From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from arcturus.aphlor.org ([188.246.204.175]:33934 "EHLO arcturus.aphlor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752711AbcJJNLb (ORCPT ); Mon, 10 Oct 2016 09:11:31 -0400 Date: Mon, 10 Oct 2016 09:11:22 -0400 From: Dave Jones To: Al Viro Cc: Chris Mason , Josef Bacik , David Sterba , linux-btrfs@vger.kernel.org, Linux Kernel Subject: Re: btrfs_direct_IO oops Message-ID: <20161010131122.cjmoof6yblwl7tak@codemonkey.org.uk> References: <20161008180806.fmpwtw4vcc7lzd36@codemonkey.org.uk> <20161008182903.GU19539@ZenIV.linux.org.uk> <20161008232008.nouzkd54kiquvpir@codemonkey.org.uk> <20161009151106.damzuhyjpdzq4x2w@codemonkey.org.uk> <20161010034356.GY19539@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20161010034356.GY19539@ZenIV.linux.org.uk> Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Mon, Oct 10, 2016 at 04:43:57AM +0100, Al Viro wrote: > Very interesting. Could you slap something like > diff --git a/lib/iov_iter.c b/lib/iov_iter.c > index 0ce3411..1ef00e7 100644 > --- a/lib/iov_iter.c > +++ b/lib/iov_iter.c > @@ -682,8 +682,9 @@ static void pipe_advance(struct iov_iter *i, size_t size) > { > struct pipe_inode_info *pipe = i->pipe; > struct pipe_buffer *buf; > - int idx = i->idx; > - size_t off = i->iov_offset; > + int old_idx = idx = i->idx; > + size_t old_off = off = i->iov_offset; > + size_t old_size = size; > > if (unlikely(i->count < size)) > size = i->count; > @@ -713,6 +714,9 @@ static void pipe_advance(struct iov_iter *i, size_t size) > pipe->nrbufs--; > } > } > + if (!sanity(i)) > + printk(KERN_ERR "buggered pipe_advance(%zd) [%d,%zd]", > + old_size, old_idx, old_off); > } > > void iov_iter_advance(struct iov_iter *i, size_t size) > > in there and try to reproduce that one? My compiler choked on that, but I fixed it up. The printk didn't trigger though.. idx = 0, offset = 0 curbuf = 0, nrbufs = 1, buffers = 16 [ffffffffb9a21100 ffffea00126019c0 0 4096] [ (null) ffffea0013746440 0 0] [ (null) ffffea00132956c0 0 0] [ (null) ffffea0013295700 0 0] [ (null) ffffea0013295740 0 0] [ (null) ffffea0013295780 0 0] [ (null) ffffea00132957c0 0 0] [ (null) ffffea0013595c00 0 0] [ (null) ffffea0012b1b6c0 0 0] [ (null) (null) 0 0] [ (null) (null) 0 0] [ (null) (null) 0 0] [ (null) (null) 0 0] [ (null) (null) 0 0] [ (null) (null) 0 0] [ (null) (null) 0 0] ------------[ cut here ]------------ WARNING: CPU: 1 PID: 13581 at lib/iov_iter.c:327 sanity+0x102/0x150 CPU: 1 PID: 13581 Comm: trinity-c17 Not tainted 4.8.0-think+ #9 ffffc90000963ae8 ffffffffb93e22d1 0000000000000000 0000000000000000 ffffffffb9c1e1cb ffffffffb93fa5b2 ffffc90000963b28 ffffffffb908b010 00000147d43c0e7f ffffffffb9c1e1cb 0000000000000147 0000000000000010 Call Trace: [] dump_stack+0x6c/0x9b [] ? sanity+0x102/0x150 [] __warn+0x110/0x130 [] warn_slowpath_null+0x2c/0x40 [] sanity+0x102/0x150 [] copy_page_to_iter+0x2be/0x480 [] ? workingset_activation+0xc1/0x120 [] ? workingset_refault+0x190/0x190 [] generic_file_read_iter+0x245/0xd30 [] generic_file_splice_read+0xfd/0x230 [] ? pipe_to_user+0x40/0x40 [] do_splice_to+0x98/0xd0 [] splice_direct_to_actor+0xd4/0x2c0 [] ? generic_pipe_buf_nosteal+0x10/0x10 [] do_splice_direct+0xc5/0x110 [] do_sendfile+0x242/0x470 [] SyS_sendfile64+0x7d/0xf0 [] do_syscall_64+0x7f/0x200 [] entry_SYSCALL64_slow_path+0x25/0x25 ---[ end trace 6773f425063b7f84 ]---