posix/lock: implement meta-lock/unlock functionality

problem : The lock state needs to be protected when rebalance is reading the
lock state on the source. Otherwise there will be locks left unmigrated.
Hence, to synchronize incoming lock requests with lock-migration, meta lock
is needed. Any new lock request will be queued if there is an active meta-lock
and with sucessful lock migration, will be unwound with EREMOTE, so that
dht module can wind the request to the correct destination.

On a successful lock migration, "pl_inode->migrated" flag is enabled. Hence,
any further request would be unwound with EREMOTE and will be redirected to
new destination.

More details can be found here:
https://github.com/gluster/glusterfs-specs/blob/master/accepted/Lock-Migration.md

design discussion:
https://www.gluster.org/pipermail/gluster-devel/2016-January/048088.html

Change-Id: Ief033d5652b5ca4ba6f499110a521cae283d6aba
BUG: 1331720
Signed-off-by: Susant Palai <spalai@redhat.com>
Reviewed-on: http://review.gluster.org/14251
Tested-by: Prasanna Kumar Kalever <pkalever@redhat.com>
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, 19 insertions, 0 deletions

diff --git a/xlators/features/locks/src/locks.h b/xlators/features/locks/src/locks.h
index b8763091d00..e363f425b65 100644
--- a/xlators/features/locks/src/locks.h
+++ b/xlators/features/locks/src/locks.h
@@ -62,6 +62,8 @@ struct __posix_lock {
         char              *client_uid;
         gf_lkowner_t       owner;
         pid_t              client_pid;    /* pid of client process */
+
+        int                blocking;
 };
 typedef struct __posix_lock posix_lock_t;
 
@@ -155,6 +157,10 @@ struct __pl_inode {
         struct list_head reservelk_list;        /* list of reservelks */
         struct list_head blocked_reservelks;        /* list of blocked reservelks */
         struct list_head blocked_calls;  /* List of blocked lock calls while a reserve is held*/
+        struct list_head metalk_list;    /* Meta lock list */
+         /* This is to store the incoming lock
+            requests while meta lock is enabled */
+        struct list_head queued_locks;
         int              mandatory;      /* if mandatory locking is enabled */
 
         inode_t          *refkeeper;     /* hold refs on an inode while locks are
@@ -167,6 +173,18 @@ struct __pl_inode {
 };
 typedef struct __pl_inode pl_inode_t;
 
+struct __pl_metalk {
+        pthread_mutex_t mutex;
+        /* For pl_inode meta lock list */
+        struct list_head        list;
+        /* For pl_ctx_t list */
+        struct list_head        client_list;
+        char                   *client_uid;
+
+        pl_inode_t             *pl_inode;
+        int                     ref;
+};
+typedef struct __pl_metalk pl_meta_lock_t;
 
 typedef struct {
         mlk_mode_t      mandatory_mode; /* holds current mandatory locking mode */
@@ -206,6 +224,7 @@ typedef struct _locks_ctx {
         pthread_mutex_t      lock;
         struct list_head     inodelk_lockers;
         struct list_head     entrylk_lockers;
+        struct list_head     metalk_list;
 } pl_ctx_t;