dht: add "nuke" functionality for efficient server-side deletion

This turns a special xattr into an rmdir with flags set.  When that hits
the posix translator on the server side, that causes the file/directory
to be moved into the special "landfill" directory.  From there, the
posix janitor thread will take care of deleting it entirely on the
server side - traversing it recursively if necessary.  A couple of
secondary issues were fixed to make this effective.

 * FUSE now ensures that setxattr values are NUL terminated.

 * The janitor thread now gets woken up immediately when something is
   placed in 'landfill' instead of only when file descriptors need to be
   closed.

 * The default landfill-emptying interval was reduced to 10s.

To use the feature, issue a setxattr something like this:

   setfattr -n glusterfs.dht.nuke -v "" /mnt/glusterfs/vol/some_dir

The value doesn't actually matter; the mere receipt of a request with
this key is sufficient.  Some day it might be useful to allow setting a
required value as a sort of password, so that only those who know it can
access the underlying special functionality.

Change-Id: I8a343c2cdb40a76d5a06c707191fb67babb8514f
Signed-off-by: Jeff Darcy <jdarcy@redhat.com>
Reviewed-on: http://review.gluster.org/13878
Smoke: Gluster Build System <jenkins@build.gluster.com>
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
CentOS-regression: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Raghavendra G <rgowdapp@redhat.com>

1 files changed, 41 insertions, 0 deletions

diff --git a/tests/features/nuke.t b/tests/features/nuke.t
new file mode 100755
index 00000000000..ad9479ffaa5
--- /dev/null
+++ b/tests/features/nuke.t
@@ -0,0 +1,41 @@
+#!/bin/bash
+
+. $(dirname $0)/../include.rc
+
+create_files () {
+	mkdir $1
+	for i in $(seq 0 99); do
+		mkdir $1/dir$i
+		for j in $(seq 0 99); do
+			touch $1/dir$i/file$j
+		done
+	done
+}
+
+count_files () {
+	ls $1 | wc -l
+}
+
+LANDFILL=$B0/${V0}1/.glusterfs/landfill
+
+TEST glusterd
+
+TEST $CLI volume create $V0 $H0:$B0/${V0}1
+TEST $CLI volume start $V0
+TEST $GFS -s $H0 --volfile-id $V0 $M0
+
+TEST create_files $M0/foo
+TEST [ $(count_files $LANDFILL) = "0" ]
+
+# This should immediately send the whole directory to the landfill.
+TEST setfattr -n glusterfs.dht.nuke -v trinity $M0/foo
+
+# Make sure the directory's not visible on the mountpoint, and is visible in
+# the brick's landfill.
+TEST ! ls $M0/foo
+TEST [ $(count_files $LANDFILL) = "1" ]
+
+# Make sure the janitor thread cleans it up in a timely fashion.
+EXPECT_WITHIN 20 "0" count_files $LANDFILL
+
+cleanup