diff options
| -rw-r--r-- | fs/dcache.c | 94 | ||||
| -rw-r--r-- | fs/namei.c | 3 | ||||
| -rw-r--r-- | include/linux/dcache.h | 8 |
3 files changed, 82 insertions, 23 deletions
diff --git a/fs/dcache.c b/fs/dcache.c index ea2de7c..59fcffc 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -1987,28 +1987,36 @@ EXPORT_SYMBOL(d_obtain_root); struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode, struct qstr *name) { - struct dentry *found; - struct dentry *new; + struct dentry *found, *res; /* * First check if a dentry matching the name already exists, * if not go ahead and create it now. */ found = d_hash_and_lookup(dentry->d_parent, name); - if (!found) { - new = d_alloc(dentry->d_parent, name); - if (!new) { - found = ERR_PTR(-ENOMEM); - } else { - found = d_splice_alias(inode, new); - if (found) { - dput(new); - return found; - } - return new; + if (found) { + iput(inode); + return found; + } + if (d_in_lookup(dentry)) { + found = d_alloc_parallel(dentry->d_parent, name, + dentry->d_wait); + if (IS_ERR(found) || !d_in_lookup(found)) { + iput(inode); + return found; } + } else { + found = d_alloc(dentry->d_parent, name); + if (!found) { + iput(inode); + return ERR_PTR(-ENOMEM); + } + } + res = d_splice_alias(inode, found); + if (res) { + dput(found); + return res; } - iput(inode); return found; } EXPORT_SYMBOL(d_add_ci); @@ -2391,8 +2399,23 @@ static inline void end_dir_add(struct inode *dir, unsigned n) smp_store_release(&dir->i_dir_seq, n + 2); } +static void d_wait_lookup(struct dentry *dentry) +{ + if (d_in_lookup(dentry)) { + DECLARE_WAITQUEUE(wait, current); + add_wait_queue(dentry->d_wait, &wait); + do { + set_current_state(TASK_UNINTERRUPTIBLE); + spin_unlock(&dentry->d_lock); + schedule(); + spin_lock(&dentry->d_lock); + } while (d_in_lookup(dentry)); + } +} + struct dentry *d_alloc_parallel(struct dentry *parent, - const struct qstr *name) + const struct qstr *name, + wait_queue_head_t *wq) { unsigned int len = name->len; unsigned int hash = name->hash; @@ -2463,18 +2486,47 @@ retry: } dget(dentry); hlist_bl_unlock(b); - /* impossible until we actually enable parallel lookups */ - BUG(); - /* and this will be "wait for it to stop being in-lookup" */ - /* this one will be handled in the next commit */ + /* somebody is doing lookup for it right now; wait for it */ + spin_lock(&dentry->d_lock); + d_wait_lookup(dentry); + /* + * it's not in-lookup anymore; in principle we should repeat + * everything from dcache lookup, but it's likely to be what + * d_lookup() would've found anyway. If it is, just return it; + * otherwise we really have to repeat the whole thing. + */ + if (unlikely(dentry->d_name.hash != hash)) + goto mismatch; + if (unlikely(dentry->d_parent != parent)) + goto mismatch; + if (unlikely(d_unhashed(dentry))) + goto mismatch; + if (parent->d_flags & DCACHE_OP_COMPARE) { + int tlen = dentry->d_name.len; + const char *tname = dentry->d_name.name; + if (parent->d_op->d_compare(parent, dentry, tlen, tname, name)) + goto mismatch; + } else { + if (unlikely(dentry->d_name.len != len)) + goto mismatch; + if (unlikely(dentry_cmp(dentry, str, len))) + goto mismatch; + } + /* OK, it *is* a hashed match; return it */ + spin_unlock(&dentry->d_lock); dput(new); return dentry; } /* we can't take ->d_lock here; it's OK, though. */ new->d_flags |= DCACHE_PAR_LOOKUP; + new->d_wait = wq; hlist_bl_add_head_rcu(&new->d_u.d_in_lookup_hash, b); hlist_bl_unlock(b); return new; +mismatch: + spin_unlock(&dentry->d_lock); + dput(dentry); + goto retry; } EXPORT_SYMBOL(d_alloc_parallel); @@ -2485,9 +2537,11 @@ void __d_lookup_done(struct dentry *dentry) hlist_bl_lock(b); dentry->d_flags &= ~DCACHE_PAR_LOOKUP; __hlist_bl_del(&dentry->d_u.d_in_lookup_hash); + wake_up_all(dentry->d_wait); + dentry->d_wait = NULL; hlist_bl_unlock(b); INIT_HLIST_NODE(&dentry->d_u.d_alias); - /* more stuff will land here */ + INIT_LIST_HEAD(&dentry->d_lru); } EXPORT_SYMBOL(__d_lookup_done); @@ -1605,13 +1605,14 @@ static struct dentry *lookup_slow(const struct qstr *name, { struct dentry *dentry = ERR_PTR(-ENOENT), *old; struct inode *inode = dir->d_inode; + DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq); inode_lock(inode); /* Don't go there if it's already dead */ if (unlikely(IS_DEADDIR(inode))) goto out; again: - dentry = d_alloc_parallel(dir, name); + dentry = d_alloc_parallel(dir, name, &wq); if (IS_ERR(dentry)) goto out; if (unlikely(!d_in_lookup(dentry))) { diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 3eea562..6b1d8bb 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -123,7 +123,10 @@ struct dentry { unsigned long d_time; /* used by d_revalidate */ void *d_fsdata; /* fs-specific data */ - struct list_head d_lru; /* LRU list */ + union { + struct list_head d_lru; /* LRU list */ + wait_queue_head_t *d_wait; /* in-lookup ones only */ + }; struct list_head d_child; /* child of parent list */ struct list_head d_subdirs; /* our children */ /* @@ -251,7 +254,8 @@ extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op /* allocate/de-allocate */ extern struct dentry * d_alloc(struct dentry *, const struct qstr *); extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *); -extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *); +extern struct dentry * d_alloc_parallel(struct dentry *, const struct qstr *, + wait_queue_head_t *); extern struct dentry * d_splice_alias(struct inode *, struct dentry *); extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); extern struct dentry * d_exact_alias(struct dentry *, struct inode *); |