NFS/pnfs: Fix a live lock between recalled layouts and layoutget

commit 62e2a47ceab8f3f7d2e3f0e03fdd1c5e0059fd8b upstream.

When the server is recalling a layout, we should ignore the count of
outstanding layoutget calls, since the server is expected to return
either NFS4ERR_RECALLCONFLICT or NFS4ERR_RETURNCONFLICT for as long as
the recall is outstanding.
Currently, we may end up livelocking, causing the layout to eventually
be forcibly revoked.

Fixes: bf0291dd2267 ("pNFS: Ensure LAYOUTGET and LAYOUTRETURN are properly serialised")
Cc: stable@vger.kernel.org
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index f2da20ce68754445d241a8839489f6074199d80a..39ac4824b97def8be97eb8f029ccbd2367912f8f 100644 (file)
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -1199,7 +1199,7 @@ pnfs_prepare_layoutreturn(struct pnfs_layout_hdr *lo,
                enum pnfs_iomode *iomode)
 {
        /* Serialise LAYOUTGET/LAYOUTRETURN */
-       if (atomic_read(&lo->plh_outstanding) != 0)
+       if (atomic_read(&lo->plh_outstanding) != 0 && lo->plh_return_seq == 0)
                return false;
        if (test_and_set_bit(NFS_LAYOUT_RETURN_LOCK, &lo->plh_flags))
                return false;