2024-06-12 21:11:07

by Darrick J. Wong

Subject: Re: [PATCH v4 01/22] fs: Add generic_atomic_write_valid_size()

On Fri, Jun 07, 2024 at 02:38:58PM +0000, John Garry wrote:
> Add a generic helper for FSes to validate that an atomic write is
> appropriately sized (along with the other checks).
>
> Signed-off-by: John Garry <[email protected]>
> ---
> include/linux/fs.h | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 069cbab62700..e13d34f8c24e 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -3645,4 +3645,16 @@ bool generic_atomic_write_valid(loff_t pos, struct iov_iter *iter)
> return true;
> }
>
> +static inline
> +bool generic_atomic_write_valid_size(loff_t pos, struct iov_iter *iter,
> + unsigned int unit_min, unsigned int unit_max)
> +{
> + size_t len = iov_iter_count(iter);
> +
> + if (len < unit_min || len > unit_max)
> + return false;
> +
> + return generic_atomic_write_valid(pos, iter);
> +}

Now that I look back at "fs: Initial atomic write support" I wonder why
not pass the iocb and the iov_iter instead of pos and the iov_iter?
And can these be collapsed into a single generic_atomic_write_checks()
function?

--D

> +
> #endif /* _LINUX_FS_H */
> --
> 2.31.1
>
>

2024-06-13 07:36:55

by John Garry

Subject: Re: [PATCH v4 01/22] fs: Add generic_atomic_write_valid_size()

On 12/06/2024 22:10, Darrick J. Wong wrote:
> On Fri, Jun 07, 2024 at 02:38:58PM +0000, John Garry wrote:
>> Add a generic helper for FSes to validate that an atomic write is
>> appropriately sized (along with the other checks).
>>
>> Signed-off-by: John Garry <[email protected]>
>> ---
>> include/linux/fs.h | 12 ++++++++++++
>> 1 file changed, 12 insertions(+)
>>
>> diff --git a/include/linux/fs.h b/include/linux/fs.h
>> index 069cbab62700..e13d34f8c24e 100644
>> --- a/include/linux/fs.h
>> +++ b/include/linux/fs.h
>> @@ -3645,4 +3645,16 @@ bool generic_atomic_write_valid(loff_t pos, struct iov_iter *iter)
>> return true;
>> }
>>
>> +static inline
>> +bool generic_atomic_write_valid_size(loff_t pos, struct iov_iter *iter,
>> + unsigned int unit_min, unsigned int unit_max)
>> +{
>> + size_t len = iov_iter_count(iter);
>> +
>> + if (len < unit_min || len > unit_max)
>> + return false;
>> +
>> + return generic_atomic_write_valid(pos, iter);
>> +}
>
> Now that I look back at "fs: Initial atomic write support" I wonder why
> not pass the iocb and the iov_iter instead of pos and the iov_iter?

The original user of generic_atomic_write_valid()
[blkdev_dio_unaligned() or blkdev_dio_invalid() with the rename] used
these same args, so I just went with that.

> And can these be collapsed into a single generic_atomic_write_checks()
> function?

bdev file operations would then need to use
generic_atomic_write_valid_size(), and there is no unit_min and unit_max
size there, apart from bdev awu min and max. And if I checked them, we
would be duplicating checks (of awu min and max) in the block layer.

Cheers,
John