[PATCH AUTOSEL for 4.9 106/156] target/file: Do not return error for UNMAP if length is zero

[alexander . levin]

From: Jiang Yi <jiangyil...@gmail.com>

[ 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 <jiangyil...@gmail.com>
Signed-off-by: Nicholas Bellinger <n...@linux-iscsi.org>
Signed-off-by: Sasha Levin <alexander.le...@verizon.com>
---
 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 29f807b29e74..97928b42ad62 100644
--- a/drivers/target/target_core_file.c
+++ b/drivers/target/target_core_file.c
@@ -466,6 +466,10 @@ fd_execute_unmap(struct se_cmd *cmd, 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