Re: [PATCH 17/30] iomap: switch __iomap_dio_rw to use iomap_iter

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On Mon, Aug 09, 2021 at 08:12:31AM +0200, Christoph Hellwig wrote:
> Switch __iomap_dio_rw to use iomap_iter.
> 
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>

I like the reduction in ->submit_io arguments.  The conversion seems
straightforward enough.

Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>

--D

> ---
>  fs/btrfs/inode.c      |   5 +-
>  fs/iomap/direct-io.c  | 164 +++++++++++++++++++++---------------------
>  include/linux/iomap.h |   4 +-
>  3 files changed, 86 insertions(+), 87 deletions(-)
> 
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 0117d867ecf876..3b0595e8bdd929 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -8194,9 +8194,10 @@ static struct btrfs_dio_private *btrfs_create_dio_private(struct bio *dio_bio,
>  	return dip;
>  }
>  
> -static blk_qc_t btrfs_submit_direct(struct inode *inode, struct iomap *iomap,
> +static blk_qc_t btrfs_submit_direct(const struct iomap_iter *iter,
>  		struct bio *dio_bio, loff_t file_offset)
>  {
> +	struct inode *inode = iter->inode;
>  	const bool write = (btrfs_op(dio_bio) == BTRFS_MAP_WRITE);
>  	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
>  	const bool raid56 = (btrfs_data_alloc_profile(fs_info) &
> @@ -8212,7 +8213,7 @@ static blk_qc_t btrfs_submit_direct(struct inode *inode, struct iomap *iomap,
>  	int ret;
>  	blk_status_t status;
>  	struct btrfs_io_geometry geom;
> -	struct btrfs_dio_data *dio_data = iomap->private;
> +	struct btrfs_dio_data *dio_data = iter->iomap.private;
>  	struct extent_map *em = NULL;
>  
>  	dip = btrfs_create_dio_private(dio_bio, inode, file_offset);
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index 41ccbfc9dc820a..4ecd255e0511ce 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -1,7 +1,7 @@
>  // SPDX-License-Identifier: GPL-2.0
>  /*
>   * Copyright (C) 2010 Red Hat, Inc.
> - * Copyright (c) 2016-2018 Christoph Hellwig.
> + * Copyright (c) 2016-2021 Christoph Hellwig.
>   */
>  #include <linux/module.h>
>  #include <linux/compiler.h>
> @@ -59,19 +59,17 @@ int iomap_dio_iopoll(struct kiocb *kiocb, bool spin)
>  }
>  EXPORT_SYMBOL_GPL(iomap_dio_iopoll);
>  
> -static void iomap_dio_submit_bio(struct iomap_dio *dio, struct iomap *iomap,
> -		struct bio *bio, loff_t pos)
> +static void iomap_dio_submit_bio(const struct iomap_iter *iter,
> +		struct iomap_dio *dio, struct bio *bio, loff_t pos)
>  {
>  	atomic_inc(&dio->ref);
>  
>  	if (dio->iocb->ki_flags & IOCB_HIPRI)
>  		bio_set_polled(bio, dio->iocb);
>  
> -	dio->submit.last_queue = bdev_get_queue(iomap->bdev);
> +	dio->submit.last_queue = bdev_get_queue(iter->iomap.bdev);
>  	if (dio->dops && dio->dops->submit_io)
> -		dio->submit.cookie = dio->dops->submit_io(
> -				file_inode(dio->iocb->ki_filp),
> -				iomap, bio, pos);
> +		dio->submit.cookie = dio->dops->submit_io(iter, bio, pos);
>  	else
>  		dio->submit.cookie = submit_bio(bio);
>  }
> @@ -181,24 +179,23 @@ static void iomap_dio_bio_end_io(struct bio *bio)
>  	}
>  }
>  
> -static void
> -iomap_dio_zero(struct iomap_dio *dio, struct iomap *iomap, loff_t pos,
> -		unsigned len)
> +static void iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio,
> +		loff_t pos, unsigned len)
>  {
>  	struct page *page = ZERO_PAGE(0);
>  	int flags = REQ_SYNC | REQ_IDLE;
>  	struct bio *bio;
>  
>  	bio = bio_alloc(GFP_KERNEL, 1);
> -	bio_set_dev(bio, iomap->bdev);
> -	bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
> +	bio_set_dev(bio, iter->iomap.bdev);
> +	bio->bi_iter.bi_sector = iomap_sector(&iter->iomap, pos);
>  	bio->bi_private = dio;
>  	bio->bi_end_io = iomap_dio_bio_end_io;
>  
>  	get_page(page);
>  	__bio_add_page(bio, page, len, 0);
>  	bio_set_op_attrs(bio, REQ_OP_WRITE, flags);
> -	iomap_dio_submit_bio(dio, iomap, bio, pos);
> +	iomap_dio_submit_bio(iter, dio, bio, pos);
>  }
>  
>  /*
> @@ -206,8 +203,8 @@ iomap_dio_zero(struct iomap_dio *dio, struct iomap *iomap, loff_t pos,
>   * mapping, and whether or not we want FUA.  Note that we can end up
>   * clearing the WRITE_FUA flag in the dio request.
>   */
> -static inline unsigned int
> -iomap_dio_bio_opflags(struct iomap_dio *dio, struct iomap *iomap, bool use_fua)
> +static inline unsigned int iomap_dio_bio_opflags(struct iomap_dio *dio,
> +		const struct iomap *iomap, bool use_fua)
>  {
>  	unsigned int opflags = REQ_SYNC | REQ_IDLE;
>  
> @@ -229,13 +226,16 @@ iomap_dio_bio_opflags(struct iomap_dio *dio, struct iomap *iomap, bool use_fua)
>  	return opflags;
>  }
>  
> -static loff_t
> -iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
> -		struct iomap_dio *dio, struct iomap *iomap)
> +static loff_t iomap_dio_bio_iter(const struct iomap_iter *iter,
> +		struct iomap_dio *dio)
>  {
> +	const struct iomap *iomap = &iter->iomap;
> +	struct inode *inode = iter->inode;
>  	unsigned int blkbits = blksize_bits(bdev_logical_block_size(iomap->bdev));
>  	unsigned int fs_block_size = i_blocksize(inode), pad;
>  	unsigned int align = iov_iter_alignment(dio->submit.iter);
> +	loff_t length = iomap_length(iter);
> +	loff_t pos = iter->pos;
>  	unsigned int bio_opf;
>  	struct bio *bio;
>  	bool need_zeroout = false;
> @@ -286,7 +286,7 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
>  		/* zero out from the start of the block to the write offset */
>  		pad = pos & (fs_block_size - 1);
>  		if (pad)
> -			iomap_dio_zero(dio, iomap, pos - pad, pad);
> +			iomap_dio_zero(iter, dio, pos - pad, pad);
>  	}
>  
>  	/*
> @@ -339,7 +339,7 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
>  
>  		nr_pages = bio_iov_vecs_to_alloc(dio->submit.iter,
>  						 BIO_MAX_VECS);
> -		iomap_dio_submit_bio(dio, iomap, bio, pos);
> +		iomap_dio_submit_bio(iter, dio, bio, pos);
>  		pos += n;
>  	} while (nr_pages);
>  
> @@ -355,7 +355,7 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
>  		/* zero out from the end of the write to the end of the block */
>  		pad = pos & (fs_block_size - 1);
>  		if (pad)
> -			iomap_dio_zero(dio, iomap, pos, fs_block_size - pad);
> +			iomap_dio_zero(iter, dio, pos, fs_block_size - pad);
>  	}
>  out:
>  	/* Undo iter limitation to current extent */
> @@ -365,35 +365,38 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
>  	return ret;
>  }
>  
> -static loff_t
> -iomap_dio_hole_actor(loff_t length, struct iomap_dio *dio)
> +static loff_t iomap_dio_hole_iter(const struct iomap_iter *iter,
> +		struct iomap_dio *dio)
>  {
> -	length = iov_iter_zero(length, dio->submit.iter);
> +	loff_t length = iov_iter_zero(iomap_length(iter), dio->submit.iter);
> +
>  	dio->size += length;
>  	return length;
>  }
>  
> -static loff_t
> -iomap_dio_inline_actor(struct inode *inode, loff_t pos, loff_t length,
> -		struct iomap_dio *dio, struct iomap *iomap)
> +static loff_t iomap_dio_inline_iter(const struct iomap_iter *iomi,
> +		struct iomap_dio *dio)
>  {
> +	const struct iomap *iomap = &iomi->iomap;
>  	struct iov_iter *iter = dio->submit.iter;
> -	void *inline_data = iomap_inline_data(iomap, pos);
> +	void *inline_data = iomap_inline_data(iomap, iomi->pos);
> +	loff_t length = iomap_length(iomi);
> +	loff_t pos = iomi->pos;
>  	size_t copied;
>  
>  	if (WARN_ON_ONCE(!iomap_inline_data_valid(iomap)))
>  		return -EIO;
>  
>  	if (dio->flags & IOMAP_DIO_WRITE) {
> -		loff_t size = inode->i_size;
> +		loff_t size = iomi->inode->i_size;
>  
>  		if (pos > size)
>  			memset(iomap_inline_data(iomap, size), 0, pos - size);
>  		copied = copy_from_iter(inline_data, length, iter);
>  		if (copied) {
>  			if (pos + copied > size)
> -				i_size_write(inode, pos + copied);
> -			mark_inode_dirty(inode);
> +				i_size_write(iomi->inode, pos + copied);
> +			mark_inode_dirty(iomi->inode);
>  		}
>  	} else {
>  		copied = copy_to_iter(inline_data, length, iter);
> @@ -402,30 +405,27 @@ iomap_dio_inline_actor(struct inode *inode, loff_t pos, loff_t length,
>  	return copied;
>  }
>  
> -static loff_t
> -iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
> -		void *data, struct iomap *iomap, struct iomap *srcmap)
> +static loff_t iomap_dio_iter(const struct iomap_iter *iter,
> +		struct iomap_dio *dio)
>  {
> -	struct iomap_dio *dio = data;
> -
> -	switch (iomap->type) {
> +	switch (iter->iomap.type) {
>  	case IOMAP_HOLE:
>  		if (WARN_ON_ONCE(dio->flags & IOMAP_DIO_WRITE))
>  			return -EIO;
> -		return iomap_dio_hole_actor(length, dio);
> +		return iomap_dio_hole_iter(iter, dio);
>  	case IOMAP_UNWRITTEN:
>  		if (!(dio->flags & IOMAP_DIO_WRITE))
> -			return iomap_dio_hole_actor(length, dio);
> -		return iomap_dio_bio_actor(inode, pos, length, dio, iomap);
> +			return iomap_dio_hole_iter(iter, dio);
> +		return iomap_dio_bio_iter(iter, dio);
>  	case IOMAP_MAPPED:
> -		return iomap_dio_bio_actor(inode, pos, length, dio, iomap);
> +		return iomap_dio_bio_iter(iter, dio);
>  	case IOMAP_INLINE:
> -		return iomap_dio_inline_actor(inode, pos, length, dio, iomap);
> +		return iomap_dio_inline_iter(iter, dio);
>  	case IOMAP_DELALLOC:
>  		/*
>  		 * DIO is not serialised against mmap() access at all, and so
>  		 * if the page_mkwrite occurs between the writeback and the
> -		 * iomap_apply() call in the DIO path, then it will see the
> +		 * iomap_iter() call in the DIO path, then it will see the
>  		 * DELALLOC block that the page-mkwrite allocated.
>  		 */
>  		pr_warn_ratelimited("Direct I/O collision with buffered writes! File: %pD4 Comm: %.20s\n",
> @@ -456,16 +456,19 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
>  {
>  	struct address_space *mapping = iocb->ki_filp->f_mapping;
>  	struct inode *inode = file_inode(iocb->ki_filp);
> -	size_t count = iov_iter_count(iter);
> -	loff_t pos = iocb->ki_pos;
> -	loff_t end = iocb->ki_pos + count - 1, ret = 0;
> +	struct iomap_iter iomi = {
> +		.inode		= inode,
> +		.pos		= iocb->ki_pos,
> +		.len		= iov_iter_count(iter),
> +		.flags		= IOMAP_DIRECT,
> +	};
> +	loff_t end = iomi.pos + iomi.len - 1, ret = 0;
>  	bool wait_for_completion =
>  		is_sync_kiocb(iocb) || (dio_flags & IOMAP_DIO_FORCE_WAIT);
> -	unsigned int iomap_flags = IOMAP_DIRECT;
>  	struct blk_plug plug;
>  	struct iomap_dio *dio;
>  
> -	if (!count)
> +	if (!iomi.len)
>  		return NULL;
>  
>  	dio = kmalloc(sizeof(*dio), GFP_KERNEL);
> @@ -486,29 +489,30 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
>  	dio->submit.last_queue = NULL;
>  
>  	if (iov_iter_rw(iter) == READ) {
> -		if (pos >= dio->i_size)
> +		if (iomi.pos >= dio->i_size)
>  			goto out_free_dio;
>  
>  		if (iocb->ki_flags & IOCB_NOWAIT) {
> -			if (filemap_range_needs_writeback(mapping, pos, end)) {
> +			if (filemap_range_needs_writeback(mapping, iomi.pos,
> +					end)) {
>  				ret = -EAGAIN;
>  				goto out_free_dio;
>  			}
> -			iomap_flags |= IOMAP_NOWAIT;
> +			iomi.flags |= IOMAP_NOWAIT;
>  		}
>  
>  		if (iter_is_iovec(iter))
>  			dio->flags |= IOMAP_DIO_DIRTY;
>  	} else {
> -		iomap_flags |= IOMAP_WRITE;
> +		iomi.flags |= IOMAP_WRITE;
>  		dio->flags |= IOMAP_DIO_WRITE;
>  
>  		if (iocb->ki_flags & IOCB_NOWAIT) {
> -			if (filemap_range_has_page(mapping, pos, end)) {
> +			if (filemap_range_has_page(mapping, iomi.pos, end)) {
>  				ret = -EAGAIN;
>  				goto out_free_dio;
>  			}
> -			iomap_flags |= IOMAP_NOWAIT;
> +			iomi.flags |= IOMAP_NOWAIT;
>  		}
>  
>  		/* for data sync or sync, we need sync completion processing */
> @@ -527,12 +531,13 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
>  
>  	if (dio_flags & IOMAP_DIO_OVERWRITE_ONLY) {
>  		ret = -EAGAIN;
> -		if (pos >= dio->i_size || pos + count > dio->i_size)
> +		if (iomi.pos >= dio->i_size ||
> +		    iomi.pos + iomi.len > dio->i_size)
>  			goto out_free_dio;
> -		iomap_flags |= IOMAP_OVERWRITE_ONLY;
> +		iomi.flags |= IOMAP_OVERWRITE_ONLY;
>  	}
>  
> -	ret = filemap_write_and_wait_range(mapping, pos, end);
> +	ret = filemap_write_and_wait_range(mapping, iomi.pos, end);
>  	if (ret)
>  		goto out_free_dio;
>  
> @@ -542,9 +547,10 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
>  		 * If this invalidation fails, let the caller fall back to
>  		 * buffered I/O.
>  		 */
> -		if (invalidate_inode_pages2_range(mapping, pos >> PAGE_SHIFT,
> -				end >> PAGE_SHIFT)) {
> -			trace_iomap_dio_invalidate_fail(inode, pos, count);
> +		if (invalidate_inode_pages2_range(mapping,
> +				iomi.pos >> PAGE_SHIFT, end >> PAGE_SHIFT)) {
> +			trace_iomap_dio_invalidate_fail(inode, iomi.pos,
> +							iomi.len);
>  			ret = -ENOTBLK;
>  			goto out_free_dio;
>  		}
> @@ -559,31 +565,23 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
>  	inode_dio_begin(inode);
>  
>  	blk_start_plug(&plug);
> -	do {
> -		ret = iomap_apply(inode, pos, count, iomap_flags, ops, dio,
> -				iomap_dio_actor);
> -		if (ret <= 0) {
> -			/* magic error code to fall back to buffered I/O */
> -			if (ret == -ENOTBLK) {
> -				wait_for_completion = true;
> -				ret = 0;
> -			}
> -			break;
> -		}
> -		pos += ret;
> -
> -		if (iov_iter_rw(iter) == READ && pos >= dio->i_size) {
> -			/*
> -			 * We only report that we've read data up to i_size.
> -			 * Revert iter to a state corresponding to that as
> -			 * some callers (such as splice code) rely on it.
> -			 */
> -			iov_iter_revert(iter, pos - dio->i_size);
> -			break;
> -		}
> -	} while ((count = iov_iter_count(iter)) > 0);
> +	while ((ret = iomap_iter(&iomi, ops)) > 0)
> +		iomi.processed = iomap_dio_iter(&iomi, dio);
>  	blk_finish_plug(&plug);
>  
> +	/*
> +	 * We only report that we've read data up to i_size.
> +	 * Revert iter to a state corresponding to that as some callers (such
> +	 * as the splice code) rely on it.
> +	 */
> +	if (iov_iter_rw(iter) == READ && iomi.pos >= dio->i_size)
> +		iov_iter_revert(iter, iomi.pos - dio->i_size);
> +
> +	/* magic error code to fall back to buffered I/O */
> +	if (ret == -ENOTBLK) {
> +		wait_for_completion = true;
> +		ret = 0;
> +	}
>  	if (ret < 0)
>  		iomap_dio_set_error(dio, ret);
>  
> diff --git a/include/linux/iomap.h b/include/linux/iomap.h
> index aac4176ea16439..66e04aedd2ca83 100644
> --- a/include/linux/iomap.h
> +++ b/include/linux/iomap.h
> @@ -322,8 +322,8 @@ int iomap_writepages(struct address_space *mapping,
>  struct iomap_dio_ops {
>  	int (*end_io)(struct kiocb *iocb, ssize_t size, int error,
>  		      unsigned flags);
> -	blk_qc_t (*submit_io)(struct inode *inode, struct iomap *iomap,
> -			struct bio *bio, loff_t file_offset);
> +	blk_qc_t (*submit_io)(const struct iomap_iter *iter, struct bio *bio,
> +			      loff_t file_offset);
>  };
>  
>  /*
> -- 
> 2.30.2
> 



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