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>

1 files changed, 10 insertions, 17 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index b692c7e..3199fe6 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1723,7 +1723,7 @@ EXPORT_SYMBOL(d_add_ci);
  * Do the slow-case of the dentry name compare.
  *
  * Unlike the dentry_cmp() function, we need to atomically
- * load the name, length and inode information, so that the
+ * load the name and length information, so that the
  * filesystem can rely on them, and can use the 'name' and
  * 'len' information without worrying about walking off the
  * end of memory etc.
@@ -1741,22 +1741,18 @@ enum slow_d_compare {
 
 static noinline enum slow_d_compare slow_dentry_cmp(
 		const struct dentry *parent,
-		struct inode *inode,
 		struct dentry *dentry,
 		unsigned int seq,
 		const struct qstr *name)
 {
 	int tlen = dentry->d_name.len;
 	const char *tname = dentry->d_name.name;
-	struct inode *i = dentry->d_inode;
 
 	if (read_seqcount_retry(&dentry->d_seq, seq)) {
 		cpu_relax();
 		return D_COMP_SEQRETRY;
 	}
-	if (parent->d_op->d_compare(parent, inode,
-				dentry, i,
-				tlen, tname, name))
+	if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
 		return D_COMP_NOMATCH;
 	return D_COMP_OK;
 }
@@ -1766,7 +1762,6 @@ static noinline enum slow_d_compare slow_dentry_cmp(
  * @parent: parent dentry
  * @name: qstr of name we wish to find
  * @seqp: returns d_seq value at the point where the dentry was found
- * @inode: returns dentry->d_inode when the inode was found valid.
  * Returns: dentry, or NULL
  *
  * __d_lookup_rcu is the dcache lookup function for rcu-walk name
@@ -1793,7 +1788,7 @@ static noinline enum slow_d_compare slow_dentry_cmp(
  */
 struct dentry *__d_lookup_rcu(const struct dentry *parent,
 				const struct qstr *name,
-				unsigned *seqp, struct inode *inode)
+				unsigned *seqp)
 {
 	u64 hashlen = name->hash_len;
 	const unsigned char *str = name->name;
@@ -1827,11 +1822,10 @@ struct dentry *__d_lookup_rcu(const struct dentry *parent,
 seqretry:
 		/*
 		 * The dentry sequence count protects us from concurrent
-		 * renames, and thus protects inode, parent and name fields.
+		 * renames, and thus protects parent and name fields.
 		 *
 		 * The caller must perform a seqcount check in order
-		 * to do anything useful with the returned dentry,
-		 * including using the 'd_inode' pointer.
+		 * to do anything useful with the returned dentry.
 		 *
 		 * NOTE! We do a "raw" seqcount_begin here. That means that
 		 * we don't wait for the sequence count to stabilize if it
@@ -1845,12 +1839,12 @@ seqretry:
 			continue;
 		if (d_unhashed(dentry))
 			continue;
-		*seqp = seq;
 
 		if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) {
 			if (dentry->d_name.hash != hashlen_hash(hashlen))
 				continue;
-			switch (slow_dentry_cmp(parent, inode, dentry, seq, name)) {
+			*seqp = seq;
+			switch (slow_dentry_cmp(parent, dentry, seq, name)) {
 			case D_COMP_OK:
 				return dentry;
 			case D_COMP_NOMATCH:
@@ -1862,6 +1856,7 @@ seqretry:
 
 		if (dentry->d_name.hash_len != hashlen)
 			continue;
+		*seqp = seq;
 		if (!dentry_cmp(dentry, str, hashlen_len(hashlen)))
 			return dentry;
 	}
@@ -1959,9 +1954,7 @@ struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
 		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, parent->d_inode,
-						dentry, dentry->d_inode,
-						tlen, tname, name))
+			if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
 				goto next;
 		} else {
 			if (dentry->d_name.len != len)
@@ -1998,7 +1991,7 @@ struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
 	 */
 	name->hash = full_name_hash(name->name, name->len);
 	if (dir->d_flags & DCACHE_OP_HASH) {
-		int err = dir->d_op->d_hash(dir, dir->d_inode, name);
+		int err = dir->d_op->d_hash(dir, name);
 		if (unlikely(err < 0))
 			return ERR_PTR(err);
 	}