From: Eric Sandeen <sandeen@sandeen.net>
To: Dave Chinner <david@fromorbit.com>, fstests@vger.kernel.org
Subject: Re: [PATCH 4/5] generic: add mmap write vs truncate/remap test
Date: Fri, 19 Sep 2014 19:17:20 -0500 [thread overview]
Message-ID: <541CC790.7060306@sandeen.net> (raw)
In-Reply-To: <1410918113-23516-5-git-send-email-david@fromorbit.com>
On 9/16/14 8:41 PM, Dave Chinner wrote:
> This test exposed a problem with mapped writes to the tail page of a
> file in XFS and potentially ext4. Eric did all the hard work of
> taking the bug report and generating the reproducable test case
> on ext4, but I haven't been able to reproduce then problem on ext4.
>
> Regardless, make it a generic test so that we can ensure that all
> filesystems handle the case correctly.
Oof, kermit on #xfs points out that even this is sufficient to show
a problem:
mkfs.ext4 -b 1024 -F empty.img
mount -o loop empty.img mnt
sync
xfs_io -f -t \
-c "pwrite 0 0x210 " \
-c "mmap -rw 0 0xd08 " \
-c "mwrite -S 0x50 0x210 0xaf8" \
-c "truncate 0x1000" \
mnt/testfile
echo "==== Pre-Remount ==="
hexdump -C mnt/testfile | tail -n 8
umount mnt/
mount -o loop empty.img mnt
echo "==== Post-Remount =="
hexdump -C mnt/testfile | tail -n 8
i'm not sure about the testcase - mmapping beyond EOF? - but seeing data
change after remount looks scary regardless.
==== Pre-Remount ===
00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00000210 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 |PPPPPPPPPPPPPPPP|
*
00000d00 50 50 50 50 50 50 50 50 00 00 00 00 00 00 00 00 |PPPPPPPP........|
00000d10 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00001000
==== Post-Remount ==
00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00000210 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 |PPPPPPPPPPPPPPPP|
*
00000400 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00001000
-Eric
next prev parent reply other threads:[~2014-09-20 0:17 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-17 1:41 [PATCH 0/5] xfstests: cleanups and new tests Dave Chinner
2014-09-17 1:41 ` [PATCH 1/5] generic: more tests should clean up TESTDIR on success Dave Chinner
2014-09-17 4:17 ` Eric Sandeen
2014-09-17 1:41 ` [PATCH 2/5] check: more tests that shouldn't check the scratch device Dave Chinner
2014-09-17 4:27 ` Eric Sandeen
2014-09-17 1:41 ` [PATCH 3/5] generic: add mmap write vs truncate test Dave Chinner
2014-09-19 19:38 ` Eric Sandeen
2014-09-17 1:41 ` [PATCH 4/5] generic: add mmap write vs truncate/remap test Dave Chinner
2014-09-17 4:32 ` Eric Sandeen
2014-09-17 4:51 ` Dave Chinner
2014-09-19 19:35 ` [PATCH 4.5/5] generic: tidy up " Eric Sandeen
2014-09-19 19:35 ` [PATCH 4/5] generic: add " Eric Sandeen
2014-09-20 0:17 ` Eric Sandeen [this message]
2014-09-20 23:32 ` Dave Chinner
2014-09-17 1:41 ` [PATCH 5/5] generic: add write vs fcollapse test Dave Chinner
2014-09-17 12:40 ` Brian Foster
2014-09-18 1:33 ` Dave Chinner
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