Patch "target/file: Do not return error for UNMAP if length is zero" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

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

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
target-file-do-not-return-error-for-unmap-if-length-is-zero.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Jiang Yi <[email protected]>
Date: Fri, 11 Aug 2017 11:29:44 +0800
Subject: target/file: Do not return error for UNMAP if length is zero

From: Jiang Yi <[email protected]>

[ 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.

---
 drivers/target/target_core_file.c |    4 ++++
 1 file changed, 4 insertions(+)

@@ -466,6 +466,10 @@ fd_execute_unmap(struct se_cmd *cmd, sec
 	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)

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/target-file-do-not-return-error-for-unmap-if-length-is-zero.patch