The patch increases the parallelism of mb_cache_entry utilization by introducing new spinlocks to the mb_cache structure to protect the mb_cache local block and index hash chains, while the global mb_cache_lru_list and mb_cache_list continue to be protected by the global mb_cache_spinlock.
Signed-off-by: T. Makphaibulchoke <t...@hp.com> --- fs/mbcache.c | 419 +++++++++++++++++++++++++++++++++++++----------- include/linux/mbcache.h | 5 + 2 files changed, 334 insertions(+), 90 deletions(-) diff --git a/fs/mbcache.c b/fs/mbcache.c index 8c32ef3..01a0c09 100644 --- a/fs/mbcache.c +++ b/fs/mbcache.c @@ -26,6 +26,16 @@ * back on the lru list. */ +/* Locking protocol: + * + * The nth hash chain of both the c_block_hash and c_index_hash are + * protected by the mth entry of the c_bdev_locks and c_key_locks respectively, + * where m is equal to n & c_lock_mask. + * + * While holding a c_bdev_locks, a thread can acquire either a c_key_locks + * or mb_cache_spinlock. + */ + #include <linux/kernel.h> #include <linux/module.h> @@ -57,6 +67,8 @@ #define MB_CACHE_WRITER ((unsigned short)~0U >> 1) +#define MAX_LOCK_RETRY 2048 + static DECLARE_WAIT_QUEUE_HEAD(mb_cache_queue); MODULE_AUTHOR("Andreas Gruenbacher <a.gruenbac...@computer.org>"); @@ -109,11 +121,28 @@ static void __mb_cache_entry_unhash(struct mb_cache_entry *ce) { if (__mb_cache_entry_is_hashed(ce)) { + struct mb_cache *cache = ce->e_cache; + spinlock_t *key_lock = &cache->c_key_locks[ce->e_key_lock]; + list_del_init(&ce->e_block_list); + spin_lock(key_lock); list_del(&ce->e_index.o_list); + spin_unlock(key_lock); } } +static void +__mb_cache_entry_unhash_lock(struct mb_cache_entry *ce) +{ + struct mb_cache *cache = ce->e_cache; + int lock_index = ce->e_bdev_lock; + + spin_lock(&cache->c_bdev_locks[lock_index]); + mb_assert(lock_index == ce->e_bdev_lock); + __mb_cache_entry_unhash(ce); + spin_unlock(&cache->c_bdev_locks[lock_index]); +} + static void __mb_cache_entry_forget(struct mb_cache_entry *ce, gfp_t gfp_mask) @@ -127,8 +156,9 @@ __mb_cache_entry_forget(struct mb_cache_entry *ce, gfp_t gfp_mask) static void -__mb_cache_entry_release_unlock(struct mb_cache_entry *ce) - __releases(mb_cache_spinlock) +__mb_cache_entry_release_unlock(struct mb_cache_entry *ce, + spinlock_t *hash_lock) + __releases(hash_lock) { /* Wake up all processes queuing for this cache entry. */ if (ce->e_queued) @@ -139,13 +169,17 @@ __mb_cache_entry_release_unlock(struct mb_cache_entry *ce) 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); + spin_unlock(hash_lock); + spin_lock(&mb_cache_spinlock); + if (list_empty(&ce->e_lru_list)) + list_add_tail(&ce->e_lru_list, &mb_cache_lru_list); + spin_unlock(&mb_cache_spinlock); + } else + spin_unlock(hash_lock); return; forget: - spin_unlock(&mb_cache_spinlock); + spin_unlock(hash_lock); + mb_assert(list_empty(&ce->e_lru_list)); __mb_cache_entry_forget(ce, GFP_KERNEL); } @@ -164,31 +198,59 @@ forget: static int mb_cache_shrink_fn(struct shrinker *shrink, struct shrink_control *sc) { - LIST_HEAD(free_list); struct mb_cache *cache; - struct mb_cache_entry *entry, *tmp; int count = 0; int nr_to_scan = sc->nr_to_scan; gfp_t gfp_mask = sc->gfp_mask; + int max_loop = nr_to_scan << 1; mb_debug("trying to free %d entries", nr_to_scan); - spin_lock(&mb_cache_spinlock); - while (nr_to_scan-- && !list_empty(&mb_cache_lru_list)) { - struct mb_cache_entry *ce = - list_entry(mb_cache_lru_list.next, + while ((nr_to_scan > 0) && (max_loop-- > 0)) { + struct mb_cache *cache; + struct mb_cache_entry *ce; + int nloops = 0; + int lock_index; + + spin_lock(&mb_cache_spinlock); + if (list_empty(&mb_cache_lru_list)) { + spin_unlock(&mb_cache_spinlock); + break; + } + ce = list_entry(mb_cache_lru_list.next, struct mb_cache_entry, e_lru_list); - list_move_tail(&ce->e_lru_list, &free_list); + list_del_init(&ce->e_lru_list); + spin_unlock(&mb_cache_spinlock); + + cache = ce->e_cache; + lock_index = ce->e_bdev_lock; + spin_lock(&cache->c_bdev_locks[lock_index]); + while ((lock_index != ce->e_bdev_lock) && + (nloops++ < MAX_LOCK_RETRY)) { + spin_unlock(&cache->c_bdev_locks[lock_index]); + lock_index = ce->e_bdev_lock; + spin_lock(&cache->c_bdev_locks[lock_index]); + } + if (nloops >= MAX_LOCK_RETRY) { + mb_assert(FALSE); + continue; + } + if (ce->e_used || ce->e_queued) { + spin_unlock(&cache->c_bdev_locks[lock_index]); + continue; + } + __mb_cache_entry_unhash(ce); + spin_unlock(&cache->c_bdev_locks[lock_index]); + __mb_cache_entry_forget(ce, gfp_mask); + nr_to_scan--; } + spin_lock(&mb_cache_spinlock); list_for_each_entry(cache, &mb_cache_list, c_cache_list) { mb_debug("cache %s (%d)", cache->c_name, atomic_read(&cache->c_entry_count)); count += atomic_read(&cache->c_entry_count); } spin_unlock(&mb_cache_spinlock); - list_for_each_entry_safe(entry, tmp, &free_list, e_lru_list) { - __mb_cache_entry_forget(entry, gfp_mask); - } return (count / 100) * sysctl_vfs_cache_pressure; } @@ -209,6 +271,7 @@ mb_cache_create(const char *name, int bucket_bits) { int n, bucket_count = 1 << bucket_bits; struct mb_cache *cache = NULL; + int num_locks; cache = kmalloc(sizeof(struct mb_cache), GFP_KERNEL); if (!cache) @@ -234,6 +297,28 @@ mb_cache_create(const char *name, int bucket_bits) if (!cache->c_entry_cache) goto fail2; + num_locks = 1 << (bucket_bits - 4); + cache->c_bdev_locks = kmalloc(num_locks * sizeof(spinlock_t), + GFP_KERNEL); + if (!cache->c_bdev_locks) { + kfree(cache->c_entry_cache); + goto fail2; + } + + cache->c_key_locks = kmalloc(num_locks * sizeof(spinlock_t), + GFP_KERNEL); + if (!cache->c_key_locks) { + kfree(cache->c_bdev_locks); + kfree(cache->c_entry_cache); + goto fail2; + } + + cache->c_lock_mask = num_locks - 1; + for (n = 0; n < num_locks; n++) + spin_lock_init(&cache->c_bdev_locks[n]); + for (n = 0; n < num_locks; n++) + spin_lock_init(&cache->c_key_locks[n]); + /* * Set an upper limit on the number of cache entries so that the hash * chains won't grow too long. @@ -276,13 +361,36 @@ mb_cache_shrink(struct block_device *bdev) 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); + int lock_index; + int nloops = 0; + struct mb_cache_entry *ce = + list_entry(l, struct mb_cache_entry, e_lru_list); + struct mb_cache *cache = ce->e_cache; + + lock_index = ce->e_bdev_lock; + spin_lock(&cache->c_bdev_locks[lock_index]); + while ((lock_index != ce->e_bdev_lock) && + (nloops++ < MAX_LOCK_RETRY)) { + spin_unlock(&cache->c_bdev_locks[lock_index]); + lock_index = ce->e_bdev_lock; + spin_lock(&cache->c_bdev_locks[lock_index]); + } + if (nloops > MAX_LOCK_RETRY) { + mb_assert(FALSE); + continue; + } + if (ce->e_used || ce->e_queued) { + spin_unlock(&cache->c_bdev_locks[lock_index]); + continue; + } + + __mb_cache_entry_unhash(ce); + spin_unlock(&cache->c_bdev_locks[lock_index]); + __mb_cache_entry_forget(ce, GFP_KERNEL); } } @@ -306,15 +414,16 @@ mb_cache_destroy(struct mb_cache *cache) 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); + struct mb_cache_entry *ce = + list_entry(l, struct mb_cache_entry, e_lru_list); + __mb_cache_entry_unhash_lock(ce); + __mb_cache_entry_forget(ce, GFP_KERNEL); } if (atomic_read(&cache->c_entry_count) > 0) { @@ -325,6 +434,8 @@ mb_cache_destroy(struct mb_cache *cache) kmem_cache_destroy(cache->c_entry_cache); + kfree(cache->c_key_locks); + kfree(cache->c_bdev_locks); kfree(cache->c_index_hash); kfree(cache->c_block_hash); kfree(cache); @@ -344,26 +455,60 @@ mb_cache_entry_alloc(struct mb_cache *cache, gfp_t gfp_flags) struct mb_cache_entry *ce = NULL; if (atomic_read(&cache->c_entry_count) >= cache->c_max_entries) { + struct list_head *l, *ltmp; + +retry: spin_lock(&mb_cache_spinlock); - if (!list_empty(&mb_cache_lru_list)) { - ce = list_entry(mb_cache_lru_list.next, - struct mb_cache_entry, e_lru_list); - list_del_init(&ce->e_lru_list); - __mb_cache_entry_unhash(ce); + list_for_each_safe(l, ltmp, &mb_cache_lru_list) { + ce = list_entry(l, struct mb_cache_entry, e_lru_list); + if (ce->e_cache == cache) { + int lock_index = ce->e_bdev_lock; + spinlock_t *bdev_lock = &cache-> + c_bdev_locks[lock_index]; + int nloops = 0; + + list_del_init(&ce->e_lru_list); + spin_unlock(&mb_cache_spinlock); + spin_lock(bdev_lock); + while ((lock_index != ce->e_bdev_lock) && + (nloops++ < MAX_LOCK_RETRY)) { + spin_unlock(bdev_lock); + lock_index = ce->e_bdev_lock; + bdev_lock = &cache-> + c_bdev_locks[lock_index]; + spin_lock(bdev_lock); + } + if (nloops > MAX_LOCK_RETRY) { + mb_assert(FALSE); + continue; + } + if (ce->e_used || ce->e_queued) { + pr_warn("%s: ce %p is still being referenced..\n", + __func__, ce); + spin_unlock(bdev_lock); + goto retry; + } + __mb_cache_entry_unhash(ce); + ce->e_used = 1 + MB_CACHE_WRITER; + spin_unlock(bdev_lock); + return ce; + } } spin_unlock(&mb_cache_spinlock); } - if (!ce) { - 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_LIST_HEAD(&ce->e_block_list); - ce->e_cache = cache; - ce->e_queued = 0; - } + + 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_LIST_HEAD(&ce->e_block_list); + INIT_LIST_HEAD(&ce->e_index.o_list); + ce->e_cache = cache; + ce->e_queued = 0; ce->e_used = 1 + MB_CACHE_WRITER; + ce->e_bdev_lock = 0; + ce->e_key_lock = 0; return ce; } @@ -390,27 +535,42 @@ mb_cache_entry_insert(struct mb_cache_entry *ce, struct block_device *bdev, unsigned int bucket; struct list_head *l; int error = -EBUSY; + int lock_index; + spinlock_t *key_lock; + int key_index; bucket = hash_long((unsigned long)bdev + (block & 0xffffffff), cache->c_bucket_bits); - spin_lock(&mb_cache_spinlock); + lock_index = bucket & cache->c_lock_mask; + if ((ce->e_used != 1 + MB_CACHE_WRITER) || ce->e_queued) + pr_warn("%s: attempt to insert an in-used ce %p.\n", + __func__, ce); + __mb_cache_entry_unhash_lock(ce); + + spin_lock(&cache->c_bdev_locks[lock_index]); 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; + if (ce->e_bdev == bdev && ce->e_block == block) { + spin_unlock(&cache->c_bdev_locks[lock_index]); + return error; + } } - __mb_cache_entry_unhash(ce); + + ce->e_bdev_lock = lock_index; ce->e_bdev = bdev; ce->e_block = block; list_add(&ce->e_block_list, &cache->c_block_hash[bucket]); ce->e_index.o_key = key; bucket = hash_long(key, cache->c_bucket_bits); + key_index = bucket & cache->c_lock_mask; + key_lock = &cache->c_key_locks[key_index]; + spin_lock(key_lock); + ce->e_key_lock = key_index; list_add(&ce->e_index.o_list, &cache->c_index_hash[bucket]); - error = 0; -out: - spin_unlock(&mb_cache_spinlock); - return error; + spin_unlock(key_lock); + spin_unlock(&cache->c_bdev_locks[lock_index]); + return 0; } @@ -424,8 +584,14 @@ out: void mb_cache_entry_release(struct mb_cache_entry *ce) { - spin_lock(&mb_cache_spinlock); - __mb_cache_entry_release_unlock(ce); + struct mb_cache *cache = ce->e_cache; + spinlock_t *hash_lock; + int lock_index = ce->e_bdev_lock; + + hash_lock = &cache->c_bdev_locks[lock_index]; + spin_lock(hash_lock); + mb_assert(lock_index == ce->e_bdev_lock); + __mb_cache_entry_release_unlock(ce, hash_lock); } @@ -438,10 +604,21 @@ mb_cache_entry_release(struct mb_cache_entry *ce) void mb_cache_entry_free(struct mb_cache_entry *ce) { - spin_lock(&mb_cache_spinlock); + struct mb_cache *cache = ce->e_cache; + spinlock_t *hash_lock; + int lock_index = ce->e_bdev_lock; + + if (!list_empty(&ce->e_lru_list)) { + pr_warn("%s: attempt to free ce %p still in-used.\n", + __func__, ce); + return; + } mb_assert(list_empty(&ce->e_lru_list)); + hash_lock = &cache->c_bdev_locks[lock_index]; + spin_lock(hash_lock); + mb_assert(lock_index == ce->e_bdev_lock); __mb_cache_entry_unhash(ce); - __mb_cache_entry_release_unlock(ce); + __mb_cache_entry_release_unlock(ce, hash_lock); } @@ -460,32 +637,43 @@ mb_cache_entry_get(struct mb_cache *cache, struct block_device *bdev, unsigned int bucket; struct list_head *l; struct mb_cache_entry *ce; + spinlock_t *hash_lock; + int hash_index; + int lock_index; bucket = hash_long((unsigned long)bdev + (block & 0xffffffff), cache->c_bucket_bits); - spin_lock(&mb_cache_spinlock); + hash_index = bucket & cache->c_lock_mask; + hash_lock = &cache->c_bdev_locks[hash_index]; + spin_lock(hash_lock); list_for_each(l, &cache->c_block_hash[bucket]) { ce = list_entry(l, struct mb_cache_entry, e_block_list); + mb_assert(hash_index == ce->e_bdev_lock); if (ce->e_bdev == bdev && ce->e_block == block) { DEFINE_WAIT(wait); + spin_lock(&mb_cache_spinlock); if (!list_empty(&ce->e_lru_list)) list_del_init(&ce->e_lru_list); + spin_unlock(&mb_cache_spinlock); while (ce->e_used > 0) { ce->e_queued++; prepare_to_wait(&mb_cache_queue, &wait, TASK_UNINTERRUPTIBLE); - spin_unlock(&mb_cache_spinlock); + lock_index = ce->e_bdev_lock; + spin_unlock(hash_lock); schedule(); - spin_lock(&mb_cache_spinlock); - ce->e_queued--; + spin_lock(hash_lock); + mb_assert(lock_index == ce->e_bdev_lock); + 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); + mb_assert(hash_index == ce->e_bdev_lock); + __mb_cache_entry_release_unlock(ce, hash_lock); return NULL; } goto cleanup; @@ -494,47 +682,76 @@ mb_cache_entry_get(struct mb_cache *cache, struct block_device *bdev, ce = NULL; cleanup: - spin_unlock(&mb_cache_spinlock); + spin_unlock(hash_lock); 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, - struct block_device *bdev, unsigned int key) +__mb_cache_entry_find_unlock(struct list_head *l, struct list_head *head, + struct block_device *bdev, unsigned int key, int lock_index) { + struct mb_cache_entry *ce; + struct mb_cache *cache; + spinlock_t *key_lock; + int found = 0; + + mb_assert(l != head); + if (l == head) + return NULL; + + ce = list_entry(l, struct mb_cache_entry, e_index.o_list); + cache = ce->e_cache; + mb_assert((lock_index >= 0) && (lock_index <= cache->c_lock_mask)); + key_lock = &cache->c_key_locks[lock_index]; + while (l != head) { - struct mb_cache_entry *ce = - list_entry(l, struct mb_cache_entry, e_index.o_list); + ce = list_entry(l, struct mb_cache_entry, e_index.o_list); + mb_assert(lock_index == ce->e_key_lock); if (ce->e_bdev == bdev && ce->e_index.o_key == key) { - DEFINE_WAIT(wait); + found = 1; + break; + } + l = l->next; + } + spin_unlock(key_lock); - if (!list_empty(&ce->e_lru_list)) - list_del_init(&ce->e_lru_list); + if (found) { + int hash_index; + spinlock_t *hash_lock; + DEFINE_WAIT(wait); - /* 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); + hash_index = ce->e_bdev_lock; + hash_lock = &cache->c_bdev_locks[hash_index]; - if (!__mb_cache_entry_is_hashed(ce)) { - __mb_cache_entry_release_unlock(ce); - spin_lock(&mb_cache_spinlock); - return ERR_PTR(-EAGAIN); - } - return ce; + spin_lock(&mb_cache_spinlock); + if (!list_empty(&ce->e_lru_list)) + list_del_init(&ce->e_lru_list); + spin_unlock(&mb_cache_spinlock); + + spin_lock(hash_lock); + /* 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(hash_lock); + schedule(); + spin_lock(hash_lock); + mb_assert(hash_index == ce->e_bdev_lock); + ce->e_queued++; } - l = l->next; + finish_wait(&mb_cache_queue, &wait); + + if (!__mb_cache_entry_is_hashed(ce)) { + __mb_cache_entry_release_unlock(ce, hash_lock); + return ERR_PTR(-EAGAIN); + } + spin_unlock(hash_lock); + return ce; } return NULL; } @@ -559,11 +776,18 @@ mb_cache_entry_find_first(struct mb_cache *cache, struct block_device *bdev, unsigned int bucket = hash_long(key, cache->c_bucket_bits); struct list_head *l; struct mb_cache_entry *ce; + int lock_index = bucket & cache->c_lock_mask; + spinlock_t *key_lock = &cache->c_key_locks[lock_index]; - spin_lock(&mb_cache_spinlock); + spin_lock(key_lock); l = cache->c_index_hash[bucket].next; - ce = __mb_cache_entry_find(l, &cache->c_index_hash[bucket], bdev, key); - spin_unlock(&mb_cache_spinlock); + if (l == &cache->c_index_hash[bucket]) { + spin_unlock(key_lock); + return NULL; + } + ce = __mb_cache_entry_find_unlock(l, &cache->c_index_hash[bucket], + bdev, key, lock_index); + mb_assert(!ce || (lock_index == ce->e_key_lock)); return ce; } @@ -593,12 +817,27 @@ mb_cache_entry_find_next(struct mb_cache_entry *prev, 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; + struct mb_cache_entry *ce = NULL; + int lock_index = bucket & cache->c_lock_mask; + spinlock_t *lock; - spin_lock(&mb_cache_spinlock); + lock = &cache->c_key_locks[lock_index]; + spin_lock(lock); + mb_assert(lock_index == prev->e_key_lock); l = prev->e_index.o_list.next; - ce = __mb_cache_entry_find(l, &cache->c_index_hash[bucket], bdev, key); - __mb_cache_entry_release_unlock(prev); + if (l == &cache->c_index_hash[bucket]) + spin_unlock(lock); + else { + ce = __mb_cache_entry_find_unlock(l, &cache-> + c_index_hash[bucket], bdev, key, lock_index); + mb_assert(!ce || (lock_index == ce->e_key_lock)); + } + + lock_index = prev->e_bdev_lock; + lock = &cache->c_bdev_locks[lock_index]; + spin_lock(lock); + mb_assert(lock_index == prev->e_bdev_lock); + __mb_cache_entry_release_unlock(prev, lock); return ce; } diff --git a/include/linux/mbcache.h b/include/linux/mbcache.h index 5525d37..68d8409 100644 --- a/include/linux/mbcache.h +++ b/include/linux/mbcache.h @@ -9,6 +9,8 @@ struct mb_cache_entry { struct mb_cache *e_cache; unsigned short e_used; unsigned short e_queued; + unsigned int e_bdev_lock; + unsigned int e_key_lock; struct block_device *e_bdev; sector_t e_block; struct list_head e_block_list; @@ -27,6 +29,9 @@ struct mb_cache { struct kmem_cache *c_entry_cache; struct list_head *c_block_hash; struct list_head *c_index_hash; + spinlock_t *c_bdev_locks; + spinlock_t *c_key_locks; + unsigned int c_lock_mask; }; /* Functions on caches */ -- 1.7.11.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/