summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
-rw-r--r--fs/dcache.c94
-rw-r--r--fs/namei.c3
-rw-r--r--include/linux/dcache.h8
3 files changed, 82 insertions, 23 deletions
diff --git a/fs/dcache.c b/fs/dcache.c
index ea2de7c19b08..59fcffcbf096 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);
diff --git a/fs/namei.c b/fs/namei.c
index aa04320e1f37..7babb5e5f276 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -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 3eea562f5f27..6b1d8bbb3496 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 *);