From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.stoffel.org (mail.stoffel.org [172.104.24.175]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 17870217F4A; Fri, 25 Oct 2024 21:26:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=172.104.24.175 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729891591; cv=none; b=Wo0/zqNp9ivOf/VInSl5MPW2xOyyzN3eynF1P4F+WLSTGNUNX1A7UDUkc+0MRY7E+RBXs8yh8kJVgVSVgkC5kXFNyBe3pRSOpdQcf3azLDs/U50hVGA2uex9ZOwrJLbBxyg31yoU8a/aRgUua0qChpgasV19t4Kx3UUdZDeJ598= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729891591; c=relaxed/simple; bh=KcIaVgPkw+hE3Yu4bPeVYuAuBk96QgsL9DKxY5WuKSU=; h=MIME-Version:Content-Type:Message-ID:Date:From:To:Cc:Subject: In-Reply-To:References; b=jT1JxGK50WHiK0VJ+1dtDqLtcqBZ7laGMuBEqx71kh+1YHaq4LmtIzPH6lRFVurD3I14vZiIKBPy0e7RCYQEoFFqipeFtpvT3tICgyikvdJOd1p1WTD08bVeEvE2XTTCSiN3PPNWRc+Y25kRhdgM2w8QUKSR+EK2MrQ/PZ5WNnE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=stoffel.org; spf=pass smtp.mailfrom=stoffel.org; arc=none smtp.client-ip=172.104.24.175 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=stoffel.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=stoffel.org Received: from quad.stoffel.org (syn-097-095-183-072.res.spectrum.com [97.95.183.72]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mail.stoffel.org (Postfix) with ESMTPSA id 7E1F81E11C; Fri, 25 Oct 2024 17:26:21 -0400 (EDT) Received: by quad.stoffel.org (Postfix, from userid 1000) id D8984A0A9A; Fri, 25 Oct 2024 17:26:19 -0400 (EDT) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <26396.3323.858567.266417@quad.stoffel.home> Date: Fri, 25 Oct 2024 17:26:19 -0400 From: "John Stoffel" To: Kent Overstreet Cc: John Stoffel , manas18244@iiitd.ac.in, linux-bcachefs@vger.kernel.org, linux-kernel@vger.kernel.org, Anup Sharma , Shuah Khan , syzbot+e8eff054face85d7ea41@syzkaller.appspotmail.com X-Clacks-Overhead: GNU Terry Pratchett Subject: Re: [PATCH] Revert "bcachefs: Add asserts to bch2_dev_btree_bitmap_marked_sectors()" In-Reply-To: References: <20241021-revert-assert-bch2-v1-1-e869c7c55bb6@iiitd.ac.in> <26394.37450.21740.720541@quad.stoffel.home> X-Mailer: VM 8.3.x under 28.2 (x86_64-pc-linux-gnu) >>>>> "Kent" == Kent Overstreet writes: > On Thu, Oct 24, 2024 at 02:30:34PM -0400, John Stoffel wrote: >> >>>>> "Kent" == Kent Overstreet writes: >> >> > On Mon, Oct 21, 2024 at 10:18:57PM +0530, Manas via B4 Relay wrote: >> >> From: Manas >> >> >> >> This reverts commit 60f2b1bcf519416dbffee219132aa949d0c39d0e. >> >> >> >> This syzbot bug[1] is triggered due to the BUG_ON assertions added in >> >> __bch2_dev_btree_bitmap_mark. During runtime, m->btree_bitmap_shift is >> >> 63 '?'. This triggers both the assertions. >> >> > The BUG_ON() doesn't need to be deleted; we just need to fix the >> > validation so it doesn't fire (it doesn't particularly matter if it's >> > removed or not, ubsan would catch it without the BUG_ON()). >> >> Shouldn't the BUG_ON() be replaced with making the filesystem readonly >> instead if you're going to keep it? I'd rather have the filesystem >> still be mounted and able to be read, but not writeable, instead of >> having my system crash before I can do anything. > Not in this case. In general, if there's a chance of the BUG_ON() > hitting in the wild after the code has passed testing then it > shouldn't be a BUG_ON(), but this is low level validation that we're > relying on. So I'm having a hard time parsing this reply. And I don't think you make a good case for leaving or even having a BUG_ON() here at all. If there's a chance of it hitting in the wild, it should be removed. But you don't want to remove it because it will never hit? That's just lazy... :-) I just don't see why a filesystem should have the opportunity to kill an entire system because that one filesystem has problems. > In general higher level code absolutely requires that the low level > validation is correct, because if it's not that will trigger all sorts > of undefined behaviour in the upper layers. > By "low level validation" I mean _only_ the validate functions that > check simple invariants within a single data type that is read or > written atomically to disk - "is data type garbage or not". Sure. > If it's an invariant that involves multiple objects - "does this > extent refer to a valid device/snapshot ID" - that's not something > we can check in validate, because then an extent or what have you > would become invalid depending on what happens in the rest of the > filesystem. Those sorts of checks do in fact need proper error > paths. Right.