[lustre-devel] [PATCH 19/22] ext4: don't check before replay

[Alexey Lyashkov]

> 22 июля 2019 г., в 9:56, Oleg Drokin <green at whamcloud.com> написал(а):
> 
> 
> 
>> On Jul 22, 2019, at 2:46 AM, NeilBrown <neilb at suse.com> wrote:
>> 
>> On Mon, Jul 22 2019, Alexey Lyashkov wrote:
>> 
>>> Why?
>>> Purpose of this patch is simple and don’t addressed a failover in general.
>>> Crash can occurred in commit time - when journal _partially_ flushed to the FS. Checking any FS metadata in this time is wrong, because we have no guarantee to be consistence.
>>> But checking an after journal replay is fine, it check have verification no corruption hit and FS is fine. 
>> 
>> If the corruption can occur in non-ldiskfs usage, and would be fixed by
>> a journal replay, then yes - the patch looks like a good idea.
Yes, bug should fixed by journal replay. BUT this check was run _before_ journal replay and patch move groups check _after_ journal replay done.


>> 
>> Possibly I misunderstood the source of the corruption... maybe if that
>> could be made clearer in the commit message, that would help.
> 
> I think the argument is: wtf do we even look at metadata (or anything, really)
> before journal replay.
> The patch is actually good because it does move the read after the journal replay
> though?

Oleg,

you are right. 
> 
> 
>> 
>>> 
>>> 
>>>> 22 июля 2019 г., в 8:29, NeilBrown <neilb at suse.com> написал(а):
>>>> 
>>>> On Sun, Jul 21 2019, James Simmons wrote:
>>>> 
>>>>> When ldiskfs run in failover mode whith read-only disk.
>>>>> Part of allocation updates are lost and ldiskfs may fail
>>>>> while mounting this is due to inconsistent state of
>>>>> group-descriptor. Group-descriptor check is added after
>>>>> journal replay.
>>>> 
>>>> I think this needs to be enabled by a mount option or super-block flag.
>>>> 
>>>> NeilBrown
>>>> 
>>>> 
>>>>> 
>>>>> Signed-off-by: James Simmons <jsimmons at infradead.org>
>>>>> ---
>>>>> fs/ext4/super.c | 11 ++++++-----
>>>>> 1 file changed, 6 insertions(+), 5 deletions(-)
>>>>> 
>>>>> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
>>>>> index a3179b2..b818acb 100644
>>>>> --- a/fs/ext4/super.c
>>>>> +++ b/fs/ext4/super.c
>>>>> @@ -4255,11 +4255,6 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>>>>> 		}
>>>>> 	}
>>>>> 	sbi->s_gdb_count = db_count;
>>>>> -	if (!ext4_check_descriptors(sb, logical_sb_block, &first_not_zeroed)) {
>>>>> -		ext4_msg(sb, KERN_ERR, "group descriptors corrupted!");
>>>>> -		ret = -EFSCORRUPTED;
>>>>> -		goto failed_mount2;
>>>>> -	}
>>>>> 
>>>>> 	timer_setup(&sbi->s_err_report, print_daily_error_info, 0);
>>>>> 
>>>>> @@ -4401,6 +4396,12 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>>>>> 	sbi->s_journal->j_commit_callback = ext4_journal_commit_callback;
>>>>> 
>>>>> no_journal:
>>>>> +	if (!ext4_check_descriptors(sb, logical_sb_block, &first_not_zeroed)) {
>>>>> +		ext4_msg(sb, KERN_ERR, "group descriptors corrupted!");
>>>>> +		ret = -EFSCORRUPTED;
>>>>> +		goto failed_mount_wq;
>>>>> +	}
>>>>> +
>>>>> 	if (!test_opt(sb, NO_MBCACHE)) {
>>>>> 		sbi->s_ea_block_cache = ext4_xattr_create_cache();
>>>>> 		if (!sbi->s_ea_block_cache) {
>>>>> -- 
>>>>> 1.8.3.1
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> 
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