linux-kernel - [PATCH] proc: smaller readlock section in readdir("/proc")

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Message-ID: <20180627195339.GD18113@avx2>
Date:   Wed, 27 Jun 2018 22:53:39 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     akpm@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH] proc: smaller readlock section in readdir("/proc")

Readdir context is thread local, so ->pos is thread local,
move it out of readlock.

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

 fs/proc/generic.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -286,9 +286,9 @@ int proc_readdir_de(struct file *file, struct dir_context *ctx,
 	if (!dir_emit_dots(file, ctx))
 		return 0;
 
+	i = ctx->pos - 2;
 	read_lock(&proc_subdir_lock);
 	de = pde_subdir_first(de);
-	i = ctx->pos - 2;
 	for (;;) {
 		if (!de) {
 			read_unlock(&proc_subdir_lock);
@@ -309,8 +309,8 @@ int proc_readdir_de(struct file *file, struct dir_context *ctx,
 			pde_put(de);
 			return 0;
 		}
-		read_lock(&proc_subdir_lock);
 		ctx->pos++;
+		read_lock(&proc_subdir_lock);
 		next = pde_subdir_next(de);
 		pde_put(de);
 		de = next;