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Date:   Mon, 7 Jun 2021 08:46:22 -0700
From:   "Darrick J. Wong" <djwong@...nel.org>
To:     Jan Kara <jack@...e.cz>
Cc:     linux-fsdevel@...r.kernel.org,
        Christoph Hellwig <hch@...radead.org>,
        Dave Chinner <david@...morbit.com>, ceph-devel@...r.kernel.org,
        Chao Yu <yuchao0@...wei.com>,
        Damien Le Moal <damien.lemoal@....com>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        Jeff Layton <jlayton@...nel.org>,
        Johannes Thumshirn <jth@...nel.org>,
        linux-cifs@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, linux-mm@...ck.org,
        linux-xfs@...r.kernel.org, Miklos Szeredi <miklos@...redi.hu>,
        Steve French <sfrench@...ba.org>, Ted Tso <tytso@....edu>,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH 04/14] mm: Add functions to lock invalidate_lock for two
 mappings

On Mon, Jun 07, 2021 at 04:52:14PM +0200, Jan Kara wrote:
> Some operations such as reflinking blocks among files will need to lock
> invalidate_lock for two mappings. Add helper functions to do that.
> 
> Signed-off-by: Jan Kara <jack@...e.cz>

Straightforward lift from xfs, though now with vfs lock ordering
rules...

Reviewed-by: Darrick J. Wong <djwong@...nel.org>

--D

> ---
>  include/linux/fs.h |  6 ++++++
>  mm/filemap.c       | 38 ++++++++++++++++++++++++++++++++++++++
>  2 files changed, 44 insertions(+)
> 
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index d8afbc9661d7..ddc11bafc183 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -849,6 +849,12 @@ static inline void filemap_invalidate_unlock_shared(
>  void lock_two_nondirectories(struct inode *, struct inode*);
>  void unlock_two_nondirectories(struct inode *, struct inode*);
>  
> +void filemap_invalidate_lock_two(struct address_space *mapping1,
> +				 struct address_space *mapping2);
> +void filemap_invalidate_unlock_two(struct address_space *mapping1,
> +				   struct address_space *mapping2);
> +
> +
>  /*
>   * NOTE: in a 32bit arch with a preemptable kernel and
>   * an UP compile the i_size_read/write must be atomic
> diff --git a/mm/filemap.c b/mm/filemap.c
> index c8e7e451d81e..b8e9bccecd9f 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -1009,6 +1009,44 @@ struct page *__page_cache_alloc(gfp_t gfp)
>  EXPORT_SYMBOL(__page_cache_alloc);
>  #endif
>  
> +/*
> + * filemap_invalidate_lock_two - lock invalidate_lock for two mappings
> + *
> + * Lock exclusively invalidate_lock of any passed mapping that is not NULL.
> + *
> + * @mapping1: the first mapping to lock
> + * @mapping2: the second mapping to lock
> + */
> +void filemap_invalidate_lock_two(struct address_space *mapping1,
> +				 struct address_space *mapping2)
> +{
> +	if (mapping1 > mapping2)
> +		swap(mapping1, mapping2);
> +	if (mapping1)
> +		down_write(&mapping1->invalidate_lock);
> +	if (mapping2 && mapping1 != mapping2)
> +		down_write_nested(&mapping2->invalidate_lock, 1);
> +}
> +EXPORT_SYMBOL(filemap_invalidate_lock_two);
> +
> +/*
> + * filemap_invalidate_unlock_two - unlock invalidate_lock for two mappings
> + *
> + * Unlock exclusive invalidate_lock of any passed mapping that is not NULL.
> + *
> + * @mapping1: the first mapping to unlock
> + * @mapping2: the second mapping to unlock
> + */
> +void filemap_invalidate_unlock_two(struct address_space *mapping1,
> +				   struct address_space *mapping2)
> +{
> +	if (mapping1)
> +		up_write(&mapping1->invalidate_lock);
> +	if (mapping2 && mapping1 != mapping2)
> +		up_write(&mapping2->invalidate_lock);
> +}
> +EXPORT_SYMBOL(filemap_invalidate_unlock_two);
> +
>  /*
>   * In order to wait for pages to become available there must be
>   * waitqueues associated with pages. By using a hash table of
> -- 
> 2.26.2
> 

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