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>

1 files changed, 8 insertions, 5 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index fe19ac13f75f..138be96e25b6 100644
--- 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;
         }