storage/posix: Add limit to number of hard links.

Summary:
Too may hard links blow up btrfs by exceeding max xattr size (recordign
pgfid for each hardlink). Add a limit to prevent this explosion.

This is a port D4682329 to 3.8

Reviewed By: sshreyas

Change-Id: I614a247834fb8f2b2743c0c67d11cefafff0dbaa
Reviewed-on: https://review.gluster.org/18232
Reviewed-by: Shreyas Siravara <sshreyas@fb.com>
CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
Smoke: Gluster Build System <jenkins@build.gluster.org>

1 files changed, 44 insertions, 0 deletions

diff --git a/tests/basic/hardlink-limit.t b/tests/basic/hardlink-limit.t
new file mode 100644
index 00000000000..e90a3ce427c
--- /dev/null
+++ b/tests/basic/hardlink-limit.t
@@ -0,0 +1,44 @@
+#!/bin/bash
+
+. $(dirname $0)/../include.rc
+. $(dirname $0)/../volume.rc
+. $(dirname $0)/../dht.rc
+
+cleanup;
+
+TEST glusterd
+TEST pidof glusterd
+TEST $CLI volume info;
+
+TEST $CLI volume create $V0 replica 2  $H0:$B0/${V0}{1,2,3,4};
+
+EXPECT "$V0" volinfo_field $V0 'Volume Name';
+EXPECT 'Created' volinfo_field $V0 'Status';
+EXPECT '4' brick_count $V0
+
+TEST $CLI volume start $V0;
+EXPECT 'Started' volinfo_field $V0 'Status';
+TEST $CLI volume set $V0 storage.max-hardlinks 3
+TEST glusterfs -s $H0 --volfile-id $V0 $M0;
+
+TEST dd if=/dev/zero of=$M0/testfile count=1
+
+# max-hardlinks is 3, should be able to create 2 links.
+TEST link $M0/testfile $M0/testfile.link1
+TEST link $M0/testfile $M0/testfile.link2
+
+# But not 3.
+TEST ! link $M0/testfile $M0/testfile.link3
+# If we remove one...
+TEST rm $M0/testfile.link1
+# Now we can add one.
+TEST link $M0/testfile $M0/testfile.link3
+
+# But not another
+TEST ! link $M0/testfile $M0/testfile.link4
+
+# Unless we disable the limit...
+TEST $CLI volume set $V0 storage.max-hardlinks 0
+TEST link $M0/testfile $M0/testfile.link4
+
+cleanup;