Don't pass inode to ->d_hash() and ->d_compare()

Instances either don't look at it at all (the majority of cases) or
only want it to find the superblock (which can be had as dentry->d_sb).
A few cases that want more are actually safe with dentry->d_inode -
the only precaution needed is the check that it hadn't been replaced with
NULL by rmdir() or by overwriting rename(), which case should be simply
treated as cache miss.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

2 files changed, 10 insertions, 15 deletions

diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index bdd82b2339d9..f94a362f408e 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -11,10 +11,8 @@ be able to use diff(1).
 prototypes:
         int (*d_revalidate)(struct dentry *, unsigned int);
         int (*d_weak_revalidate)(struct dentry *, unsigned int);
-        int (*d_hash)(const struct dentry *, const struct inode *,
-                        struct qstr *);
-        int (*d_compare)(const struct dentry *, const struct inode *,
-                        const struct dentry *, const struct inode *,
+        int (*d_hash)(const struct dentry *, struct qstr *);
+        int (*d_compare)(const struct dentry *, const struct dentry *,
                         unsigned int, const char *, const struct qstr *);
         int (*d_delete)(struct dentry *);
         void (*d_release)(struct dentry *);
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index 4a35f6614a66..51ba44e3fc40 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -901,10 +901,8 @@ defined:
 struct dentry_operations {
         int (*d_revalidate)(struct dentry *, unsigned int);
         int (*d_weak_revalidate)(struct dentry *, unsigned int);
-        int (*d_hash)(const struct dentry *, const struct inode *,
-                        struct qstr *);
-        int (*d_compare)(const struct dentry *, const struct inode *,
-                        const struct dentry *, const struct inode *,
+        int (*d_hash)(const struct dentry *, struct qstr *);
+        int (*d_compare)(const struct dentry *, const struct dentry *,
                         unsigned int, const char *, const struct qstr *);
         int (*d_delete)(const struct dentry *);
         void (*d_release)(struct dentry *);
@@ -949,25 +947,24 @@ struct dentry_operations {
 
   d_hash: called when the VFS adds a dentry to the hash table. The first
         dentry passed to d_hash is the parent directory that the name is
-        to be hashed into. The inode is the dentry's inode.
+        to be hashed into.
 
         Same locking and synchronisation rules as d_compare regarding
         what is safe to dereference etc.
 
   d_compare: called to compare a dentry name with a given name. The first
         dentry is the parent of the dentry to be compared, the second is
-        the parent's inode, then the dentry and inode (may be NULL) of the
-        child dentry. len and name string are properties of the dentry to be
-        compared. qstr is the name to compare it with.
+        the child dentry. len and name string are properties of the dentry
+        to be compared. qstr is the name to compare it with.
 
         Must be constant and idempotent, and should not take locks if
-        possible, and should not or store into the dentry or inodes.
-        Should not dereference pointers outside the dentry or inodes without
+        possible, and should not or store into the dentry.
+        Should not dereference pointers outside the dentry without
         lots of care (eg.  d_parent, d_inode, d_name should not be used).
 
         However, our vfsmount is pinned, and RCU held, so the dentries and
         inodes won't disappear, neither will our sb or filesystem module.
-        ->i_sb and ->d_sb may be used.
+        ->d_sb may be used.
 
         It is a tricky calling convention because it needs to be called under
         "rcu-walk", ie. without any locks or references on things.