diff options
| -rw-r--r-- | fs/dcache.c | 16 | ||||
| -rw-r--r-- | include/linux/dcache.h | 41 |
2 files changed, 34 insertions, 23 deletions
diff --git a/fs/dcache.c b/fs/dcache.c index 523cbf0780f0..bb18ea91d717 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -877,12 +877,6 @@ void dput_to_list(struct dentry *dentry, struct list_head *list) spin_unlock(&dentry->d_lock); } -/* This must be called with d_lock held */ -static inline void __dget_dlock(struct dentry *dentry) -{ - dentry->d_lockref.count++; -} - struct dentry *dget_parent(struct dentry *dentry) { int gotref; @@ -964,7 +958,7 @@ static struct dentry *__d_find_alias(struct inode *inode) hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) { spin_lock(&alias->d_lock); if (!d_unhashed(alias)) { - __dget_dlock(alias); + dget_dlock(alias); spin_unlock(&alias->d_lock); return alias; } @@ -1569,8 +1563,7 @@ static enum d_walk_ret find_submount(void *_data, struct dentry *dentry) { struct dentry **victim = _data; if (d_mountpoint(dentry)) { - __dget_dlock(dentry); - *victim = dentry; + *victim = dget_dlock(dentry); return D_WALK_QUIT; } return D_WALK_CONTINUE; @@ -1715,8 +1708,7 @@ struct dentry *d_alloc(struct dentry * parent, const struct qstr *name) * don't need child lock because it is not subject * to concurrency here */ - __dget_dlock(parent); - dentry->d_parent = parent; + dentry->d_parent = dget_dlock(parent); hlist_add_head(&dentry->d_sib, &parent->d_children); spin_unlock(&parent->d_lock); @@ -2683,7 +2675,7 @@ struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode) spin_unlock(&alias->d_lock); alias = NULL; } else { - __dget_dlock(alias); + dget_dlock(alias); __d_rehash(alias); spin_unlock(&alias->d_lock); } diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 48b393545ec2..1666c387861f 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -287,20 +287,40 @@ extern char *dentry_path(const struct dentry *, char *, int); /* Allocation counts.. */ /** - * dget, dget_dlock - get a reference to a dentry - * @dentry: dentry to get a reference to + * dget_dlock - get a reference to a dentry + * @dentry: dentry to get a reference to * - * Given a dentry or %NULL pointer increment the reference count - * if appropriate and return the dentry. A dentry will not be - * destroyed when it has references. + * Given a live dentry, increment the reference count and return the dentry. + * Caller must hold @dentry->d_lock. Making sure that dentry is alive is + * caller's resonsibility. There are many conditions sufficient to guarantee + * that; e.g. anything with non-negative refcount is alive, so's anything + * hashed, anything positive, anyone's parent, etc. */ static inline struct dentry *dget_dlock(struct dentry *dentry) { - if (dentry) - dentry->d_lockref.count++; + dentry->d_lockref.count++; return dentry; } + +/** + * dget - get a reference to a dentry + * @dentry: dentry to get a reference to + * + * Given a dentry or %NULL pointer increment the reference count + * if appropriate and return the dentry. A dentry will not be + * destroyed when it has references. Conversely, a dentry with + * no references can disappear for any number of reasons, starting + * with memory pressure. In other words, that primitive is + * used to clone an existing reference; using it on something with + * zero refcount is a bug. + * + * NOTE: it will spin if @dentry->d_lock is held. From the deadlock + * avoidance point of view it is equivalent to spin_lock()/increment + * refcount/spin_unlock(), so calling it under @dentry->d_lock is + * always a bug; so's calling it under ->d_lock on any of its descendents. + * + */ static inline struct dentry *dget(struct dentry *dentry) { if (dentry) @@ -311,12 +331,11 @@ static inline struct dentry *dget(struct dentry *dentry) extern struct dentry *dget_parent(struct dentry *dentry); /** - * d_unhashed - is dentry hashed - * @dentry: entry to check + * d_unhashed - is dentry hashed + * @dentry: entry to check * - * Returns true if the dentry passed is not currently hashed. + * Returns true if the dentry passed is not currently hashed. */ - static inline int d_unhashed(const struct dentry *dentry) { return hlist_bl_unhashed(&dentry->d_hash); |