DAOS-18870 DFS: Reserve a new DFS OID for GIT.

src/client/dfs/common.c

@@ -788,7 +788,7 @@ set_sb_params(bool for_update, daos_iod_t *iods, daos_key_t *dkey)
 
 int
 open_sb(daos_handle_t coh, bool create, bool punch, int omode, daos_obj_id_t super_oid,
-	dfs_attr_t *attr, daos_handle_t *oh, dfs_layout_ver_t *ver)
+	dfs_attr_t *attr, daos_handle_t *oh, dfs_layout_ver_t *ver, dfs_sb_ver_t *sb_ver_out)
 {
 	d_sg_list_t      sgls[SB_AKEYS];
 	d_iov_t          sg_iovs[SB_AKEYS];
@@ -919,6 +919,8 @@ open_sb(daos_handle_t coh, bool create, bool punch, int omode, daos_obj_id_t sup
 	D_DEBUG(DB_ALL, "DFS Library Layout version: %d\n", DFS_LAYOUT_VERSION);
 
 	*ver                    = layout_ver;
+	if (sb_ver_out)
+		*sb_ver_out = sb_ver;
 	attr->da_chunk_size     = (chunk_size) ? chunk_size : DFS_DEFAULT_CHUNK_SIZE;
 	attr->da_oclass_id      = oclass;
 	attr->da_dir_oclass_id  = dir_oclass;

src/client/dfs/cont.c

@@ -1,6 +1,6 @@
 /**
- * (C) Copyright 2018-2024 Intel Corporation.
- * (C) Copyright 2025-2026 Hewlett Packard Enterprise Development LP
+ * Copyright 2018-2024 Intel Corporation.
+ * Copyright 2025-2026 Hewlett Packard Enterprise Development LP
  *
  * SPDX-License-Identifier: BSD-2-Clause-Patent
  */
@@ -290,8 +290,18 @@ dfs_cont_create(daos_handle_t poh, uuid_t *cuuid, dfs_attr_t *attr, daos_handle_
 		D_GOTO(err_prop, rc = daos_der2errno(rc));
 	}
 
-	/* store SB & root OIDs as container property */
-	roots.cr_oids[2] = roots.cr_oids[3]          = DAOS_OBJ_NIL;
+	/* select oclass and generate GIT (Global Inode Table) OID */
+	roots.cr_oids[2].lo = RESERVED_LO;
+	roots.cr_oids[2].hi = GIT_HI;
+	rc = daos_obj_generate_oid_by_rf(poh, rf, &roots.cr_oids[2], 0, dattr.da_dir_oclass_id,
+					 dir_oclass_hint, 0, pa_domain);
+	if (rc) {
+		D_ERROR("Failed to generate GIT OID " DF_RC "\n", DP_RC(rc));
+		D_GOTO(err_prop, rc = daos_der2errno(rc));
+	}
+
+	/* store SB, root & GIT OIDs as container property */
+	roots.cr_oids[3] = DAOS_OBJ_NIL;
 
 	if (roots_entry == NULL) {
 		/* need to add roots prop to list */
@@ -330,7 +340,7 @@ dfs_cont_create(daos_handle_t poh, uuid_t *cuuid, dfs_attr_t *attr, daos_handle_
 	}
 
 	/** Create SB */
-	rc = open_sb(coh, true, false, DAOS_OO_RW, roots.cr_oids[0], &dattr, &super_oh, NULL);
+	rc = open_sb(coh, true, false, DAOS_OO_RW, roots.cr_oids[0], &dattr, &super_oh, NULL, NULL);
 	if (rc)
 		D_GOTO(err_close, rc);
 
@@ -1179,7 +1189,7 @@ dfs_recreate_sb(daos_handle_t coh, dfs_attr_t *attr)
 	}
 
 	/** Recreate SB */
-	rc = open_sb(coh, true, true, DAOS_OO_RW, roots->cr_oids[0], attr, &super_oh, NULL);
+	rc = open_sb(coh, true, true, DAOS_OO_RW, roots->cr_oids[0], attr, &super_oh, NULL, NULL);
 	if (rc)
 		D_GOTO(out_prop, rc);
 
@@ -1255,7 +1265,8 @@ dfs_relink_root(daos_handle_t coh)
 	}
 
 	/** Verify SB */
-	rc = open_sb(coh, false, false, DAOS_OO_RW, roots->cr_oids[0], &attr, &super_oh, &layout_v);
+	rc = open_sb(coh, false, false, DAOS_OO_RW, roots->cr_oids[0], &attr, &super_oh, &layout_v,
+		     NULL);
 	if (rc)
 		D_GOTO(out_prop, rc);
 

src/client/dfs/dfs_internal.h

@@ -1,5 +1,6 @@
 /**
  * (C) Copyright 2019-2024 Intel Corporation.
+ * (C) Copyright 2026 Hewlett Packard Enterprise Development LP
  *
  * SPDX-License-Identifier: BSD-2-Clause-Patent
  */
@@ -53,7 +54,7 @@
 /** Magic Value */
 #define DFS_SB_MAGIC       0xda05df50da05df50
 /** DFS SB version value */
-#define DFS_SB_VERSION     2
+#define DFS_SB_VERSION     3
 /** DFS Layout Version Value */
 #define DFS_LAYOUT_VERSION 3
 /** Magic value for serializing / deserializing a DFS handle */
@@ -94,6 +95,10 @@
 #define RESERVED_LO        0
 #define SB_HI              0
 #define ROOT_HI            1
+#define GIT_HI             2
+
+/** SB version that introduced hardlink support (GIT object) */
+#define DFS_MIN_GIT_SB_VERSION 3
 
 /** DFS mode mask (3rd bit) */
 #define MODE_MASK          (1 << 2)
@@ -175,6 +180,10 @@ struct dfs {
 	daos_obj_id_t        super_oid;
 	/** Open object handle of SB */
 	daos_handle_t        super_oh;
+	/** Global Index Table object OID */
+	daos_obj_id_t        git_oid;
+	/** Open object handle of GIT */
+	daos_handle_t        git_oh;
 	/** Root object info */
 	dfs_obj_t            root;
 	/** DFS container attributes (Default chunk size, oclass, etc.) */
@@ -361,7 +370,7 @@ oid_gen(dfs_t *dfs, daos_oclass_id_t oclass, bool file, daos_obj_id_t *oid)
 	/** set oid and lo, bump the current hi value */
 	oid->lo = dfs->oid.lo;
 	daos_obj_oid_cycle(&dfs->oid);
-	if (unlikely(dfs->oid.lo == RESERVED_LO && dfs->oid.hi <= 1))
+	if (unlikely(dfs->oid.lo == RESERVED_LO && dfs->oid.hi <= GIT_HI))
 		daos_obj_oid_cycle(&dfs->oid); /* Avoid reserved oids */
 	oid->hi = dfs->oid.hi;
 	D_MUTEX_UNLOCK(&dfs->lock);
@@ -402,7 +411,7 @@ get_oclass_hints(const char *hints, daos_oclass_hints_t *dir_hints, daos_oclass_
 		 uint64_t rf);
 int
 open_sb(daos_handle_t coh, bool create, bool punch, int omode, daos_obj_id_t super_oid,
-	dfs_attr_t *attr, daos_handle_t *oh, dfs_layout_ver_t *ver);
+	dfs_attr_t *attr, daos_handle_t *oh, dfs_layout_ver_t *ver, dfs_sb_ver_t *sb_ver);
 int
 insert_entry(dfs_layout_ver_t ver, daos_handle_t oh, daos_handle_t th, const char *name, size_t len,
 	     uint64_t flags, struct dfs_entry *entry);

src/client/dfs/mnt.c

@@ -1,6 +1,6 @@
 /**
- * (C) Copyright 2018-2024 Intel Corporation.
- * (C) Copyright 2026 Hewlett Packard Enterprise Development LP
+ * Copyright 2018-2024 Intel Corporation.
+ * Copyright 2026 Hewlett Packard Enterprise Development LP
  *
  * SPDX-License-Identifier: BSD-2-Clause-Patent
  */
@@ -573,6 +573,7 @@ dfs_mount_int(daos_handle_t poh, daos_handle_t coh, int flags, daos_epoch_t epoc
 	struct daos_prop_entry    *entry;
 	struct daos_prop_co_roots *roots;
 	struct dfs_entry           root_dir;
+	dfs_sb_ver_t               sb_ver;
 	int                        amode, omode;
 	int                        rc;
 	int                        i;
@@ -642,10 +643,14 @@ dfs_mount_int(daos_handle_t poh, daos_handle_t coh, int flags, daos_epoch_t epoc
 
 	/** Verify SB */
 	rc = open_sb(coh, false, false, omode, dfs->super_oid, &dfs->attr, &dfs->super_oh,
-		     &dfs->layout_v);
+		     &dfs->layout_v, &sb_ver);
 	if (rc)
 		D_GOTO(err_dfs, rc);
 
+	/** Load GIT OID only if SB version supports hardlinks */
+	if (sb_ver >= DFS_MIN_GIT_SB_VERSION)
+		dfs->git_oid = roots->cr_oids[2];
+
 	/** set oid hints for files and dirs */
 	if (dfs->attr.da_hints[0] != 0) {
 		entry = daos_prop_entry_get(prop, DAOS_PROP_CO_REDUN_FAC);
@@ -717,17 +722,26 @@ dfs_mount_int(daos_handle_t poh, daos_handle_t coh, int flags, daos_epoch_t epoc
 		dfs->root_stbuf.st_atim.tv_nsec = root_dir.mtime_nano;
 	}
 
+	/** Open Global Index Table object */
+	if (!daos_obj_id_is_nil(dfs->git_oid)) {
+		rc = daos_obj_open(dfs->coh, dfs->git_oid, omode, &dfs->git_oh, NULL);
+		if (rc) {
+			D_ERROR("Failed to open GIT object: " DF_RC "\n", DP_RC(rc));
+			D_GOTO(err_root, rc = daos_der2errno(rc));
+		}
+	}
+
 	/** if RW, allocate an OID for the namespace */
 	if (amode == O_RDWR) {
 		dfs->last_hi = (unsigned int)d_rand();
-		/** Avoid potential conflict with SB or ROOT */
-		if (dfs->last_hi <= 1)
-			dfs->last_hi = 2;
+		/** Avoid potential conflict with SB, ROOT, or GIT */
+		if (dfs->last_hi <= GIT_HI)
+			dfs->last_hi = GIT_HI + 1;
 
 		rc = daos_cont_alloc_oids(coh, 1, &dfs->oid.lo, NULL);
 		if (rc) {
 			D_ERROR("daos_cont_alloc_oids() Failed, " DF_RC "\n", DP_RC(rc));
-			D_GOTO(err_root, rc = daos_der2errno(rc));
+			D_GOTO(err_git, rc = daos_der2errno(rc));
 		}
 
 		dfs->oid.hi = dfs->last_hi;
@@ -743,6 +757,9 @@ dfs_mount_int(daos_handle_t poh, daos_handle_t coh, int flags, daos_epoch_t epoc
 	daos_prop_free(prop);
 	return rc;
 
+err_git:
+	if (daos_handle_is_valid(dfs->git_oh))
+		daos_obj_close(dfs->git_oh, NULL);
 err_root:
 	daos_obj_close(dfs->root.oh, NULL);
 err_super:
@@ -850,6 +867,8 @@ dfs_umount(dfs_t *dfs)
 	if (daos_handle_is_valid(dfs->th))
 		daos_tx_close(dfs->th, NULL);
 
+	if (daos_handle_is_valid(dfs->git_oh))
+		daos_obj_close(dfs->git_oh, NULL);
 	daos_obj_close(dfs->root.oh, NULL);
 	daos_obj_close(dfs->super_oh, NULL);
 
@@ -983,6 +1002,7 @@ struct dfs_glob {
 	daos_obj_id_t    super_oid;
 	daos_obj_id_t    root_oid;
 	daos_epoch_t     th_epoch;
+	daos_obj_id_t    git_oid;
 };
 
 static inline void
@@ -1065,6 +1085,7 @@ dfs_local2global(dfs_t *dfs, d_iov_t *glob)
 	dfs_params->amode       = dfs->amode;
 	dfs_params->super_oid   = dfs->super_oid;
 	dfs_params->root_oid    = dfs->root.oid;
+	dfs_params->git_oid     = dfs->git_oid;
 	dfs_params->uid         = dfs->uid;
 	dfs_params->gid         = dfs->gid;
 	dfs_params->id          = dfs->attr.da_id;
@@ -1144,6 +1165,7 @@ dfs_global2local(daos_handle_t poh, daos_handle_t coh, int flags, d_iov_t glob,
 	dfs->super_oid       = dfs_params->super_oid;
 	dfs->root.oid        = dfs_params->root_oid;
 	dfs->root.parent_oid = dfs->super_oid;
+	dfs->git_oid         = dfs_params->git_oid;
 	if (daos_obj_id_is_nil(dfs->super_oid) || daos_obj_id_is_nil(dfs->root.oid)) {
 		D_ERROR("Invalid superblock or root object ID\n");
 		D_FREE(dfs);
@@ -1179,6 +1201,17 @@ dfs_global2local(daos_handle_t poh, daos_handle_t coh, int flags, d_iov_t glob,
 		D_GOTO(err_dfs, rc = daos_der2errno(rc));
 	}
 
+	/* Open GIT (Global Index Table) Object */
+	if (!daos_obj_id_is_nil(dfs->git_oid)) {
+		rc = daos_obj_open(coh, dfs->git_oid, obj_mode, &dfs->git_oh, NULL);
+		if (rc) {
+			D_ERROR("daos_obj_open() failed for GIT, " DF_RC "\n", DP_RC(rc));
+			daos_obj_close(dfs->super_oh, NULL);
+			daos_obj_close(dfs->root.oh, NULL);
+			D_GOTO(err_dfs, rc = daos_der2errno(rc));
+		}
+	}
+
 	/** Create transaction handle */
 	dfs->th_epoch = dfs_params->th_epoch;
 	if (dfs->th_epoch == DAOS_EPOCH_MAX) {
@@ -1189,6 +1222,8 @@ dfs_global2local(daos_handle_t poh, daos_handle_t coh, int flags, d_iov_t glob,
 			D_ERROR("daos_tx_open_snap() failed, " DF_RC "\n", DP_RC(rc));
 			daos_obj_close(dfs->super_oh, NULL);
 			daos_obj_close(dfs->root.oh, NULL);
+			if (daos_handle_is_valid(dfs->git_oh))
+				daos_obj_close(dfs->git_oh, NULL);
 			D_GOTO(err_dfs, rc = daos_der2errno(rc));
 		}
 	}