From: Darrick J. Wong <darrick.wong@oracle.com>
Date: Mon, 29 Oct 2018 23:41:01 +0000 (+1100)
Subject: vfs: skip zero-length dedupe requests
X-Git-Tag: v4.20-rc1~23^2~22
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=9aae20500d9cd3e7d55d0536d359bdd1c869db89;p=users%2Fdwmw2%2Flinux.git

vfs: skip zero-length dedupe requests

Don't bother calling the filesystem for a zero-length dedupe request;
we can return zero and exit.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
---

diff --git a/fs/read_write.c b/fs/read_write.c
index 0f0a6efdd502c..f5395d8da741e 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -2009,6 +2009,11 @@ int vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos,
 	if (!dst_file->f_op->dedupe_file_range)
 		goto out_drop_write;
 
+	if (len == 0) {
+		ret = 0;
+		goto out_drop_write;
+	}
+
 	ret = dst_file->f_op->dedupe_file_range(src_file, src_pos,
 						dst_file, dst_pos, len);
 out_drop_write: