Re: [PATCH v3 3/7] fs: create kiocb_{start,end}_write() helpers

[Jan Kara <jack@suse.cz>]

On Thu 17-08-23 17:13:33, Amir Goldstein wrote:
> aio, io_uring, cachefiles and overlayfs, all open code an ugly variant
> of file_{start,end}_write() to silence lockdep warnings.
> 
> Create helpers for this lockdep dance so we can use the helpers in all
> the callers.
> 
> Suggested-by: Jan Kara <jack@suse.cz>
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  include/linux/fs.h | 36 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
> 
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index ced388aff51f..2548048a6e6c 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2579,6 +2579,42 @@ static inline void file_end_write(struct file *file)
>  	sb_end_write(file_inode(file)->i_sb);
>  }
>  
> +/**
> + * kiocb_start_write - get write access to a superblock for async file io
> + * @iocb: the io context we want to submit the write with
> + *
> + * This is a variant of sb_start_write() for async io submission.
> + * Should be matched with a call to kiocb_end_write().
> + */
> +static inline void kiocb_start_write(struct kiocb *iocb)
> +{
> +	struct inode *inode = file_inode(iocb->ki_filp);
> +
> +	sb_start_write(inode->i_sb);
> +	/*
> +	 * Fool lockdep by telling it the lock got released so that it
> +	 * doesn't complain about the held lock when we return to userspace.
> +	 */
> +	__sb_writers_release(inode->i_sb, SB_FREEZE_WRITE);
> +}
> +
> +/**
> + * kiocb_end_write - drop write access to a superblock after async file io
> + * @iocb: the io context we sumbitted the write with
> + *
> + * Should be matched with a call to kiocb_start_write().
> + */
> +static inline void kiocb_end_write(struct kiocb *iocb)
> +{
> +	struct inode *inode = file_inode(iocb->ki_filp);
> +
> +	/*
> +	 * Tell lockdep we inherited freeze protection from submission thread.
> +	 */
> +	__sb_writers_acquired(inode->i_sb, SB_FREEZE_WRITE);
> +	sb_end_write(inode->i_sb);
> +}
> +
>  /*
>   * This is used for regular files where some users -- especially the
>   * currently executed binary in a process, previously handled via
> -- 
> 2.34.1
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR