The patch titled
Subject: lib/kobject.c: use kvasprintf_const for formatting ->name
has been added to the -mm tree. Its filename is
kobject-use-kvasprintf_const-for-formatting-name.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/kobject-use-kvasprintf_const-for-formatting-name.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/kobject-use-kvasprintf_const-for-formatting-name.patch
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------------------------------------------------------
From: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Subject: lib/kobject.c: use kvasprintf_const for formatting ->name
Sometimes kobject_set_name_vargs is called with a format string conaining
no %, or a format string of precisely "%s", where the single vararg
happens to point to .rodata. kvasprintf_const detects these cases for us
and returns a copy of that pointer instead of duplicating the string, thus
saving some run-time memory. Otherwise, it falls back to kvasprintf. We
just need to always deallocate ->name using kfree_const.
Unfortunately, the dance we need to do to perform the '/' -> '!'
sanitization makes the resulting code rather ugly.
I instrumented kstrdup_const to provide some statistics on the memory
saved, and for me this gave an additional ~14KB after boot (306KB was
already saved; this patch bumped that to 320KB). I have
KMALLOC_SHIFT_LOW==3, and since 80% of the kvasprintf_const hits were
satisfied by an 8-byte allocation, the 14K would roughly be quadrupled
when KMALLOC_SHIFT_LOW==5. Whether these numbers are sufficient to
justify the ugliness I'll leave to others to decide.
Signed-off-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Cc: Greg KH <greg@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/kobject.c | 30 ++++++++++++++++++++++--------
1 file changed, 22 insertions(+), 8 deletions(-)
diff -puN lib/kobject.c~kobject-use-kvasprintf_const-for-formatting-name lib/kobject.c
--- a/lib/kobject.c~kobject-use-kvasprintf_const-for-formatting-name
+++ a/lib/kobject.c
@@ -257,18 +257,32 @@ static int kobject_add_internal(struct k
int kobject_set_name_vargs(struct kobject *kobj, const char *fmt,
va_list vargs)
{
- char *s;
+ const char *s;
if (kobj->name && !fmt)
return 0;
- s = kvasprintf(GFP_KERNEL, fmt, vargs);
+ s = kvasprintf_const(GFP_KERNEL, fmt, vargs);
if (!s)
return -ENOMEM;
- /* ewww... some of these buggers have '/' in the name ... */
- strreplace(s, '/', '!');
- kfree(kobj->name);
+ /*
+ * ewww... some of these buggers have '/' in the name ... If
+ * that's the case, we need to make sure we have an actual
+ * allocated copy to modify, since kvasprintf_const may have
+ * returned something from .rodata.
+ */
+ if (strchr(s, '/')) {
+ char *t;
+
+ t = kstrdup(s, GFP_KERNEL);
+ kfree_const(s);
+ if (!t)
+ return -ENOMEM;
+ strreplace(t, '/', '!');
+ s = t;
+ }
+ kfree_const(kobj->name);
kobj->name = s;
return 0;
@@ -466,7 +480,7 @@ int kobject_rename(struct kobject *kobj,
envp[0] = devpath_string;
envp[1] = NULL;
- name = dup_name = kstrdup(new_name, GFP_KERNEL);
+ name = dup_name = kstrdup_const(new_name, GFP_KERNEL);
if (!name) {
error = -ENOMEM;
goto out;
@@ -486,7 +500,7 @@ int kobject_rename(struct kobject *kobj,
kobject_uevent_env(kobj, KOBJ_MOVE, envp);
out:
- kfree(dup_name);
+ kfree_const(dup_name);
kfree(devpath_string);
kfree(devpath);
kobject_put(kobj);
@@ -632,7 +646,7 @@ static void kobject_cleanup(struct kobje
/* free name if we allocated it */
if (name) {
pr_debug("kobject: '%s': free name\n", name);
- kfree(name);
+ kfree_const(name);
}
}
_
Patches currently in -mm which might be from linux@xxxxxxxxxxxxxxxxxx are
lib-dynamic_debugc-use-kstrdup_const.patch
lib-introduce-kvasprintf_const.patch
kobject-use-kvasprintf_const-for-formatting-name.patch
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