return sum < 0 ? 0 : sum;
}
-int proc_nr_dentry(ctl_table *table, int write, void __user *buffer,
+int proc_nr_dentry(struct ctl_table *table, int write, void __user *buffer,
size_t *lenp, loff_t *ppos)
{
dentry_stat.nr_dentry = get_nr_dentry();
}
EXPORT_SYMBOL(d_drop);
-/*
- * Finish off a dentry we've decided to kill.
- * dentry->d_lock must be held, returns with it unlocked.
- * If ref is non-zero, then decrement the refcount too.
- * Returns dentry requiring refcount drop, or NULL if we're done.
- */
-static struct dentry *
-dentry_kill(struct dentry *dentry, int unlock_on_failure)
- __releases(dentry->d_lock)
+static void __dentry_kill(struct dentry *dentry)
{
- struct inode *inode;
struct dentry *parent = NULL;
bool can_free = true;
-
- if (unlikely(dentry->d_flags & DCACHE_DENTRY_KILLED)) {
- can_free = dentry->d_flags & DCACHE_MAY_FREE;
- spin_unlock(&dentry->d_lock);
- goto out;
- }
-
- inode = dentry->d_inode;
- if (inode && !spin_trylock(&inode->i_lock)) {
-relock:
- if (unlock_on_failure) {
- spin_unlock(&dentry->d_lock);
- cpu_relax();
- }
- return dentry; /* try again with same dentry */
- }
if (!IS_ROOT(dentry))
parent = dentry->d_parent;
- if (parent && !spin_trylock(&parent->d_lock)) {
- if (inode)
- spin_unlock(&inode->i_lock);
- goto relock;
- }
/*
* The dentry is now unrecoverably dead to the world.
can_free = false;
}
spin_unlock(&dentry->d_lock);
-out:
if (likely(can_free))
dentry_free(dentry);
+}
+
+/*
+ * Finish off a dentry we've decided to kill.
+ * dentry->d_lock must be held, returns with it unlocked.
+ * If ref is non-zero, then decrement the refcount too.
+ * Returns dentry requiring refcount drop, or NULL if we're done.
+ */
+static struct dentry *dentry_kill(struct dentry *dentry)
+ __releases(dentry->d_lock)
+{
+ struct inode *inode = dentry->d_inode;
+ struct dentry *parent = NULL;
+
+ if (inode && unlikely(!spin_trylock(&inode->i_lock)))
+ goto failed;
+
+ if (!IS_ROOT(dentry)) {
+ parent = dentry->d_parent;
+ if (unlikely(!spin_trylock(&parent->d_lock))) {
+ if (inode)
+ spin_unlock(&inode->i_lock);
+ goto failed;
+ }
+ }
+
+ __dentry_kill(dentry);
+ return parent;
+
+failed:
+ spin_unlock(&dentry->d_lock);
+ cpu_relax();
+ return dentry; /* try again with same dentry */
+}
+
+static inline struct dentry *lock_parent(struct dentry *dentry)
+{
+ struct dentry *parent = dentry->d_parent;
+ if (IS_ROOT(dentry))
+ return NULL;
+ if (unlikely((int)dentry->d_lockref.count < 0))
+ return NULL;
+ if (likely(spin_trylock(&parent->d_lock)))
+ return parent;
+ rcu_read_lock();
+ spin_unlock(&dentry->d_lock);
+again:
+ parent = ACCESS_ONCE(dentry->d_parent);
+ spin_lock(&parent->d_lock);
+ /*
+ * We can't blindly lock dentry until we are sure
+ * that we won't violate the locking order.
+ * Any changes of dentry->d_parent must have
+ * been done with parent->d_lock held, so
+ * spin_lock() above is enough of a barrier
+ * for checking if it's still our child.
+ */
+ if (unlikely(parent != dentry->d_parent)) {
+ spin_unlock(&parent->d_lock);
+ goto again;
+ }
+ rcu_read_unlock();
+ if (parent != dentry)
+ spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
+ else
+ parent = NULL;
return parent;
}
return;
kill_it:
- dentry = dentry_kill(dentry, 1);
+ dentry = dentry_kill(dentry);
if (dentry)
goto repeat;
}
struct dentry *dentry, *parent;
while (!list_empty(list)) {
+ struct inode *inode;
dentry = list_entry(list->prev, struct dentry, d_lru);
spin_lock(&dentry->d_lock);
+ parent = lock_parent(dentry);
+
/*
* The dispose list is isolated and dentries are not accounted
* to the LRU here, so we can simply remove it from the list
*/
if ((int)dentry->d_lockref.count > 0) {
spin_unlock(&dentry->d_lock);
+ if (parent)
+ spin_unlock(&parent->d_lock);
continue;
}
- parent = dentry_kill(dentry, 0);
- /*
- * If dentry_kill returns NULL, we have nothing more to do.
- */
- if (!parent)
+
+ if (unlikely(dentry->d_flags & DCACHE_DENTRY_KILLED)) {
+ bool can_free = dentry->d_flags & DCACHE_MAY_FREE;
+ spin_unlock(&dentry->d_lock);
+ if (parent)
+ spin_unlock(&parent->d_lock);
+ if (can_free)
+ dentry_free(dentry);
continue;
+ }
- if (unlikely(parent == dentry)) {
- /*
- * trylocks have failed and d_lock has been held the
- * whole time, so it could not have been added to any
- * other lists. Just add it back to the shrink list.
- */
+ inode = dentry->d_inode;
+ if (inode && unlikely(!spin_trylock(&inode->i_lock))) {
d_shrink_add(dentry, list);
spin_unlock(&dentry->d_lock);
+ if (parent)
+ spin_unlock(&parent->d_lock);
continue;
}
+
+ __dentry_kill(dentry);
+
/*
* We need to prune ancestors too. This is necessary to prevent
* quadratic behavior of shrink_dcache_parent(), but is also
* fragmentation.
*/
dentry = parent;
- while (dentry && !lockref_put_or_lock(&dentry->d_lockref))
- dentry = dentry_kill(dentry, 1);
+ while (dentry && !lockref_put_or_lock(&dentry->d_lockref)) {
+ parent = lock_parent(dentry);
+ if (dentry->d_lockref.count != 1) {
+ dentry->d_lockref.count--;
+ spin_unlock(&dentry->d_lock);
+ if (parent)
+ spin_unlock(&parent->d_lock);
+ break;
+ }
+ inode = dentry->d_inode; /* can't be NULL */
+ if (unlikely(!spin_trylock(&inode->i_lock))) {
+ spin_unlock(&dentry->d_lock);
+ if (parent)
+ spin_unlock(&parent->d_lock);
+ cpu_relax();
+ continue;
+ }
+ __dentry_kill(dentry);
+ dentry = parent;
+ }
}
}
}
EXPORT_SYMBOL(d_obtain_alias);
-/**
- * d_splice_alias - splice a disconnected dentry into the tree if one exists
- * @inode: the inode which may have a disconnected dentry
- * @dentry: a negative dentry which we want to point to the inode.
- *
- * If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and
- * DCACHE_DISCONNECTED), then d_move that in place of the given dentry
- * and return it, else simply d_add the inode to the dentry and return NULL.
- *
- * This is needed in the lookup routine of any filesystem that is exportable
- * (via knfsd) so that we can build dcache paths to directories effectively.
- *
- * If a dentry was found and moved, then it is returned. Otherwise NULL
- * is returned. This matches the expected return value of ->lookup.
- *
- * Cluster filesystems may call this function with a negative, hashed dentry.
- * In that case, we know that the inode will be a regular file, and also this
- * will only occur during atomic_open. So we need to check for the dentry
- * being already hashed only in the final case.
- */
-struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
-{
- struct dentry *new = NULL;
-
- if (IS_ERR(inode))
- return ERR_CAST(inode);
-
- if (inode && S_ISDIR(inode->i_mode)) {
- spin_lock(&inode->i_lock);
- new = __d_find_alias(inode, 1);
- if (new) {
- BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
- spin_unlock(&inode->i_lock);
- security_d_instantiate(new, inode);
- d_move(new, dentry);
- iput(inode);
- } else {
- /* already taking inode->i_lock, so d_add() by hand */
- __d_instantiate(dentry, inode);
- spin_unlock(&inode->i_lock);
- security_d_instantiate(dentry, inode);
- d_rehash(dentry);
- }
- } else {
- d_instantiate(dentry, inode);
- if (d_unhashed(dentry))
- d_rehash(dentry);
- }
- return new;
-}
-EXPORT_SYMBOL(d_splice_alias);
-
/**
* d_add_ci - lookup or allocate new dentry with case-exact name
* @inode: the inode case-insensitive lookup has found
/* anon->d_lock still locked, returns locked */
}
+/**
+ * d_splice_alias - splice a disconnected dentry into the tree if one exists
+ * @inode: the inode which may have a disconnected dentry
+ * @dentry: a negative dentry which we want to point to the inode.
+ *
+ * If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and
+ * DCACHE_DISCONNECTED), then d_move that in place of the given dentry
+ * and return it, else simply d_add the inode to the dentry and return NULL.
+ *
+ * If a non-IS_ROOT directory is found, the filesystem is corrupt, and
+ * we should error out: directories can't have multiple aliases.
+ *
+ * This is needed in the lookup routine of any filesystem that is exportable
+ * (via knfsd) so that we can build dcache paths to directories effectively.
+ *
+ * If a dentry was found and moved, then it is returned. Otherwise NULL
+ * is returned. This matches the expected return value of ->lookup.
+ *
+ * Cluster filesystems may call this function with a negative, hashed dentry.
+ * In that case, we know that the inode will be a regular file, and also this
+ * will only occur during atomic_open. So we need to check for the dentry
+ * being already hashed only in the final case.
+ */
+struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
+{
+ struct dentry *new = NULL;
+
+ if (IS_ERR(inode))
+ return ERR_CAST(inode);
+
+ if (inode && S_ISDIR(inode->i_mode)) {
+ spin_lock(&inode->i_lock);
+ new = __d_find_any_alias(inode);
+ if (new) {
+ if (!IS_ROOT(new) || !(new->d_flags & DCACHE_DISCONNECTED)) {
+ spin_unlock(&inode->i_lock);
+ dput(new);
+ return ERR_PTR(-EIO);
+ }
+ write_seqlock(&rename_lock);
+ __d_materialise_dentry(dentry, new);
+ write_sequnlock(&rename_lock);
+ __d_drop(new);
+ _d_rehash(new);
+ spin_unlock(&new->d_lock);
+ spin_unlock(&inode->i_lock);
+ security_d_instantiate(new, inode);
+ iput(inode);
+ } else {
+ /* already taking inode->i_lock, so d_add() by hand */
+ __d_instantiate(dentry, inode);
+ spin_unlock(&inode->i_lock);
+ security_d_instantiate(dentry, inode);
+ d_rehash(dentry);
+ }
+ } else {
+ d_instantiate(dentry, inode);
+ if (d_unhashed(dentry))
+ d_rehash(dentry);
+ }
+ return new;
+}
+EXPORT_SYMBOL(d_splice_alias);
+
/**
* d_materialise_unique - introduce an inode into the tree
* @dentry: candidate dentry
projects / firefly-linux-kernel-4.4.55.git / blobdiff