linux-kernel - [PATCH RFC 2/2] nfs: pr_warn if plh_segs or plh_return

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Message-Id: <20250428-nfs-6-16-v1-2-2d45b80facef@kernel.org>
Date: Mon, 28 Apr 2025 13:24:39 -0700
From: Jeff Layton <jlayton@...nel.org>
To: Trond Myklebust <trondmy@...nel.org>, Anna Schumaker <anna@...nel.org>
Cc: Omar Sandoval <osandov@...ndov.com>, Chris Mason <clm@...com>, 
 linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Jeff Layton <jlayton@...nel.org>
Subject: [PATCH RFC 2/2] nfs: pr_warn if plh_segs or plh_return_segs are
 non-empty when freeing

pnfs_layoutreturn_before_put_layout_hdr() currently throws a WARN if
plh_segs still has entries when the layout_hdr is freed.

Add a new routine that prints info about leftover segments when this
occurs, before dumping the stack. Call that for both plh_segs and
plh_return_segs lists.

Suggested-by: Omar Sandoval <osandov@...ndov.com>
Signed-off-by: Jeff Layton <jlayton@...nel.org>
---
 fs/nfs/pnfs.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 0bcb5a4bd420c157069ee63457518b206223b7cb..4387b1f77a3140b88a0644db1a565a4b71ab64bf 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -302,6 +302,22 @@ pnfs_detach_layout_hdr(struct pnfs_layout_hdr *lo)
 	nfsi->read_io = 0;
 }
 
+static void
+pnfs_warn_dangling_lsegs(struct list_head *list, const char *name)
+{
+	struct pnfs_layout_segment *lseg;
+
+	if (list_empty(list))
+		return;
+
+	pr_warn("NFS: BUG unfreed layout segments on %s\n", name);
+	list_for_each_entry(lseg, list, pls_list)
+		pr_warn("%p: refs=%d flags=0x%lx seq=%u\n", lseg,
+			refcount_read(&lseg->pls_refcount), lseg->pls_flags,
+			lseg->pls_seq);
+	dump_stack();
+}
+
 void
 pnfs_put_layout_hdr(struct pnfs_layout_hdr *lo)
 {
@@ -315,8 +331,8 @@ pnfs_put_layout_hdr(struct pnfs_layout_hdr *lo)
 	pnfs_layoutreturn_before_put_layout_hdr(lo);
 
 	if (refcount_dec_and_lock(&lo->plh_refcount, &inode->i_lock)) {
-		if (!list_empty(&lo->plh_segs))
-			WARN_ONCE(1, "NFS: BUG unfreed layout segments.\n");
+		pnfs_warn_dangling_lsegs(&lo->plh_segs, "plh_segs");
+		pnfs_warn_dangling_lsegs(&lo->plh_return_segs, "plh_return_segs");
 		pnfs_mark_layout_stateid_invalid(lo, &tmp_list);
 		pnfs_detach_layout_hdr(lo);
 		i_state = inode->i_state;

-- 
2.49.0