On Mon, 9 Dec 2024 at 14:28, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
>
> Do you have any objections to the diff below?
I'd split it up a bit more, and in particular, I think I'd want
DNAME_INLINE_LEN to be defined in terms of the long-words, rather than
doing it the other way around with that
BUILD_BUG_ON(DNAME_INLINE_LEN != sizeof(struct short_name_store));
IOW, I'd *start* with something like the attached, and then build on that..
(By all means turn that
unsigned long d_iname_words[DNAME_INLINE_WORDS];
into a struct so that you can then do the struct assignment for it - I
just hate the pattern of starting with a byte size and then doing
"DNAME_INLINE_LEN / sizeof(unsigned long)".
Hmm?
Linus
fs/dcache.c | 2 +-
include/linux/dcache.h | 13 +++++++++----
2 files changed, 10 insertions(+), 5 deletions(-)
diff --git a/fs/dcache.c b/fs/dcache.c
index b4d5e9e1e43d..d6a451325133 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -3196,7 +3196,7 @@ static void __init dcache_init(void)
*/
dentry_cache = KMEM_CACHE_USERCOPY(dentry,
SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_ACCOUNT,
- d_iname);
+ d_iname_words);
/* Hash may have been set up in dcache_init_early */
if (!hashdist)
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index bff956f7b2b9..0daaecd53353 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -68,15 +68,17 @@ extern const struct qstr dotdot_name;
* large memory footprint increase).
*/
#ifdef CONFIG_64BIT
-# define DNAME_INLINE_LEN 40 /* 192 bytes */
+# define DNAME_INLINE_WORDS 5 /* 192 bytes */
#else
# ifdef CONFIG_SMP
-# define DNAME_INLINE_LEN 36 /* 128 bytes */
+# define DNAME_INLINE_WORDS 9 /* 128 bytes */
# else
-# define DNAME_INLINE_LEN 44 /* 128 bytes */
+# define DNAME_INLINE_WORDS 11 /* 128 bytes */
# endif
#endif
+#define DNAME_INLINE_LEN (DNAME_INLINE_WORDS*sizeof(unsigned long))
+
#define d_lock d_lockref.lock
struct dentry {
@@ -88,7 +90,10 @@ struct dentry {
struct qstr d_name;
struct inode *d_inode; /* Where the name belongs to - NULL is
* negative */
- unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */
+ union { /* small names */
+ unsigned long d_iname_words[DNAME_INLINE_WORDS];
+ DECLARE_FLEX_ARRAY(unsigned char, d_iname);
+ };
/* --- cacheline 1 boundary (64 bytes) was 32 bytes ago --- */
/* Ref lookup also touches following */
