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([2604:6000:1014:c7c6:c428:5029:cbb2:41f]) by smtp.gmail.com with ESMTPSA id z38sm5555659qtj.83.2019.09.28.11.36.05 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 28 Sep 2019 11:36:05 -0700 (PDT) Message-ID: Subject: Re: while (1) in btrfs_relocate_block_group didn't end From: Cebtenzzre To: linux-btrfs@vger.kernel.org Date: Sat, 28 Sep 2019 14:36:04 -0400 In-Reply-To: <6476e5f02a4bdf26c8f342db11f6dc1675c94394.camel@gmail.com> References: <6476e5f02a4bdf26c8f342db11f6dc1675c94394.camel@gmail.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.34.0 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Mon, 2019-09-16 at 17:20 -0400, Cebtenzzre wrote: > On Sat, 2019-09-14 at 17:36 -0400, Cebtenzzre wrote: > > Hi, > > > > I started a balance of one block group, and I saw this in dmesg: > > > > BTRFS info (device sdi1): balance: start -dvrange=2236714319872..2236714319873 > > BTRFS info (device sdi1): relocating block group 2236714319872 flags data|raid0 > > BTRFS info (device sdi1): found 1 extents > > BTRFS info (device sdi1): found 1 extents > > BTRFS info (device sdi1): found 1 extents > > BTRFS info (device sdi1): found 1 extents > > BTRFS info (device sdi1): found 1 extents > > > > [...] > > > > I am using Arch Linux with kernel version 5.2.14-arch2, and I specified > > "slub_debug=P,kmalloc-2k" in the kernel cmdline to detect and protect > > against a use-after-free that I found when I had KASAN enabled. Would > > that kernel parameter result in a silent retry if it hit the use-after- > > free? > > Please disregard the quoted message. This behavior does appear to be a > result of using the slub_debug option instead of KASAN. It is not > directly caused by BTRFS. Actually, I just reproduced this behavior without slub_debug in the cmdline, on Linux 5.3.0 with "[PATCH] btrfs: relocation: Fix KASAN report about use-after-free due to dead reloc tree cleanup race" ( https://patchwork.kernel.org/patch/11153729/) applied. So, this issue is still relevant and possible to trigger, though under different conditions (different volume, kernel version, and cmdline). -- Cebtenzzre