linux-kernel - [PATCH] x86/mm/pat: Do a small optimization when dump PAT memtype list

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-ID: <55B1ACFD.9020200@intel.com>
Date:	Fri, 24 Jul 2015 11:11:57 +0800
From:	Pan Xinhui <xinhuix.pan@...el.com>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	Borislav Petkov <bp@...en8.de>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
	"bp@...e.de" <bp@...e.de>, "Kani, Toshimitsu" <toshi.kani@...com>,
	"jgross@...e.com" <jgross@...e.com>,
	"mcgrof@...e.com" <mcgrof@...e.com>,
	"mnipxh@....com" <mnipxh@....com>,
	"yanmin_zhang@...ux.intel.com" <yanmin_zhang@...ux.intel.com>,
	"Elliott, Robert (Server Storage)" <Elliott@...com>
Subject: [PATCH] x86/mm/pat: Do a small optimization when dump PAT memtype
 list

From: Pan Xinhui <xinhuix.pan@...el.com>

There are many nodes in the PAT memtype rb-tree. When we dump this tree
we call kzalloc every time to copy nodes. Actually these kzalloc are not
necessary. Lets do a optimization now.

Let seq_file core create an *entry* when open and free it when release.
*entry* is stored as seq->private, so we can use it in seq_operations
callback who traverse/output the PAT memtype rb-tree only. Lots of
unnecessary kzalloc could be avoided now.

Signed-off-by: Pan Xinhui <xinhuix.pan@...el.com>
---
v1 -> v2:
	Use seq_open/release_private. let seq_file core handle memory alloc/free.
	seq_operations callbacks now only traverse/output the PAT rb-tree.
---
 arch/x86/mm/pat.c | 28 ++++++++++------------------
 1 file changed, 10 insertions(+), 18 deletions(-)

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 268b2c8..53920be 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -1001,41 +1001,33 @@ EXPORT_SYMBOL_GPL(pgprot_writethrough);
 
 #if defined(CONFIG_DEBUG_FS) && defined(CONFIG_X86_PAT)
 
-static struct memtype *memtype_get_idx(loff_t pos)
+static struct memtype *memtype_get_idx(struct memtype *entry, loff_t pos)
 {
-	struct memtype *print_entry;
 	int ret;
 
-	print_entry  = kzalloc(sizeof(struct memtype), GFP_KERNEL);
-	if (!print_entry)
-		return NULL;
-
 	spin_lock(&memtype_lock);
-	ret = rbt_memtype_copy_nth_element(print_entry, pos);
+	ret = rbt_memtype_copy_nth_element(entry, pos);
 	spin_unlock(&memtype_lock);
 
-	if (!ret) {
-		return print_entry;
-	} else {
-		kfree(print_entry);
-		return NULL;
-	}
+	return ret ? NULL : entry;
 }
 
 static void *memtype_seq_start(struct seq_file *seq, loff_t *pos)
 {
+	struct memtype *entry = seq->private;
+
 	if (*pos == 0) {
 		++*pos;
 		seq_puts(seq, "PAT memtype list:\n");
 	}
 
-	return memtype_get_idx(*pos);
+	return memtype_get_idx(entry, *pos);
 }
 
 static void *memtype_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 {
 	++*pos;
-	return memtype_get_idx(*pos);
+	return memtype_get_idx((struct memtype *)v, *pos);
 }
 
 static void memtype_seq_stop(struct seq_file *seq, void *v)
@@ -1048,7 +1040,6 @@ static int memtype_seq_show(struct seq_file *seq, void *v)
 
 	seq_printf(seq, "%s @ 0x%Lx-0x%Lx\n", cattr_name(print_entry->type),
 			print_entry->start, print_entry->end);
-	kfree(print_entry);
 
 	return 0;
 }
@@ -1062,14 +1053,15 @@ static const struct seq_operations memtype_seq_ops = {
 
 static int memtype_seq_open(struct inode *inode, struct file *file)
 {
-	return seq_open(file, &memtype_seq_ops);
+	return seq_open_private(file, &memtype_seq_ops,
+							sizeof(struct memtype));
 }
 
 static const struct file_operations memtype_fops = {
 	.open    = memtype_seq_open,
 	.read    = seq_read,
 	.llseek  = seq_lseek,
-	.release = seq_release,
+	.release = seq_release_private,
 };
 
 static int __init pat_memtype_list_init(void)
-- 
1.9.1
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/