From patchwork Fri Jul 6 19:32:33 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Omar Sandoval X-Patchwork-Id: 10512419 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 28CFA6024A for ; Fri, 6 Jul 2018 19:32:53 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 1738C287A9 for ; Fri, 6 Jul 2018 19:32:53 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 0B10F287AC; Fri, 6 Jul 2018 19:32:53 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9562A287A9 for ; Fri, 6 Jul 2018 19:32:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934753AbeGFTcu (ORCPT ); Fri, 6 Jul 2018 15:32:50 -0400 Received: from mail-pg1-f169.google.com ([209.85.215.169]:34905 "EHLO mail-pg1-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934739AbeGFTcs (ORCPT ); Fri, 6 Jul 2018 15:32:48 -0400 Received: by mail-pg1-f169.google.com with SMTP id e6-v6so319641pgv.2 for ; Fri, 06 Jul 2018 12:32:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=osandov-com.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=If2uZrQuTLVYJ8g0CUZfSQeRiZQEBbyzXaBZzmxRkb4=; b=kVt+jCs1d821SL1v2n89Cg0oMd7cxgJnAKV1Xl/Vyzm9f1qUm0qlcb3UgufTtjT9sC xlesnj5oOydk7zz3slf51LS8sN3IEdnVQdaahKDF58/PEhnuE8vdgp2aAtSxLP1Qh6Fe uOzmTHyA/Vck2d+mFjKwqa093LvGrd/mGjwvFMYoH+Ht1jzLhHa/XOqC0lVgwQlMKmUw s/menhh39J9BfzUN3P4m2sYmbUckxl8Yu8f9XEZGLvlcoY6pcmZFkFhyCeuedMvKubU5 GbDiDO9lj2gKrel9wusSk6T9ww7G5Sv3DUIZcFHagEkQwLH3pbp3tXIstMXSi2S3h9U3 TkeQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=If2uZrQuTLVYJ8g0CUZfSQeRiZQEBbyzXaBZzmxRkb4=; b=IfSjD6N4Q3gfju0kp5WsTp0R3YNtPPfyCqrLfF7aEBau9++INErd/eTfPkJkwf5QXt kOMzfm1R5/GqIgDGYSae/1ME8YcQOR5RKe1H9PLKufrwegefRMuWVVhF+s8Pr6dkfUpv eeAnM6EK2oxJWrHYeNqxpyTUG6gxcFYQjbs2y3opghEFP/PhmgoJKSwYmNG2PexEneH6 eZtYFKLiNfltSpXidPZXiYguDdUVDOyFK52NlCjae23QWdXwxIEciE0dOjKngNGsz1sI JB/kUFFEep6LZ0KTSG9PhapJxK/TwPOqwO9CXgto5j28fmalc1s3HbhYE04aIlf8jm03 Hcng== X-Gm-Message-State: APt69E31qv5gWq9jnL2699K28rCIm0MkqiG+tPLSxA069R+rOUmIyQzo 76W2PcgnRPd5KA3EXZjPS/JEs4zkkJg= X-Google-Smtp-Source: AAOMgpc1NntupZRfXHPgQp9elHChBJEHxuLxkq9rate3OgRA89JimWeMvsebo+yiaJ4+boK7lUcLLw== X-Received: by 2002:a63:8a41:: with SMTP id y62-v6mr10179041pgd.291.1530905567336; Fri, 06 Jul 2018 12:32:47 -0700 (PDT) Received: from vader.thefacebook.com ([2620:10d:c090:200::4:984e]) by smtp.gmail.com with ESMTPSA id a11-v6sm12846162pgq.32.2018.07.06.12.32.46 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 06 Jul 2018 12:32:46 -0700 (PDT) From: Omar Sandoval To: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Alexey Dobriyan Cc: Eric Biederman , kernel-team@fb.com Subject: [PATCH 2/7] proc/kcore: replace kclist_lock rwlock with rwsem Date: Fri, 6 Jul 2018 12:32:33 -0700 Message-Id: X-Mailer: git-send-email 2.18.0 In-Reply-To: References: Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Omar Sandoval Now we only need kclist_lock from user context and at fs init time, and the following changes need to sleep while holding the kclist_lock. Signed-off-by: Omar Sandoval --- fs/proc/kcore.c | 32 +++++++++++++++----------------- 1 file changed, 15 insertions(+), 17 deletions(-) diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c index afd1ff8c2d3f..eb1be07bdb3d 100644 --- a/fs/proc/kcore.c +++ b/fs/proc/kcore.c @@ -59,8 +59,8 @@ struct memelfnote }; static LIST_HEAD(kclist_head); -static DEFINE_RWLOCK(kclist_lock); -static int kcore_need_update = 1; +static DECLARE_RWSEM(kclist_lock); +static atomic_t kcore_need_update = ATOMIC_INIT(1); /* This doesn't grab kclist_lock, so it should only be used at init time. */ void @@ -117,8 +117,8 @@ static void __kcore_update_ram(struct list_head *list) struct kcore_list *tmp, *pos; LIST_HEAD(garbage); - write_lock(&kclist_lock); - if (kcore_need_update) { + down_write(&kclist_lock); + if (atomic_cmpxchg(&kcore_need_update, 1, 0)) { list_for_each_entry_safe(pos, tmp, &kclist_head, list) { if (pos->type == KCORE_RAM || pos->type == KCORE_VMEMMAP) @@ -127,9 +127,8 @@ static void __kcore_update_ram(struct list_head *list) list_splice_tail(list, &kclist_head); } else list_splice(list, &garbage); - kcore_need_update = 0; proc_root_kcore->size = get_kcore_size(&nphdr, &size); - write_unlock(&kclist_lock); + up_write(&kclist_lock); free_kclist_ents(&garbage); } @@ -450,11 +449,11 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) int nphdr; unsigned long start; - read_lock(&kclist_lock); + down_read(&kclist_lock); size = get_kcore_size(&nphdr, &elf_buflen); if (buflen == 0 || *fpos >= size) { - read_unlock(&kclist_lock); + up_read(&kclist_lock); return 0; } @@ -471,11 +470,11 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) tsz = buflen; elf_buf = kzalloc(elf_buflen, GFP_ATOMIC); if (!elf_buf) { - read_unlock(&kclist_lock); + up_read(&kclist_lock); return -ENOMEM; } elf_kcore_store_hdr(elf_buf, nphdr, elf_buflen); - read_unlock(&kclist_lock); + up_read(&kclist_lock); if (copy_to_user(buffer, elf_buf + *fpos, tsz)) { kfree(elf_buf); return -EFAULT; @@ -490,7 +489,7 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) if (buflen == 0) return acc; } else - read_unlock(&kclist_lock); + up_read(&kclist_lock); /* * Check to see if our file offset matches with any of @@ -503,12 +502,12 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) while (buflen) { struct kcore_list *m; - read_lock(&kclist_lock); + down_read(&kclist_lock); list_for_each_entry(m, &kclist_head, list) { if (start >= m->addr && start < (m->addr+m->size)) break; } - read_unlock(&kclist_lock); + up_read(&kclist_lock); if (&m->list == &kclist_head) { if (clear_user(buffer, tsz)) @@ -561,7 +560,7 @@ static int open_kcore(struct inode *inode, struct file *filp) if (!filp->private_data) return -ENOMEM; - if (kcore_need_update) + if (atomic_read(&kcore_need_update)) kcore_update_ram(); if (i_size_read(inode) != proc_root_kcore->size) { inode_lock(inode); @@ -591,9 +590,8 @@ static int __meminit kcore_callback(struct notifier_block *self, switch (action) { case MEM_ONLINE: case MEM_OFFLINE: - write_lock(&kclist_lock); - kcore_need_update = 1; - write_unlock(&kclist_lock); + atomic_set(&kcore_need_update, 1); + break; } return NOTIFY_OK; }