[PATCH] fs: combine __d_alloc's allocations into one

[PATCH] fs: combine __d_alloc's allocations into one

[Ahmad Fatoum]

Instead of doing two allocations, one for the struct dentry and one for
the full name, just do one allocation and place them after each other.

This has the extra benefit of fixing a leak of the dentry allocation
when the second allocation for the file name fails.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 fs/fs.c                | 13 ++++---------
 include/linux/dcache.h |  2 +-
 2 files changed, 5 insertions(+), 10 deletions(-)

diff --git a/fs/fs.c b/fs/fs.c
index 96ca60341ea4..f8b7340d809d 100644
--- a/fs/fs.c
+++ b/fs/fs.c
@@ -795,7 +795,6 @@ static void dentry_kill(struct dentry *dentry)
 		dput(dentry->d_parent);
 
 	list_del(&dentry->d_child);
-	free(dentry->name);
 	free(dentry);
 }
 
@@ -1427,15 +1426,11 @@ static struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
 {
 	struct dentry *dentry;
 
-	dentry = xzalloc(sizeof(*dentry));
-	if (!dentry)
-		return NULL;
-
 	if (!name)
 		name = &slash_name;
 
-	dentry->name = malloc(name->len + 1);
-	if (!dentry->name)
+	dentry = xzalloc(struct_size(dentry, name, name->len + 1));
+	if (!dentry)
 		return NULL;
 
 	memcpy(dentry->name, name->name, name->len);
@@ -3006,9 +3001,9 @@ static char *__dpath(struct dentry *dentry, struct dentry *root)
 
 	ppath = __dpath(dentry->d_parent, root);
 	if (ppath)
-		res = basprintf("%s/%s", ppath, dentry->name);
+		res = basprintf("%s/%s", ppath, dentry->d_name.name);
 	else
-		res = basprintf("/%s", dentry->name);
+		res = basprintf("/%s", dentry->d_name.name);
 	free(ppath);
 
 	return res;
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index ed7e5c2cbcff..1b51a5656703 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -80,7 +80,7 @@ struct dentry {
 	struct dcookie_struct *d_cookie; /* cookie, if any */
 #endif
 	int d_mounted;
-	unsigned char *name;		/* all names */
+	unsigned char name[];		/* all names */
 };
 
 struct dentry_operations {
-- 
2.39.5

Re: [PATCH] fs: combine __d_alloc's allocations into one

[Sascha Hauer]

On Thu, 13 Mar 2025 07:45:40 +0100, Ahmad Fatoum wrote:
> Instead of doing two allocations, one for the struct dentry and one for
> the full name, just do one allocation and place them after each other.
> 
> This has the extra benefit of fixing a leak of the dentry allocation
> when the second allocation for the file name fails.
> 
> 
> [...]

Applied, thanks!

[1/1] fs: combine __d_alloc's allocations into one
      https://git.pengutronix.de/cgit/barebox/commit/?id=9b21612c3bc0 (link may not be stable)

Best regards,
-- 
Sascha Hauer <s.hauer@pengutronix.de>