[PATCH 0/2] Don't do pNFS I/O when not holding a layout

[PATCH 0/2] Don't do pNFS I/O when not holding a layout

[trondmy]

From: Trond Myklebust <trond.myklebust@hammerspace.com>

We recently discovered a couple of issues in the pNFS client that can
cause it to return a layout while some of the layout segments being
returned are still in use for I/O.

The following 2 patches will add appropriate tests to ensure this
cannot happen, and that the layoutreturn call is delayed until
the outstanding I/O is finished.

Trond Myklebust (2):
  NFS: Don't move layouts to plh_return_segs list while in use
  NFS: Don't return layout segments that are in use

 fs/nfs/pnfs.c | 46 ++++++++++++++++------------------------------
 1 file changed, 16 insertions(+), 30 deletions(-)

-- 
2.26.2

[PATCH 1/2] NFS: Don't move layouts to plh_return_segs list while in use

[trondmy]

From: Trond Myklebust <trond.myklebust@hammerspace.com>

If the layout segment is still in use for a read or a write, we should
not move it to the layout plh_return_segs list. If we do, we can end
up returning the layout while I/O is still in progress.

Fixes: e0b7d420f72a ("pNFS: Don't discard layout segments that are marked for return")
Cc: stable@vger.kernel.org # v4.19+
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 fs/nfs/pnfs.c | 12 +-----------
 1 file changed, 1 insertion(+), 11 deletions(-)

diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index d8cdb94c6668..262ce01c7abe 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -2392,16 +2392,6 @@ pnfs_layout_process(struct nfs4_layoutget *lgp)
 	return ERR_PTR(-EAGAIN);
 }
 
-static int
-mark_lseg_invalid_or_return(struct pnfs_layout_segment *lseg,
-		struct list_head *tmp_list)
-{
-	if (!mark_lseg_invalid(lseg, tmp_list))
-		return 0;
-	pnfs_cache_lseg_for_layoutreturn(lseg->pls_layout, lseg);
-	return 1;
-}
-
 /**
  * pnfs_mark_matching_lsegs_return - Free or return matching layout segments
  * @lo: pointer to layout header
@@ -2438,7 +2428,7 @@ pnfs_mark_matching_lsegs_return(struct pnfs_layout_hdr *lo,
 				lseg, lseg->pls_range.iomode,
 				lseg->pls_range.offset,
 				lseg->pls_range.length);
-			if (mark_lseg_invalid_or_return(lseg, tmp_list))
+			if (mark_lseg_invalid(lseg, tmp_list))
 				continue;
 			remaining++;
 			set_bit(NFS_LSEG_LAYOUTRETURN, &lseg->pls_flags);
-- 
2.26.2

[PATCH 2/2] NFS: Don't return layout segments that are in use

[trondmy]

From: Trond Myklebust <trond.myklebust@hammerspace.com>

If the NFS_LAYOUT_RETURN_REQUESTED flag is set, we want to return the
layout as soon as possible, meaning that the affected layout segments
should be marked as invalid, and should no longer be in use for I/O.

Fixes: f0b429819b5f ("pNFS: Ignore non-recalled layouts in pnfs_layout_need_return()")
Cc: stable@vger.kernel.org # v4.19+
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 fs/nfs/pnfs.c | 34 +++++++++++++++-------------------
 1 file changed, 15 insertions(+), 19 deletions(-)

diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 262ce01c7abe..b5baf36d4de5 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -1226,31 +1226,27 @@ pnfs_send_layoutreturn(struct pnfs_layout_hdr *lo,
 	return status;
 }
 
+static bool
+pnfs_layout_segments_returnable(struct pnfs_layout_hdr *lo,
+				enum pnfs_iomode iomode,
+				u32 seq)
+{
+	struct pnfs_layout_range recall_range = {
+		.length = NFS4_MAX_UINT64,
+		.iomode = iomode,
+	};
+	return pnfs_mark_matching_lsegs_return(lo, &lo->plh_return_segs,
+					       &recall_range, seq) != -EBUSY;
+}
+
 /* Return true if layoutreturn is needed */
 static bool
 pnfs_layout_need_return(struct pnfs_layout_hdr *lo)
 {
-	struct pnfs_layout_segment *s;
-	enum pnfs_iomode iomode;
-	u32 seq;
-
 	if (!test_bit(NFS_LAYOUT_RETURN_REQUESTED, &lo->plh_flags))
 		return false;
-
-	seq = lo->plh_return_seq;
-	iomode = lo->plh_return_iomode;
-
-	/* Defer layoutreturn until all recalled lsegs are done */
-	list_for_each_entry(s, &lo->plh_segs, pls_list) {
-		if (seq && pnfs_seqid_is_newer(s->pls_seq, seq))
-			continue;
-		if (iomode != IOMODE_ANY && s->pls_range.iomode != iomode)
-			continue;
-		if (test_bit(NFS_LSEG_LAYOUTRETURN, &s->pls_flags))
-			return false;
-	}
-
-	return true;
+	return pnfs_layout_segments_returnable(lo, lo->plh_return_iomode,
+					       lo->plh_return_seq);
 }
 
 static void pnfs_layoutreturn_before_put_layout_hdr(struct pnfs_layout_hdr *lo)
-- 
2.26.2