pnfs: only tear down lsegs that precede seqid in LAYOUTRETURN args

LAYOUTRETURN is "special" in that servers and clients are expected to
work with old stateids. When the client sends a LAYOUTRETURN with an old
stateid in it then the server is expected to only tear down layout
segments that were present when that seqid was current. Ensure that the
client handles its accounting accordingly.

Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 3ad6bd3..21ff53f 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -270,7 +270,7 @@
 	};
 
 	set_bit(NFS_LAYOUT_INVALID_STID, &lo->plh_flags);
-	return pnfs_mark_matching_lsegs_invalid(lo, lseg_list, &range);
+	return pnfs_mark_matching_lsegs_invalid(lo, lseg_list, &range, 0);
 }
 
 static int
@@ -308,7 +308,7 @@
 
 	spin_lock(&inode->i_lock);
 	pnfs_layout_set_fail_bit(lo, pnfs_iomode_to_fail_bit(iomode));
-	pnfs_mark_matching_lsegs_invalid(lo, &head, &range);
+	pnfs_mark_matching_lsegs_invalid(lo, &head, &range, 0);
 	spin_unlock(&inode->i_lock);
 	pnfs_free_lseg_list(&head);
 	dprintk("%s Setting layout IOMODE_%s fail bit\n", __func__,
@@ -522,13 +522,35 @@
 	return rv;
 }
 
-/* Returns count of number of matching invalid lsegs remaining in list
- * after call.
+/*
+ * Compare 2 layout stateid sequence ids, to see which is newer,
+ * taking into account wraparound issues.
+ */
+static bool pnfs_seqid_is_newer(u32 s1, u32 s2)
+{
+	return (s32)(s1 - s2) > 0;
+}
+
+/**
+ * pnfs_mark_matching_lsegs_invalid - tear down lsegs or mark them for later
+ * @lo: layout header containing the lsegs
+ * @tmp_list: list head where doomed lsegs should go
+ * @recall_range: optional recall range argument to match (may be NULL)
+ * @seq: only invalidate lsegs obtained prior to this sequence (may be 0)
+ *
+ * Walk the list of lsegs in the layout header, and tear down any that should
+ * be destroyed. If "recall_range" is specified then the segment must match
+ * that range. If "seq" is non-zero, then only match segments that were handed
+ * out at or before that sequence.
+ *
+ * Returns number of matching invalid lsegs remaining in list after scanning
+ * it and purging them.
  */
 int
 pnfs_mark_matching_lsegs_invalid(struct pnfs_layout_hdr *lo,
 			    struct list_head *tmp_list,
-			    const struct pnfs_layout_range *recall_range)
+			    const struct pnfs_layout_range *recall_range,
+			    u32 seq)
 {
 	struct pnfs_layout_segment *lseg, *next;
 	int remaining = 0;
@@ -540,10 +562,12 @@
 	list_for_each_entry_safe(lseg, next, &lo->plh_segs, pls_list)
 		if (!recall_range ||
 		    should_free_lseg(&lseg->pls_range, recall_range)) {
-			dprintk("%s: freeing lseg %p iomode %d "
+			if (seq && pnfs_seqid_is_newer(lseg->pls_seq, seq))
+				continue;
+			dprintk("%s: freeing lseg %p iomode %d seq %u"
 				"offset %llu length %llu\n", __func__,
-				lseg, lseg->pls_range.iomode, lseg->pls_range.offset,
-				lseg->pls_range.length);
+				lseg, lseg->pls_range.iomode, lseg->pls_seq,
+				lseg->pls_range.offset, lseg->pls_range.length);
 			if (!mark_lseg_invalid(lseg, tmp_list))
 				remaining++;
 		}
@@ -730,15 +754,6 @@
 	pnfs_destroy_layouts_byclid(clp, false);
 }
 
-/*
- * Compare 2 layout stateid sequence ids, to see which is newer,
- * taking into account wraparound issues.
- */
-static bool pnfs_seqid_is_newer(u32 s1, u32 s2)
-{
-	return (s32)(s1 - s2) > 0;
-}
-
 /* update lo->plh_stateid with new if is more recent */
 void
 pnfs_set_layout_stateid(struct pnfs_layout_hdr *lo, const nfs4_stateid *new,
@@ -1014,7 +1029,7 @@
 	pnfs_get_layout_hdr(lo);
 	empty = list_empty(&lo->plh_segs);
 	pnfs_clear_layoutcommit(ino, &tmp_list);
-	pnfs_mark_matching_lsegs_invalid(lo, &tmp_list, NULL);
+	pnfs_mark_matching_lsegs_invalid(lo, &tmp_list, NULL, 0);
 
 	if (NFS_SERVER(ino)->pnfs_curr_ld->return_range) {
 		struct pnfs_layout_range range = {
@@ -1721,7 +1736,7 @@
 		 * inode invalid, and don't bother validating the stateid
 		 * sequence number.
 		 */
-		pnfs_mark_matching_lsegs_invalid(lo, &free_me, NULL);
+		pnfs_mark_matching_lsegs_invalid(lo, &free_me, NULL, 0);
 
 		nfs4_stateid_copy(&lo->plh_stateid, &res->stateid);
 		lo->plh_barrier = be32_to_cpu(res->stateid.seqid);
@@ -1775,7 +1790,8 @@
 int
 pnfs_mark_matching_lsegs_return(struct pnfs_layout_hdr *lo,
 				struct list_head *tmp_list,
-				const struct pnfs_layout_range *return_range)
+				const struct pnfs_layout_range *return_range,
+				u32 seq)
 {
 	struct pnfs_layout_segment *lseg, *next;
 	int remaining = 0;
@@ -1798,8 +1814,11 @@
 				continue;
 			remaining++;
 			set_bit(NFS_LSEG_LAYOUTRETURN, &lseg->pls_flags);
-			pnfs_set_plh_return_info(lo, return_range->iomode, lseg->pls_seq);
 		}
+
+	if (remaining)
+		pnfs_set_plh_return_info(lo, return_range->iomode, seq);
+
 	return remaining;
 }
 
@@ -1822,7 +1841,8 @@
 	 * segments at hand when sending layoutreturn. See pnfs_put_lseg()
 	 * for how it works.
 	 */
-	if (!pnfs_mark_matching_lsegs_return(lo, &free_me, &range)) {
+	if (!pnfs_mark_matching_lsegs_return(lo, &free_me,
+						&range, lseg->pls_seq)) {
 		nfs4_stateid stateid;
 		enum pnfs_iomode iomode = lo->plh_return_iomode;