From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C821EC77B75 for ; Mon, 8 May 2023 01:17:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=SNvXEGqcYfeB4HwehtUoZe/sUS8dcUXitISkuPxvNG0=; b=izUvpkWY8xBUa8 ooFO70xxHlc+SxMfOugWdpsSkxOU0yhCpHCbVFvC2Ome8DpZv0uepFSwOOLNWT4yzvcc/fTaMMktG u/cdwtarH9AT/KX4CelWlNtM/OOz0Wnv+U2dEH/NMPbAHdmcKxGryofgQaz4gB5E1L3+A5ceCIBmQ UNxP8utDc+j+97RhPXc1eBya3U7lN3MzuS32sWOUNks6JJnby/eZYBVeIUAjj+Fxxqg8ezoKUFa/l IHkv62+9f7LWn+yqG5JbkX4cle+jS4uhL60l5W+AIKGDkbVaKuCI6dk2mFJn9ewYmXGyTizvenLdi AvKXq8VNcWOghd7dsCLg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1pvpVG-00GvbY-0J; Mon, 08 May 2023 01:17:26 +0000 Received: from mcgrof by bombadil.infradead.org with local (Exim 4.96 #2 (Red Hat Linux)) id 1pvpV7-00GvZ6-3A; Mon, 08 May 2023 01:17:17 +0000 From: Luis Chamberlain To: hch@infradead.org, djwong@kernel.org, sandeen@sandeen.net, song@kernel.org, rafael@kernel.org, gregkh@linuxfoundation.org, viro@zeniv.linux.org.uk, jack@suse.cz, jikos@kernel.org, bvanassche@acm.org, ebiederm@xmission.com Cc: mchehab@kernel.org, keescook@chromium.org, p.raghav@samsung.com, da.gomez@samsung.com, linux-fsdevel@vger.kernel.org, kernel@tuxforce.de, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Luis Chamberlain Subject: [PATCH 5/6] fs: add iterate_supers_excl() and iterate_supers_reverse_excl() Date: Sun, 7 May 2023 18:17:16 -0700 Message-Id: <20230508011717.4034511-6-mcgrof@kernel.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20230508011717.4034511-1-mcgrof@kernel.org> References: <20230508011717.4034511-1-mcgrof@kernel.org> MIME-Version: 1.0 X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org There are use cases where we wish to traverse the superblock list but also capture errors, and in which case we want to avoid having our callers issue a lock themselves since we can do the locking for the callers. Provide a iterate_supers_excl() which calls a function with the write lock held. If an error occurs we capture it and propagate it. Likewise there are use cases where we wish to traverse the superblock list but in reverse order. The new iterate_supers_reverse_excl() helpers does this but also also captures any errors encountered. Reviewed-by: Jan Kara Signed-off-by: Luis Chamberlain --- fs/super.c | 91 ++++++++++++++++++++++++++++++++++++++++++++++ include/linux/fs.h | 2 + 2 files changed, 93 insertions(+) diff --git a/fs/super.c b/fs/super.c index 28c633b81f8f..d5eab6b38b03 100644 --- a/fs/super.c +++ b/fs/super.c @@ -753,6 +753,97 @@ void iterate_supers(void (*f)(struct super_block *, void *), void *arg) spin_unlock(&sb_lock); } +/** + * iterate_supers_excl - exclusively call func for all active superblocks + * @f: function to call + * @arg: argument to pass to it + * + * Scans the superblock list and calls given function, passing it + * locked superblock and given argument. Returns 0 unless an error + * occurred on calling the function on any superblock. + */ +int iterate_supers_excl(int (*f)(struct super_block *, void *), void *arg) +{ + struct super_block *sb, *p = NULL; + int error = 0; + + spin_lock(&sb_lock); + list_for_each_entry(sb, &super_blocks, s_list) { + if (hlist_unhashed(&sb->s_instances)) + continue; + sb->s_count++; + spin_unlock(&sb_lock); + + down_write(&sb->s_umount); + if (sb->s_root && (sb->s_flags & SB_BORN)) { + error = f(sb, arg); + if (error) { + up_write(&sb->s_umount); + spin_lock(&sb_lock); + __put_super(sb); + break; + } + } + up_write(&sb->s_umount); + + spin_lock(&sb_lock); + if (p) + __put_super(p); + p = sb; + } + if (p) + __put_super(p); + spin_unlock(&sb_lock); + + return error; +} + +/** + * iterate_supers_reverse_excl - exclusively calls func in reverse order + * @f: function to call + * @arg: argument to pass to it + * + * Scans the superblock list and calls given function, passing it + * locked superblock and given argument, in reverse order, and holding + * the s_umount write lock. Returns if an error occurred. + */ +int iterate_supers_reverse_excl(int (*f)(struct super_block *, void *), + void *arg) +{ + struct super_block *sb, *p = NULL; + int error = 0; + + spin_lock(&sb_lock); + list_for_each_entry_reverse(sb, &super_blocks, s_list) { + if (hlist_unhashed(&sb->s_instances)) + continue; + sb->s_count++; + spin_unlock(&sb_lock); + + down_write(&sb->s_umount); + if (sb->s_root && (sb->s_flags & SB_BORN)) { + error = f(sb, arg); + if (error) { + up_write(&sb->s_umount); + spin_lock(&sb_lock); + __put_super(sb); + break; + } + } + up_write(&sb->s_umount); + + spin_lock(&sb_lock); + if (p) + __put_super(p); + p = sb; + } + if (p) + __put_super(p); + spin_unlock(&sb_lock); + + return error; +} + /** * iterate_supers_type - call function for superblocks of given type * @type: fs type diff --git a/include/linux/fs.h b/include/linux/fs.h index d9b46c858103..22dd697ab703 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2935,6 +2935,8 @@ extern struct super_block *get_active_super(struct block_device *bdev); extern void drop_super(struct super_block *sb); extern void drop_super_exclusive(struct super_block *sb); extern void iterate_supers(void (*)(struct super_block *, void *), void *); +extern int iterate_supers_excl(int (*f)(struct super_block *, void *), void *arg); +extern int iterate_supers_reverse_excl(int (*)(struct super_block *, void *), void *); extern void iterate_supers_type(struct file_system_type *, void (*)(struct super_block *, void *), void *); -- 2.39.2 _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec