linux-kernel - Re: [PATCH v3] proc: report open files as size in stat() for /proc/pid/fd

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Message-Id: <20221018161357.4891fcdb94ecc63035b6792a@linux-foundation.org>
Date:   Tue, 18 Oct 2022 16:13:57 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Ivan Babrou <ivan@...udflare.com>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...udflare.com, Alexey Dobriyan <adobriyan@...il.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        "Theodore Ts'o" <tytso@....edu>,
        David Laight <David.Laight@...lab.com>,
        Jonathan Corbet <corbet@....net>,
        David Hildenbrand <david@...hat.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Christoph Anton Mitterer <mail@...istoph.anton.mitterer.name>,
        Mike Rapoport <rppt@...nel.org>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Kalesh Singh <kaleshsingh@...gle.com>
Subject: Re: [PATCH v3] proc: report open files as size in stat() for
 /proc/pid/fd

On Mon, 17 Oct 2022 21:58:44 -0700 Ivan Babrou <ivan@...udflare.com> wrote:

> v3: Made use of bitmap_weight() to count the bits.

Thanks, I queued the below delta:

--- a/fs/proc/fd.c~proc-report-open-files-as-size-in-stat-for-proc-pid-fd-v3
+++ a/fs/proc/fd.c
@@ -283,7 +283,7 @@ static int proc_readfd_count(struct inod
 {
 	struct task_struct *p = get_proc_task(inode);
 	struct fdtable *fdt;
-	unsigned int i, size, open_fds = 0;
+	unsigned int open_fds = 0;
 
 	if (!p)
 		return -ENOENT;
@@ -293,10 +293,7 @@ static int proc_readfd_count(struct inod
 		rcu_read_lock();
 
 		fdt = files_fdtable(p->files);
-		size = fdt->max_fds;
-
-		for (i = size / BITS_PER_LONG; i > 0;)
-			open_fds += hweight64(fdt->open_fds[--i]);
+		open_fds = bitmap_weight(fdt->open_fds, fdt->max_fds);
 
 		rcu_read_unlock();
 	}
_


Also, let's explicitly include the header file to avoid possible
accidents with unexpected Kconfigs.

--- a/fs/proc/fd.c~proc-report-open-files-as-size-in-stat-for-proc-pid-fd-v3-fix
+++ a/fs/proc/fd.c
@@ -7,6 +7,7 @@
 #include <linux/namei.h>
 #include <linux/pid.h>
 #include <linux/ptrace.h>
+#include <linux/bitmap.h>
 #include <linux/security.h>
 #include <linux/file.h>
 #include <linux/seq_file.h>
_