[PATCH v7 2/3] block, fs: restore kiocb based write hint processing

struct kiocb has a 2 bytes hole that developed post commit 41d36a9f3e53
("fs: remove kiocb.ki_hint").
But write hint has made a comeback with commit 449813515d3e ("block, fs:
Restore the per-bio/request data lifetime fields").

This patch uses the leftover space in kiocb to carve 1 byte field
ki_write_hint.
Restore the code that operates on kiocb to use ki_write_hint instead of
inode hint value.

This does not bring any behavior change, but needed to enable per-io
hints (by another patch).

Signed-off-by: Kanchan Joshi <[email protected]>
Signed-off-by: Nitesh Shetty <[email protected]>
Reviewed-by: Hannes Reinecke <[email protected]>
---
 block/fops.c         | 6 +++---
 fs/aio.c             | 1 +
 fs/cachefiles/io.c   | 1 +
 fs/direct-io.c       | 2 +-
 fs/iomap/direct-io.c | 2 +-
 include/linux/fs.h   | 8 ++++++++
 io_uring/rw.c        | 1 +
 7 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/block/fops.c b/block/fops.c
index e696ae53bf1e..85b9b97d372c 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -74,7 +74,7 @@ static ssize_t __blkdev_direct_IO_simple(struct kiocb *iocb,
 		bio_init(&bio, bdev, vecs, nr_pages, dio_bio_write_op(iocb));
 	}
 	bio.bi_iter.bi_sector = pos >> SECTOR_SHIFT;
-	bio.bi_write_hint = file_inode(iocb->ki_filp)->i_write_hint;
+	bio.bi_write_hint = iocb->ki_write_hint;
 	bio.bi_ioprio = iocb->ki_ioprio;
 	if (iocb->ki_flags & IOCB_ATOMIC)
 		bio.bi_opf |= REQ_ATOMIC;
@@ -203,7 +203,7 @@ static ssize_t __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
 
 	for (;;) {
 		bio->bi_iter.bi_sector = pos >> SECTOR_SHIFT;
-		bio->bi_write_hint = file_inode(iocb->ki_filp)->i_write_hint;
+		bio->bi_write_hint = iocb->ki_write_hint;
 		bio->bi_private = dio;
 		bio->bi_end_io = blkdev_bio_end_io;
 		bio->bi_ioprio = iocb->ki_ioprio;
@@ -319,7 +319,7 @@ static ssize_t __blkdev_direct_IO_async(struct kiocb *iocb,
 	dio->flags = 0;
 	dio->iocb = iocb;
 	bio->bi_iter.bi_sector = pos >> SECTOR_SHIFT;
-	bio->bi_write_hint = file_inode(iocb->ki_filp)->i_write_hint;
+	bio->bi_write_hint = iocb->ki_write_hint;
 	bio->bi_end_io = blkdev_bio_end_io_async;
 	bio->bi_ioprio = iocb->ki_ioprio;
 
diff --git a/fs/aio.c b/fs/aio.c
index e8920178b50f..db618817e670 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1517,6 +1517,7 @@ static int aio_prep_rw(struct kiocb *req, const struct iocb *iocb, int rw_type)
 	req->ki_flags = req->ki_filp->f_iocb_flags | IOCB_AIO_RW;
 	if (iocb->aio_flags & IOCB_FLAG_RESFD)
 		req->ki_flags |= IOCB_EVENTFD;
+	req->ki_write_hint = file_write_hint(req->ki_filp);
 	if (iocb->aio_flags & IOCB_FLAG_IOPRIO) {
 		/*
 		 * If the IOCB_FLAG_IOPRIO flag of aio_flags is set, then
diff --git a/fs/cachefiles/io.c b/fs/cachefiles/io.c
index 6a821a959b59..c3db102ae64e 100644
--- a/fs/cachefiles/io.c
+++ b/fs/cachefiles/io.c
@@ -309,6 +309,7 @@ int __cachefiles_write(struct cachefiles_object *object,
 	ki->iocb.ki_pos		= start_pos;
 	ki->iocb.ki_flags	= IOCB_DIRECT | IOCB_WRITE;
 	ki->iocb.ki_ioprio	= get_current_ioprio();
+	ki->iocb.ki_write_hint  = file_write_hint(file);
 	ki->object		= object;
 	ki->start		= start_pos;
 	ki->len			= len;
diff --git a/fs/direct-io.c b/fs/direct-io.c
index bbd05f1a2145..73629e26becb 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -409,7 +409,7 @@ dio_bio_alloc(struct dio *dio, struct dio_submit *sdio,
 		bio->bi_end_io = dio_bio_end_io;
 	if (dio->is_pinned)
 		bio_set_flag(bio, BIO_PAGE_PINNED);
-	bio->bi_write_hint = file_inode(dio->iocb->ki_filp)->i_write_hint;
+	bio->bi_write_hint = dio->iocb->ki_write_hint;
 
 	sdio->bio = bio;
 	sdio->logical_offset_in_bio = sdio->cur_page_fs_offset;
diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index f637aa0706a3..fff43f121ee6 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -397,7 +397,7 @@ 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 = inode->i_write_hint;
+		bio->bi_write_hint = dio->iocb->ki_write_hint;
 		bio->bi_ioprio = dio->iocb->ki_ioprio;
 		bio->bi_private = dio;
 		bio->bi_end_io = iomap_dio_bio_end_io;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index e3c603d01337..3dfe6de7b611 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -370,6 +370,7 @@ struct kiocb {
 	void			*private;
 	int			ki_flags;
 	u16			ki_ioprio; /* See linux/ioprio.h */
+	enum rw_hint		ki_write_hint;
 	union {
 		/*
 		 * Only used for async buffered reads, where it denotes the
@@ -2337,12 +2338,18 @@ static inline bool HAS_UNMAPPED_ID(struct mnt_idmap *idmap,
 	       !vfsgid_valid(i_gid_into_vfsgid(idmap, inode));
 }
 
+static inline enum rw_hint file_write_hint(struct file *filp)
+{
+	return file_inode(filp)->i_write_hint;
+}
+
 static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
 {
 	*kiocb = (struct kiocb) {
 		.ki_filp = filp,
 		.ki_flags = filp->f_iocb_flags,
 		.ki_ioprio = get_current_ioprio(),
+		.ki_write_hint = file_write_hint(filp),
 	};
 }
 
@@ -2353,6 +2360,7 @@ static inline void kiocb_clone(struct kiocb *kiocb, struct kiocb *kiocb_src,
 		.ki_filp = filp,
 		.ki_flags = kiocb_src->ki_flags,
 		.ki_ioprio = kiocb_src->ki_ioprio,
+		.ki_write_hint = kiocb_src->ki_write_hint,
 		.ki_pos = kiocb_src->ki_pos,
 	};
 }
diff --git a/io_uring/rw.c b/io_uring/rw.c
index f023ff49c688..510123d3d837 100644
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -1023,6 +1023,7 @@ int io_write(struct io_kiocb *req, unsigned int issue_flags)
 	if (unlikely(ret))
 		return ret;
 	req->cqe.res = iov_iter_count(&io->iter);
+	rw->kiocb.ki_write_hint = file_write_hint(rw->kiocb.ki_filp);
 
 	if (force_nonblock) {
 		/* If the file doesn't support async, just async punt */
-- 
2.25.1


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