[PATCH AUTOSEL for 3.18 40/59] target/file: Do not return error for UNMAP if length is zero

[alexander . levin]

From: Jiang Yi <jiangyilism@xxxxxxxxx>

[ Upstream commit 594e25e73440863981032d76c9b1e33409ceff6e ]

The function fd_execute_unmap() in target_core_file.c calles

ret = file->f_op->fallocate(file, mode, pos, len);

Some filesystems implement fallocate() to return error if
length is zero (e.g. btrfs) but according to SCSI Block
Commands spec UNMAP should return success for zero length.

Signed-off-by: Jiang Yi <jiangyilism@xxxxxxxxx>
Signed-off-by: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
---
 drivers/target/target_core_file.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/target/target_core_file.c b/drivers/target/target_core_file.c
index 9233b653cc72..98dd0044dca3 100644
--- a/drivers/target/target_core_file.c
+++ b/drivers/target/target_core_file.c
@@ -592,6 +592,10 @@ fd_do_unmap(struct se_cmd *cmd, void *priv, sector_t lba, sector_t nolb)
 	struct inode *inode = file->f_mapping->host;
 	int ret;
 
+	if (!nolb) {
+		return 0;
+	}
+
 	if (cmd->se_dev->dev_attrib.pi_prot_type) {
 		ret = fd_do_prot_unmap(cmd, lba, nolb);
 		if (ret)
-- 
2.11.0