Re: [PATCH 5/9] fscrypt: keep multiple bios in flight in fscrypt_zeroout_range_inline_crypt

[Eric Biggers <ebiggers@kernel.org>]

On Fri, Oct 31, 2025 at 10:34:35AM +0100, Christoph Hellwig wrote:
> This should slightly improve performance for large zeroing operations,
> but more importantly prepares for blk-crypto refactoring that requires
> all fscrypt users to call submit_bio directly.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/crypto/bio.c | 84 +++++++++++++++++++++++++++++++------------------
>  1 file changed, 53 insertions(+), 31 deletions(-)
> 
> diff --git a/fs/crypto/bio.c b/fs/crypto/bio.c
> index 68b0424d879a..e59d342b4240 100644
> --- a/fs/crypto/bio.c
> +++ b/fs/crypto/bio.c
> @@ -47,49 +47,71 @@ bool fscrypt_decrypt_bio(struct bio *bio)
>  }
>  EXPORT_SYMBOL(fscrypt_decrypt_bio);
>  
> +struct fscrypt_zero_done {
> +	atomic_t		pending;
> +	blk_status_t		status;
> +	struct completion	done;
> +};
> +
> +static void fscrypt_zeroout_range_done(struct fscrypt_zero_done *done)
> +{
> +	if (atomic_dec_and_test(&done->pending))
> +		complete(&done->done);
> +}
> +
> +static void fscrypt_zeroout_range_end_io(struct bio *bio)
> +{
> +	struct fscrypt_zero_done *done = bio->bi_private;
> +
> +	if (bio->bi_status)
> +		cmpxchg(&done->status, 0, bio->bi_status);
> +	fscrypt_zeroout_range_done(done);
> +	bio_put(bio);
> +}
> +
>  static int fscrypt_zeroout_range_inline_crypt(const struct inode *inode,
>  					      pgoff_t lblk, sector_t sector,
>  					      unsigned int len)
>  {
>  	const unsigned int blockbits = inode->i_blkbits;
>  	const unsigned int blocks_per_page = 1 << (PAGE_SHIFT - blockbits);
> -	struct bio *bio;
> -	int ret, err = 0;
> -	int num_pages = 0;
> +	struct fscrypt_zero_done done = {};
>  
> -	/* This always succeeds since __GFP_DIRECT_RECLAIM is set. */
> -	bio = bio_alloc(inode->i_sb->s_bdev, BIO_MAX_VECS, REQ_OP_WRITE,
> -			GFP_NOFS);
> +	atomic_set(&done.pending, 1);
> +	init_completion(&done.done);

This could use:

	struct fscrypt_zero_done done = {
		.pending = ATOMIC_INIT(1),
		.done = COMPLETION_INITIALIZER_ONSTACK(done.done),
	};

Either way:

Reviewed-by: Eric Biggers <ebiggers@kernel.org>

- Eric