target/file: Do not return error for UNMAP if length is zero

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@gmail.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

diff --git a/drivers/target/target_core_file.c b/drivers/target/target_core_file.c
index c629817a8854bea49a18c6b3f93f3f8923f99079..9b2c0c773022c0013de3bbce849ca78af117b2c5 100644 (file)
--- a/drivers/target/target_core_file.c
+++ b/drivers/target/target_core_file.c
@@ -482,6 +482,10 @@ 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)