[PATCH 04/13] block: Restore write hint support

[Bart Van Assche <bvanassche@acm.org>]

This patch partially reverts commit c75e707fe1aa ("block: remove the
per-bio/request write hint"). The following aspects of that commit have
been reverted:
- Pass the struct kiocb write hint information to struct bio.
- Pass the struct bio write hint information to struct request.
- Do not merge requests with different write hints.
- Passing write hint information from the VFS layer to the block layer.
- In F2FS, initialization of bio.bi_write_hint.

The following aspects of that commit have been dropped:
- Debugfs support for retrieving and modifying write hints.
- md-raid, BTRFS, ext4, gfs2 and zonefs write hint support.
- The write_hints[] array in struct request_queue.

Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 block/bio.c                 |  2 ++
 block/blk-crypto-fallback.c |  1 +
 block/blk-merge.c           | 14 ++++++++++++++
 block/blk-mq.c              |  2 ++
 block/bounce.c              |  1 +
 block/fops.c                |  3 +++
 fs/buffer.c                 | 13 ++++++++-----
 fs/direct-io.c              |  1 +
 fs/f2fs/data.c              |  2 ++
 fs/iomap/buffered-io.c      |  2 ++
 fs/iomap/direct-io.c        |  1 +
 fs/mpage.c                  |  1 +
 include/linux/blk-mq.h      |  1 +
 include/linux/blk_types.h   |  1 +
 14 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 816d412c06e9..755fcde5cb66 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -251,6 +251,7 @@ void bio_init(struct bio *bio, struct block_device *bdev, struct bio_vec *table,
 	bio->bi_opf = opf;
 	bio->bi_flags = 0;
 	bio->bi_ioprio = 0;
+	bio->bi_write_hint = 0;
 	bio->bi_status = 0;
 	bio->bi_iter.bi_sector = 0;
 	bio->bi_iter.bi_size = 0;
@@ -813,6 +814,7 @@ static int __bio_clone(struct bio *bio, struct bio *bio_src, gfp_t gfp)
 {
 	bio_set_flag(bio, BIO_CLONED);
 	bio->bi_ioprio = bio_src->bi_ioprio;
+	bio->bi_write_hint = bio_src->bi_write_hint;
 	bio->bi_iter = bio_src->bi_iter;
 
 	if (bio->bi_bdev) {
diff --git a/block/blk-crypto-fallback.c b/block/blk-crypto-fallback.c
index e6468eab2681..b1e7415f8439 100644
--- a/block/blk-crypto-fallback.c
+++ b/block/blk-crypto-fallback.c
@@ -172,6 +172,7 @@ static struct bio *blk_crypto_fallback_clone_bio(struct bio *bio_src)
 	if (bio_flagged(bio_src, BIO_REMAPPED))
 		bio_set_flag(bio, BIO_REMAPPED);
 	bio->bi_ioprio		= bio_src->bi_ioprio;
+	bio->bi_write_hint	= bio_src->bi_write_hint;
 	bio->bi_iter.bi_sector	= bio_src->bi_iter.bi_sector;
 	bio->bi_iter.bi_size	= bio_src->bi_iter.bi_size;
 
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 65e75efa9bd3..b1854d6bd081 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -817,6 +817,13 @@ static struct request *attempt_merge(struct request_queue *q,
 	if (req->ioprio != next->ioprio)
 		return NULL;
 
+	/*
+	 * Don't allow merge of different write hints, or for a hint with
+	 * non-hint IO.
+	 */
+	if (req->write_hint != next->write_hint)
+		return NULL;
+
 	/*
 	 * If we are allowed to merge, then append bio list
 	 * from next to rq and release next. merge_requests_fn
@@ -944,6 +951,13 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
 	if (rq->ioprio != bio_prio(bio))
 		return false;
 
+	/*
+	 * Don't allow merge of different write hints, or for a hint with
+	 * non-hint IO.
+	 */
+	if (rq->write_hint != bio->bi_write_hint)
+		return false;
+
 	return true;
 }
 
diff --git a/block/blk-mq.c b/block/blk-mq.c
index ec922c6bccbe..1326d1661f0e 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2563,6 +2563,7 @@ static void blk_mq_bio_to_request(struct request *rq, struct bio *bio,
 		rq->cmd_flags |= REQ_FAILFAST_MASK;
 
 	rq->__sector = bio->bi_iter.bi_sector;
+	rq->write_hint = bio->bi_write_hint;
 	blk_rq_bio_prep(rq, bio, nr_segs);
 
 	/* This can't fail, since GFP_NOIO includes __GFP_DIRECT_RECLAIM. */
@@ -3160,6 +3161,7 @@ int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
 	}
 	rq->nr_phys_segments = rq_src->nr_phys_segments;
 	rq->ioprio = rq_src->ioprio;
+	rq->write_hint = rq_src->write_hint;
 
 	if (rq->bio && blk_crypto_rq_bio_prep(rq, rq->bio, gfp_mask) < 0)
 		goto free_and_out;
diff --git a/block/bounce.c b/block/bounce.c
index 7cfcb242f9a1..d6a5219f29dd 100644
--- a/block/bounce.c
+++ b/block/bounce.c
@@ -169,6 +169,7 @@ static struct bio *bounce_clone_bio(struct bio *bio_src)
 	if (bio_flagged(bio_src, BIO_REMAPPED))
 		bio_set_flag(bio, BIO_REMAPPED);
 	bio->bi_ioprio		= bio_src->bi_ioprio;
+	bio->bi_write_hint	= bio_src->bi_write_hint;
 	bio->bi_iter.bi_sector	= bio_src->bi_iter.bi_sector;
 	bio->bi_iter.bi_size	= bio_src->bi_iter.bi_size;
 
diff --git a/block/fops.c b/block/fops.c
index acff3d5d22d4..6923de13665f 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -74,6 +74,7 @@ static ssize_t __blkdev_direct_IO_simple(struct kiocb *iocb,
 	}
 	bio.bi_iter.bi_sector = pos >> SECTOR_SHIFT;
 	bio.bi_ioprio = iocb->ki_ioprio;
+	bio.bi_write_hint = iocb->ki_hint;
 
 	ret = bio_iov_iter_get_pages(&bio, iter);
 	if (unlikely(ret))
@@ -206,6 +207,7 @@ static ssize_t __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
 		bio->bi_private = dio;
 		bio->bi_end_io = blkdev_bio_end_io;
 		bio->bi_ioprio = iocb->ki_ioprio;
+		bio->bi_write_hint = iocb->ki_hint;
 
 		ret = bio_iov_iter_get_pages(bio, iter);
 		if (unlikely(ret)) {
@@ -323,6 +325,7 @@ static ssize_t __blkdev_direct_IO_async(struct kiocb *iocb,
 	bio->bi_iter.bi_sector = pos >> SECTOR_SHIFT;
 	bio->bi_end_io = blkdev_bio_end_io_async;
 	bio->bi_ioprio = iocb->ki_ioprio;
+	bio->bi_write_hint = iocb->ki_hint;
 
 	if (iov_iter_is_bvec(iter)) {
 		/*
diff --git a/fs/buffer.c b/fs/buffer.c
index 2379564e5aea..bf1d94f7a96a 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -55,7 +55,7 @@
 
 static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
 static void submit_bh_wbc(blk_opf_t opf, struct buffer_head *bh,
-			  struct writeback_control *wbc);
+			  enum rw_hint hint, struct writeback_control *wbc);
 
 #define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
 
@@ -1904,7 +1904,8 @@ int __block_write_full_folio(struct inode *inode, struct folio *folio,
 	do {
 		struct buffer_head *next = bh->b_this_page;
 		if (buffer_async_write(bh)) {
-			submit_bh_wbc(REQ_OP_WRITE | write_flags, bh, wbc);
+			submit_bh_wbc(REQ_OP_WRITE | write_flags, bh,
+					inode->i_write_hint, wbc);
 			nr_underway++;
 		}
 		bh = next;
@@ -1958,7 +1959,8 @@ int __block_write_full_folio(struct inode *inode, struct folio *folio,
 		struct buffer_head *next = bh->b_this_page;
 		if (buffer_async_write(bh)) {
 			clear_buffer_dirty(bh);
-			submit_bh_wbc(REQ_OP_WRITE | write_flags, bh, wbc);
+			submit_bh_wbc(REQ_OP_WRITE | write_flags, bh,
+					inode->i_write_hint, wbc);
 			nr_underway++;
 		}
 		bh = next;
@@ -2770,7 +2772,7 @@ static void end_bio_bh_io_sync(struct bio *bio)
 }
 
 static void submit_bh_wbc(blk_opf_t opf, struct buffer_head *bh,
-			  struct writeback_control *wbc)
+			  enum rw_hint write_hint, struct writeback_control *wbc)
 {
 	const enum req_op op = opf & REQ_OP_MASK;
 	struct bio *bio;
@@ -2797,6 +2799,7 @@ static void submit_bh_wbc(blk_opf_t opf, struct buffer_head *bh,
 	fscrypt_set_bio_crypt_ctx_bh(bio, bh, GFP_NOIO);
 
 	bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
+	bio->bi_write_hint = write_hint;
 
 	__bio_add_page(bio, bh->b_page, bh->b_size, bh_offset(bh));
 
@@ -2816,7 +2819,7 @@ static void submit_bh_wbc(blk_opf_t opf, struct buffer_head *bh,
 
 void submit_bh(blk_opf_t opf, struct buffer_head *bh)
 {
-	submit_bh_wbc(opf, bh, NULL);
+	submit_bh_wbc(opf, bh, 0, NULL);
 }
 EXPORT_SYMBOL(submit_bh);
 
diff --git a/fs/direct-io.c b/fs/direct-io.c
index 7bc494ee56b9..bfa32c6ed3dd 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -404,6 +404,7 @@ dio_bio_alloc(struct dio *dio, struct dio_submit *sdio,
 	 */
 	bio = bio_alloc(bdev, nr_vecs, dio->opf, GFP_KERNEL);
 	bio->bi_iter.bi_sector = first_sector;
+	bio->bi_write_hint = dio->iocb->ki_hint;
 	if (dio->is_async)
 		bio->bi_end_io = dio_bio_end_aio;
 	else
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 916e317ac925..d759a7b8478f 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -478,6 +478,8 @@ static struct bio *__bio_alloc(struct f2fs_io_info *fio, int npages)
 	} else {
 		bio->bi_end_io = f2fs_write_end_io;
 		bio->bi_private = sbi;
+		bio->bi_write_hint =
+			f2fs_io_type_to_rw_hint(sbi, fio->type, fio->temp);
 	}
 	iostat_alloc_and_bind_ctx(sbi, bio, NULL);
 
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index ae8673ce08b1..a344418a82ad 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -1654,6 +1654,7 @@ iomap_alloc_ioend(struct inode *inode, struct iomap_writepage_ctx *wpc,
 			       REQ_OP_WRITE | wbc_to_write_flags(wbc),
 			       GFP_NOFS, &iomap_ioend_bioset);
 	bio->bi_iter.bi_sector = sector;
+	bio->bi_write_hint = inode->i_write_hint;
 	wbc_init_bio(wbc, bio);
 
 	ioend = container_of(bio, struct iomap_ioend, io_inline_bio);
@@ -1684,6 +1685,7 @@ iomap_chain_bio(struct bio *prev)
 	new = bio_alloc(prev->bi_bdev, BIO_MAX_VECS, prev->bi_opf, GFP_NOFS);
 	bio_clone_blkg_association(new, prev);
 	new->bi_iter.bi_sector = bio_end_sector(prev);
+	new->bi_write_hint = prev->bi_write_hint;
 
 	bio_chain(prev, new);
 	bio_get(prev);		/* for iomap_finish_ioend */
diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index bcd3f8cf5ea4..afb704f98a97 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -380,6 +380,7 @@ static loff_t iomap_dio_bio_iter(const struct iomap_iter *iter,
 		fscrypt_set_bio_crypt_ctx(bio, inode, pos >> inode->i_blkbits,
 					  GFP_KERNEL);
 		bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
+		bio->bi_write_hint = dio->iocb->ki_hint;
 		bio->bi_ioprio = dio->iocb->ki_ioprio;
 		bio->bi_private = dio;
 		bio->bi_end_io = iomap_dio_bio_end_io;
diff --git a/fs/mpage.c b/fs/mpage.c
index 242e213ee064..5d444d2c39f1 100644
--- a/fs/mpage.c
+++ b/fs/mpage.c
@@ -612,6 +612,7 @@ static int __mpage_writepage(struct folio *folio, struct writeback_control *wbc,
 				GFP_NOFS);
 		bio->bi_iter.bi_sector = blocks[0] << (blkbits - 9);
 		wbc_init_bio(wbc, bio);
+		bio->bi_write_hint = inode->i_write_hint;
 	}
 
 	/*
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 958ed7e89b30..d2605fb5ee63 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -137,6 +137,7 @@ struct request {
 	struct blk_crypto_keyslot *crypt_keyslot;
 #endif
 
+	unsigned short write_hint;
 	unsigned short ioprio;
 
 	enum mq_rq_state state;
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index d5c5e59ddbd2..6d1617f2123b 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -269,6 +269,7 @@ struct bio {
 						 */
 	unsigned short		bi_flags;	/* BIO_* below */
 	unsigned short		bi_ioprio;
+	unsigned short		bi_write_hint;
 	blk_status_t		bi_status;
 	atomic_t		__bi_remaining;