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Message-ID: <4983e1e3-2dea-89c0-8c48-688691e3a0cd@huawei.com>
Date: Wed, 2 Aug 2017 17:00:13 +0800
From: Yunlong Song <yunlong.song@...wei.com>
To: Chao Yu <yuchao0@...wei.com>, Yunlong Song <sylinux@....com>,
Chao Yu <chao@...nel.org>
CC: jaegeuk <jaegeuk@...nel.org>, miaoxie <miaoxie@...wei.com>,
"bintian.wang" <bintian.wang@...wei.com>,
linux-fsdevel <linux-fsdevel@...r.kernel.org>,
linux-f2fs-devel <linux-f2fs-devel@...ts.sourceforge.net>,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] f2fs: update cur_valid_map_mir together with
cur_valid_map
Agree, it's safe to bug_on or readonly to protect data. This patch is fine.
On 2017/8/2 16:47, Chao Yu wrote:
> Hi Yunlong,
>
> On 2017/8/2 16:02, Yunlong Song wrote:
>> Hi Chao,
>> For the memory overflow or cache bit-transition case, when CHECK_FS
>> is on, should f2fs
>> enter panic or just provide WARNing information? I prefer WARNing,
>> because it is not f2fs's
>> fault, f2fs does not need to pay for it, why not use WARN_ON instead?
> Actually, if that happens, I think both original and mirror bitmap datas are not
> trustable, it's harmful to continue to trigger write IOs based on those bitmap
> datas. So IMO, it would be better to trigger bug_on.
>
> At least, if only warning is showed, we'd better to turn f2fs to readonly and
> fail current write IO.
>
> Thanks,
>
>> On 2017/8/2 9:34, Chao Yu wrote:
>>> Hi Yunlong,
>>>
>>> On 2017/8/2 0:59, Yunlong Song wrote:
>>>> Hi Chao,
>>>> I think there is no need to test mirror bitmap when original bitmap's check
>>>> get passed, it is an instruction waste for "test". By the way, previous patch
>>>> uses WARN to skip trigger panic when the memory is flipped, I think it is proper
>>>> to not trigger panic in this situation, because it is not code bug at all in
>>>> such case.
>>> Original idea is trying to use bitmap mirror to detect bitmap corruption caused
>>> by memory overflow or bit-transition of cache.
>>>
>>> So if we encounter inconsistency in between original bitmap and mirror bitmap,
>>> there may be memory overflow or cache bit-transition, we need to detect that;
>>> another case is that both bitmap is consistent, but we are trying to reuse valid
>>> block address or free invalid block address, indeed that is a bug.
>>>
>>> Below modification can cover above two cases, which make original idea of
>>> introducing mirror bitmap check working correctly.
>>>
>>> Thanks,
>>>
>>>> On 08/01/2017 23:44, Chao Yu <mailto:chao@...nel.org> wrote:
>>>>
>>>> Hi Yunlong,
>>>>
>>>> How about checking consistence in between original and mirror bitmap all
>>>> the time as below?
>>>>
>>>> ---
>>>> fs/f2fs/segment.c | 41 +++++++++++++++++++++++++++--------------
>>>> 1 file changed, 27 insertions(+), 14 deletions(-)
>>>>
>>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>>> index a26c24dae70c..f32a19cf486a 100644
>>>> --- a/fs/f2fs/segment.c
>>>> +++ b/fs/f2fs/segment.c
>>>> @@ -1510,6 +1510,7 @@ static void update_sit_entry(struct f2fs_sb_info *sbi,
>>>> block_t blkaddr, int del)
>>>> struct seg_entry *se;
>>>> unsigned int segno, offset;
>>>> long int new_vblocks;
>>>> + bool exist, mir_exist;
>>>>
>>>> segno = GET_SEGNO(sbi, blkaddr);
>>>>
>>>> @@ -1526,17 +1527,23 @@ static void update_sit_entry(struct f2fs_sb_info
>>>> *sbi, block_t blkaddr, int del)
>>>>
>>>> /* Update valid block bitmap */
>>>> if (del > 0) {
>>>> - if (f2fs_test_and_set_bit(offset, se->cur_valid_map)) {
>>>> + exist = f2fs_test_and_set_bit(offset, se->cur_valid_map);
>>>> #ifdef CONFIG_F2FS_CHECK_FS
>>>> - if (f2fs_test_and_set_bit(offset,
>>>> - se->cur_valid_map_mir))
>>>> - f2fs_bug_on(sbi, 1);
>>>> - else
>>>> - WARN_ON(1);
>>>> -#else
>>>> + mir_exist = f2fs_test_and_set_bit(offset,
>>>> + se->cur_valid_map_mir);
>>>> + if (exist != mir_exist) {
>>>> + f2fs_msg(sbi->sb, KERN_ERR, "Inconsistent error "
>>>> + "when setting bitmap, blk:%u, old bit:%d",
>>>> + blkaddr, exist);
>>>> f2fs_bug_on(sbi, 1);
>>>> + }
>>>> #endif
>>>> + if (exist) {
>>>> + f2fs_msg(sbi->sb, KERN_ERR,
>>>> + "Bitmap was set, blk:%u", blkaddr);
>>>> + f2fs_bug_on(sbi, 1);
>>>> }
>>>> +
>>>> if (f2fs_discard_en(sbi) &&
>>>> !f2fs_test_and_set_bit(offset, se->discard_map))
>>>> sbi->discard_blks--;
>>>> @@ -1547,17 +1554,23 @@ static void update_sit_entry(struct f2fs_sb_info
>>>> *sbi, block_t blkaddr, int del)
>>>> se->ckpt_valid_blocks++;
>>>> }
>>>> } else {
>>>> - if (!f2fs_test_and_clear_bit(offset, se->cur_valid_map)) {
>>>> + exist = f2fs_test_and_clear_bit(offset, se->cur_valid_map);
>>>> #ifdef CONFIG_F2FS_CHECK_FS
>>>> - if (!f2fs_test_and_clear_bit(offset,
>>>> - se->cur_valid_map_mir))
>>>> - f2fs_bug_on(sbi, 1);
>>>> - else
>>>> - WARN_ON(1);
>>>> -#else
>>>> + mir_exist = f2fs_test_and_clear_bit(offset,
>>>> + se->cur_valid_map_mir);
>>>> + if (exist != mir_exist) {
>>>> + f2fs_msg(sbi->sb, KERN_ERR, "Inconsistent error "
>>>> + "when clearing bitmap, blk:%u, old bit:%d",
>>>> + blkaddr, exist);
>>>> f2fs_bug_on(sbi, 1);
>>>> + }
>>>> #endif
>>>> + if (!exist) {
>>>> + f2fs_msg(sbi->sb, KERN_ERR,
>>>> + "Bitmap was cleared, blk:%u", blkaddr);
>>>> + f2fs_bug_on(sbi, 1);
>>>> }
>>>> +
>>>> if (f2fs_discard_en(sbi) &&
>>>> f2fs_test_and_clear_bit(offset, se->discard_map))
>>>> sbi->discard_blks++;
>>>> --
>>>> 2.13.0.90.g1eb437020
>>>>
>>>> On 2017/8/1 15:56, Yunlong Song wrote:
>>>> > When cur_valid_map passes the f2fs_test_and_set(,clear)_bit test,
>>>> > cur_valid_map_mir update is skipped unlikely, so fix it.
>>>> >
>>>> > Signed-off-by: Yunlong Song <yunlong.song@...wei.com>
>>>> > ---
>>>> > fs/f2fs/segment.c | 8 ++++++++
>>>> > 1 file changed, 8 insertions(+)
>>>> >
>>>> > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>>> > index 151968e..6f7731a 100644
>>>> > --- a/fs/f2fs/segment.c
>>>> > +++ b/fs/f2fs/segment.c
>>>> > @@ -1535,6 +1535,10 @@ static void update_sit_entry(struct f2fs_sb_info
>>>> *sbi, block_t blkaddr, int del)
>>>> > f2fs_bug_on(sbi, 1);
>>>> > #endif
>>>> > }
>>>> > +#ifdef CONFIG_F2FS_CHECK_FS
>>>> > + else
>>>> > + f2fs_set_bit(offset, se->cur_valid_map_mir);
>>>> > +#endif
>>>> > if (f2fs_discard_en(sbi) &&
>>>> > !f2fs_test_and_set_bit(offset, se->discard_map))
>>>> > sbi->discard_blks--;
>>>> > @@ -1556,6 +1560,10 @@ static void update_sit_entry(struct f2fs_sb_info
>>>> *sbi, block_t blkaddr, int del)
>>>> > f2fs_bug_on(sbi, 1);
>>>> > #endif
>>>> > }
>>>> > +#ifdef CONFIG_F2FS_CHECK_FS
>>>> > + else
>>>> > + f2fs_clear_bit(offset, se->cur_valid_map_mir);
>>>> > +#endif
>>>> > if (f2fs_discard_en(sbi) &&
>>>> > f2fs_test_and_clear_bit(offset, se->discard_map))
>>>> > sbi->discard_blks++;
>>>> >
>>>>
>>> .
>>>
>
> .
>
--
Thanks,
Yunlong Song
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