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@rasmusvillemoes.dk> Cc: Greg KH <greg@kroah.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -257,18 +257,32 @@ static int kobject_add_internal(struct kobject *kobj)
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int kobject_set_name_vargs(struct kobject *kobj, const char *fmt,
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va_list vargs)
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{
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char *s;
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const char *s;
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if (kobj->name && !fmt)
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return 0;
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s = kvasprintf(GFP_KERNEL, fmt, vargs);
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s = kvasprintf_const(GFP_KERNEL, fmt, vargs);
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if (!s)
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return -ENOMEM;
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/* ewww... some of these buggers have '/' in the name ... */
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strreplace(s, '/', '!');
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kfree(kobj->name);
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/*
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* ewww... some of these buggers have '/' in the name ... If
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* that's the case, we need to make sure we have an actual
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* allocated copy to modify, since kvasprintf_const may have
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* returned something from .rodata.
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*/
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if (strchr(s, '/')) {
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char *t;
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t = kstrdup(s, GFP_KERNEL);
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kfree_const(s);
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if (!t)
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return -ENOMEM;
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strreplace(t, '/', '!');
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s = t;
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}
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kfree_const(kobj->name);
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kobj->name = s;
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return 0;
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@ -466,7 +480,7 @@ int kobject_rename(struct kobject *kobj, const char *new_name)
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envp[0] = devpath_string;
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envp[1] = NULL;
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name = dup_name = kstrdup(new_name, GFP_KERNEL);
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name = dup_name = kstrdup_const(new_name, GFP_KERNEL);
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if (!name) {
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error = -ENOMEM;
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goto out;
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@ -486,7 +500,7 @@ int kobject_rename(struct kobject *kobj, const char *new_name)
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kobject_uevent_env(kobj, KOBJ_MOVE, envp);
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out:
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kfree(dup_name);
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kfree_const(dup_name);
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kfree(devpath_string);
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kfree(devpath);
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kobject_put(kobj);
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@ -634,7 +648,7 @@ static void kobject_cleanup(struct kobject *kobj)
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/* free name if we allocated it */
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if (name) {
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pr_debug("kobject: '%s': free name\n", name);
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kfree(name);
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kfree_const(name);
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}
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}
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