linux-ext4 - Re: [PATCH 2/7] mm: Protect operations adding pages to page cache with i_mapping

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Date:   Tue, 13 Apr 2021 13:57:46 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     Jan Kara <jack@...e.cz>
Cc:     linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-xfs@...r.kernel.org, Ted Tso <tytso@....edu>,
        Christoph Hellwig <hch@...radead.org>,
        Amir Goldstein <amir73il@...il.com>,
        Dave Chinner <david@...morbit.com>
Subject: Re: [PATCH 2/7] mm: Protect operations adding pages to page cache
 with i_mapping_lock

>  	if (error == AOP_TRUNCATED_PAGE)
>  		put_page(page);
> +	up_read(&mapping->host->i_mapping_sem);
>  	return error;

Please add an unlock_mapping label above this up_read and consolidate
most of the other unlocks by jumping there (put_and_wait_on_page_locked
probablt can't use it).

>  truncated:
>  	unlock_page(page);
> @@ -2309,6 +2324,7 @@ static int filemap_update_page(struct kiocb *iocb,
>  	return AOP_TRUNCATED_PAGE;

The trunated case actually seems to miss the unlock.

Similarly I think filemap_fault would benefit from a common
unlock path.