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[94.245.46.61]) by smtp.gmail.com with ESMTPSA id q15sm373739lfp.157.2021.07.15.03.58.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Jul 2021 03:58:15 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Thu, 15 Jul 2021 12:58:13 +0200 To: Chen Wandun Cc: akpm@linux-foundation.org, serapheim.dimitro@delphix.com, urezki@gmail.com, wangkefeng.wang@huawei.com, weiyongjun1@huawei.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hulk Robot Subject: Re: [PATCH] mm/vmalloc: fix wrong behavior in vread Message-ID: <20210715105813.GA1879@pc638.lan> References: <20210714015959.3204871-1-chenwandun@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210714015959.3204871-1-chenwandun@huawei.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 14, 2021 at 09:59:59AM +0800, Chen Wandun wrote: > commit f608788cd2d6 ("mm/vmalloc: use rb_tree instead of list for vread() > lookups") use rb_tree instread of list to speed up lookup, but function > __find_vmap_area is try to find a vmap_area that include target address, > if target address is smaller than the leftmost node in vmap_area_root, > it will return NULL, then vread will read nothing. This behavior is > different from the primitive semantics. > > The correct way is find the first vmap_are that bigger than target addr, > that is what function find_vmap_area_exceed_addr does. > > Fixes: f608788cd2d6 ("mm/vmalloc: use rb_tree instead of list for vread() lookups") > Reported-by: Hulk Robot > Signed-off-by: Chen Wandun > --- > mm/vmalloc.c | 29 ++++++++++++++++++++++++++++- > 1 file changed, 28 insertions(+), 1 deletion(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index d5cd52805149..47c3a551b6dc 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -787,6 +787,28 @@ unsigned long vmalloc_nr_pages(void) > return atomic_long_read(&nr_vmalloc_pages); > } > > +static struct vmap_area *find_vmap_area_exceed_addr(unsigned long addr) > +{ > + struct vmap_area *va = NULL; > + struct rb_node *n = vmap_area_root.rb_node; > + > + while (n) { > + struct vmap_area *tmp; > + > + tmp = rb_entry(n, struct vmap_area, rb_node); > + if (tmp->va_end > addr) { > + va = tmp; > + if (tmp->va_start <= addr) > + break; > + > + n = n->rb_left; > + } else > + n = n->rb_right; > + } > + > + return va; > +} > + Can we combine pvm_find_va_enclose_addr() with your new function making it as one function? The aim is to reduce copy-paste and not create such new "find" functions. The pvm_find_va_enclose_addr() seems does the same but only in reverse order. So something like: find_vmap_area_exceed_addr(bool reverse) Thanks! -- Vlad Rezki