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

Oleg Drokin green at whamcloud.com
Sun Jul 21 23:56:24 PDT 2019



> 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.
> 
> 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?


> 
>> 
>> 
>>> 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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