linux-ext4 - [PATCH 1/5] make sure that DCACHE_INLINE

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Message-ID: <20241210024827.1612355-1-viro@zeniv.linux.org.uk>
Date: Tue, 10 Dec 2024 02:48:23 +0000
From: Al Viro <viro@...iv.linux.org.uk>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-fsdevel@...r.kernel.org,
	linux-ext4@...r.kernel.org
Subject: [PATCH 1/5] make sure that DCACHE_INLINE_LEN is a multiple of word size

... calling the number of words DCACHE_INLINE_WORDS.

The next step will be to have a structure to hold inline name arrays
(both in dentry and in name_snapshot) and use that to alias the
existing arrays of unsigned char there.  That will allow both
full-structure copies and convenient word-by-word accesses.

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 fs/dcache.c            | 4 +---
 include/linux/dcache.h | 8 +++++---
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index b4d5e9e1e43d..ea0f0bea511b 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2748,9 +2748,7 @@ static void swap_names(struct dentry *dentry, struct dentry *target)
 			/*
 			 * Both are internal.
 			 */
-			unsigned int i;
-			BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN, sizeof(long)));
-			for (i = 0; i < DNAME_INLINE_LEN / sizeof(long); i++) {
+			for (int i = 0; i < DNAME_INLINE_WORDS; i++) {
 				swap(((long *) &dentry->d_iname)[i],
 				     ((long *) &target->d_iname)[i]);
 			}
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index bff956f7b2b9..42dd89beaf4e 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 {
-- 
2.39.5