From: Sergey Senozhatsky <senozhatsky@chromium.org>
To: Martin Doucha <mdoucha@suse.cz>
Cc: Minchan Kim <minchan@kernel.org>, Petr Vorel <pvorel@suse.cz>,
ltp@lists.linux.it, linux-block@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
Nitin Gupta <ngupta@vflare.org>,
Sergey Senozhatsky <senozhatsky@chromium.org>,
Jens Axboe <axboe@kernel.dk>,
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>,
Yang Xu <xuyang2018.jy@fujitsu.com>
Subject: Re: [PATCH 0/1] Possible bug in zram on ppc64le on vfat
Date: Fri, 11 Nov 2022 09:48:31 +0900 [thread overview]
Message-ID: <Y22b3wWs2QfMjJHi@google.com> (raw)
In-Reply-To: <3ac740c0-954b-5e68-b413-0adc7bc5a2b5@suse.cz>
On (22/11/10 15:29), Martin Doucha wrote:
> New version of LTP test zram01 found a sysfile issue with zram devices
> mounted using VFAT filesystem. When when all available space is filled, e.g.
> by `dd if=/dev/zero of=/mnt/zram0/file`, the corresponding sysfile
> /sys/block/zram0/mm_stat will report that the compressed data size on the
> device is 0 and total memory usage is also 0. LTP test zram01 uses these
> values to calculate compression ratio, which results in division by zero.
>
> The issue is specific to PPC64LE architecture and the VFAT filesystem. No
> other tested filesystem has this issue and I could not reproduce it on other
> archs (s390 not tested). The issue appears randomly about every 3 test runs
> on SLE-15SP2 and 15SP3 (kernel 5.3). It appears less frequently on SLE-12SP5
> (kernel 4.12). Other SLE version were not tested with the new test version
> yet. The previous version of the test did not check the VFAT filesystem on
> zram devices.
Whoooaa...
> I've tried to debug the issue and collected some interesting data (all
> values come from zram device with 25M size limit and zstd compression
> algorithm):
> - mm_stat values are correct after mkfs.vfat:
> 65536 220 65536 26214400 65536 0 0 0
>
> - mm_stat values stay correct after mount:
> 65536 220 65536 26214400 65536 0 0 0
>
> - the bug is triggered by filling the filesystem to capacity (using dd):
> 4194304 0 0 26214400 327680 64 0 0
Can you try using /dev/urandom for dd, not /dev/zero?
Do you still see zeroes in sysfs output or some random values?
next prev parent reply other threads:[~2022-11-11 0:48 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-07 19:11 [PATCH 0/1] Possible bug in zram on ppc64le on vfat Petr Vorel
2022-11-07 19:11 ` [PATCH 1/1] zram01.sh: Workaround division by 0 on vfat on ppc64le Petr Vorel
[not found] ` <CAEemH2fYv_=9UWdWB7VDiFOd8EC89qdCbxnPcTPAtGnkwLOYFg@mail.gmail.com>
2022-11-21 8:59 ` [LTP] " Petr Vorel
2022-11-07 21:25 ` [PATCH 0/1] Possible bug in zram on ppc64le on vfat Minchan Kim
2022-11-07 21:47 ` Petr Vorel
2022-11-07 22:42 ` Petr Vorel
2022-11-08 1:05 ` Sergey Senozhatsky
2022-11-09 22:08 ` Petr Vorel
2022-11-10 23:04 ` Minchan Kim
2022-11-11 9:29 ` Petr Vorel
2022-11-10 14:29 ` Martin Doucha
2022-11-11 0:48 ` Sergey Senozhatsky [this message]
2022-11-21 9:41 ` Petr Vorel
2022-11-22 14:56 ` Martin Doucha
2022-11-22 15:07 ` Petr Vorel
2022-11-29 4:38 ` Sergey Senozhatsky
2023-05-02 15:23 ` Martin Doucha
2022-11-11 9:18 ` Petr Vorel
2023-08-04 6:37 ` Ian Wienand
2023-08-07 4:44 ` Ian Wienand
2023-08-07 5:19 ` Sergey Senozhatsky
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