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-rw-r--r--fs/dcache.c128
1 files changed, 72 insertions, 56 deletions
diff --git a/fs/dcache.c b/fs/dcache.c
index 2a6bd9a4ae97..ad25c4cec7d5 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -296,8 +296,12 @@ static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent)
__releases(parent->d_lock)
__releases(dentry->d_inode->i_lock)
{
- dentry->d_parent = NULL;
list_del(&dentry->d_u.d_child);
+ /*
+ * Inform try_to_ascend() that we are no longer attached to the
+ * dentry tree
+ */
+ dentry->d_flags |= DCACHE_DISCONNECTED;
if (parent)
spin_unlock(&parent->d_lock);
dentry_iput(dentry);
@@ -1012,6 +1016,35 @@ void shrink_dcache_for_umount(struct super_block *sb)
}
/*
+ * This tries to ascend one level of parenthood, but
+ * we can race with renaming, so we need to re-check
+ * the parenthood after dropping the lock and check
+ * that the sequence number still matches.
+ */
+static struct dentry *try_to_ascend(struct dentry *old, int locked, unsigned seq)
+{
+ struct dentry *new = old->d_parent;
+
+ rcu_read_lock();
+ spin_unlock(&old->d_lock);
+ spin_lock(&new->d_lock);
+
+ /*
+ * might go back up the wrong parent if we have had a rename
+ * or deletion
+ */
+ if (new != old->d_parent ||
+ (old->d_flags & DCACHE_DISCONNECTED) ||
+ (!locked && read_seqretry(&rename_lock, seq))) {
+ spin_unlock(&new->d_lock);
+ new = NULL;
+ }
+ rcu_read_unlock();
+ return new;
+}
+
+
+/*
* Search for at least 1 mount point in the dentry's subdirs.
* We descend to the next level whenever the d_subdirs
* list is non-empty and continue searching.
@@ -1066,24 +1099,10 @@ resume:
* All done at this level ... ascend and resume the search.
*/
if (this_parent != parent) {
- struct dentry *tmp;
- struct dentry *child;
-
- tmp = this_parent->d_parent;
- rcu_read_lock();
- spin_unlock(&this_parent->d_lock);
- child = this_parent;
- this_parent = tmp;
- spin_lock(&this_parent->d_lock);
- /* might go back up the wrong parent if we have had a rename
- * or deletion */
- if (this_parent != child->d_parent ||
- (!locked && read_seqretry(&rename_lock, seq))) {
- spin_unlock(&this_parent->d_lock);
- rcu_read_unlock();
+ struct dentry *child = this_parent;
+ this_parent = try_to_ascend(this_parent, locked, seq);
+ if (!this_parent)
goto rename_retry;
- }
- rcu_read_unlock();
next = child->d_u.d_child.next;
goto resume;
}
@@ -1181,24 +1200,10 @@ resume:
* All done at this level ... ascend and resume the search.
*/
if (this_parent != parent) {
- struct dentry *tmp;
- struct dentry *child;
-
- tmp = this_parent->d_parent;
- rcu_read_lock();
- spin_unlock(&this_parent->d_lock);
- child = this_parent;
- this_parent = tmp;
- spin_lock(&this_parent->d_lock);
- /* might go back up the wrong parent if we have had a rename
- * or deletion */
- if (this_parent != child->d_parent ||
- (!locked && read_seqretry(&rename_lock, seq))) {
- spin_unlock(&this_parent->d_lock);
- rcu_read_unlock();
+ struct dentry *child = this_parent;
+ this_parent = try_to_ascend(this_parent, locked, seq);
+ if (!this_parent)
goto rename_retry;
- }
- rcu_read_unlock();
next = child->d_u.d_child.next;
goto resume;
}
@@ -1523,6 +1528,28 @@ struct dentry * d_alloc_root(struct inode * root_inode)
}
EXPORT_SYMBOL(d_alloc_root);
+static struct dentry * __d_find_any_alias(struct inode *inode)
+{
+ struct dentry *alias;
+
+ if (list_empty(&inode->i_dentry))
+ return NULL;
+ alias = list_first_entry(&inode->i_dentry, struct dentry, d_alias);
+ __dget(alias);
+ return alias;
+}
+
+static struct dentry * d_find_any_alias(struct inode *inode)
+{
+ struct dentry *de;
+
+ spin_lock(&inode->i_lock);
+ de = __d_find_any_alias(inode);
+ spin_unlock(&inode->i_lock);
+ return de;
+}
+
+
/**
* d_obtain_alias - find or allocate a dentry for a given inode
* @inode: inode to allocate the dentry for
@@ -1552,7 +1579,7 @@ struct dentry *d_obtain_alias(struct inode *inode)
if (IS_ERR(inode))
return ERR_CAST(inode);
- res = d_find_alias(inode);
+ res = d_find_any_alias(inode);
if (res)
goto out_iput;
@@ -1565,7 +1592,7 @@ struct dentry *d_obtain_alias(struct inode *inode)
spin_lock(&inode->i_lock);
- res = __d_find_alias(inode, 0);
+ res = __d_find_any_alias(inode);
if (res) {
spin_unlock(&inode->i_lock);
dput(tmp);
@@ -1585,10 +1612,13 @@ struct dentry *d_obtain_alias(struct inode *inode)
__bit_spin_unlock(0, (unsigned long *)&tmp->d_sb->s_anon.first);
spin_unlock(&tmp->d_lock);
spin_unlock(&inode->i_lock);
+ security_d_instantiate(tmp, inode);
return tmp;
out_iput:
+ if (res && !IS_ERR(res))
+ security_d_instantiate(res, inode);
iput(inode);
return res;
}
@@ -1781,7 +1811,7 @@ struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
* false-negative result. d_lookup() protects against concurrent
* renames using rename_lock seqlock.
*
- * See Documentation/vfs/dcache-locking.txt for more details.
+ * See Documentation/filesystems/path-lookup.txt for more details.
*/
hlist_bl_for_each_entry_rcu(dentry, node, &b->head, d_hash) {
struct inode *i;
@@ -1901,7 +1931,7 @@ struct dentry *__d_lookup(struct dentry *parent, struct qstr *name)
* false-negative result. d_lookup() protects against concurrent
* renames using rename_lock seqlock.
*
- * See Documentation/vfs/dcache-locking.txt for more details.
+ * See Documentation/filesystems/path-lookup.txt for more details.
*/
rcu_read_lock();
@@ -2920,28 +2950,14 @@ resume:
spin_unlock(&dentry->d_lock);
}
if (this_parent != root) {
- struct dentry *tmp;
- struct dentry *child;
-
- tmp = this_parent->d_parent;
+ struct dentry *child = this_parent;
if (!(this_parent->d_flags & DCACHE_GENOCIDE)) {
this_parent->d_flags |= DCACHE_GENOCIDE;
this_parent->d_count--;
}
- rcu_read_lock();
- spin_unlock(&this_parent->d_lock);
- child = this_parent;
- this_parent = tmp;
- spin_lock(&this_parent->d_lock);
- /* might go back up the wrong parent if we have had a rename
- * or deletion */
- if (this_parent != child->d_parent ||
- (!locked && read_seqretry(&rename_lock, seq))) {
- spin_unlock(&this_parent->d_lock);
- rcu_read_unlock();
+ this_parent = try_to_ascend(this_parent, locked, seq);
+ if (!this_parent)
goto rename_retry;
- }
- rcu_read_unlock();
next = child->d_u.d_child.next;
goto resume;
}
generated by cgit v1.2.3 (git 2.39.1) at 2024-07-15 23:42:36 +0000