[PATCH v2 1/2] fs,block: Introduce RWF_ZONE_APPEND and handling in direct IO path

[Kanchan Joshi]

Introduce RWF_ZONE_APPEND flag to represent zone-append. User-space
sends this with write. Add IOCB_ZONE_APPEND which is set in
kiocb->ki_flags on receiving RWF_ZONE_APPEND.
Make direct IO submission path use IOCB_ZONE_APPEND to send bio with
append op. Direct IO completion returns zone-relative offset, in sector
unit, to upper layer using kiocb->ki_complete interface.
Report error if zone-append is requested on regular file or on sync
kiocb (i.e. one without ki_complete).

Signed-off-by: Kanchan Joshi <joshi.k@xxxxxxxxxxx>
Signed-off-by: SelvaKumar S <selvakuma.s1@xxxxxxxxxxx>
Signed-off-by: Arnav Dawn <a.dawn@xxxxxxxxxxx>
Signed-off-by: Nitesh Shetty <nj.shetty@xxxxxxxxxxx>
Signed-off-by: Javier Gonzalez <javier.gonz@xxxxxxxxxxx>
---
 fs/block_dev.c          | 28 ++++++++++++++++++++++++----
 include/linux/fs.h      |  9 +++++++++
 include/uapi/linux/fs.h |  5 ++++-
 3 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 47860e5..5180268 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -185,6 +185,10 @@ static unsigned int dio_bio_write_op(struct kiocb *iocb)
 	/* avoid the need for a I/O completion work item */
 	if (iocb->ki_flags & IOCB_DSYNC)
 		op |= REQ_FUA;
+
+	if (iocb->ki_flags & IOCB_ZONE_APPEND)
+		op |= REQ_OP_ZONE_APPEND;
+
 	return op;
 }
 
@@ -295,6 +299,14 @@ static int blkdev_iopoll(struct kiocb *kiocb, bool wait)
 	return blk_poll(q, READ_ONCE(kiocb->ki_cookie), wait);
 }
 
+static inline long blkdev_bio_end_io_append(struct bio *bio)
+{
+	sector_t zone_sectors = blk_queue_zone_sectors(bio->bi_disk->queue);
+
+	/* calculate zone relative offset for zone append */
+	return bio->bi_iter.bi_sector & (zone_sectors - 1);
+}
+
 static void blkdev_bio_end_io(struct bio *bio)
 {
 	struct blkdev_dio *dio = bio->bi_private;
@@ -307,15 +319,19 @@ static void blkdev_bio_end_io(struct bio *bio)
 		if (!dio->is_sync) {
 			struct kiocb *iocb = dio->iocb;
 			ssize_t ret;
+			long res2 = 0;
 
 			if (likely(!dio->bio.bi_status)) {
 				ret = dio->size;
 				iocb->ki_pos += ret;
+
+				if (iocb->ki_flags & IOCB_ZONE_APPEND)
+					res2 = blkdev_bio_end_io_append(bio);
 			} else {
 				ret = blk_status_to_errno(dio->bio.bi_status);
 			}
 
-			dio->iocb->ki_complete(iocb, ret, 0);
+			dio->iocb->ki_complete(iocb, ret, res2);
 			if (dio->multi_bio)
 				bio_put(&dio->bio);
 		} else {
@@ -382,6 +398,7 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
 		bio->bi_private = dio;
 		bio->bi_end_io = blkdev_bio_end_io;
 		bio->bi_ioprio = iocb->ki_ioprio;
+		bio->bi_opf = is_read ? REQ_OP_READ : dio_bio_write_op(iocb);
 
 		ret = bio_iov_iter_get_pages(bio, iter);
 		if (unlikely(ret)) {
@@ -391,11 +408,9 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
 		}
 
 		if (is_read) {
-			bio->bi_opf = REQ_OP_READ;
 			if (dio->should_dirty)
 				bio_set_pages_dirty(bio);
 		} else {
-			bio->bi_opf = dio_bio_write_op(iocb);
 			task_io_account_write(bio->bi_iter.bi_size);
 		}
 
@@ -465,12 +480,17 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
 static ssize_t
 blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
 {
+	bool is_sync = is_sync_kiocb(iocb);
 	int nr_pages;
 
+	/* zone-append is supported only on async-kiocb */
+	if (is_sync && iocb->ki_flags & IOCB_ZONE_APPEND)
+		return -EINVAL;
+
 	nr_pages = iov_iter_npages(iter, BIO_MAX_PAGES + 1);
 	if (!nr_pages)
 		return 0;
-	if (is_sync_kiocb(iocb) && nr_pages <= BIO_MAX_PAGES)
+	if (is_sync && nr_pages <= BIO_MAX_PAGES)
 		return __blkdev_direct_IO_simple(iocb, iter, nr_pages);
 
 	return __blkdev_direct_IO(iocb, iter, min(nr_pages, BIO_MAX_PAGES));
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 6c4ab4d..3202d9a 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -315,6 +315,7 @@ enum rw_hint {
 #define IOCB_SYNC		(1 << 5)
 #define IOCB_WRITE		(1 << 6)
 #define IOCB_NOWAIT		(1 << 7)
+#define IOCB_ZONE_APPEND	(1 << 8)
 
 struct kiocb {
 	struct file		*ki_filp;
@@ -3456,6 +3457,14 @@ static inline int kiocb_set_rw_flags(struct kiocb *ki, rwf_t flags)
 		ki->ki_flags |= (IOCB_DSYNC | IOCB_SYNC);
 	if (flags & RWF_APPEND)
 		ki->ki_flags |= IOCB_APPEND;
+	if (flags & RWF_ZONE_APPEND) {
+		/* currently support block device only */
+		umode_t mode = file_inode(ki->ki_filp)->i_mode;
+
+		if (!(S_ISBLK(mode)))
+			return -EOPNOTSUPP;
+		ki->ki_flags |= IOCB_ZONE_APPEND;
+	}
 	return 0;
 }
 
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index 379a612..1ce06e9 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -299,8 +299,11 @@ typedef int __bitwise __kernel_rwf_t;
 /* per-IO O_APPEND */
 #define RWF_APPEND	((__force __kernel_rwf_t)0x00000010)
 
+/* per-IO O_APPEND */
+#define RWF_ZONE_APPEND	((__force __kernel_rwf_t)0x00000020)
+
 /* mask of flags supported by the kernel */
 #define RWF_SUPPORTED	(RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT |\
-			 RWF_APPEND)
+			 RWF_APPEND | RWF_ZONE_APPEND)
 
 #endif /* _UAPI_LINUX_FS_H */
-- 
2.7.4