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SubjectRe: [RFC PATCH 1/2] autofs: set compat flag on sbi when daemon uses 32bit addressation
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On 14/09/17 17:24, Stanislav Kinsburskiy wrote:
>
>
> 14.09.2017 02:38, Ian Kent пишет:
>> On 01/09/17 19:21, Stanislav Kinsburskiy wrote:
>>> Signed-off-by: Stanislav Kinsburskiy <skinsbursky@virtuozzo.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.

I'm wondering what the symptoms are?

> 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).

Right, the O_DIRECT patch from Linus was expected to fix the structure
alignment problem. The stuct field offsets are ok aren't they?

> 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?

If we are seeing hangs, incorrect struct fields or similar something
should be done about it but if all is actually working ok then the
O_DIRECT fix is doing it's job and further changes aren't necessary.

Ian

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