[PATCH v11 2/2] xfs: add FALLOC_FL_WRITE_ZEROES to XFS code base

[Lukas Herbolt <lukas@herbolt.com>]

Add support for FALLOC_FL_WRITE_ZEROES if the underlying device
enable the unmap write zeroes operation.

Co-developed-by: Pankaj Raghav <p.raghav@samsung.com>
Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
Signed-off-by: Lukas Herbolt <lukas@herbolt.com>

---
 v11 changes:
	- split into 2 patches separating the bmapi_flags addition
	- 2 step allocation, to avoid zeroing beyond EOF

 fs/xfs/xfs_file.c | 41 +++++++++++++++++++++++++++++------------
 1 file changed, 29 insertions(+), 12 deletions(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index fd049a1fc9c6..f8c1611e3267 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1293,29 +1293,45 @@ xfs_falloc_zero_range(
 	unsigned int		blksize = i_blocksize(inode);
 	loff_t			new_size = 0;
 	int			error;
+	bool                    need_convert = false;
 
 	trace_xfs_zero_file_space(ip);
 
+	if (mode & FALLOC_FL_WRITE_ZEROES) {
+		if (xfs_is_always_cow_inode(ip) ||
+		    !bdev_write_zeroes_unmap_sectors(
+			    xfs_inode_buftarg(ip)->bt_bdev))
+			return -EOPNOTSUPP;
+		need_convert = true;
+	}
+
 	error = xfs_falloc_newsize(file, mode, offset, len, &new_size);
 	if (error)
 		return error;
 
 	if (xfs_falloc_force_zero(ip, ac)) {
 		error = xfs_zero_range(ip, offset, len, ac, NULL);
-	} else {
-		error = xfs_free_file_space(ip, offset, len, ac);
-		if (error)
-			return error;
-
-		len = round_up(offset + len, blksize) -
-			round_down(offset, blksize);
-		offset = round_down(offset, blksize);
-		error = xfs_alloc_file_space(ip, offset, len,
-				XFS_BMAPI_PREALLOC);
+		goto set_filesize;
 	}
+	error = xfs_free_file_space(ip, offset, len, ac);
 	if (error)
 		return error;
-	return xfs_falloc_setsize(file, new_size);
+
+	len = round_up(offset + len, blksize) - round_down(offset, blksize);
+	offset = round_down(offset, blksize);
+	error = xfs_alloc_file_space(ip, offset, len, XFS_BMAPI_PREALLOC);
+
+set_filesize:
+	if (error)
+		return error;
+
+	error = xfs_falloc_setsize(file, new_size);
+	if (error)
+		return error;
+	if (need_convert)
+		error = xfs_alloc_file_space(ip, offset, len,
+				XFS_BMAPI_CONVERT | XFS_BMAPI_ZERO);
+	return error;
 }
 
 static int
@@ -1377,7 +1393,7 @@ xfs_falloc_allocate_range(
 		(FALLOC_FL_ALLOCATE_RANGE | FALLOC_FL_KEEP_SIZE |	\
 		 FALLOC_FL_PUNCH_HOLE |	FALLOC_FL_COLLAPSE_RANGE |	\
 		 FALLOC_FL_ZERO_RANGE |	FALLOC_FL_INSERT_RANGE |	\
-		 FALLOC_FL_UNSHARE_RANGE)
+		 FALLOC_FL_UNSHARE_RANGE | FALLOC_FL_WRITE_ZEROES)
 
 STATIC long
 __xfs_file_fallocate(
@@ -1420,6 +1436,7 @@ __xfs_file_fallocate(
 	case FALLOC_FL_INSERT_RANGE:
 		error = xfs_falloc_insert_range(file, offset, len);
 		break;
+	case FALLOC_FL_WRITE_ZEROES:
 	case FALLOC_FL_ZERO_RANGE:
 		error = xfs_falloc_zero_range(file, mode, offset, len, ac);
 		break;
-- 
2.53.0