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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Trond Myklebust <trond.myklebust@hammerspace.com>
Subject: [PATCH 4.19 064/116] NFS: Dont corrupt the value of pg_bytes_written in nfs_do_recoalesce()
Date:   Mon, 31 May 2021 15:14:00 +0200
Message-Id: <20210531130642.333988973@linuxfoundation.org>
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From: Trond Myklebust <trond.myklebust@hammerspace.com>

commit 0d0ea309357dea0d85a82815f02157eb7fcda39f upstream.

The value of mirror->pg_bytes_written should only be updated after a
successful attempt to flush out the requests on the list.

Fixes: a7d42ddb3099 ("nfs: add mirroring support to pgio layer")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/nfs/pagelist.c |   12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -987,17 +987,16 @@ static void nfs_pageio_doio(struct nfs_p
 {
 	struct nfs_pgio_mirror *mirror = nfs_pgio_current_mirror(desc);
 
-
 	if (!list_empty(&mirror->pg_list)) {
 		int error = desc->pg_ops->pg_doio(desc);
 		if (error < 0)
 			desc->pg_error = error;
-		else
+		if (list_empty(&mirror->pg_list)) {
 			mirror->pg_bytes_written += mirror->pg_count;
-	}
-	if (list_empty(&mirror->pg_list)) {
-		mirror->pg_count = 0;
-		mirror->pg_base = 0;
+			mirror->pg_count = 0;
+			mirror->pg_base = 0;
+			mirror->pg_recoalesce = 0;
+		}
 	}
 }
 
@@ -1095,7 +1094,6 @@ static int nfs_do_recoalesce(struct nfs_
 
 	do {
 		list_splice_init(&mirror->pg_list, &head);
-		mirror->pg_bytes_written -= mirror->pg_count;
 		mirror->pg_count = 0;
 		mirror->pg_base = 0;
 		mirror->pg_recoalesce = 0;