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Mon, 19 Dec 2022 03:01:06 -0500 X-MC-Unique: 7NJ4EhN1P5auwNSH5O_5-Q-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 4C765101A521; Mon, 19 Dec 2022 08:01:06 +0000 (UTC) Received: from localhost (ovpn-12-41.pek2.redhat.com [10.72.12.41]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 1CD1E40C1074; Mon, 19 Dec 2022 08:01:03 +0000 (UTC) Date: Mon, 19 Dec 2022 16:01:00 +0800 From: Baoquan He To: Lorenzo Stoakes Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, urezki@gmail.com, stephen.s.brennan@oracle.com, willy@infradead.org, akpm@linux-foundation.org, hch@infradead.org Subject: Re: [PATCH v2 2/7] mm/vmalloc.c: add flags to mark vm_map_ram area Message-ID: References: <20221217015435.73889-1-bhe@redhat.com> <20221217015435.73889-3-bhe@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: A857C18001D X-Stat-Signature: md4tutrb6gj95oj8csmnx1sy4pfc6aek X-HE-Tag: 1671436871-175746 X-HE-Meta: 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 /cA== 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 12/17/22 at 11:44am, Lorenzo Stoakes wrote: > On Sat, Dec 17, 2022 at 09:54:30AM +0800, Baoquan He wrote: > > @@ -2229,8 +2236,12 @@ void vm_unmap_ram(const void *mem, unsigned int count) > > return; > > } > > > > - va = find_vmap_area(addr); > > + spin_lock(&vmap_area_lock); > > + va = __find_vmap_area((unsigned long)addr, &vmap_area_root); > > BUG_ON(!va); > > + if (va) > > + va->flags &= ~VMAP_RAM; > > + spin_unlock(&vmap_area_lock); > > debug_check_no_locks_freed((void *)va->va_start, > > (va->va_end - va->va_start)); > > free_unmap_vmap_area(va); > > Would it be better to perform the BUG_ON() after the lock is released? You > already check if va exists before unmasking so it's safe. It's a little unclear to me why we care BUG_ON() is performed before or after the lock released. We won't have a stable kernel after BUG_ON()(), right? > > Also, do we want to clear VMAP_BLOCK here? I do, but I don't find a good place to clear VMAP_BLOCK. In v1, I tried to clear it in free_vmap_area_noflush() as below, Uladzislau dislikes it. So I remove it. My thinking is when we unmap and free the vmap area, the vmap_area is moved from vmap_area_root into &free_vmap_area_root. When we allocate a new vmap_area via alloc_vmap_area(), we will allocate a new va by kmem_cache_alloc_node(), the va->flags must be 0. Seems not initializing it to 0 won't impact thing. diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 5d3fd3e6fe09..d6f376060d83 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -1815,6 +1815,7 @@ static void free_vmap_area_noflush(struct vmap_area *va) spin_lock(&vmap_area_lock); unlink_va(va, &vmap_area_root); + va->flags = 0; spin_unlock(&vmap_area_lock); nr_lazy = atomic_long_add_return((va->va_end - va->va_start) >> >