git: 335517b9b02b - stable/13 - nfscl: Fix interaction between mmap'd and VOP_WRITE file updates

From: Rick Macklem <>
Date: Tue, 21 Feb 2023 23:33:59 UTC
The branch stable/13 has been updated by rmacklem:


commit 335517b9b02bc37f4d532998dc8e3ce5757cdef6
Author:     Rick Macklem <>
AuthorDate: 2023-02-08 22:25:01 +0000
Commit:     Rick Macklem <>
CommitDate: 2023-02-21 23:32:40 +0000

    nfscl: Fix interaction between mmap'd and VOP_WRITE file updates
    asomers@ found a problem with the NFS client, where a write to
    an NFS mounted file done via mmap(2) was lost when fspacectl(2)
    was done before it.  This turned out to be caused by clearing the
    dirty bit on pages when the client was doing commit RPCs,
    due to the second argument to vfs_busy_pages() being set to 1.
    Commit RPCs tell the server to commit previously written data to
    stable storage.  However, Commit RPCs do not write data from the
    client to the server.  As such, if the dirty bit on the page has
    been set by a mmap'd write to an address in the page, it should
    not be cleared.  Clearing it causes the mmap'd write to by lost.
    This patch fixes the problem by changing the 2nd argument to
    vfs_busy_pages() to 0 for this case.
    I doubt this bug has affected many, since it was inherited from
    the old NFS client and was in 4.3 FreeBSD twenty years ago.
    Although fspacectl(2) is FreeBSD 14 specific, a write(2) would
    cause the same failure.
    PR:     269328
    (cherry picked from commit 847967bc4e198a258b030a5864e64e029e7452e5)
 sys/fs/nfsclient/nfs_clvnops.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sys/fs/nfsclient/nfs_clvnops.c b/sys/fs/nfsclient/nfs_clvnops.c
index 02e5e3540d72..d1d84b05bbd7 100644
--- a/sys/fs/nfsclient/nfs_clvnops.c
+++ b/sys/fs/nfsclient/nfs_clvnops.c
@@ -3023,7 +3023,7 @@ again:
 				wcred = bp->b_wcred;
 			else if (wcred != bp->b_wcred)
 				wcred = NOCRED;
-			vfs_busy_pages(bp, 1);
+			vfs_busy_pages(bp, 0);