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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A2870C433EF for ; Mon, 27 Sep 2021 07:22:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 867F86023D for ; Mon, 27 Sep 2021 07:22:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233230AbhI0HYQ (ORCPT ); Mon, 27 Sep 2021 03:24:16 -0400 Received: from smtp-out1.suse.de ([195.135.220.28]:44966 "EHLO smtp-out1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233205AbhI0HYI (ORCPT ); Mon, 27 Sep 2021 03:24:08 -0400 Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 10BFD220C3 for ; Mon, 27 Sep 2021 07:22:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1632727350; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=DesgMaRyn1FL6S66XszhVS/WQmsD5fm/RuNh79CgLW0=; b=Ap1mZU0eCZ6j+BV3yrIEFB0afAips0KMqwRPSPPmSXec0MZNo8j9GtcqHUhgKEtu0lx3ur ilTH4CWUb2StxH/pu+X13VkReyT7GEd3e8z7L1fnKnNUoFqx1MW+D+eCBy1dh/RIiD7JaB txMv6PLqzJsMgR2WH6836FQC+r1mCQs= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 6B2BC13A1E for ; Mon, 27 Sep 2021 07:22:29 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 0CYPDjVxUWEVLAAAMHmgww (envelope-from ) for ; Mon, 27 Sep 2021 07:22:29 +0000 From: Qu Wenruo To: linux-btrfs@vger.kernel.org Subject: [PATCH v3 03/26] btrfs: use async_chunk::async_cow to replace the confusing pending pointer Date: Mon, 27 Sep 2021 15:21:45 +0800 Message-Id: <20210927072208.21634-4-wqu@suse.com> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20210927072208.21634-1-wqu@suse.com> References: <20210927072208.21634-1-wqu@suse.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org For structure async_chunk, we use a very strange member layout to grab structure async_cow who owns this async_chunk. At initialization, it goes like this: async_chunk[i].pending = &ctx->num_chunks; Then at async_cow_free() we do a super weird freeing: /* * Since the pointer to 'pending' is at the beginning of the array of * async_chunk's, freeing it ensures the whole array has been freed. */ if (atomic_dec_and_test(async_chunk->pending)) kvfree(async_chunk->pending); This is absolutely an abuse of kvfree(). Replace async_chunk::pending with async_chunk::async_cow, so that we can grab the async_cow structure directly, without this strange dancing. And with this change, there is no requirement for any specific member location. Signed-off-by: Qu Wenruo --- fs/btrfs/inode.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index a643be30c18a..3aa820d64b94 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -455,11 +455,10 @@ struct async_chunk { struct list_head extents; struct cgroup_subsys_state *blkcg_css; struct btrfs_work work; - atomic_t *pending; + struct async_cow *async_cow; }; struct async_cow { - /* Number of chunks in flight; must be first in the structure */ atomic_t num_chunks; struct async_chunk chunks[]; }; @@ -1324,18 +1323,17 @@ static noinline void async_cow_submit(struct btrfs_work *work) static noinline void async_cow_free(struct btrfs_work *work) { struct async_chunk *async_chunk; + struct async_cow *async_cow; async_chunk = container_of(work, struct async_chunk, work); if (async_chunk->inode) btrfs_add_delayed_iput(async_chunk->inode); if (async_chunk->blkcg_css) css_put(async_chunk->blkcg_css); - /* - * Since the pointer to 'pending' is at the beginning of the array of - * async_chunk's, freeing it ensures the whole array has been freed. - */ - if (atomic_dec_and_test(async_chunk->pending)) - kvfree(async_chunk->pending); + + async_cow = async_chunk->async_cow; + if (atomic_dec_and_test(&async_cow->num_chunks)) + kvfree(async_cow); } static int cow_file_range_async(struct btrfs_inode *inode, @@ -1396,7 +1394,7 @@ static int cow_file_range_async(struct btrfs_inode *inode, * lightweight reference for the callback lifetime */ ihold(&inode->vfs_inode); - async_chunk[i].pending = &ctx->num_chunks; + async_chunk[i].async_cow = ctx; async_chunk[i].inode = &inode->vfs_inode; async_chunk[i].start = start; async_chunk[i].end = cur_end; -- 2.33.0