Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752449AbdIFUDm (ORCPT ); Wed, 6 Sep 2017 16:03:42 -0400 Received: from scorn.kernelslacker.org ([45.56.101.199]:57794 "EHLO scorn.kernelslacker.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752163AbdIFUDk (ORCPT ); Wed, 6 Sep 2017 16:03:40 -0400 Date: Wed, 6 Sep 2017 16:03:37 -0400 From: Dave Jones To: "Darrick J. Wong" Cc: Al Viro , Linux Kernel , linux-xfs@vger.kernel.org Subject: Re: iov_iter_pipe warning. Message-ID: <20170906200337.b5wj3gpfebliindw@codemonkey.org.uk> Mail-Followup-To: Dave Jones , "Darrick J. Wong" , Al Viro , Linux Kernel , linux-xfs@vger.kernel.org References: <20170412170723.GQ29622@ZenIV.linux.org.uk> <20170412190318.srkkdytf2ebrjzrg@codemonkey.org.uk> <20170421175430.GT29622@ZenIV.linux.org.uk> <20170428152955.mafs3f22srmm34aw@codemonkey.org.uk> <20170428164313.GK29622@ZenIV.linux.org.uk> <20170428165024.ofyl2atpjwohekqa@codemonkey.org.uk> <20170428172024.GL29622@ZenIV.linux.org.uk> <20170807201818.kykqzexce6ap6aik@codemonkey.org.uk> <20170828203130.y6dq5fqovev6wmrv@codemonkey.org.uk> <20170829042542.GO4757@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170829042542.GO4757@magnolia> User-Agent: NeoMutt/20170609 (1.8.3) X-Spam-Note: SpamAssassin invocation failed Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7846 Lines: 179 On Mon, Aug 28, 2017 at 09:25:42PM -0700, Darrick J. Wong wrote: > On Mon, Aug 28, 2017 at 04:31:30PM -0400, Dave Jones wrote: > > On Mon, Aug 07, 2017 at 04:18:18PM -0400, Dave Jones wrote: > > > On Fri, Apr 28, 2017 at 06:20:25PM +0100, Al Viro wrote: > > > > On Fri, Apr 28, 2017 at 12:50:24PM -0400, Dave Jones wrote: > > > > > currently running v4.11-rc8-75-gf83246089ca0 > > > > > > > > > > sunrpc bit is for the other unrelated problem I'm chasing. > > > > > > > > > > note also, I saw the backtrace without the fs/splice.c changes. > > > > > > > > Interesting... Could you add this and see if that triggers? > > > > > > > > diff --git a/fs/splice.c b/fs/splice.c > > > > index 540c4a44756c..12a12d9c313f 100644 > > > > --- a/fs/splice.c > > > > +++ b/fs/splice.c > > > > @@ -306,6 +306,9 @@ ssize_t generic_file_splice_read(struct file *in, loff_t *ppos, > > > > kiocb.ki_pos = *ppos; > > > > ret = call_read_iter(in, &kiocb, &to); > > > > if (ret > 0) { > > > > + if (WARN_ON(iov_iter_count(&to) != len - ret)) > > > > + printk(KERN_ERR "ops %p: was %zd, left %zd, returned %d\n", > > > > + in->f_op, len, iov_iter_count(&to), ret); > > > > *ppos = kiocb.ki_pos; > > > > file_accessed(in); > > > > } else if (ret < 0) { > > > > > > Hey Al, > > > Due to a git stash screw up on my part, I've had this leftover WARN_ON > > > in my tree for the last couple months. (That screw-up might turn out to be > > > serendipitous if this is a real bug..) > > > > > > Today I decided to change things up and beat up on xfs for a change, and > > > was able to trigger this again. > > > > > > Is this check no longer valid, or am I triggering the same bug we were chased > > > down in nfs, but now in xfs ? (None of the other detritus from that debugging > > > back in April made it, just those three lines above). > > > > Revisiting this. I went back and dug out some of the other debug diffs [1] > > from that old thread. > > > > I can easily trigger this spew on xfs. > > > > > > WARNING: CPU: 1 PID: 2251 at fs/splice.c:292 test_it+0xd4/0x1d0 > > CPU: 1 PID: 2251 Comm: trinity-c42 Not tainted 4.13.0-rc7-think+ #1 > > task: ffff880459173a40 task.stack: ffff88044f7d0000 > > RIP: 0010:test_it+0xd4/0x1d0 > > RSP: 0018:ffff88044f7d7878 EFLAGS: 00010283 > > RAX: 0000000000000000 RBX: ffff88044f44b968 RCX: ffffffff81511ea0 > > RDX: 0000000000000003 RSI: dffffc0000000000 RDI: ffff88044f44ba68 > > RBP: ffff88044f7d78c8 R08: ffff88046b218ec0 R09: 0000000000000000 > > R10: ffff88044f7d7518 R11: 0000000000000000 R12: 0000000000001000 > > R13: 0000000000000001 R14: 00000000ffffffff R15: 0000000000000001 > > FS: 00007fdbc09b2700(0000) GS:ffff88046b200000(0000) knlGS:0000000000000000 > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > CR2: 0000000000000000 CR3: 0000000459e1d000 CR4: 00000000001406e0 > > Call Trace: > > generic_file_splice_read+0x414/0x4e0 > > ? opipe_prep.part.14+0x180/0x180 > > ? lockdep_init_map+0xb2/0x2b0 > > ? rw_verify_area+0x65/0x150 > > do_splice_to+0xab/0xc0 > > splice_direct_to_actor+0x1f5/0x540 > > ? generic_pipe_buf_nosteal+0x10/0x10 > > ? do_splice_to+0xc0/0xc0 > > ? rw_verify_area+0x9d/0x150 > > do_splice_direct+0x1b9/0x230 > > ? splice_direct_to_actor+0x540/0x540 > > ? __sb_start_write+0x164/0x1c0 > > ? do_sendfile+0x7b3/0x840 > > do_sendfile+0x428/0x840 > > ? do_compat_pwritev64+0xb0/0xb0 > > ? __might_sleep+0x72/0xe0 > > ? kasan_check_write+0x14/0x20 > > SyS_sendfile64+0xa4/0x120 > > ? SyS_sendfile+0x150/0x150 > > ? mark_held_locks+0x23/0xb0 > > ? do_syscall_64+0xc0/0x3e0 > > ? SyS_sendfile+0x150/0x150 > > do_syscall_64+0x1bc/0x3e0 > > ? syscall_return_slowpath+0x240/0x240 > > ? mark_held_locks+0x23/0xb0 > > ? return_from_SYSCALL_64+0x2d/0x7a > > ? trace_hardirqs_on_caller+0x182/0x260 > > ? trace_hardirqs_on_thunk+0x1a/0x1c > > entry_SYSCALL64_slow_path+0x25/0x25 > > RIP: 0033:0x7fdbc02dd219 > > RSP: 002b:00007ffc5024fa48 EFLAGS: 00000246 > > ORIG_RAX: 0000000000000028 > > RAX: ffffffffffffffda RBX: 0000000000000028 RCX: 00007fdbc02dd219 > > RDX: 00007fdbbe348000 RSI: 0000000000000011 RDI: 0000000000000015 > > RBP: 00007ffc5024faf0 R08: 000000000000006d R09: 0094e82f2c730a50 > > R10: 0000000000001000 R11: 0000000000000246 R12: 0000000000000002 > > R13: 00007fdbc0885058 R14: 00007fdbc09b2698 R15: 00007fdbc0885000 > > ---[ end trace a5847ef0f7be7e20 ]--- > > asked to read 4096, claims to have read 1 > > actual size of data in pipe 4096 > > [0:4096] > > f_op: ffffffffa058c920, f_flags: 49154, pos: 0/1, size: 0 > > > > > > I'm still trying to narrow down an exact reproducer, but it seems having > > trinity do a combination of sendfile & writev, with pipes and regular > > files as fd's is the best repro. > > > > Is this a real problem, or am I chasing ghosts ? That it doesn't happen > > on ext4 or btrfs is making me wonder... > > I haven't heard of any problems w/ directio xfs lately, but OTOH > I think it's the only filesystem that uses iomap_dio_rw, which would > explain why ext4/btrfs don't have this problem. Another warning, from likely the same root cause. WARNING: CPU: 3 PID: 572 at lib/iov_iter.c:962 iov_iter_pipe+0xe2/0xf0 CPU: 3 PID: 572 Comm: trinity-c45 Not tainted 4.13.0-think+ #5 task: ffff88042e5f8040 task.stack: ffff880454cb0000 RIP: 0010:iov_iter_pipe+0xe2/0xf0 RSP: 0018:ffff880454cb7950 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff880454cb79c0 RCX: ffffffff818fc581 RDX: 0000000000000003 RSI: dffffc0000000000 RDI: ffff88043f07fa80 RBP: ffff88043f07f968 R08: 0000000000000000 R09: 0000000000000000 R10: ffff880454cb7468 R11: 0000000000000000 R12: 000000000003fff8 R13: 0000000000000010 R14: ffff88043f07fa80 R15: ffff88043f07fa78 FS: 00007fac217a1700(0000) GS:ffff88046b400000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 000000043f37e001 CR4: 00000000001606e0 Call Trace: generic_file_splice_read+0x8d/0x340 ? pipe_unlock+0x15/0x30 ? splice_from_pipe+0x10e/0x160 ? pipe_to_user+0x80/0x80 ? splice_shrink_spd+0x40/0x40 ? init_wait_entry+0x100/0x100 ? rw_verify_area+0x87/0x130 splice_direct_to_actor+0x186/0x420 ? generic_pipe_buf_nosteal+0x10/0x10 ? do_splice_to+0xc0/0xc0 ? __fget_light+0x181/0x200 do_splice_direct+0x173/0x1e0 ? splice_direct_to_actor+0x420/0x420 ? mark_held_locks+0x1c/0x90 ? retint_kernel+0x10/0x10 do_sendfile+0x3a2/0x6d0 ? do_compat_pwritev64+0xa0/0xa0 ? copy_user_generic_unrolled+0x83/0xb0 SyS_sendfile64+0xa4/0x130 ? SyS_sendfile+0x140/0x140 ? mark_held_locks+0x1c/0x90 ? do_syscall_64+0xae/0x3e0 ? SyS_sendfile+0x140/0x140 do_syscall_64+0x182/0x3e0 ? syscall_return_slowpath+0x250/0x250 ? rcu_read_lock_sched_held+0x90/0xa0 ? __context_tracking_exit.part.5+0x226/0x290 ? mark_held_locks+0x1c/0x90 ? return_from_SYSCALL_64+0x2d/0x7a ? trace_hardirqs_on_caller+0x17a/0x250 ? trace_hardirqs_on_thunk+0x1a/0x1c entry_SYSCALL64_slow_path+0x25/0x25 RIP: 0033:0x7fac210cc219 RSP: 002b:00007ffd7fe8ab38 EFLAGS: 00000246 ORIG_RAX: 0000000000000028 RAX: ffffffffffffffda RBX: 0000000000000028 RCX: 00007fac210cc219 RDX: 00007fac215de000 RSI: 000000000000001b RDI: 000000000000000b RBP: 00007ffd7fe8abe0 R08: 00000000c8c8c8c8 R09: 00000000000000c9 R10: 0000000000040000 R11: 0000000000000246 R12: 0000000000000002 R13: 00007fac2165f058 R14: 00007fac217a1698 R15: 00007fac2165f000 Code: 10 48 c7 43 08 00 00 00 00 e8 bb 79 b1 ff 4c 89 63 10 48 8d 7b 24 e8 ae 78 b1 ff 89 6b 24 5b 5d 41 5c 41 5d 41 5e 41 5f c3 0f 0b <0f> ff e9 65 ff ff ff 0f 1f 80 00 00 00 00 41 57 41 56 41 55 49 ---[ end trace 4507dec15e49aca7 ]--- 962 WARN_ON(pipe->nrbufs == pipe->buffers);