[PATCHv8 4/6] fs: introduce per-io hint support flag

[Keith Busch <kbusch@meta.com>]

From: Keith Busch <kbusch@kernel.org>

A block device may support write hints on a per-io basis. The raw block
file operations can effectively use these, but real filesystems are not
ready to make use of this. Provide a file_operations flag to indicate
support, and set it for the block file operations.

Signed-off-by: Keith Busch <kbusch@kernel.org>
---
 block/fops.c       | 2 +-
 include/linux/fs.h | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/block/fops.c b/block/fops.c
index d0b16d3975fd6..15a63e26161ea 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -869,7 +869,7 @@ const struct file_operations def_blk_fops = {
 	.splice_write	= iter_file_splice_write,
 	.fallocate	= blkdev_fallocate,
 	.uring_cmd	= blkdev_uring_cmd,
-	.fop_flags	= FOP_BUFFER_RASYNC,
+	.fop_flags	= FOP_BUFFER_RASYNC | FOP_PER_IO_HINTS,
 };
 
 static __init int blkdev_init(void)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 04e875a37f604..026dc9801dc20 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2117,6 +2117,8 @@ struct file_operations {
 #define FOP_HUGE_PAGES		((__force fop_flags_t)(1 << 4))
 /* Treat loff_t as unsigned (e.g., /dev/mem) */
 #define FOP_UNSIGNED_OFFSET	((__force fop_flags_t)(1 << 5))
+/* File system can handle per-io hints */
+#define FOP_PER_IO_HINTS       ((__force fop_flags_t)(1 << 6))
 
 /* Wrap a directory iterator that needs exclusive inode access */
 int wrap_directory_iterator(struct file *, struct dir_context *,
-- 
2.43.5