linux-kernel - Re: [PATCH -next] ext4: Fix remount with 'abort' option isn't effective

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Date:   Thu, 23 Dec 2021 09:41:31 +0800
From:   yebin <yebin10@...wei.com>
To:     Lukas Czerner <lczerner@...hat.com>
CC:     <tytso@....edu>, <adilger.kernel@...ger.ca>,
        <linux-ext4@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <jack@...e.cz>
Subject: Re: [PATCH -next] ext4: Fix remount with 'abort' option isn't
 effective



On 2021/12/22 17:19, Lukas Czerner wrote:
> On Wed, Dec 22, 2021 at 09:06:22AM +0800, yebin wrote:
>>
>> On 2021/12/21 22:43, Lukas Czerner wrote:
>>> Hi,
>>>
>>> nice catch. This is a bug indeed. However I am currently in a process of
>>> changing the ctx_set/clear/test_ helpers because currently it generates
>>> functions that are unused.
>>>
>>> While I am at it I can just create a custom ctx_set_mount_flags()
>>> helper that would behave as expected so that we won't have to specify
>>> "1 < EXT4_MF_FS_ABORTED" which is not really obvious and hence error
>>> prone.
>> Actually, I fixed the first version as follows:
> Allright, this looks better.
>
>> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
>> index b72d989b77fb..199920ffc7d3 100644
>> --- a/fs/ext4/super.c
>> +++ b/fs/ext4/super.c
>> @@ -2049,8 +2049,8 @@ struct ext4_fs_context {
>>   	unsigned int	mask_s_mount_opt;
>>   	unsigned int	vals_s_mount_opt2;
>>   	unsigned int	mask_s_mount_opt2;
>> -	unsigned int	vals_s_mount_flags;
>> -	unsigned int	mask_s_mount_flags;
>> +	unsigned long	vals_s_mount_flags;
>> +	unsigned long	mask_s_mount_flags;
>>   	unsigned int	opt_flags;	/* MOPT flags */
>>   	unsigned int	spec;
>>   	u32		s_max_batch_time;
>> @@ -2166,7 +2166,12 @@ static inline bool ctx_test_##name(struct ext4_fs_context *ctx, int flag)\
>>   EXT4_SET_CTX(flags);
>>   EXT4_SET_CTX(mount_opt);
>>   EXT4_SET_CTX(mount_opt2);
>> -EXT4_SET_CTX(mount_flags);
>> +
>> +static inline void ctx_set_mount_flags(struct ext4_fs_context *ctx, int bit)
> Maybe ctx_set_mount_flag since you can't really set more than one this
> way?
So I think it's a little inappropriate to use the current repair scheme.
>> +{
>> +	set_bit(bit, &ctx->mask_s_mount_flags);
>> +	set_bit(bit, &ctx->vals_s_mount_flags);
>> +}
>>
>>
>> I think 'mask_s_mount_flags' is useless now.
> So how would we know what flags have changed ? Sure, there is currently
> no need to clear the flag but that can come in future and once it does
> we'll only need to create a clear helper, the rest will be ready.
> I'd rather keep it.
>
> -Lukas
 From this point of view, I agree with you.
>>> My plan is to send my patch set including this one tomorrow, will that
>>> be fine with you ?
>>>
>>> -Lukas
>>>
>>> On Tue, Dec 21, 2021 at 08:32:14PM +0800, Ye Bin wrote:
>>>> We test remount with 'abort' option as follows:
>>>> [root@...alhost home]# mount  /dev/sda test
>>>> [root@...alhost home]# mount | grep test
>>>> /dev/sda on /home/test type ext4 (rw,relatime)
>>>> [root@...alhost home]# mount -o remount,abort test
>>>> [root@...alhost home]# mount | grep test
>>>> /dev/sda on /home/test type ext4 (rw,relatime)
>>>>
>>>> Obviously, remount 'abort' option isn't effective.
>>>> After 6e47a3cc68fc commit we process abort option with 'ctx_set_mount_flags':
>>>> static inline void ctx_set_mount_flags(struct ext4_fs_context *ctx, int flag)
>>>> {
>>>> 	ctx->mask_s_mount_flags |= flag;
>>>> 	ctx->vals_s_mount_flags |= flag;
>>>> }
>>>>
>>>> But we test 'abort' option with 'ext4_test_mount_flag':
>>>> static inline int ext4_test_mount_flag(struct super_block *sb, int bit)
>>>> {
>>>>           return test_bit(bit, &EXT4_SB(sb)->s_mount_flags);
>>>> }
>>>>
>>>> To solve this issue, pass (1 <<  EXT4_MF_FS_ABORTED) to 'ctx_set_mount_flags'.
>>>>
>>>> Fixes:6e47a3cc68fc("ext4: get rid of super block and sbi from handle_mount_ops()")
>>>> Signed-off-by: Ye Bin <yebin10@...wei.com>
>>>> ---
>>>>    fs/ext4/super.c | 2 +-
>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
>>>> index b72d989b77fb..071b7b3c5678 100644
>>>> --- a/fs/ext4/super.c
>>>> +++ b/fs/ext4/super.c
>>>> @@ -2236,7 +2236,7 @@ static int ext4_parse_param(struct fs_context *fc, struct fs_parameter *param)
>>>>    			 param->key);
>>>>    		return 0;
>>>>    	case Opt_abort:
>>>> -		ctx_set_mount_flags(ctx, EXT4_MF_FS_ABORTED);
>>>> +		ctx_set_mount_flags(ctx, 1 << EXT4_MF_FS_ABORTED);
>>>>    		return 0;
>>>>    	case Opt_i_version:
>>>>    		ctx_set_flags(ctx, SB_I_VERSION);
>>>> -- 
>>>> 2.31.1
>>>>
>>> .
>>>
> .
>