Add a new lock, dcache_hash_lock, to protect the dcache hash table from concurrent modification. d_hash is also protected by d_lock. Signed-off-by: Nick Piggin --- fs/dcache.c | 38 +++++++++++++++++++++++++++----------- include/linux/dcache.h | 3 +++ 2 files changed, 30 insertions(+), 11 deletions(-) Index: linux-2.6/fs/dcache.c =================================================================== --- linux-2.6.orig/fs/dcache.c 2010-11-17 00:52:37.000000000 +1100 +++ linux-2.6/fs/dcache.c 2010-11-17 01:05:47.000000000 +1100 @@ -35,12 +35,27 @@ #include #include "internal.h" +/* + * Usage: + * dcache_hash_lock protects dcache hash table + * + * Ordering: + * dcache_lock + * dentry->d_lock + * dcache_hash_lock + * + * if (dentry1 < dentry2) + * dentry1->d_lock + * dentry2->d_lock + */ int sysctl_vfs_cache_pressure __read_mostly = 100; EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure); - __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lock); +__cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_hash_lock); +__cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lock); __cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock); +EXPORT_SYMBOL(dcache_hash_lock); EXPORT_SYMBOL(dcache_lock); static struct kmem_cache *dentry_cache __read_mostly; @@ -1195,7 +1210,9 @@ struct dentry *d_obtain_alias(struct ino tmp->d_flags |= DCACHE_DISCONNECTED; tmp->d_flags &= ~DCACHE_UNHASHED; list_add(&tmp->d_alias, &inode->i_dentry); + spin_lock(&dcache_hash_lock); hlist_add_head(&tmp->d_hash, &inode->i_sb->s_anon); + spin_unlock(&dcache_hash_lock); spin_unlock(&tmp->d_lock); spin_unlock(&dcache_lock); @@ -1581,7 +1598,9 @@ void d_rehash(struct dentry * entry) { spin_lock(&dcache_lock); spin_lock(&entry->d_lock); + spin_lock(&dcache_hash_lock); _d_rehash(entry); + spin_unlock(&dcache_hash_lock); spin_unlock(&entry->d_lock); spin_unlock(&dcache_lock); } @@ -1661,8 +1680,6 @@ static void switch_names(struct dentry * */ static void d_move_locked(struct dentry * dentry, struct dentry * target) { - struct hlist_head *list; - if (!dentry->d_inode) printk(KERN_WARNING "VFS: moving negative dcache entry\n"); @@ -1679,14 +1696,11 @@ static void d_move_locked(struct dentry } /* Move the dentry to the target hash queue, if on different bucket */ - if (d_unhashed(dentry)) - goto already_unhashed; - - hlist_del_rcu(&dentry->d_hash); - -already_unhashed: - list = d_hash(target->d_parent, target->d_name.hash); - __d_rehash(dentry, list); + spin_lock(&dcache_hash_lock); + if (!d_unhashed(dentry)) + hlist_del_rcu(&dentry->d_hash); + __d_rehash(dentry, d_hash(target->d_parent, target->d_name.hash)); + spin_unlock(&dcache_hash_lock); /* Unhash the target: dput() will then get rid of it */ __d_drop(target); @@ -1883,7 +1897,9 @@ struct dentry *d_materialise_unique(stru found_lock: spin_lock(&actual->d_lock); found: + spin_lock(&dcache_hash_lock); _d_rehash(actual); + spin_unlock(&dcache_hash_lock); spin_unlock(&actual->d_lock); spin_unlock(&dcache_lock); out_nolock: Index: linux-2.6/include/linux/dcache.h =================================================================== --- linux-2.6.orig/include/linux/dcache.h 2010-11-17 00:52:37.000000000 +1100 +++ linux-2.6/include/linux/dcache.h 2010-11-17 01:05:46.000000000 +1100 @@ -181,6 +181,7 @@ struct dentry_operations { #define DCACHE_CANT_MOUNT 0x0100 +extern spinlock_t dcache_hash_lock; extern spinlock_t dcache_lock; extern seqlock_t rename_lock; @@ -204,7 +205,9 @@ static inline void __d_drop(struct dentr { if (!(dentry->d_flags & DCACHE_UNHASHED)) { dentry->d_flags |= DCACHE_UNHASHED; + spin_lock(&dcache_hash_lock); hlist_del_rcu(&dentry->d_hash); + spin_unlock(&dcache_hash_lock); } } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/