linux-kernel - [PATCH] proc: save decrement during lookup/readdir in /proc/$PID

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Message-ID: <20161122195143.GA29812@avx2>
Date:   Tue, 22 Nov 2016 22:51:44 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     akpm@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH] proc: save decrement during lookup/readdir in /proc/$PID

Comparison for "<" works equally well as comparison for "<="
but one SUB/LEA is saved (no, it is not optimised away, at least here).

Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
---

 fs/proc/base.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2412,14 +2412,14 @@ static struct dentry *proc_pident_lookup(struct inode *dir,
 	 * Yes, it does not scale. And it should not. Don't add
 	 * new entries into /proc/<tgid>/ without very good reasons.
 	 */
-	last = &ents[nents - 1];
-	for (p = ents; p <= last; p++) {
+	last = &ents[nents];
+	for (p = ents; p < last; p++) {
 		if (p->len != dentry->d_name.len)
 			continue;
 		if (!memcmp(dentry->d_name.name, p->name, p->len))
 			break;
 	}
-	if (p > last)
+	if (p >= last)
 		goto out;
 
 	error = proc_pident_instantiate(dir, dentry, task, p);
@@ -2444,7 +2444,7 @@ static int proc_pident_readdir(struct file *file, struct dir_context *ctx,
 	if (ctx->pos >= nents + 2)
 		goto out;
 
-	for (p = ents + (ctx->pos - 2); p <= ents + nents - 1; p++) {
+	for (p = ents + (ctx->pos - 2); p < ents + nents; p++) {
 		if (!proc_fill_cache(file, ctx, p->name, p->len,
 				proc_pident_instantiate, task, p))
 			break;