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Date:   Tue, 3 Oct 2023 12:40:17 +0200
From:   Jan Kara <jack@...e.cz>
To:     "Matthew Wilcox (Oracle)" <willy@...radead.org>
Cc:     Jan Kara <jack@...e.com>, linux-ext4@...r.kernel.org,
        linux-fsdevel@...r.kernel.org,
        "Fabio M . De Francesco" <fmdefrancesco@...il.com>
Subject: Re: [PATCH 02/10] ext2: Convert ext2_check_page to ext2_check_folio

On Thu 21-09-23 21:07:39, Matthew Wilcox (Oracle) wrote:
> Support in this function for large folios is limited to supporting
> filesystems with block size > PAGE_SIZE.  This new functionality will only
> be supported on machines without HIGHMEM, so the problem of kmap_local
> only being able to map a single page in the folio can be ignored.
> We will not use large folios for ext2 directories on HIGHMEM machines.

OK, but can we perhaps enforce this with some checks & error messages
instead of a silent failure? Like:

#ifdef CONFIG_HIGHMEM
	if (sb->s_blocksize > PAGE_SIZE)
		bail with error
#endif

somewhere in ext2_fill_super()? Or maybe force allocation of lowmem pages
when blocksize > PAGE_SIZE?

								Honza

> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> ---
>  fs/ext2/dir.c | 28 ++++++++++++++--------------
>  1 file changed, 14 insertions(+), 14 deletions(-)
> 
> diff --git a/fs/ext2/dir.c b/fs/ext2/dir.c
> index b335f17f682f..03867381eec2 100644
> --- a/fs/ext2/dir.c
> +++ b/fs/ext2/dir.c
> @@ -96,19 +96,19 @@ static void ext2_commit_chunk(struct page *page, loff_t pos, unsigned len)
>  	unlock_page(page);
>  }
>  
> -static bool ext2_check_page(struct page *page, int quiet, char *kaddr)
> +static bool ext2_check_folio(struct folio *folio, int quiet, char *kaddr)
>  {
> -	struct inode *dir = page->mapping->host;
> +	struct inode *dir = folio->mapping->host;
>  	struct super_block *sb = dir->i_sb;
>  	unsigned chunk_size = ext2_chunk_size(dir);
>  	u32 max_inumber = le32_to_cpu(EXT2_SB(sb)->s_es->s_inodes_count);
>  	unsigned offs, rec_len;
> -	unsigned limit = PAGE_SIZE;
> +	unsigned limit = folio_size(folio);
>  	ext2_dirent *p;
>  	char *error;
>  
> -	if ((dir->i_size >> PAGE_SHIFT) == page->index) {
> -		limit = dir->i_size & ~PAGE_MASK;
> +	if (dir->i_size < folio_pos(folio) + limit) {
> +		limit = offset_in_folio(folio, dir->i_size);
>  		if (limit & (chunk_size - 1))
>  			goto Ebadsize;
>  		if (!limit)
> @@ -132,7 +132,7 @@ static bool ext2_check_page(struct page *page, int quiet, char *kaddr)
>  	if (offs != limit)
>  		goto Eend;
>  out:
> -	SetPageChecked(page);
> +	folio_set_checked(folio);
>  	return true;
>  
>  	/* Too bad, we had an error */
> @@ -160,22 +160,22 @@ static bool ext2_check_page(struct page *page, int quiet, char *kaddr)
>  bad_entry:
>  	if (!quiet)
>  		ext2_error(sb, __func__, "bad entry in directory #%lu: : %s - "
> -			"offset=%lu, inode=%lu, rec_len=%d, name_len=%d",
> -			dir->i_ino, error, (page->index<<PAGE_SHIFT)+offs,
> +			"offset=%llu, inode=%lu, rec_len=%d, name_len=%d",
> +			dir->i_ino, error, folio_pos(folio) + offs,
>  			(unsigned long) le32_to_cpu(p->inode),
>  			rec_len, p->name_len);
>  	goto fail;
>  Eend:
>  	if (!quiet) {
>  		p = (ext2_dirent *)(kaddr + offs);
> -		ext2_error(sb, "ext2_check_page",
> +		ext2_error(sb, "ext2_check_folio",
>  			"entry in directory #%lu spans the page boundary"
> -			"offset=%lu, inode=%lu",
> -			dir->i_ino, (page->index<<PAGE_SHIFT)+offs,
> +			"offset=%llu, inode=%lu",
> +			dir->i_ino, folio_pos(folio) + offs,
>  			(unsigned long) le32_to_cpu(p->inode));
>  	}
>  fail:
> -	SetPageError(page);
> +	folio_set_error(folio);
>  	return false;
>  }
>  
> @@ -195,9 +195,9 @@ static void *ext2_get_page(struct inode *dir, unsigned long n,
>  
>  	if (IS_ERR(folio))
>  		return ERR_CAST(folio);
> -	page_addr = kmap_local_folio(folio, n & (folio_nr_pages(folio) - 1));
> +	page_addr = kmap_local_folio(folio, 0);
>  	if (unlikely(!folio_test_checked(folio))) {
> -		if (!ext2_check_page(&folio->page, quiet, page_addr))
> +		if (!ext2_check_folio(folio, quiet, page_addr))
>  			goto fail;
>  	}
>  	*page = &folio->page;
> -- 
> 2.40.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR

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