Re: [PATCH 08/11] ext4: consolidate fsverity_info lookup

["Darrick J. Wong" <djwong@kernel.org>]

On Thu, Jan 22, 2026 at 09:22:04AM +0100, Christoph Hellwig wrote:
> Look up the fsverity_info once in ext4_mpage_readpages, and then use it
> for the readahead, local verification of holes and pass it along to the
> I/O completion workqueue in struct bio_post_read_ctx.
> 
> This amortizes the lookup better once it becomes less efficient.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/ext4/readpage.c | 33 ++++++++++++++-------------------
>  1 file changed, 14 insertions(+), 19 deletions(-)
> 
> diff --git a/fs/ext4/readpage.c b/fs/ext4/readpage.c
> index 02f918cf1945..6092d6d59063 100644
> --- a/fs/ext4/readpage.c
> +++ b/fs/ext4/readpage.c
> @@ -61,6 +61,7 @@ enum bio_post_read_step {
>  
>  struct bio_post_read_ctx {
>  	struct bio *bio;
> +	struct fsverity_info *vi;
>  	struct work_struct work;
>  	unsigned int cur_step;
>  	unsigned int enabled_steps;
> @@ -96,7 +97,7 @@ static void verity_work(struct work_struct *work)
>  	struct bio_post_read_ctx *ctx =
>  		container_of(work, struct bio_post_read_ctx, work);
>  	struct bio *bio = ctx->bio;
> -	struct inode *inode = bio_first_folio_all(bio)->mapping->host;
> +	struct fsverity_info *vi = ctx->vi;
>  
>  	/*
>  	 * fsverity_verify_bio() may call readahead() again, and although verity
> @@ -109,7 +110,7 @@ static void verity_work(struct work_struct *work)
>  	mempool_free(ctx, bio_post_read_ctx_pool);
>  	bio->bi_private = NULL;
>  
> -	fsverity_verify_bio(*fsverity_info_addr(inode), bio);
> +	fsverity_verify_bio(vi, bio);
>  
>  	__read_end_io(bio);
>  }
> @@ -172,22 +173,16 @@ static void mpage_end_io(struct bio *bio)
>  	__read_end_io(bio);
>  }
>  
> -static inline bool ext4_need_verity(const struct inode *inode, pgoff_t idx)
> -{
> -	return fsverity_active(inode) &&
> -	       idx < DIV_ROUND_UP(inode->i_size, PAGE_SIZE);
> -}
> -
>  static void ext4_set_bio_post_read_ctx(struct bio *bio,
>  				       const struct inode *inode,
> -				       pgoff_t first_idx)
> +				       struct fsverity_info *vi)
>  {
>  	unsigned int post_read_steps = 0;
>  
>  	if (fscrypt_inode_uses_fs_layer_crypto(inode))
>  		post_read_steps |= 1 << STEP_DECRYPT;
>  
> -	if (ext4_need_verity(inode, first_idx))
> +	if (vi)
>  		post_read_steps |= 1 << STEP_VERITY;
>  
>  	if (post_read_steps) {
> @@ -196,6 +191,7 @@ static void ext4_set_bio_post_read_ctx(struct bio *bio,
>  			mempool_alloc(bio_post_read_ctx_pool, GFP_NOFS);
>  
>  		ctx->bio = bio;
> +		ctx->vi = vi;
>  		ctx->enabled_steps = post_read_steps;
>  		bio->bi_private = ctx;
>  	}
> @@ -223,6 +219,7 @@ int ext4_mpage_readpages(struct inode *inode,
>  	sector_t first_block;
>  	unsigned page_block;
>  	struct block_device *bdev = inode->i_sb->s_bdev;
> +	struct fsverity_info *vi = NULL;
>  	int length;
>  	unsigned relative_block = 0;
>  	struct ext4_map_blocks map;
> @@ -244,9 +241,11 @@ int ext4_mpage_readpages(struct inode *inode,
>  			folio = readahead_folio(rac);
>  
>  		if (first_folio) {
> -			if (ext4_need_verity(inode, folio->index))
> -				fsverity_readahead(*fsverity_info_addr(inode),
> -						folio, nr_pages);
> +			if (folio->index <
> +			    DIV_ROUND_UP(inode->i_size, PAGE_SIZE))

I keep seeing this predicate, maybe it should go into fsverity.h as a
helper function with the comment about mmap that I was muttering about
in the previous patch?

Or maybe a "get verity info for given folio index" helper?

/*
 * Grab the fsverity context needed to verify the contents of the folio.
 *
 * <Big fat comment from before, about mmap and whatnot>
 */
static inline struct fsverity_info *vi
fsverity_folio_info(const struct folio *folio)
{
	struct inode *inode = folio->mapping->host;

	if (folio->index < DIV_ROUND_UP(inode->i_size, PAGE_SIZE))
		return fsverity_get_info(inode);
	return NULL;
}

then ext4 just does:

		vi = fsverity_folio_info(folio);
		if (vi)
			fsverity_readahead(vi, folio, nr_pages);

Hrm?

--D

> +				vi = fsverity_get_info(inode);
> +			if (vi)
> +				fsverity_readahead(vi, folio, nr_pages);
>  			first_folio = false;
>  		}
>  
> @@ -337,11 +336,7 @@ int ext4_mpage_readpages(struct inode *inode,
>  			folio_zero_segment(folio, first_hole << blkbits,
>  					  folio_size(folio));
>  			if (first_hole == 0) {
> -				struct fsverity_info *vi =
> -					*fsverity_info_addr(folio->mapping->host);
> -
> -				if (ext4_need_verity(inode, folio->index) &&
> -				    !fsverity_verify_folio(vi, folio))
> +				if (vi && !fsverity_verify_folio(vi, folio))
>  					goto set_error_page;
>  				folio_end_read(folio, true);
>  				continue;
> @@ -369,7 +364,7 @@ int ext4_mpage_readpages(struct inode *inode,
>  					REQ_OP_READ, GFP_KERNEL);
>  			fscrypt_set_bio_crypt_ctx(bio, inode, next_block,
>  						  GFP_KERNEL);
> -			ext4_set_bio_post_read_ctx(bio, inode, folio->index);
> +			ext4_set_bio_post_read_ctx(bio, inode, vi);
>  			bio->bi_iter.bi_sector = first_block << (blkbits - 9);
>  			bio->bi_end_io = mpage_end_io;
>  			if (rac)
> -- 
> 2.47.3
> 
>