From: Patrick Farrell <paf@cray.com>
Date: Mon, 9 Jun 2014 18:26:27 +0000 (-0500)
Subject: LU-5153 fld: lsf_lock in update_from_controller
X-Git-Tag: 2.6.0-RC1~112
X-Git-Url: https://git.whamcloud.com/?p=fs%2Flustre-release.git;a=commitdiff_plain;h=f288434cd97d4ce6314054ff73fe0e9ee03eb139

LU-5153 fld: lsf_lock in update_from_controller

The lsf_lock mutex must be held for calls to
fld_index_create, and is currently taken before calls to
fld_insert_entry.

This patch adds a comment and an assertion to
fld_insert_entry, and takes the mutex for the call in
fld_update_from_controller.

Also adds subsystem description from Di Wang to header file.

Signed-off-by: Patrick Farrell <paf@cray.com>
Change-Id: I3dcc9a53589d128343d9f386eaf7265f39ff5840
Reviewed-on: http://review.whamcloud.com/10631
Tested-by: Jenkins
Reviewed-by: wangdi <di.wang@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
---

diff --git a/lustre/fld/fld_handler.c b/lustre/fld/fld_handler.c
index fbf0369..eae79ea 100644
--- a/lustre/fld/fld_handler.c
+++ b/lustre/fld/fld_handler.c
@@ -180,7 +180,10 @@ int fld_update_from_controller(const struct lu_env *env,
 			if (lsra->lsra_lsr[i].lsr_index != index)
 				GOTO(out, rc = -EINVAL);
 
+			mutex_lock(&fld->lsf_lock);
 			rc1 = fld_insert_entry(env, fld, &lsra->lsra_lsr[i]);
+			mutex_unlock(&fld->lsf_lock);
+
 			if (rc1 != 0)
 				GOTO(out, rc = rc1);
 		}
diff --git a/lustre/fld/fld_index.c b/lustre/fld/fld_index.c
index bcd795e..56042a0 100644
--- a/lustre/fld/fld_index.c
+++ b/lustre/fld/fld_index.c
@@ -159,6 +159,8 @@ out:
  * changed between declare and create.
  * Because the fld entry can only be increamental, so we will only check
  * whether it can be merged from the left.
+ *
+ * Caller must hold fld->lsf_lock
  **/
 int fld_index_create(const struct lu_env *env, struct lu_server_fld *fld,
 		     const struct lu_seq_range *new_range, struct thandle *th)
@@ -261,6 +263,19 @@ int fld_index_lookup(const struct lu_env *env, struct lu_server_fld *fld,
         RETURN(rc);
 }
 
+/**
+ * insert entry in fld store.
+ *
+ * \param  env    relevant lu_env
+ * \param  fld    fld store
+ * \param  range  range to be inserted
+ *
+ * \retval  0  success
+ * \retval  -ve error
+ *
+ * Caller must hold fld->lsf_lock
+ **/
+
 int fld_insert_entry(const struct lu_env *env,
 		     struct lu_server_fld *fld,
 		     const struct lu_seq_range *range)
@@ -269,6 +284,8 @@ int fld_insert_entry(const struct lu_env *env,
 	int rc;
 	ENTRY;
 
+	LASSERT(mutex_is_locked(&fld->lsf_lock));
+
 	th = dt_trans_create(env, lu2dt_dev(fld->lsf_obj->do_lu.lo_dev));
 	if (IS_ERR(th))
 		RETURN(PTR_ERR(th));
diff --git a/lustre/fld/fld_internal.h b/lustre/fld/fld_internal.h
index 515cf88..ae8dce1 100644
--- a/lustre/fld/fld_internal.h
+++ b/lustre/fld/fld_internal.h
@@ -35,6 +35,24 @@
  *
  * lustre/fld/fld_internal.h
  *
+ * Subsystem Description:
+ * FLD is FID Location Database, which stores where (IE, on which MDT)
+ * FIDs are located.
+ * The database is basically a record file, each record consists of a FID
+ * sequence range, MDT/OST index, and flags. The FLD for the whole FS
+ * is only stored on the sequence controller(MDT0) right now, but each target
+ * also has its local FLD, which only stores the local sequence.
+ *
+ * The FLD subsystem usually has two tasks:
+ * 1. maintain the database, i.e. when the sequence controller allocates
+ * new sequence ranges to some nodes, it will call the FLD API to insert the
+ * location information <sequence_range, node_index> in FLDB.
+ *
+ * 2. Handle requests from other nodes, i.e. if client needs to know where
+ * the FID is located, if it can not find the information in the local cache,
+ * it will send a FLD lookup RPC to the FLD service, and the FLD service will
+ * look up the FLDB entry and return the location information to client.
+ *
  * Author: Yury Umanets <umka@clusterfs.com>
  * Author: Tom WangDi <wangdi@clusterfs.com>
  */