[PATCH RFC 1/2] nfs: free leftover lsegs before freeing a layout in pnfs_put_layout_hdr

[Jeff Layton <jlayton@kernel.org>]

Entries on the plh_return_segs list have already had their refcount go
to zero, and are only hanging around so that a LAYOUTRETURN can be
issued.

If there are still leftover lsegs on the plh_return_segs list when the
last pnfs_layout_hdr reference is put, then that means that the
layoutreturn just before the final refcount_dec_and_lock() has failed,
or that new lsegs have somehow raced onto plh_return_segs.

In either case, nothing else will be aware of the entries on that list,
since there are no more outstanding references. On the last
pnfs_layout_put(), do a final call to pnfs_mark_layout_stateid_invalid()
to shuffle any leftover segments to a tmp_list. Then free that list
after dropping the i_lock.

Reported-by: Omar Sandoval <osandov@osandov.com>
Closes: https://lore.kernel.org/linux-nfs/Z_ArpQC_vREh_hEA@telecaster/
Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/nfs/pnfs.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 5f582713bf05eb72eb34b2e2c06d1edcd3c258d3..0bcb5a4bd420c157069ee63457518b206223b7cb 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -307,6 +307,7 @@ pnfs_put_layout_hdr(struct pnfs_layout_hdr *lo)
 {
 	struct inode *inode;
 	unsigned long i_state;
+	LIST_HEAD(tmp_list);
 
 	if (!lo)
 		return;
@@ -316,9 +317,11 @@ pnfs_put_layout_hdr(struct pnfs_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_mark_layout_stateid_invalid(lo, &tmp_list);
 		pnfs_detach_layout_hdr(lo);
 		i_state = inode->i_state;
 		spin_unlock(&inode->i_lock);
+		pnfs_free_lseg_list(&tmp_list);
 		pnfs_free_layout_hdr(lo);
 		/* Notify pnfs_destroy_layout_final() that we're done */
 		if (i_state & (I_FREEING | I_CLEAR))

-- 
2.49.0