linux-kernel - Re: [RFC PATCH 1/2] autofs: set compat flag on sbi when daemon uses 32bit addressation

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Message-ID: <b35f6e37-5138-7ede-4c6c-0aa016645977@virtuozzo.com>
Date:   Thu, 14 Sep 2017 11:24:41 +0200
From:   Stanislav Kinsburskiy <skinsbursky@...tuozzo.com>
To:     Ian Kent <raven@...maw.net>
Cc:     autofs@...r.kernel.org, linux-kernel@...r.kernel.org,
        devel@...nvz.org, ldv@...linux.org
Subject: Re: [RFC PATCH 1/2] autofs: set compat flag on sbi when daemon uses
 32bit addressation



14.09.2017 02:38, Ian Kent пишет:
> On 01/09/17 19:21, Stanislav Kinsburskiy wrote:
>> Signed-off-by: Stanislav Kinsburskiy <skinsbursky@...tuozzo.com>
>> ---
>>  fs/autofs4/autofs_i.h  |    3 +++
>>  fs/autofs4/dev-ioctl.c |    3 +++
>>  fs/autofs4/inode.c     |    4 +++-
>>  3 files changed, 9 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/autofs4/autofs_i.h b/fs/autofs4/autofs_i.h
>> index 4737615..3da105f 100644
>> --- a/fs/autofs4/autofs_i.h
>> +++ b/fs/autofs4/autofs_i.h
>> @@ -120,6 +120,9 @@ struct autofs_sb_info {
>>  	struct list_head active_list;
>>  	struct list_head expiring_list;
>>  	struct rcu_head rcu;
>> +#ifdef CONFIG_COMPAT
>> +	unsigned is32bit:1;
>> +#endif
>>  };
>>  
>>  static inline struct autofs_sb_info *autofs4_sbi(struct super_block *sb)
>> diff --git a/fs/autofs4/dev-ioctl.c b/fs/autofs4/dev-ioctl.c
>> index b7c816f..467d6c4 100644
>> --- a/fs/autofs4/dev-ioctl.c
>> +++ b/fs/autofs4/dev-ioctl.c
>> @@ -397,6 +397,9 @@ static int autofs_dev_ioctl_setpipefd(struct file *fp,
>>  		sbi->pipefd = pipefd;
>>  		sbi->pipe = pipe;
>>  		sbi->catatonic = 0;
>> +#ifdef CONFIG_COMPAT
>> +		sbi->is32bit = is_compat_task();
>> +#endif
>>  	}
>>  out:
>>  	put_pid(new_pid);
>> diff --git a/fs/autofs4/inode.c b/fs/autofs4/inode.c
>> index 09e7d68..21d3c0b 100644
>> --- a/fs/autofs4/inode.c
>> +++ b/fs/autofs4/inode.c
>> @@ -301,7 +301,9 @@ int autofs4_fill_super(struct super_block *s, void *data, int silent)
>>  	} else {
>>  		sbi->oz_pgrp = get_task_pid(current, PIDTYPE_PGID);
>>  	}
>> -
>> +#ifdef CONFIG_COMPAT
>> +	sbi->is32bit = is_compat_task();
>> +#endif
>>  	if (autofs_type_trigger(sbi->type))
>>  		__managed_dentry_set_managed(root);
>>  
>>
> 
> Not sure about this.
> 
> Don't you think it would be better to avoid the in code #ifdefs by doing some
> checks and defines in the header file and defining what's need to just use
> is_compat_task().
> 

Yes, might be...

> Not sure 2 patches are needed for this either ......
> 

Well, I found this issue occasionally.
And, frankly speaking, it's not clear to me, whether this issue is important at all, so I wanted to clarify this first.
Thanks to O_DIRECT, the only way to catch the issue is to try to read more, than expected, in compat task (that's how I found it).
I don't see any other flaw so far. And if so, that, probably, we shouldn't care about the issue at all.
What do you think?


> Ian
>