From 021ba8e98fe5c6691b3cc3669faafa02403aa211 Mon Sep 17 00:00:00 2001
From: "Darrick J. Wong" <darrick.wong@oracle.com>
Date: Mon, 16 Apr 2018 23:07:36 -0700
Subject: [PATCH] xfs: cap the length of deduplication requests
Git-commit: 021ba8e98fe5c6691b3cc3669faafa02403aa211
Patch-mainline: v4.17-rc4
References: bsc#1132373, bsc#1132219

Since deduplication potentially has to read in all the pages in both
files in order to compare the contents, cap the deduplication request
length at MAX_RW_COUNT/2 (roughly 1GB) so that we have /some/ upper bound
on the request length and can't just lock up the kernel forever.  Found
by running generic/304 after commit 1ddae54555b62 ("common/rc: add
missing 'local' keywords").

Reported-by: matorola@gmail.com
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Acked-by: Anthony Iliopoulos <ailiopoulos@suse.com>

---
 fs/xfs/xfs_file.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index eed073cc4778..e70fb8ccecea 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -880,8 +880,18 @@ xfs_file_dedupe_range(
 	struct file	*dst_file,
 	u64		dst_loff)
 {
+	struct inode	*srci = file_inode(src_file);
+	u64		max_dedupe;
 	int		error;
 
+	/*
+	 * Since we have to read all these pages in to compare them, cut
+	 * it off at MAX_RW_COUNT/2 rounded down to the nearest block.
+	 * That means we won't do more than MAX_RW_COUNT IO per request.
+	 */
+	max_dedupe = (MAX_RW_COUNT >> 1) & ~(i_blocksize(srci) - 1);
+	if (len > max_dedupe)
+		len = max_dedupe;
 	error = xfs_reflink_remap_range(src_file, loff, dst_file, dst_loff,
 				     len, true);
 	if (error)
-- 
2.16.4