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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D6BAAC4332F for ; Tue, 20 Dec 2022 16:56:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233979AbiLTQ4D (ORCPT ); Tue, 20 Dec 2022 11:56:03 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47304 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229723AbiLTQz7 (ORCPT ); Tue, 20 Dec 2022 11:55:59 -0500 Received: from mail-lj1-x22b.google.com (mail-lj1-x22b.google.com [IPv6:2a00:1450:4864:20::22b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 832CC1176 for ; Tue, 20 Dec 2022 08:55:57 -0800 (PST) Received: by mail-lj1-x22b.google.com with SMTP id q2so3753687ljp.6 for ; Tue, 20 Dec 2022 08:55:57 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:date:from:from:to:cc:subject:date:message-id:reply-to; bh=RV2b+N4EY8X7AP+wxiTDOB1h8DJAj0YpeZrRZGqmAGU=; b=igIjFRYBlJmWR+sZzIcsLQyE8jdrcsZ97Cj+D0lh8XfZDlJVuOVWRPQt09Trny3eXg bg2r5Razpu5YSMx9vnnA7dWArKG/M1TKW/pRjYwznlxc47EnxLyCIvEFR7S+IpfqW6wA jh3FMFMBbPDbKyRZSxiiojjYCT66FLvvfoyGbTbpMXeO+Rfg0qMOhpPUrK131Ptn9K3x iwULuAoKCHJJM346zXtDA5zd6Yeoe9ZSs5EKzGS/2kNLrW5lFF3UJkeVBK3HPgZRh/gE BCeZc1TQ9C2mek0+Pej07us+LIxQ2EvvnoIrH7joXWeS5wi/PwfpGQhrluFFh3q/LL0o xvyw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:date:from:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=RV2b+N4EY8X7AP+wxiTDOB1h8DJAj0YpeZrRZGqmAGU=; b=Bv/oYSNMIqQ0ITpZiIS6wDgjSiU/xXID419WkBjt/g42wdumfgkqG3616zjXe7vQAg fiT9HPblReGGm4ex5r1N5YAv2ZPpvNfb617a3vMPoISdpK3YaY3Nus79Y8VsjSjCH0Xf NNinbielJFwvEypwfMwKfkuALwaMcHrzzUpeUVq3h/PTOKQNA1hsF44OwZq1+cl2dgRV GPnGHjOBt9WrFx6z+pBK7suDvTlIAyDNRItOSz7VNpcZ1J+TF0dgjuaPTkwMS2F2XflD iE3GqFtAakAZTO1qvsfKZzKrB+qimLAPHqYXUYiu3rvKBmFmT3YtuWG4y5J3u1PuZaGJ k7jw== X-Gm-Message-State: ANoB5pnI7O9BGLSYAumSh9kfQiKu1SWFRw92FJ9fPUVCyT/UaZgSeTnQ Wyi4zPnDIN5bxKTeFpIr2qY= X-Google-Smtp-Source: AA0mqf4k8IpjOpJrh6S3u5p9mOLpoXNiRbJdsIh5YoWG5Dxh22i4epGSO1G9gwynRJDnANzyqfU1Kg== X-Received: by 2002:a05:651c:1145:b0:277:744:1f34 with SMTP id h5-20020a05651c114500b0027707441f34mr18843183ljo.25.1671555355739; Tue, 20 Dec 2022 08:55:55 -0800 (PST) Received: from pc636 (host-90-233-218-120.mobileonline.telia.com. [90.233.218.120]) by smtp.gmail.com with ESMTPSA id t23-20020a2e8e77000000b00279e618444dsm1061417ljk.122.2022.12.20.08.55.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 20 Dec 2022 08:55:55 -0800 (PST) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Tue, 20 Dec 2022 17:55:53 +0100 To: Baoquan He 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: <20221217015435.73889-3-bhe@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > Through vmalloc API, a virtual kernel area is reserved for physical > address mapping. And vmap_area is used to track them, while vm_struct > is allocated to associate with the vmap_area to store more information > and passed out. > > However, area reserved via vm_map_ram() is an exception. It doesn't have > vm_struct to associate with vmap_area. And we can't recognize the > vmap_area with '->vm == NULL' as a vm_map_ram() area because the normal > freeing path will set va->vm = NULL before unmapping, please see > function remove_vm_area(). > A normal "free" path sets it to NULL in order to prevent a double-free of same VA. We can avoid of touching the va->vm if needed and do an unlink on entry in the remove_vm_area() when a lock is taken to find an area. Will it help you? > Meanwhile, there are two types of vm_map_ram area. One is the whole > vmap_area being reserved and mapped at one time; the other is the > whole vmap_area with VMAP_BLOCK_SIZE size being reserved, while mapped > into split regions with smaller size several times via vb_alloc(). > > To mark the area reserved through vm_map_ram(), add flags field into > struct vmap_area. Bit 0 indicates whether it's a vm_map_ram area, > while bit 1 indicates whether it's a vmap_block type of vm_map_ram > area. > > This is a preparatoin for later use. > > Signed-off-by: Baoquan He > --- > include/linux/vmalloc.h | 1 + > mm/vmalloc.c | 22 +++++++++++++++++----- > 2 files changed, 18 insertions(+), 5 deletions(-) > > diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h > index 096d48aa3437..69250efa03d1 100644 > --- a/include/linux/vmalloc.h > +++ b/include/linux/vmalloc.h > @@ -76,6 +76,7 @@ struct vmap_area { > unsigned long subtree_max_size; /* in "free" tree */ > struct vm_struct *vm; /* in "busy" tree */ > }; > + unsigned long flags; /* mark type of vm_map_ram area */ > }; > > /* archs that select HAVE_ARCH_HUGE_VMAP should override one or more of these */ > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 5d3fd3e6fe09..190f29bbaaa7 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -1586,7 +1586,8 @@ preload_this_cpu_lock(spinlock_t *lock, gfp_t gfp_mask, int node) > static struct vmap_area *alloc_vmap_area(unsigned long size, > unsigned long align, > unsigned long vstart, unsigned long vend, > - int node, gfp_t gfp_mask) > + int node, gfp_t gfp_mask, > + unsigned long va_flags) > { > struct vmap_area *va; > unsigned long freed; > @@ -1630,6 +1631,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size, > va->va_start = addr; > va->va_end = addr + size; > va->vm = NULL; > + va->flags = va_flags; > > spin_lock(&vmap_area_lock); > insert_vmap_area(va, &vmap_area_root, &vmap_area_list); > @@ -1887,6 +1889,10 @@ struct vmap_area *find_vmap_area(unsigned long addr) > > #define VMAP_BLOCK_SIZE (VMAP_BBMAP_BITS * PAGE_SIZE) > > +#define VMAP_RAM 0x1 > +#define VMAP_BLOCK 0x2 > +#define VMAP_FLAGS_MASK 0x3 > Maybe to rename a VMAP_BLOCK to something like VMAP_BLOCK_RESERVED or VMAP_PER_CPU_BLOCK? > struct vmap_block_queue { > spinlock_t lock; > struct list_head free; > @@ -1962,7 +1968,8 @@ static void *new_vmap_block(unsigned int order, gfp_t gfp_mask) > > va = alloc_vmap_area(VMAP_BLOCK_SIZE, VMAP_BLOCK_SIZE, > VMALLOC_START, VMALLOC_END, > - node, gfp_mask); > + node, gfp_mask, > + VMAP_RAM|VMAP_BLOCK); > A new_vmap_block() is for a per-cpu path. As far as i see the VMAP_BLOCK flag is used to mark a VA that corresponds to a reserved per-cpu free area. Whereas a VMAP_RAM is for VA that was obtained over per-cpu path but over alloc_vmap_area() thus a VA should be read out over "busy" tree directly. Why do you need to set here both VMAP_RAM and VMAP_BLOCK? > if (IS_ERR(va)) { > kfree(vb); > return ERR_CAST(va); > @@ -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, > Agree with Lorenzo. BUG_ON() should be out of spinlock(). Furthermore i think it makes sense to go with WARN_ON_ONCE() and do not kill a system. Instead emit a warning and bailout. What do you think? Maybe separate patch for it? > (va->va_end - va->va_start)); > free_unmap_vmap_area(va); > @@ -2265,7 +2276,8 @@ void *vm_map_ram(struct page **pages, unsigned int count, int node) > } else { > struct vmap_area *va; > va = alloc_vmap_area(size, PAGE_SIZE, > - VMALLOC_START, VMALLOC_END, node, GFP_KERNEL); > + VMALLOC_START, VMALLOC_END, > + node, GFP_KERNEL, VMAP_RAM); > if (IS_ERR(va)) > return NULL; > > @@ -2505,7 +2517,7 @@ static struct vm_struct *__get_vm_area_node(unsigned long size, > if (!(flags & VM_NO_GUARD)) > size += PAGE_SIZE; > > - va = alloc_vmap_area(size, align, start, end, node, gfp_mask); > + va = alloc_vmap_area(size, align, start, end, node, gfp_mask, 0); > if (IS_ERR(va)) { > kfree(area); > return NULL; > I know we have already discussed the new parameter. But what if we just use atomic_set operation to mark VA as either vmap-ram or vmap-block? As for alloc_vmap_area() we set it just as zero. -- Uladzislau Rezki