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Mon, 22 May 2023 10:34:32 -0400 X-MC-Unique: NIbb16wIPq-7Wjn9zfXydA-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 7F68F85A5BA; Mon, 22 May 2023 14:34:31 +0000 (UTC) Received: from localhost (ovpn-12-35.pek2.redhat.com [10.72.12.35]) by smtp.corp.redhat.com (Postfix) with ESMTPS id BA6771121314; Mon, 22 May 2023 14:34:30 +0000 (UTC) Date: Mon, 22 May 2023 22:34:26 +0800 From: Baoquan He To: Thomas Gleixner Cc: "Russell King (Oracle)" , Andrew Morton , linux-mm@kvack.org, Christoph Hellwig , Uladzislau Rezki , Lorenzo Stoakes , Peter Zijlstra , John Ogness , linux-arm-kernel@lists.infradead.org, Mark Rutland , Marc Zyngier , x86@kernel.org, Nadav Amit Subject: Re: [RFC PATCH 3/3] mm/vmalloc.c: change _vm_unmap_aliases() to do purge firstly Message-ID: References: <874joc8x7d.ffs@tglx> <87r0rg73wp.ffs@tglx> <87edng6qu8.ffs@tglx> <87cz2w415t.ffs@tglx> <87jzx1xou9.ffs@tglx> <87wn10wp45.ffs@tglx> MIME-Version: 1.0 In-Reply-To: <87wn10wp45.ffs@tglx> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Rspamd-Queue-Id: 2F1551A0013 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: xuomrxsm17hbsk5rnjswarcw17d6riu5 X-HE-Tag: 1684766076-199728 X-HE-Meta: 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 pZfftMJw sFRm/g+9nUDWXaKHDUqKTPCzR8eJtJPijF7qw0KLzYkOauh7lwT1LFC0p+9Zq3ciNPZxiirvbnr3RCeE+KnJwbJMpOUUM7FV6gq/769cbI91BxD43pTSAactnPKziEQsAhpSLn6PF4AyYOMMeLixTZqYxPe2f7/IEnjOmZg/WSG5qJ15xnyglY2ytQIXQwy1N/m8o7HpiQzYGNFlB7BLT1/jz0hvQ8GJ3gmwpedLFWa7oRcE2NCe5jt3YMQJOO6YC/RS4DyWtd/faPkijdinBwNFr8Z6hSvT3xDuWwdoD1Hekl5twzzauDs2ay5/x46mUkv31 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: On 05/22/23 at 02:02pm, Thomas Gleixner wrote: > On Mon, May 22 2023 at 19:21, Baoquan He wrote: > > On 05/22/23 at 01:10am, Thomas Gleixner wrote: > > > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > > index 5ca55b357148..4b11a32df49d 100644 > > --- a/mm/vmalloc.c > > +++ b/mm/vmalloc.c > > @@ -1728,6 +1728,7 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end) > > unsigned int num_purged_areas = 0; > > struct list_head local_purge_list; > > struct vmap_area *va, *n_va; > > + struct vmap_block vb; > > > > lockdep_assert_held(&vmap_purge_lock); > > > > @@ -1736,6 +1737,14 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end) > > list_replace_init(&purge_vmap_area_list, &local_purge_list); > > spin_unlock(&purge_vmap_area_lock); > > > > + vb = container_of(va, struct vmap_block, va); > > This cannot work vmap_area is not embedded in vmap_block. vmap_block::va > is a pointer. vmap_area does not link back to vmap_block, so there is no > way to find it based on a vmap_area. Oh, the code is buggy. va->flags can tell if it's vmap_block, then we can deduce the vb pointer. diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 5ca55b357148..73d6ce441351 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -1728,6 +1728,7 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end) unsigned int num_purged_areas = 0; struct list_head local_purge_list; struct vmap_area *va, *n_va; + struct vmap_block vb; lockdep_assert_held(&vmap_purge_lock); @@ -1736,6 +1737,15 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end) list_replace_init(&purge_vmap_area_list, &local_purge_list); spin_unlock(&purge_vmap_area_lock); + if (va->flags & VMAP_FLAGS_MASK == VMAP_RAM|VMAP_BLOCK) { + vb = container_of(va, struct vmap_block, va); + if (vb->dirty_max) { /*This is pseudo code for illustration*/ + s = vb->dirty_min << PAGE_SHIFT; + e = vb->dirty_max << PAGE_SHIFT; + } + kfree(vb); + } + if (unlikely(list_empty(&local_purge_list))) goto out; @@ -2083,7 +2093,6 @@ static void free_vmap_block(struct vmap_block *vb) spin_unlock(&vmap_area_lock); free_vmap_area_noflush(vb->va); - kfree_rcu(vb, rcu_head); } > > Aside of that va is not initialized here :) Oh, this is not real code, just to illustrate how it can calculate and flush the last two pages of vmap_block. If you have the per va flushing via array patch, I can work out formal code change based on that.