fs: dcache scale dentry refcount

Make d_count non-atomic and protect it with d_lock. This allows us to ensure a
0 refcount dentry remains 0 without dcache_lock. It is also fairly natural when
we start protecting many other dentry members with d_lock.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>

2 files changed, 7 insertions, 7 deletions

diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
index a796c9417fb1..413b5642e6cf 100644
--- a/fs/autofs4/expire.c
+++ b/fs/autofs4/expire.c
@@ -198,7 +198,7 @@ static int autofs4_tree_busy(struct vfsmount *mnt,
                         else
                                 ino_count++;
 
-                        if (atomic_read(&p->d_count) > ino_count) {
+                        if (p->d_count > ino_count) {
                                 top_ino->last_used = jiffies;
                                 dput(p);
                                 return 1;
@@ -347,7 +347,7 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
 
                         /* Path walk currently on this dentry? */
                         ino_count = atomic_read(&ino->count) + 2;
-                        if (atomic_read(&dentry->d_count) > ino_count)
+                        if (dentry->d_count > ino_count)
                                 goto next;
 
                         /* Can we umount this guy */
@@ -369,7 +369,7 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
                 if (!exp_leaves) {
                         /* Path walk currently on this dentry? */
                         ino_count = atomic_read(&ino->count) + 1;
-                        if (atomic_read(&dentry->d_count) > ino_count)
+                        if (dentry->d_count > ino_count)
                                 goto next;
 
                         if (!autofs4_tree_busy(mnt, dentry, timeout, do_now)) {
@@ -383,7 +383,7 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
                 } else {
                         /* Path walk currently on this dentry? */
                         ino_count = atomic_read(&ino->count) + 1;
-                        if (atomic_read(&dentry->d_count) > ino_count)
+                        if (dentry->d_count > ino_count)
                                 goto next;
 
                         expired = autofs4_check_leaves(mnt, dentry, timeout, do_now);
diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index d34896cfb19f..7922509b5b2b 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -436,7 +436,7 @@ static struct dentry *autofs4_lookup_active(struct dentry *dentry)
                 spin_lock(&active->d_lock);
 
                 /* Already gone? */
-                if (atomic_read(&active->d_count) == 0)
+                if (active->d_count == 0)
                         goto next;
 
                 qstr = &active->d_name;
@@ -452,7 +452,7 @@ static struct dentry *autofs4_lookup_active(struct dentry *dentry)
                         goto next;
 
                 if (d_unhashed(active)) {
-                        dget(active);
+                        dget_dlock(active);
                         spin_unlock(&active->d_lock);
                         spin_unlock(&sbi->lookup_lock);
                         spin_unlock(&dcache_lock);
@@ -507,7 +507,7 @@ static struct dentry *autofs4_lookup_expiring(struct dentry *dentry)
                         goto next;
 
                 if (d_unhashed(expiring)) {
-                        dget(expiring);
+                        dget_dlock(expiring);
                         spin_unlock(&expiring->d_lock);
                         spin_unlock(&sbi->lookup_lock);
                         spin_unlock(&dcache_lock);