From owner-freebsd-fs@freebsd.org Wed May 16 12:38:45 2018 Return-Path: Delivered-To: freebsd-fs@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id D1299EDF8E8 for ; Wed, 16 May 2018 12:38:44 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from mailman.ysv.freebsd.org (mailman.ysv.freebsd.org [IPv6:2001:1900:2254:206a::50:5]) by mx1.freebsd.org (Postfix) with ESMTP id 6380486B4B for ; Wed, 16 May 2018 12:38:44 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: by mailman.ysv.freebsd.org (Postfix) id 1A9BAEDF8E7; Wed, 16 May 2018 12:38:44 +0000 (UTC) Delivered-To: fs@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id E76B3EDF8E6 for ; Wed, 16 May 2018 12:38:43 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from mxrelay.ysv.freebsd.org (mxrelay.ysv.freebsd.org [IPv6:2001:1900:2254:206a::19:3]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "mxrelay.ysv.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 7F02686B45 for ; Wed, 16 May 2018 12:38:43 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org (kenobi.freebsd.org [IPv6:2001:1900:2254:206a::16:76]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mxrelay.ysv.freebsd.org (Postfix) with ESMTPS id C546F24BF2 for ; Wed, 16 May 2018 12:38:42 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org ([127.0.1.118]) by kenobi.freebsd.org (8.15.2/8.15.2) with ESMTP id w4GCcgc9085283 for ; Wed, 16 May 2018 12:38:42 GMT (envelope-from bugzilla-noreply@freebsd.org) Received: (from www@localhost) by kenobi.freebsd.org (8.15.2/8.15.2/Submit) id w4GCcgwT085277 for fs@FreeBSD.org; Wed, 16 May 2018 12:38:42 GMT (envelope-from bugzilla-noreply@freebsd.org) X-Authentication-Warning: kenobi.freebsd.org: www set sender to bugzilla-noreply@freebsd.org using -f From: bugzilla-noreply@freebsd.org To: fs@FreeBSD.org Subject: [Bug 210316] panic after trying to r/w mount msdosfs on write protected media Date: Wed, 16 May 2018 12:38:37 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: kern X-Bugzilla-Version: CURRENT X-Bugzilla-Keywords: X-Bugzilla-Severity: Affects Only Me X-Bugzilla-Who: avg@FreeBSD.org X-Bugzilla-Status: New X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: fs@FreeBSD.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugs.freebsd.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.26 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 16 May 2018 12:38:45 -0000 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D210316 --- Comment #10 from Andriy Gapon --- (In reply to Konstantin Belousov from comment #9) Kostik, I need to refresh my memory of this problem. Meanwhile, I have a counter-question. Is there a bwrite variant where a failure is a final failure with no side effects? I mean, if that bwriteX fails, then the buffer is just discarded. Something with semantics similar to write(2). My understanding of what happens now. bufwrite calls this code: if ((oldflags & B_ASYNC) =3D=3D 0) { int rtval =3D bufwait(bp); brelse(bp); return (rtval); Then in brelse() the following block is executed: if (bp->b_iocmd =3D=3D BIO_WRITE && (bp->b_ioflags & BIO_ERROR) && (bp->b_error !=3D ENXIO || !LIST_EMPTY(&bp->b_dep)) && !(bp->b_flags & B_INVAL)) { /* * Failed write, redirty. All errors except ENXIO (which * means the device is gone) are expected to be potentially * transient - underlying media might work if tried again * after EIO, and memory might be available after an ENOMEM. * * Do this also for buffers that failed with ENXIO, but have * non-empty dependencies - the soft updates code might need * to access the buffer to untangle them. * * Must clear BIO_ERROR to prevent pages from being scrappe= d. */ bp->b_ioflags &=3D ~BIO_ERROR; bdirty(bp); I think that it would be nice to have a way to instruct the buffer code to never retry a specific synchronous write request. If we had such a mechanism we could use it in filesystems's mount code to c= heck whether we can really write to the backing media. Or should a caller of bwrite() explicitly manipulate b_flags (e.g. B_INVAL, B_RELBUF) to get the desired effect? --=20 You are receiving this mail because: You are the assignee for the bug.=