feature/dht: Directory synchronization

Design doc: https://review.gluster.org/16876

Directory creation is now synchronized with blocking inodelk of the
parent on the hashed subvolume followed by the entrylk on the hashed
subvolume between dht_mkdir, dht_rmdir, dht_rename_dir and lookup
selfheal mkdir.

To maintain internal consistency of directories across all subvols of
dht, we need locks. Specifically we are interested in:

 1. Consistency of layout of a directory. Only one writer should modify
    the layout at a time. A writer (layout setting during directory heal
    as part of lookup) shouldn't modify the layout while there are
    readers (all other fops like create, mkdir etc., which consume
    layout) and readers shouldn't read the layout while a writer is in
    progress. Readers can read the layout simultaneously. Writer takes
    a WRITE inodelk on the directory (whose layout is being modified)
    across ALL subvols. Reader takes a READ inodelk on the directory
    (whose layout is being read) on ANY subvol.

 2. Consistency of directory namespace across subvols. The path and
    associated gfid should be same on all subvols. A gfid should not be
    associated with more than one path on any subvol. All fops that can
    change directory names (mkdir, rmdir, renamedir, directory creation
    phase in lookup-heal) takes an entrylk on hashed subvol of the
    directory.

 NOTE1: In point 2 above, since dht takes entrylk on hashed subvol of a
        directory, the transaction itself is a consumer of layout on
        parent directory. So, the transaction is a reader of parent
        layout and does an inodelk on parent directory just like any
        other layout reader. So a mkdir (dir/subdir) would:

     > Acquire a READ inodelk on "dir" on any subvol.
     > Acquire an entrylk (dir, "subdir") on hashed subvol of "subdir".
     > creates directory on hashed subvol and possibly on non-hashed subvols.
     > UNLOCK (entrylk)
     > UNLOCK (inodelk)

 NOTE2: mkdir fop while setting the layout of the directory being created
        is considered as a reader, but NOT a writer. The reason is for
        a fop which can consume the layout of a directory to come either
        of the following conditions has to be true:

     > mkdir syscall from application has to complete. In this case no
       need of synchronization.
     > A lookup issued on the directory racing with mkdir has to complete.
       Since layout setting by a lookup is considered as a writer, only
       one of either mkdir or lookup will set the layout.

Code re-organization:
   All the lock related routines are moved to "dht-lock.c" file.
   New wrapper function is introduced to take blocking inodelk
   followed by entrylk 'dht_protect_namespace'

Updates #191
Change-Id: I01569094dfbe1852de6f586475be79c1ba965a31
Signed-off-by: Kotresh HR <khiremat@redhat.com>
BUG: 1443373
Reviewed-on: https://review.gluster.org/15472
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
Reviewed-by: Raghavendra G <rgowdapp@redhat.com>
Smoke: Gluster Build System <jenkins@build.gluster.org>

1 files changed, 94 insertions, 0 deletions

diff --git a/xlators/cluster/dht/src/dht-lock.h b/xlators/cluster/dht/src/dht-lock.h
new file mode 100644
index 00000000000..0557858041e
--- /dev/null
+++ b/xlators/cluster/dht/src/dht-lock.h
@@ -0,0 +1,94 @@
+/*
+  Copyright (c) 2016 Red Hat, Inc. <http://www.redhat.com>
+  This file is part of GlusterFS.
+
+  This file is licensed to you under your choice of the GNU Lesser
+  General Public License, version 3 or any later version (LGPLv3 or
+  later), or the GNU General Public License, version 2 (GPLv2), in all
+  cases as published by the Free Software Foundation.
+*/
+
+#ifndef _DHT_LOCK_H
+#define _DHT_LOCK_H
+
+#include "xlator.h"
+#include "dht-common.h"
+
+void
+dht_lock_array_free (dht_lock_t **lk_array, int count);
+
+int32_t
+dht_lock_count (dht_lock_t **lk_array, int lk_count);
+
+dht_lock_t *
+dht_lock_new (xlator_t *this, xlator_t *xl, loc_t *loc, short type,
+              const char *domain, const char *basename);
+
+int32_t
+dht_unlock_entrylk_wrapper (call_frame_t *, dht_elock_wrap_t *);
+
+void
+dht_blocking_entrylk_rec (call_frame_t *frame, int i);
+
+int
+dht_blocking_entrylk (call_frame_t *frame, dht_lock_t **lk_array,
+                      int lk_count, dht_reaction_type_t reaction,
+                      fop_inodelk_cbk_t entrylk_cbk);
+
+int32_t
+dht_unlock_inodelk (call_frame_t *frame, dht_lock_t **lk_array, int lk_count,
+                     fop_inodelk_cbk_t inodelk_cbk);
+
+int32_t
+dht_unlock_inodelk_wrapper (call_frame_t *, dht_ilock_wrap_t *);
+
+/* Acquire non-blocking inodelk on a list of xlators.
+ *
+ * @lk_array: array of lock requests lock on.
+ *
+ * @lk_count: number of locks in @lk_array
+ *
+ * @inodelk_cbk: will be called after inodelk replies are received
+ *
+ * @retval: -1 if stack_winding inodelk fails. 0 otherwise.
+ *          inodelk_cbk is called with appropriate error on errors.
+ *          On failure to acquire lock on all members of list, successful
+ *          locks are unlocked before invoking cbk.
+ */
+
+int
+dht_nonblocking_inodelk (call_frame_t *frame, dht_lock_t **lk_array,
+                         int lk_count, fop_inodelk_cbk_t inodelk_cbk);
+
+void
+dht_blocking_inodelk_rec (call_frame_t *frame, int i);
+
+/* same as dht_nonblocking_inodelk, but issues sequential blocking locks on
+ * @lk_array directly. locks are issued on some order which remains same
+ * for a list of xlators (irrespective of order of xlators within list).
+ */
+
+int
+dht_blocking_inodelk (call_frame_t *frame, dht_lock_t **lk_array,
+                      int lk_count, dht_reaction_type_t reaction,
+                      fop_inodelk_cbk_t inodelk_cbk);
+
+int32_t
+dht_blocking_entrylk_after_inodelk (call_frame_t *frame, void *cookie,
+                                    xlator_t *this, int32_t op_ret,
+                                    int32_t op_errno, dict_t *xdata);
+
+int32_t
+dht_blocking_entrylk_after_inodelk_rename (call_frame_t *frame, void *cookie,
+                                           xlator_t *this, int32_t op_ret,
+                                           int32_t op_errno, dict_t *xdata);
+
+void
+dht_unlock_namespace (call_frame_t *, dht_dir_transaction_t *);
+
+int
+dht_protect_namespace (call_frame_t *frame, loc_t *loc, xlator_t *subvol,
+                       struct dht_namespace *ns,
+                       fop_entrylk_cbk_t ns_cbk);
+
+#endif   /* _DHT_LOCK_H */