linux-ext4 - Re: [PATCH 02/11] readahead: push invalidate_lock out of page_cache_ra

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Message-ID: <vu3c3isevxhsayshrgv4yj2xfkeugbtx4jaryrdxehz57vq6ho@mkrueh7j55fe>
Date: Mon, 2 Feb 2026 14:36:18 +0100
From: Jan Kara <jack@...e.cz>
To: Christoph Hellwig <hch@....de>
Cc: Eric Biggers <ebiggers@...nel.org>, Al Viro <viro@...iv.linux.org.uk>, 
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>, David Sterba <dsterba@...e.com>, 
	Theodore Ts'o <tytso@....edu>, Jaegeuk Kim <jaegeuk@...nel.org>, Chao Yu <chao@...nel.org>, 
	Andrey Albershteyn <aalbersh@...hat.com>, Matthew Wilcox <willy@...radead.org>, 
	linux-fsdevel@...r.kernel.org, linux-btrfs@...r.kernel.org, linux-ext4@...r.kernel.org, 
	linux-f2fs-devel@...ts.sourceforge.net, fsverity@...ts.linux.dev
Subject: Re: [PATCH 02/11] readahead: push invalidate_lock out of
 page_cache_ra_unbounded

On Mon 02-02-26 07:06:31, Christoph Hellwig wrote:
> Require the invalidate_lock to be held over calls to
> page_cache_ra_unbounded instead of acquiring it in this function.
> 
> This prepares for calling page_cache_ra_unbounded from ->readahead for
> fsverity read-ahead.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>

Looks good to me. Feel free to add:

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

								Honza

> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index da029fed4e5a..c9b9fcdd0cae 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -4418,7 +4418,9 @@ static int redirty_blocks(struct inode *inode, pgoff_t page_idx, int len)
>  	pgoff_t redirty_idx = page_idx;
>  	int page_len = 0, ret = 0;
>  
> +	filemap_invalidate_lock_shared(mapping);
>  	page_cache_ra_unbounded(&ractl, len, 0);
> +	filemap_invalidate_unlock_shared(mapping);
>  
>  	do {
>  		folio = read_cache_folio(mapping, page_idx, NULL, NULL);
> diff --git a/fs/verity/pagecache.c b/fs/verity/pagecache.c
> index 1a88decace53..8e0d6fde802f 100644
> --- a/fs/verity/pagecache.c
> +++ b/fs/verity/pagecache.c
> @@ -26,10 +26,13 @@ struct page *generic_read_merkle_tree_page(struct inode *inode, pgoff_t index,
>  	    (!IS_ERR(folio) && !folio_test_uptodate(folio))) {
>  		DEFINE_READAHEAD(ractl, NULL, NULL, inode->i_mapping, index);
>  
> -		if (!IS_ERR(folio))
> +		if (!IS_ERR(folio)) {
>  			folio_put(folio);
> -		else if (num_ra_pages > 1)
> +		} else if (num_ra_pages > 1) {
> +			filemap_invalidate_lock_shared(inode->i_mapping);
>  			page_cache_ra_unbounded(&ractl, num_ra_pages, 0);
> +			filemap_invalidate_unlock_shared(inode->i_mapping);
> +		}
>  		folio = read_mapping_folio(inode->i_mapping, index, NULL);
>  	}
>  	if (IS_ERR(folio))
> diff --git a/mm/readahead.c b/mm/readahead.c
> index b415c9969176..25f81124beb6 100644
> --- a/mm/readahead.c
> +++ b/mm/readahead.c
> @@ -204,7 +204,8 @@ static struct folio *ractl_alloc_folio(struct readahead_control *ractl,
>   * not the function you want to call.  Use page_cache_async_readahead()
>   * or page_cache_sync_readahead() instead.
>   *
> - * Context: File is referenced by caller.  Mutexes may be held by caller.
> + * Context: File is referenced by caller, and ractl->mapping->invalidate_lock
> + * must be held by the caller in shared mode.  Mutexes may be held by caller.
>   * May sleep, but will not reenter filesystem to reclaim memory.
>   */
>  void page_cache_ra_unbounded(struct readahead_control *ractl,
> @@ -228,9 +229,10 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
>  	 */
>  	unsigned int nofs = memalloc_nofs_save();
>  
> +	lockdep_assert_held_read(&mapping->invalidate_lock);
> +
>  	trace_page_cache_ra_unbounded(mapping->host, index, nr_to_read,
>  				      lookahead_size);
> -	filemap_invalidate_lock_shared(mapping);
>  	index = mapping_align_index(mapping, index);
>  
>  	/*
> @@ -300,7 +302,6 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
>  	 * will then handle the error.
>  	 */
>  	read_pages(ractl);
> -	filemap_invalidate_unlock_shared(mapping);
>  	memalloc_nofs_restore(nofs);
>  }
>  EXPORT_SYMBOL_GPL(page_cache_ra_unbounded);
> @@ -314,9 +315,9 @@ EXPORT_SYMBOL_GPL(page_cache_ra_unbounded);
>  static void do_page_cache_ra(struct readahead_control *ractl,
>  		unsigned long nr_to_read, unsigned long lookahead_size)
>  {
> -	struct inode *inode = ractl->mapping->host;
> +	struct address_space *mapping = ractl->mapping;
>  	unsigned long index = readahead_index(ractl);
> -	loff_t isize = i_size_read(inode);
> +	loff_t isize = i_size_read(mapping->host);
>  	pgoff_t end_index;	/* The last page we want to read */
>  
>  	if (isize == 0)
> @@ -329,7 +330,9 @@ static void do_page_cache_ra(struct readahead_control *ractl,
>  	if (nr_to_read > end_index - index)
>  		nr_to_read = end_index - index + 1;
>  
> +	filemap_invalidate_lock_shared(mapping);
>  	page_cache_ra_unbounded(ractl, nr_to_read, lookahead_size);
> +	filemap_invalidate_unlock_shared(mapping);
>  }
>  
>  /*
> -- 
> 2.47.3
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR