Implement support for userspace controlled write-streams.

Add a new i_write_stream field in xfs inode (note: existing hole is
used), and use that to implement write stream management file operations.

Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
---
 fs/xfs/xfs_file.c   | 54 +++++++++++++++++++++++++++++++++++++++++++++
 fs/xfs/xfs_icache.c |  1 +
 fs/xfs/xfs_inode.h  |  3 +++
 fs/xfs/xfs_iomap.c  |  1 +
 4 files changed, 59 insertions(+)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 43d088a3bceb..f3b137407a60 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -2021,6 +2021,57 @@ xfs_file_mmap_prepare(
 	return 0;
 }
 
+static struct block_device *
+xfs_file_get_bdev(
+	struct inode		*inode)
+{
+	struct xfs_inode *ip = XFS_I(inode);
+	struct xfs_mount *mp = ip->i_mount;
+
+	if (XFS_IS_REALTIME_INODE(ip))
+		return mp->m_rtdev_targp->bt_bdev;
+
+	return mp->m_ddev_targp->bt_bdev;
+}
+
+static int
+xfs_file_get_max_write_streams(
+	struct file		*file)
+{
+	struct block_device *bdev = xfs_file_get_bdev(file_inode(file));
+
+	if (bdev)
+		return bdev_max_write_streams(bdev);
+
+	return 0;
+}
+
+static int
+xfs_file_get_write_stream(
+	struct file		*file)
+{
+	struct xfs_inode *ip = XFS_I(file_inode(file));
+
+	return READ_ONCE(ip->i_write_stream);
+}
+
+static int
+xfs_file_set_write_stream(
+	struct file		*file,
+	unsigned long		stream)
+{
+	struct xfs_inode *ip = XFS_I(file_inode(file));
+	int max_streams = xfs_file_get_max_write_streams(file);
+
+	if (stream > max_streams)
+		return -EINVAL;
+	xfs_ilock(ip, XFS_ILOCK_EXCL);
+	WRITE_ONCE(ip->i_write_stream, stream);
+	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+
+	return 0;
+}
+
 const struct file_operations xfs_file_operations = {
 	.llseek		= xfs_file_llseek,
 	.read_iter	= xfs_file_read_iter,
@@ -2040,6 +2091,9 @@ const struct file_operations xfs_file_operations = {
 	.fallocate	= xfs_file_fallocate,
 	.fadvise	= xfs_file_fadvise,
 	.remap_file_range = xfs_file_remap_range,
+	.get_max_write_streams	= xfs_file_get_max_write_streams,
+	.get_write_stream = xfs_file_get_write_stream,
+	.set_write_stream = xfs_file_set_write_stream,
 	.fop_flags	= FOP_MMAP_SYNC | FOP_BUFFER_RASYNC |
 			  FOP_BUFFER_WASYNC | FOP_DIO_PARALLEL_WRITE |
 			  FOP_DONTCACHE,
diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
index dbaab4ae709f..fc9c6794b7db 100644
--- a/fs/xfs/xfs_icache.c
+++ b/fs/xfs/xfs_icache.c
@@ -130,6 +130,7 @@ xfs_inode_alloc(
 	spin_lock_init(&ip->i_ioend_lock);
 	ip->i_next_unlinked = NULLAGINO;
 	ip->i_prev_unlinked = 0;
+	ip->i_write_stream = 0;
 
 	return ip;
 }
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index bd6d33557194..be3580fec318 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -38,6 +38,9 @@ typedef struct xfs_inode {
 	struct xfs_ifork	i_df;		/* data fork */
 	struct xfs_ifork	i_af;		/* attribute fork */
 
+	/* Write stream information */
+	uint8_t			i_write_stream;	/* for placement, 0 = none */
+
 	/* Transaction and locking information. */
 	struct xfs_inode_log_item *i_itemp;	/* logging information */
 	struct rw_semaphore	i_lock;		/* inode lock */
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index be86d43044df..7988c9e16635 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -148,6 +148,7 @@ xfs_bmbt_to_iomap(
 	else
 		iomap->bdev = target->bt_bdev;
 	iomap->flags = iomap_flags;
+	iomap->write_stream = ip->i_write_stream;
 
 	/*
 	 * If the inode is dirty for datasync purposes, let iomap know so it
-- 
2.25.1