[04/20] dissolve external_name.u into separate members

Commit Message

Al Viro Jan. 10, 2025, 2:42 a.m. UTC

kept separate from the previous commit to keep the noise separate
from actual changes...

Signed-off-by: Al Viro <[e-mail]>
---
 fs/dcache.c | 22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

Comments

David Howells Jan. 10, 2025, 7:34 a.m. UTC | #1

Al Viro <[e-mail]> wrote:

>  struct external_name {
> -	struct {
> -		atomic_t count;		// ->count and ->head can't be combined
> -		struct rcu_head head;	// see take_dentry_name_snapshot()
> -	} u;
> +	atomic_t count;		// ->count and ->head can't be combined
> +	struct rcu_head head;	// see take_dentry_name_snapshot()
>  	unsigned char name[];
>  };

This gets you a 4-byte hole between count and head on a 64-bit system.  Did
you want to flip the order of count and head?

David

Patch

diff --git a/fs/dcache.c b/fs/dcache.c
index f387dc97df86..7d42ca367522 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -296,10 +296,8 @@  static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *c
 }
 
 struct external_name {
-	struct {
-		atomic_t count;		// ->count and ->head can't be combined
-		struct rcu_head head;	// see take_dentry_name_snapshot()
-	} u;
+	atomic_t count;		// ->count and ->head can't be combined
+	struct rcu_head head;	// see take_dentry_name_snapshot()
 	unsigned char name[];
 };
 
@@ -344,7 +342,7 @@  void take_dentry_name_snapshot(struct name_snapshot *name, struct dentry *dentry
 		struct external_name *p;
 		p = container_of(s, struct external_name, name[0]);
 		// get a valid reference
-		if (unlikely(!atomic_inc_not_zero(&p->u.count)))
+		if (unlikely(!atomic_inc_not_zero(&p->count)))
 			goto retry;
 		name->name.name = s;
 	}
@@ -361,8 +359,8 @@  void release_dentry_name_snapshot(struct name_snapshot *name)
 	if (unlikely(name->name.name != name->inline_name.string)) {
 		struct external_name *p;
 		p = container_of(name->name.name, struct external_name, name[0]);
-		if (unlikely(atomic_dec_and_test(&p->u.count)))
-			kfree_rcu(p, u.head);
+		if (unlikely(atomic_dec_and_test(&p->count)))
+			kfree_rcu(p, head);
 	}
 }
 EXPORT_SYMBOL(release_dentry_name_snapshot);
@@ -400,7 +398,7 @@  static void dentry_free(struct dentry *dentry)
 	WARN_ON(!hlist_unhashed(&dentry->d_u.d_alias));
 	if (unlikely(dname_external(dentry))) {
 		struct external_name *p = external_name(dentry);
-		if (likely(atomic_dec_and_test(&p->u.count))) {
+		if (likely(atomic_dec_and_test(&p->count))) {
 			call_rcu(&dentry->d_u.d_rcu, __d_free_external);
 			return;
 		}
@@ -1681,7 +1679,7 @@  static struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
 			kmem_cache_free(dentry_cache, dentry); 
 			return NULL;
 		}
-		atomic_set(&p->u.count, 1);
+		atomic_set(&p->count, 1);
 		dname = p->name;
 	} else  {
 		dname = dentry->d_shortname.string;
@@ -2774,15 +2772,15 @@  static void copy_name(struct dentry *dentry, struct dentry *target)
 	if (unlikely(dname_external(dentry)))
 		old_name = external_name(dentry);
 	if (unlikely(dname_external(target))) {
-		atomic_inc(&external_name(target)->u.count);
+		atomic_inc(&external_name(target)->count);
 		dentry->d_name = target->d_name;
 	} else {
 		dentry->d_shortname = target->d_shortname;
 		dentry->d_name.name = dentry->d_shortname.string;
 		dentry->d_name.hash_len = target->d_name.hash_len;
 	}
-	if (old_name && likely(atomic_dec_and_test(&old_name->u.count)))
-		kfree_rcu(old_name, u.head);
+	if (old_name && likely(atomic_dec_and_test(&old_name->count)))
+		kfree_rcu(old_name, head);
 }
 
 /*