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, 8 insertions, 1 deletions

diff --git a/xlators/mount/fuse/src/fuse-bridge.c b/xlators/mount/fuse/src/fuse-bridge.c
index c6c38f3145b..aca1b3d14fd 100644
--- a/xlators/mount/fuse/src/fuse-bridge.c
+++ b/xlators/mount/fuse/src/fuse-bridge.c
@@ -3292,7 +3292,14 @@ fuse_setxattr (xlator_t *this, fuse_in_header_t *finh, void *msg)
         }
 
         if (fsi->size > 0) {
-                dict_value = memdup (value, fsi->size);
+                /*
+                 * Many translators expect setxattr values to be strings, but
+                 * neither dict_get_str nor data_to_str do any checking or
+                 * fixups to make sure that's the case.  To avoid nasty
+                 * surprises, allocate an extra byte and add a NUL here.
+                 */
+                dict_value = memdup (value, fsi->size+1);
+                dict_value[fsi->size] = '\0';
         }
         dict_set (state->xattr, newkey,
                   data_from_dynptr ((void *)dict_value, fsi->size));