vfs: trivial __d_lookup_rcu() cleanups

These don't change any semantics, but they clean up the code a bit and
mark some arguments appropriately 'const'.

They came up as I was doing the word-at-a-time dcache name accessor
code, and cleaning this up now allows me to send out a smaller relevant
interesting patch for the experimental stuff.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/dcache.c b/fs/dcache.c
index fe19ac13f75f5c4e65ed1afaecd1c5d1ae34ffb6..138be96e25b674b6e6c92f1fe926f2c6fc24f605 100644 (file)
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -104,7 +104,7 @@ static unsigned int d_hash_shift __read_mostly;
 
 static struct hlist_bl_head *dentry_hashtable __read_mostly;
 
-static inline struct hlist_bl_head *d_hash(struct dentry *parent,
+static inline struct hlist_bl_head *d_hash(const struct dentry *parent,
                                        unsigned long hash)
 {
        hash += ((unsigned long) parent ^ GOLDEN_RATIO_PRIME) / L1_CACHE_BYTES;
@@ -1717,8 +1717,9 @@ EXPORT_SYMBOL(d_add_ci);
  * child is looked up. Thus, an interlocking stepping of sequence lock checks
  * is formed, giving integrity down the path walk.
  */
-struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
-                               unsigned *seq, struct inode **inode)
+struct dentry *__d_lookup_rcu(const struct dentry *parent,
+                               const struct qstr *name,
+                               unsigned *seqp, struct inode **inode)
 {
        unsigned int len = name->len;
        unsigned int hash = name->hash;
@@ -1748,6 +1749,7 @@ struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
         * See Documentation/filesystems/path-lookup.txt for more details.
         */
        hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
+               unsigned seq;
                struct inode *i;
                const char *tname;
                int tlen;
@@ -1756,7 +1758,7 @@ struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
                        continue;
 
 seqretry:
-               *seq = read_seqcount_begin(&dentry->d_seq);
+               seq = read_seqcount_begin(&dentry->d_seq);
                if (dentry->d_parent != parent)
                        continue;
                if (d_unhashed(dentry))
@@ -1771,7 +1773,7 @@ seqretry:
                 * edge of memory when walking. If we could load this
                 * atomically some other way, we could drop this check.
                 */
-               if (read_seqcount_retry(&dentry->d_seq, *seq))
+               if (read_seqcount_retry(&dentry->d_seq, seq))
                        goto seqretry;
                if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) {
                        if (parent->d_op->d_compare(parent, *inode,
@@ -1788,6 +1790,7 @@ seqretry:
                 * order to do anything useful with the returned dentry
                 * anyway.
                 */
+               *seqp = seq;
                *inode = i;
                return dentry;
        }

diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index d64a55b23afda64f4b490ef475e092edcf3c32b7..61b24261e07a63a3d86b108cd9f9a8ac2763e88d 100644 (file)
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -309,7 +309,8 @@ extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
 extern struct dentry *d_lookup(struct dentry *, struct qstr *);
 extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
 extern struct dentry *__d_lookup(struct dentry *, struct qstr *);
-extern struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
+extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
+                               const struct qstr *name,
                                unsigned *seq, struct inode **inode);
 
 /**