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 X-Spam-Level: X-Spam-Status: No, score=-6.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CA11BC32751 for ; Sat, 10 Aug 2019 09:05:42 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5EC762166E for ; Sat, 10 Aug 2019 09:05:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="WvlE/0bj" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5EC762166E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id B275A6B0005; Sat, 10 Aug 2019 05:05:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id AAFD26B0006; Sat, 10 Aug 2019 05:05:39 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 978036B0007; Sat, 10 Aug 2019 05:05:39 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from mail-lj1-f200.google.com (mail-lj1-f200.google.com [209.85.208.200]) by kanga.kvack.org (Postfix) with ESMTP id 35BAA6B0005 for ; Sat, 10 Aug 2019 05:05:39 -0400 (EDT) Received: by mail-lj1-f200.google.com with SMTP id 17so19704275ljc.20 for ; Sat, 10 Aug 2019 02:05:39 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:dkim-signature:mime-version:references :in-reply-to:from:date:message-id:subject:to:cc; bh=x/iVkWacMKBMI8tUTq90sb+qNE12YPEmDRdfDkGujEg=; b=ef5v26adXsulVtf/6O9IXM+hbZpuBXHsIPVgJmgSER9qOrXN2LANh+CG9/kE/zQisp T9xW3aXwTKWYBV7pE3a4WNa6JL8qARvJIuxYRvkWikP5jYQutCfplEzSQVjopND+bLN3 JaS0+msF8q8vwCiz37JoGTl+76/mHUSawfSU2vahULVz3tOtEMu4XDiZtV+iE1ELJgFp dYEXX+Sg3leyHCgSgEC6LP/OaviRQFjOh/gV37zJJ9HbvUPWoxRJTmbA+Gglk6LBdP49 aiCCOo6nq3PIo2k9mpenNZu4iOvMu7YWJR/zC0mRp0Qm+V/OTW08wh/39RK2fLa+zQqK J/qQ== X-Gm-Message-State: APjAAAVIMSjsRnZo67R065woqIF4y/TdG8OaQwWpU8P0Xg1IQ6oX49Ic Ti+4ucwb1UmxAjtlsqhkvb+4/Z6hGFv2JPU3k1vn+VHypWPkVve5YxNKh3KAcvkOlb7zZMubGVh S1MkzCx6aZ3hDDrgl5pyezyXfU4U/6y+SiHY6ed+SitPW0ygTm0pZ+w2rObp+3P+WeQ== X-Received: by 2002:a19:dc14:: with SMTP id t20mr6744485lfg.182.1565427938319; Sat, 10 Aug 2019 02:05:38 -0700 (PDT) X-Received: by 2002:a19:dc14:: with SMTP id t20mr6744457lfg.182.1565427937299; Sat, 10 Aug 2019 02:05:37 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1565427937; cv=none; d=google.com; s=arc-20160816; b=nZiL/X5PJd6FCeK7SsLJG+wH309Nk/wFL7PqSJDFsrvH0/ldbil4HEnQCauBB6N0hY WhKJh9vJoNUd+VBR7b0OjWWgBC91gDH6ALP2HEu0/70PEhXCfpOfmEerWvVtGwCcT2YM vICYhDG0GydYEgBorWDBQiZDSgvElYlRhfpwKOgRE36CrjfPUrEtA9ZrNudrwQD58QzD 2lB3aQ66TzgD2YgCEha05v4Va5hIL5mrCwSdZzKv8O5bIhQpy/Auhbo3F9hsGMtcCbU9 OXFVxNE0Jr5h2ipHMVU3SAuIjLB41r8/6qCbzIhdXuD/DD0oK5sz51vRVWAWi8CUxxUc 2wBg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:dkim-signature; bh=x/iVkWacMKBMI8tUTq90sb+qNE12YPEmDRdfDkGujEg=; b=JHqrjC4xW6GT0f8CS9VDv4IJJ3bpeyBQNrxyjMJ22TR847Lry9sQN+h01hh/AzP0Oc 9+DxHKKy1kve+JE8X7Rj4gjDEv9Zfk8xxyHSc7iXRg0BkPx+QE7U/cC2vHGSGWc8QyUR 968FRHkawc10wnEe1g8oiLTvXh7MK8FCGLxFW7DbfZWISEWzzko6Ffloh5AFr3XWIdSV hqj1R6kQHkXrNF8dSiT8t8MruBVwICCrY16CZtOgUHusDXvvRXm0W1kiG6UbqrUdhGSq gwDY3/vka6LekbpZqaE8vdTxJudNJyNp5DFumDJpTpOdTbEHq/qhN3ARXzYBwvLzv8sg 2lsg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b="WvlE/0bj"; spf=pass (google.com: domain of vitalywool@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=vitalywool@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id j3sor53191975ljg.20.2019.08.10.02.05.37 for (Google Transport Security); Sat, 10 Aug 2019 02:05:37 -0700 (PDT) Received-SPF: pass (google.com: domain of vitalywool@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b="WvlE/0bj"; spf=pass (google.com: domain of vitalywool@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=vitalywool@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=x/iVkWacMKBMI8tUTq90sb+qNE12YPEmDRdfDkGujEg=; b=WvlE/0bjif9cFAUGbIm/f0nu8+dOOpAZMPm9E+uI8zYm4MQUaeFnTN0/mLAbdeOfCI x3IN08Godktf7mrpJ4w+H6zi9+7XgTOBEnva1iHxVbFc3hU+4fq/w5vvz7mw0oYfAeuf eRNRgpMPMdbEH6h9IYz+5voskY5PFplpNp3SZQAe/tSwhdW2g8V3wR0i/fE2r7HXSxvt zmphBIxc1HKujLmnct8w+4coO6/9/COYW9sMx37l/pGHOVNi7vxizxw122bkUMEwiYkQ 9B0b/5ViG93yQn/yadNuscw4Pd3eK/lthDz87lcR42UJ5iz/3m2qR+/GciYvZdbRmU9/ 4sjQ== X-Google-Smtp-Source: APXvYqyXg4louOiSmPQuA3Tvk5SIs5REwboG+lRAcYog6St+Vb6efmyfq6z/WGumJAIIF26yBbDsKB+52JdmLRLZQi8= X-Received: by 2002:a2e:720b:: with SMTP id n11mr4092017ljc.213.1565427936877; Sat, 10 Aug 2019 02:05:36 -0700 (PDT) MIME-Version: 1.0 References: <20190809164643.5978-1-henryburns@google.com> In-Reply-To: <20190809164643.5978-1-henryburns@google.com> From: Vitaly Wool Date: Sat, 10 Aug 2019 12:05:23 +0300 Message-ID: Subject: Re: [PATCH] mm/z3fold.c: Fix race between migration and destruction To: Henry Burns Cc: Andrew Morton , Vitaly Vul , Shakeel Butt , Jonathan Adams , Linux-MM , LKML Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi Henry, Den fre 9 aug. 2019 6:46 emHenry Burns skrev: > > In z3fold_destroy_pool() we call destroy_workqueue(&pool->compact_wq). > However, we have no guarantee that migration isn't happening in the > background at that time. > > Migration directly calls queue_work_on(pool->compact_wq), if destruction > wins that race we are using a destroyed workqueue. Thanks for the fix. Would you please comment why adding flush_workqueue() isn't enough? ~Vitaly > > > Signed-off-by: Henry Burns > --- > mm/z3fold.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 51 insertions(+) > > diff --git a/mm/z3fold.c b/mm/z3fold.c > index 78447cecfffa..e136d97ce56e 100644 > --- a/mm/z3fold.c > +++ b/mm/z3fold.c > @@ -40,6 +40,7 @@ > #include > #include > #include > +#include > #include > > /* > @@ -161,8 +162,10 @@ struct z3fold_pool { > const struct zpool_ops *zpool_ops; > struct workqueue_struct *compact_wq; > struct workqueue_struct *release_wq; > + struct wait_queue_head isolate_wait; > struct work_struct work; > struct inode *inode; > + int isolated_pages; > }; > > /* > @@ -772,6 +775,7 @@ static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp, > goto out_c; > spin_lock_init(&pool->lock); > spin_lock_init(&pool->stale_lock); > + init_waitqueue_head(&pool->isolate_wait); > pool->unbuddied = __alloc_percpu(sizeof(struct list_head)*NCHUNKS, 2); > if (!pool->unbuddied) > goto out_pool; > @@ -811,6 +815,15 @@ static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp, > return NULL; > } > > +static bool pool_isolated_are_drained(struct z3fold_pool *pool) > +{ > + bool ret; > + > + spin_lock(&pool->lock); > + ret = pool->isolated_pages == 0; > + spin_unlock(&pool->lock); > + return ret; > +} > /** > * z3fold_destroy_pool() - destroys an existing z3fold pool > * @pool: the z3fold pool to be destroyed > @@ -821,6 +834,13 @@ static void z3fold_destroy_pool(struct z3fold_pool *pool) > { > kmem_cache_destroy(pool->c_handle); > > + /* > + * We need to ensure that no pages are being migrated while we destroy > + * these workqueues, as migration can queue work on either of the > + * workqueues. > + */ > + wait_event(pool->isolate_wait, !pool_isolated_are_drained(pool)); > + > /* > * We need to destroy pool->compact_wq before pool->release_wq, > * as any pending work on pool->compact_wq will call > @@ -1317,6 +1337,28 @@ static u64 z3fold_get_pool_size(struct z3fold_pool *pool) > return atomic64_read(&pool->pages_nr); > } > > +/* > + * z3fold_dec_isolated() expects to be called while pool->lock is held. > + */ > +static void z3fold_dec_isolated(struct z3fold_pool *pool) > +{ > + assert_spin_locked(&pool->lock); > + VM_BUG_ON(pool->isolated_pages <= 0); > + pool->isolated_pages--; > + > + /* > + * If we have no more isolated pages, we have to see if > + * z3fold_destroy_pool() is waiting for a signal. > + */ > + if (pool->isolated_pages == 0 && waitqueue_active(&pool->isolate_wait)) > + wake_up_all(&pool->isolate_wait); > +} > + > +static void z3fold_inc_isolated(struct z3fold_pool *pool) > +{ > + pool->isolated_pages++; > +} > + > static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode) > { > struct z3fold_header *zhdr; > @@ -1343,6 +1385,7 @@ static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode) > spin_lock(&pool->lock); > if (!list_empty(&page->lru)) > list_del(&page->lru); > + z3fold_inc_isolated(pool); > spin_unlock(&pool->lock); > z3fold_page_unlock(zhdr); > return true; > @@ -1417,6 +1460,10 @@ static int z3fold_page_migrate(struct address_space *mapping, struct page *newpa > > queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work); > > + spin_lock(&pool->lock); > + z3fold_dec_isolated(pool); > + spin_unlock(&pool->lock); > + > page_mapcount_reset(page); > put_page(page); > return 0; > @@ -1436,10 +1483,14 @@ static void z3fold_page_putback(struct page *page) > INIT_LIST_HEAD(&page->lru); > if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) { > atomic64_dec(&pool->pages_nr); > + spin_lock(&pool->lock); > + z3fold_dec_isolated(pool); > + spin_unlock(&pool->lock); > return; > } > spin_lock(&pool->lock); > list_add(&page->lru, &pool->lru); > + z3fold_dec_isolated(pool); > spin_unlock(&pool->lock); > z3fold_page_unlock(zhdr); > } > -- > 2.22.0.770.g0f2c4a37fd-goog >