From: Christoph Hellwig <hch@infradead.org>
To: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@infradead.org>,
Theodore Ts'o <tytso@mit.edu>,
linux-ext4@vger.kernel.org, Lukas Czerner <lczerner@redhat.com>,
linux-xfs@vger.kernel.org
Subject: Re: [PATCH] ext4: introduce per-inode DAX flag
Date: Mon, 28 Aug 2017 00:38:54 -0700 [thread overview]
Message-ID: <20170828073853.GA23262@infradead.org> (raw)
In-Reply-To: <20170825233358.GC17782@dastard>
On Sat, Aug 26, 2017 at 09:33:58AM +1000, Dave Chinner wrote:
> > Nah, -o dax works very well. It's just the flag instead of the -o dax
> > option or rather switching it on a mapped file will probably be very dangerous.
>
> In what way is it dangerous, Christoph?
When I run the following script as a normal user:
FSXDIR=~/xfstests/ltp/
FILE=/mnt/foo
${FSXDIR}/fsx $FILE &
while true; do
xfs_io -c 'chattr +x' $FILE
xfs_io -c 'chattr -x' $FILE
done
I get this nice little crash:
root@testvm:~# sh test.sh
skipping zero size read
skipping insert range behind EOF
truncating to largest ever: 0x3a290
zero_range to largest ever: 0x3a8d1
zero_range to largest ever: 0x3fe3e
zero_range to largest ever: 0x40000
[ 344.898390] BUG: unable to handle kernel NULL pointer dereference at 0000000000000020
[ 344.899306] IP: iomap_page_mkwrite+0x17/0xf0
[ 344.899795] PGD 7db37067
[ 344.899796] P4D 7db37067
[ 344.900099] PUD 78c61067
[ 344.900389] PMD 0
[ 344.900665]
[ 344.901075] Oops: 0000 [#1] SMP
[ 344.901536] Modules linked in:
[ 344.901716] CPU: 3 PID: 6052 Comm: fsx Not tainted 4.12.0+ #2199
[ 344.901716] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.10.2-0-g5f4c7b1-prebuilt.qemu-project.org 04/01/2014
[ 344.901716] task: ffff880079a0da00 task.stack: ffffc900068a4000
[ 344.901716] RIP: 0010:iomap_page_mkwrite+0x17/0xf0
[ 344.901716] RSP: 0000:ffffc900068a7d38 EFLAGS: 00010246
[ 344.901716] RAX: ffff8800798dd0d0 RBX: 0000000000000200 RCX: 0000000000000001
[ 344.901716] RDX: 0000000070eb898e RSI: ffffffff82109010 RDI: ffffc900068a7df0
[ 344.901716] RBP: ffffc900068a7d60 R08: ffffffff82ff9fa8 R09: 0000000000000000
[ 344.901716] R10: ffffc900068a7cb0 R11: ffffffff8159b5cc R12: ffffffff82109010
[ 344.901716] R13: 0000000000000000 R14: ffffc900068a7df0 R15: ffff88007da89580
[ 344.901716] FS: 00007f76bc863700(0000) GS:ffff88007fd80000(0000) knlGS:0000000000000000
[ 344.901716] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 344.901716] CR2: 0000000000000020 CR3: 000000007d90b000 CR4: 00000000000006e0
[ 344.901716] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 344.901716] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 344.901716] Call Trace:
[ 344.901716] xfs_filemap_page_mkwrite+0x90/0x1d0
[ 344.901716] xfs_filemap_fault+0x114/0x180
[ 344.901716] __do_fault+0x19/0x60
[ 344.901716] __handle_mm_fault+0x68f/0xaf0
[ 344.901716] handle_mm_fault+0x82/0x130
[ 344.901716] __do_page_fault+0x222/0x4d0
[ 344.901716] trace_do_page_fault+0x85/0x210
[ 344.901716] do_async_page_fault+0x14/0x60
[ 344.901716] async_page_fault+0x28/0x30
[ 344.901716] RIP: 0033:0x7f76bbd14049
[ 344.901716] RSP: 002b:00007ffcdd6c7fe8 EFLAGS: 00010206
[ 344.901716] RAX: 000000000002f144 RBX: 0000000000000fd9 RCX: 000000000000fd98
[ 344.901716] RDX: 0000000000007ecc RSI: 00007f76bc80efe9 RDI: 00007f76bc7d7fd9
[ 344.901716] RBP: 00007f76bc7d7000 R08: 0000000000000003 R09: 000000000002e000
[ 344.901716] R10: 0000000000000001 R11: 0000000000000206 R12: 0000000000007ecc
[ 344.901716] R13: 000000000002efd9 R14: 0000000000008ea5 R15: 0000000000000000
[ 344.901716] Code: 50 ff ff ff 5d c3 0f 1f 40 00 66 2e 0f 1f 84 00 00 00 00 00 55 48 89 e5 41 57 41 56 41 55 41 54 49 89 f4 53 4c 8b 6f 48 48 8b 07 <49> 8b 55 20 48 8b 80 a0 00 00 00 4c 8b 70 20 48 8d 42 ff 83 e2
[ 344.901716] RIP: iomap_page_mkwrite+0x17/0xf0 RSP: ffffc900068a7d38
[ 344.901716] CR2: 0000000000000020
[ 344.924264] ---[ end trace c4e8d3bdccf6912b ]---
[ 344.924834] Kernel panic - not syncing: Fatal exception
[ 344.925504] Kernel Offset: disabled
[ 344.925884] ---[ end Kernel panic - not syncing: Fatal exception
next prev parent reply other threads:[~2017-08-28 7:38 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-02 16:09 [PATCH] ext4: introduce per-inode DAX flag Lukas Czerner
2017-08-05 8:46 ` Christoph Hellwig
2017-08-07 12:12 ` Lukas Czerner
2017-08-08 9:00 ` Lukas Czerner
2017-08-11 10:01 ` Christoph Hellwig
2017-08-11 12:11 ` Lukas Czerner
2017-08-11 12:58 ` Christoph Hellwig
2017-08-11 13:41 ` Lukas Czerner
2017-08-24 18:20 ` Theodore Ts'o
2017-08-25 7:54 ` Christoph Hellwig
2017-08-25 15:14 ` Theodore Ts'o
2017-08-25 15:40 ` Christoph Hellwig
2017-08-25 16:28 ` Theodore Ts'o
2017-08-25 23:33 ` Dave Chinner
2017-08-28 7:38 ` Christoph Hellwig [this message]
2017-08-28 10:10 ` Dave Chinner
2017-08-29 15:49 ` Jan Kara
2017-08-29 22:57 ` Dave Chinner
2017-08-30 10:00 ` Jan Kara
2017-08-30 12:34 ` Christoph Hellwig
2017-08-30 15:00 ` Theodore Ts'o
2017-08-30 15:30 ` Lukas Czerner
2017-08-30 15:29 ` Jan Kara
2017-08-30 16:05 ` Jan Kara
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170828073853.GA23262@infradead.org \
--to=hch@infradead.org \
--cc=david@fromorbit.com \
--cc=lczerner@redhat.com \
--cc=linux-ext4@vger.kernel.org \
--cc=linux-xfs@vger.kernel.org \
--cc=tytso@mit.edu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.