linux-kernel - [PATCH 4.7 095/186] pNFS: Fix post-layoutget error handling in pnfs_update

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Message-Id: <20160818135936.203780307@linuxfoundation.org>
Date:	Thu, 18 Aug 2016 15:58:32 +0200
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org,
	Trond Myklebust <trond.myklebust@...marydata.com>,
	Jeff Layton <jlayton@...hat.com>
Subject: [PATCH 4.7 095/186] pNFS: Fix post-layoutget error handling in pnfs_update_layout()

4.7-stable review patch.  If anyone has any objections, please let me know.

------------------

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

commit 56b38a1f7c781519eef09c1668a3c97ea911f86b upstream.

The non-retry error path is currently broken and ends up releasing the
reference to the layout twice. It also can end up clearing the
NFS_LAYOUT_FIRST_LAYOUTGET flag twice, causing a race.

In addition, the retry path will fail to decrement the plh_outstanding
counter.

Fixes: 183d9e7b112aa ("pnfs: rework LAYOUTGET retry handling")
Signed-off-by: Trond Myklebust <trond.myklebust@...marydata.com>
Reviewed-by: Jeff Layton <jlayton@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/nfs/pnfs.c |   21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -1645,6 +1645,7 @@ lookup_again:
 	lseg = send_layoutget(lo, ctx, &stateid, &arg, &timeout, gfp_flags);
 	trace_pnfs_update_layout(ino, pos, count, iomode, lo, lseg,
 				 PNFS_UPDATE_LAYOUT_SEND_LAYOUTGET);
+	atomic_dec(&lo->plh_outstanding);
 	if (IS_ERR(lseg)) {
 		switch(PTR_ERR(lseg)) {
 		case -EBUSY:
@@ -1653,26 +1654,26 @@ lookup_again:
 				lseg = NULL;
 			/* Fallthrough */
 		case -EAGAIN:
-			pnfs_put_layout_hdr(lo);
-			if (first)
-				pnfs_clear_first_layoutget(lo);
-			if (lseg) {
-				trace_pnfs_update_layout(ino, pos, count,
-					iomode, lo, lseg, PNFS_UPDATE_LAYOUT_RETRY);
-				goto lookup_again;
-			}
-			/* Fallthrough */
+			break;
 		default:
 			if (!nfs_error_is_fatal(PTR_ERR(lseg))) {
 				pnfs_layout_clear_fail_bit(lo, pnfs_iomode_to_fail_bit(iomode));
 				lseg = NULL;
 			}
+			goto out_put_layout_hdr;
+		}
+		if (lseg) {
+			if (first)
+				pnfs_clear_first_layoutget(lo);
+			trace_pnfs_update_layout(ino, pos, count,
+				iomode, lo, lseg, PNFS_UPDATE_LAYOUT_RETRY);
+			pnfs_put_layout_hdr(lo);
+			goto lookup_again;
 		}
 	} else {
 		pnfs_layout_clear_fail_bit(lo, pnfs_iomode_to_fail_bit(iomode));
 	}
 
-	atomic_dec(&lo->plh_outstanding);
 out_put_layout_hdr:
 	if (first)
 		pnfs_clear_first_layoutget(lo);