block_hashed(ce))
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hlist_bl_del_init(&ce->e_block_list);
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}
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static inline int
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__mb_cache_entry_is_index_hashed(struct mb_cache_entry *ce)
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{
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return !hlist_bl_unhashed(&ce->e_index.o_list);
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}
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static inline void
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__mb_cache_entry_unhash_index(struct mb_cache_entry *ce)
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{
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if (__mb_cache_entry_is_index_hashed(ce))
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hlist_bl_del_init(&ce->e_index.o_list);
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}
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/*
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* __mb_cache_entry_unhash_unlock()
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*
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* This function is called to unhash both the block and index hash
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* chain.
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* It assumes both the block and index hash chain is locked upon entry.
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* It also unlock both hash chains both exit
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*/
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static inline void
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__mb_cache_entry_unhash_unlock(struct mb_cache_entry *ce)
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{
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__mb_cache_entry_unhash_index(ce);
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hlist_bl_unlock(ce->e_index_hash_p);
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__mb_cache_entry_unhash_block(ce);
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hlist_bl_unlock(ce->e_block_hash_p);
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}
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static void
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__mb_cache_entry_forget(struct mb_cache_entry *ce, gfp_t gfp_mask)
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{
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struct mb_cache *cache = ce->e_cache;
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mb_assert(!(ce->e_used || ce->e_queued || atomic_read(&ce->e_refcnt)));
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kmem_cache_free(cache->c_entry_cache, ce);
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atomic_dec(&cache->c_entry_count);
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}
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static void
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__mb_cache_entry_release(struct mb_cache_entry *ce)
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{
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/* First lock the entry to serialize access to its local data. */
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__spin_lock_mb_cache_entry(ce);
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/* Wake up all processes queuing for this cache entry. */
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if (ce->e_queued)
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wake_up_all(&mb_cache_queue);
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if (ce->e_used >= MB_CACHE_WRITER)
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ce->e_used -= MB_CACHE_WRITER;
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/*
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* Make sure that all cache entries on lru_list have
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* both e_used and e_qued of 0s.
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*/
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ce->e_used--;
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if (!(ce->e_used || ce->e_queued || atomic_read(&ce->e_refcnt))) {
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if (!__mb_cache_entry_is_block_hashed(ce)) {
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__spin_unlock_mb_cache_entry(ce);
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goto forget;
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}
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/*
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* Need access to lru list, first drop entry lock,
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* then reacquire the lock in the proper order.
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*/
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spin_lock(&mb_cache_spinlock);
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if (list_empty(&ce->e_lru_list))
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list_add_tail(&ce->e_lru_list, &mb_cache_lru_list);
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spin_unlock(&mb_cache_spinlock);
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}
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__spin_unlock_mb_cache_entry(ce);
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return;
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forget:
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mb_assert(list_empty(&ce->e_lru_list));
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__mb_cache_entry_forget(ce, GFP_KERNEL);
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}
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/*
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* mb_cache_shrink_scan() memory pressure callback
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*
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* This function is called by the kernel memory management when memory
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* gets low.
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*
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* @shrink: (ignored)
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* @sc: shrink_control passed from reclaim
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*
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* Returns the number of objects freed.
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*/
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static unsigned long
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mb_cache_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
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{
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LIST_HEAD(free_list);
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struct mb_cache_entry *entry, *tmp;
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int nr_to_scan = sc->nr_to_scan;
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gfp_t gfp_mask = sc->gfp_mask;
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unsigned long freed = 0;
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mb_debug("trying to free %d entries", nr_to_scan);
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spin_lock(&mb_cache_spinlock);
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while ((nr_to_scan-- > 0) && !list_empty(&mb_cache_lru_list)) {
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struct mb_cache_entry *ce =
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list_entry(mb_cache_lru_list.next,
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struct mb_cache_entry, e_lru_list);
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list_del_init(&ce->e_lru_list);
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if (ce->e_used || ce->e_queued || atomic_read(&ce->e_refcnt))
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continue;
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spin_unlock(&mb_cache_spinlock);
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/* Prevent any find or get operation on the entry */
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hlist_bl_lock(ce->e_block_hash_p);
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hlist_bl_lock(ce->e_index_hash_p);
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/* Ignore if it is touched by a find/get */
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if (ce->e_used || ce->e_queued || atomic_read(&ce->e_refcnt) ||
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!list_empty(&ce->e_lru_list)) {
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hlist_bl_unlock(ce->e_index_hash_p);
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hlist_bl_unlock(ce->e_block_hash_p);
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spin_lock(&mb_cache_spinlock);
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continue;
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}
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__mb_cache_entry_unhash_unlock(ce);
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list_add_tail(&ce->e_lru_list, &free_list);
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spin_lock(&mb_cache_spinlock);
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}
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spin_unlock(&mb_cache_spinlock);
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list_for_each_entry_safe(entry, tmp, &free_list, e_lru_list) {
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__mb_cache_entry_forget(entry, gfp_mask);
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freed++;
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}
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return freed;
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}
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static unsigned long
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mb_cache_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
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{
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struct mb_cache *cache;
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unsigned long count = 0;
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spin_lock(&mb_cache_spinlock);
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list_for_each_entry(cache, &mb_cache_list, c_cache_list) {
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mb_debug("cache %s (%d)", cache->c_name,
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atomic_read(&cache->c_entry_count));
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count += atomic_read(&cache->c_entry_count);
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}
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spin_unlock(&mb_cache_spinlock);
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return vfs_pressure_ratio(count);
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}
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static struct shrinker mb_cache_shrinker = {
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.count_objects = mb_cache_shrink_count,
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.scan_objects = mb_cache_shrink_scan,
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.seeks = DEFAULT_SEEKS,
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};
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/*
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* mb_cache_create() create a new cache
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*
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* All entries in one cache are equal size. Cache entries may be from
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* multiple devices. If this is the first mbcache created, registers
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* the cache with kernel memory management. Returns NULL if no more
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* memory was available.
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*
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* @name: name of the cache (informal)
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* @bucket_bits: log2(number of hash buckets)
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*/
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struct mb_cache *
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mb_cache_create(const char *name, int bucket_bits)
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{
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int n, bucket_count = 1 << bucket_bits;
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struct mb_cache *cache = NULL;
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if (!mb_cache_bg_lock) {
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mb_cache_bg_lock = kmalloc(sizeof(struct blockgroup_lock),
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GFP_KERNEL);
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if (!mb_cache_bg_lock)
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return NULL;
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bgl_lock_init(mb_cache_bg_lock);
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}
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cache = kmalloc(sizeof(struct mb_cache), GFP_KERNEL);
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if (!cache)
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return NULL;
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cache->c_name = name;
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atomic_set(&cache->c_entry_count, 0);
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cache->c_bucket_bits = bucket_bits;
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cache->c_block_hash = kmalloc(bucket_count *
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sizeof(struct hlist_bl_head), GFP_KERNEL);
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if (!cache->c_block_hash)
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goto fail;
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for (n=0; n<bucket_count; n++)
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INIT_HLIST_BL_HEAD(&cache->c_block_hash[n]);
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cache->c_index_hash = kmalloc(bucket_count *
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sizeof(struct hlist_bl_head), GFP_KERNEL);
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if (!cache->c_index_hash)
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goto fail;
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for (n=0; n<bucket_count; n++)
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INIT_HLIST_BL_HEAD(&cache->c_index_hash[n]);
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if (!mb_cache_kmem_cache) {
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mb_cache_kmem_cache = kmem_cache_create(name,
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sizeof(struct mb_cache_entry), 0,
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SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD, NULL);
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if (!mb_cache_kmem_cache)
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goto fail2;
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}
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cache->c_entry_cache = mb_cache_kmem_cache;
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/*
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* Set an upper limit on the number of cache entries so that the hash
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* chains won't grow too long.
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*/
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cache->c_max_entries = bucket_count << 4;
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spin_lock(&mb_cache_spinlock);
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list_add(&cache->c_cache_list, &mb_cache_list);
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spin_unlock(&mb_cache_spinlock);
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return cache;
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fail2:
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kfree(cache->c_index_hash);
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fail:
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kfree(cache->c_block_hash);
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kfree(cache);
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return NULL;
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}
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/*
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* mb_cache_shrink()
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*
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* Removes all cache entries of a device from the cache. All cache entries
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* currently in use cannot be freed, and thus remain in the cache. All others
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* are freed.
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*
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* @bdev: which device's cache entries to shrink
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*/
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void
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mb_cache_shrink(struct block_device *bdev)
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{
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LIST_HEAD(free_list);
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struct list_head *l;
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struct mb_cache_entry *ce, *tmp;
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l = &mb_cache_lru_list;
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spin_lock(&mb_cache_spinlock);
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while (!list_is_last(l, &mb_cache_lru_list)) {
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l = l->next;
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ce = list_entry(l, struct mb_cache_entry, e_lru_list);
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if (ce->e_bdev == bdev) {
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list_del_init(&ce->e_lru_list);
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if (ce->e_used || ce->e_queued ||
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atomic_read(&ce->e_refcnt))
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continue;
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spin_unlock(&mb_cache_spinlock);
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/*
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* Prevent any find or get operation on the entry.
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*/
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hlist_bl_lock(ce->e_block_hash_p);
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hlist_bl_lock(ce->e_index_hash_p);
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/* Ignore if it is touched by a find/get */
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if (ce->e_used || ce->e_queued ||
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atomic_read(&ce->e_refcnt) ||
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!list_empty(&ce->e_lru_list)) {
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hlist_bl_unlock(ce->e_index_hash_p);
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hlist_bl_unlock(ce->e_block_hash_p);
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l = &mb_cache_lru_list;
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spin_lock(&mb_cache_spinlock);
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continue;
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}
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__mb_cache_entry_unhash_unlock(ce);
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mb_assert(!(ce->e_used || ce->e_queued ||
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atomic_read(&ce->e_refcnt)));
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list_add_tail(&ce->e_lru_list, &free_list);
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l = &mb_cache_lru_list;
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spin_lock(&mb_cache_spinlock);
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}
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}
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spin_unlock(&mb_cache_spinlock);
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list_for_each_entry_safe(ce, tmp, &free_list, e_lru_list) {
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__mb_cache_entry_forget(ce, GFP_KERNEL);
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}
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}
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/*
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* mb_cache_destroy()
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*
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* Shrinks the cache to its minimum possible size (hopefully 0 entries),
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* and then destroys it. If this was the last mbcache, un-registers the
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* mbcache from kernel memory management.
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*/
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void
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mb_cache_destroy(struct mb_cache *cache)
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{
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LIST_HEAD(free_list);
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struct mb_cache_entry *ce, *tmp;
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spin_lock(&mb_cache_spinlock);
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list_for_each_entry_safe(ce, tmp, &mb_cache_lru_list, e_lru_list) {
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if (ce->e_cache == cache)
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list_move_tail(&ce->e_lru_list, &free_list);
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}
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list_del(&cache->c_cache_list);
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spin_unlock(&mb_cache_spinlock);
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|
|
list_for_each_entry_safe(ce, tmp, &free_list, e_lru_list) {
|
|
list_del_init(&ce->e_lru_list);
|
|
/*
|
|
* Prevent any find or get operation on the entry.
|
|
*/
|
|
hlist_bl_lock(ce->e_block_hash_p);
|
|
hlist_bl_lock(ce->e_index_hash_p);
|
|
mb_assert(!(ce->e_used || ce->e_queued ||
|
|
atomic_read(&ce->e_refcnt)));
|
|
__mb_cache_entry_unhash_unlock(ce);
|
|
__mb_cache_entry_forget(ce, 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));
|
|
}
|
|
|
|
if (list_empty(&mb_cache_list)) {
|
|
kmem_cache_destroy(mb_cache_kmem_cache);
|
|
mb_cache_kmem_cache = NULL;
|
|
}
|
|
kfree(cache->c_index_hash);
|
|
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, gfp_t gfp_flags)
|
|
{
|
|
struct mb_cache_entry *ce;
|
|
|
|
if (atomic_read(&cache->c_entry_count) >= cache->c_max_entries) {
|
|
struct list_head *l;
|
|
|
|
l = &mb_cache_lru_list;
|
|
spin_lock(&mb_cache_spinlock);
|
|
while (!list_is_last(l, &mb_cache_lru_list)) {
|
|
l = l->next;
|
|
ce = list_entry(l, struct mb_cache_entry, e_lru_list);
|
|
if (ce->e_cache == cache) {
|
|
list_del_init(&ce->e_lru_list);
|
|
if (ce->e_used || ce->e_queued ||
|
|
atomic_read(&ce->e_refcnt))
|
|
continue;
|
|
spin_unlock(&mb_cache_spinlock);
|
|
/*
|
|
* Prevent any find or get operation on the
|
|
* entry.
|
|
*/
|
|
hlist_bl_lock(ce->e_block_hash_p);
|
|
hlist_bl_lock(ce->e_index_hash_p);
|
|
/* Ignore if it is touched by a find/get */
|
|
if (ce->e_used || ce->e_queued ||
|
|
atomic_read(&ce->e_refcnt) ||
|
|
!list_empty(&ce->e_lru_list)) {
|
|
hlist_bl_unlock(ce->e_index_hash_p);
|
|
hlist_bl_unlock(ce->e_block_hash_p);
|
|
l = &mb_cache_lru_list;
|
|
spin_lock(&mb_cache_spinlock);
|
|
continue;
|
|
}
|
|
mb_assert(list_empty(&ce->e_lru_list));
|
|
mb_assert(!(ce->e_used || ce->e_queued ||
|
|
atomic_read(&ce->e_refcnt)));
|
|
__mb_cache_entry_unhash_unlock(ce);
|
|
goto found;
|
|
}
|
|
}
|
|
spin_unlock(&mb_cache_spinlock);
|
|
}
|
|
|
|
ce = kmem_cache_alloc(cache->c_entry_cache, gfp_flags);
|
|
if (!ce)
|
|
return NULL;
|
|
atomic_inc(&cache->c_entry_count);
|
|
INIT_LIST_HEAD(&ce->e_lru_list);
|
|
INIT_HLIST_BL_NODE(&ce->e_block_list);
|
|
INIT_HLIST_BL_NODE(&ce->e_index.o_list);
|
|
ce->e_cache = cache;
|
|
ce->e_queued = 0;
|
|
atomic_set(&ce->e_refcnt, 0);
|
|
found:
|
|
ce->e_block_hash_p = &cache->c_block_hash[0];
|
|
ce->e_index_hash_p = &cache->c_index_hash[0];
|
|
ce->e_used = 1 + MB_CACHE_WRITER;
|
|
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
|
|
* @key: lookup key
|
|
*/
|
|
int
|
|
mb_cache_entry_insert(struct mb_cache_entry *ce, struct block_device *bdev,
|
|
sector_t block, unsigned int key)
|
|
{
|
|
struct mb_cache *cache = ce->e_cache;
|
|
unsigned int bucket;
|
|
struct hlist_bl_node *l;
|
|
struct hlist_bl_head *block_hash_p;
|
|
struct hlist_bl_head *index_hash_p;
|
|
struct mb_cache_entry *lce;
|
|
|
|
mb_assert(ce);
|
|
bucket = hash_long((unsigned long)bdev + (block & 0xffffffff),
|
|
cache->c_bucket_bits);
|
|
block_hash_p = &cache->c_block_hash[bucket];
|
|
hlist_bl_lock(block_hash_p);
|
|
hlist_bl_for_each_entry(lce, l, block_hash_p, e_block_list) {
|
|
if (lce->e_bdev == bdev && lce->e_block == block) {
|
|
hlist_bl_unlock(block_hash_p);
|
|
return -EBUSY;
|
|
}
|
|
}
|
|
mb_assert(!__mb_cache_entry_is_block_hashed(ce));
|
|
__mb_cache_entry_unhash_block(ce);
|
|
__mb_cache_entry_unhash_index(ce);
|
|
ce->e_bdev = bdev;
|
|
ce->e_block = block;
|
|
ce->e_block_hash_p = block_hash_p;
|
|
ce->e_index.o_key = key;
|
|
hlist_bl_add_head(&ce->e_block_list, block_hash_p);
|
|
hlist_bl_unlock(block_hash_p);
|
|
bucket = hash_long(key, cache->c_bucket_bits);
|
|
index_hash_p = &cache->c_index_hash[bucket];
|
|
hlist_bl_lock(index_hash_p);
|
|
ce->e_index_hash_p = index_hash_p;
|
|
hlist_bl_add_head(&ce->e_index.o_list, index_hash_p);
|
|
hlist_bl_unlock(index_hash_p);
|
|
return 0;
|
|
}
|
|
|
|
|
|
/*
|
|
* 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)
|
|
{
|
|
__mb_cache_entry_release(ce);
|
|
}
|
|
|
|
|
|
/*
|
|
* mb_cache_entry_free()
|
|
*
|
|
*/
|
|
void
|
|
mb_cache_entry_free(struct mb_cache_entry *ce)
|
|
{
|
|
mb_assert(ce);
|
|
mb_assert(list_empty(&ce->e_lru_list));
|
|
hlist_bl_lock(ce->e_index_hash_p);
|
|
__mb_cache_entry_unhash_index(ce);
|
|
hlist_bl_unlock(ce->e_index_hash_p);
|
|
hlist_bl_lock(ce->e_block_hash_p);
|
|
__mb_cache_entry_unhash_block(ce);
|
|
hlist_bl_unlock(ce->e_block_hash_p);
|
|
__mb_cache_entry_release(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 hlist_bl_node *l;
|
|
struct mb_cache_entry *ce;
|
|
struct hlist_bl_head *block_hash_p;
|
|
|
|
bucket = hash_long((unsigned long)bdev + (block & 0xffffffff),
|
|
cache->c_bucket_bits);
|
|
block_hash_p = &cache->c_block_hash[bucket];
|
|
/* First serialize access to the block corresponding hash chain. */
|
|
hlist_bl_lock(block_hash_p);
|
|
hlist_bl_for_each_entry(ce, l, block_hash_p, e_block_list) {
|
|
mb_assert(ce->e_block_hash_p == block_hash_p);
|
|
if (ce->e_bdev == bdev && ce->e_block == block) {
|
|
/*
|
|
* Prevent a free from removing the entry.
|
|
*/
|
|
atomic_inc(&ce->e_refcnt);
|
|
hlist_bl_unlock(block_hash_p);
|
|
__spin_lock_mb_cache_entry(ce);
|
|
atomic_dec(&ce->e_refcnt);
|
|
if (ce->e_used > 0) {
|
|
DEFINE_WAIT(wait);
|
|
while (ce->e_used > 0) {
|
|
ce->e_queued++;
|
|
prepare_to_wait(&mb_cache_queue, &wait,
|
|
TASK_UNINTERRUPTIBLE);
|
|
__spin_unlock_mb_cache_entry(ce);
|
|
schedule();
|
|
__spin_lock_mb_cache_entry(ce);
|
|
ce->e_queued--;
|
|
}
|
|
finish_wait(&mb_cache_queue, &wait);
|
|
}
|
|
ce->e_used += 1 + MB_CACHE_WRITER;
|
|
__spin_unlock_mb_cache_entry(ce);
|
|
|
|
if (!list_empty(&ce->e_lru_list)) {
|
|
spin_lock(&mb_cache_spinlock);
|
|
list_del_init(&ce->e_lru_list);
|
|
spin_unlock(&mb_cache_spinlock);
|
|
}
|
|
if (!__mb_cache_entry_is_block_hashed(ce)) {
|
|
__mb_cache_entry_release(ce);
|
|
return NULL;
|
|
}
|
|
return ce;
|
|
}
|
|
}
|
|
hlist_bl_unlock(block_hash_p);
|
|
return NULL;
|
|
}
|
|
|
|
#if !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0)
|
|
|
|
static struct mb_cache_entry *
|
|
__mb_cache_entry_find(struct hlist_bl_node *l, struct hlist_bl_head *head,
|
|
struct block_device *bdev, unsigned int key)
|
|
{
|
|
|
|
/* The index hash chain is alredy acquire by caller. */
|
|
while (l != NULL) {
|
|
struct mb_cache_entry *ce =
|
|
hlist_bl_entry(l, struct mb_cache_entry,
|
|
e_index.o_list);
|
|
mb_assert(ce->e_index_hash_p == head);
|
|
if (ce->e_bdev == bdev && ce->e_index.o_key == key) {
|
|
/*
|
|
* Prevent a free from removing the entry.
|
|
*/
|
|
atomic_inc(&ce->e_refcnt);
|
|
hlist_bl_unlock(head);
|
|
__spin_lock_mb_cache_entry(ce);
|
|
atomic_dec(&ce->e_refcnt);
|
|
ce->e_used++;
|
|
/* Incrementing before holding the lock gives readers
|
|
priority over writers. */
|
|
if (ce->e_used >= MB_CACHE_WRITER) {
|
|
DEFINE_WAIT(wait);
|
|
|
|
while (ce->e_used >= MB_CACHE_WRITER) {
|
|
ce->e_queued++;
|
|
prepare_to_wait(&mb_cache_queue, &wait,
|
|
TASK_UNINTERRUPTIBLE);
|
|
__spin_unlock_mb_cache_entry(ce);
|
|
schedule();
|
|
__spin_lock_mb_cache_entry(ce);
|
|
ce->e_queued--;
|
|
}
|
|
finish_wait(&mb_cache_queue, &wait);
|
|
}
|
|
__spin_unlock_mb_cache_entry(ce);
|
|
if (!list_empty(&ce->e_lru_list)) {
|
|
spin_lock(&mb_cache_spinlock);
|
|
list_del_init(&ce->e_lru_list);
|
|
spin_unlock(&mb_cache_spinlock);
|
|
}
|
|
if (!__mb_cache_entry_is_block_hashed(ce)) {
|
|
__mb_cache_entry_release(ce);
|
|
return ERR_PTR(-EAGAIN);
|
|
}
|
|
return ce;
|
|
}
|
|
l = l->next;
|
|
}
|
|
hlist_bl_unlock(head);
|
|
return NULL;
|
|
}
|
|
|
|
|
|
/*
|
|
* mb_cache_entry_find_first()
|
|
*
|
|
* Find the first cache entry on a given device with a certain key in
|
|
* an additional index. Additional 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
|
|
* @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, struct block_device *bdev,
|
|
unsigned int key)
|
|
{
|
|
unsigned int bucket = hash_long(key, cache->c_bucket_bits);
|
|
struct hlist_bl_node *l;
|
|
struct mb_cache_entry *ce = NULL;
|
|
struct hlist_bl_head *index_hash_p;
|
|
|
|
index_hash_p = &cache->c_index_hash[bucket];
|
|
hlist_bl_lock(index_hash_p);
|
|
if (!hlist_bl_empty(index_hash_p)) {
|
|
l = hlist_bl_first(index_hash_p);
|
|
ce = __mb_cache_entry_find(l, index_hash_p, bdev, key);
|
|
} else
|
|
hlist_bl_unlock(index_hash_p);
|
|
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
|
|
* @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,
|
|
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 hlist_bl_node *l;
|
|
struct mb_cache_entry *ce;
|
|
struct hlist_bl_head *index_hash_p;
|
|
|
|
index_hash_p = &cache->c_index_hash[bucket];
|
|
mb_assert(prev->e_index_hash_p == index_hash_p);
|
|
hlist_bl_lock(index_hash_p);
|
|
mb_assert(!hlist_bl_empty(index_hash_p));
|
|
l = prev->e_index.o_list.next;
|
|
ce = __mb_cache_entry_find(l, index_hash_p, bdev, key);
|
|
__mb_cache_entry_release(prev);
|
|
return ce;
|
|
}
|
|
|
|
#endif /* !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0) */
|
|
|
|
static int __init init_mbcache(void)
|
|
{
|
|
register_shrinker(&mb_cache_shrinker);
|
|
return 0;
|
|
}
|
|
|
|
static void __exit exit_mbcache(void)
|
|
{
|
|
unregister_shrinker(&mb_cache_shrinker);
|
|
}
|
|
|
|
module_init(init_mbcache)
|
|
module_exit(exit_mbcache)
|
|
|