[PATCH 5.15 248/731] NFSv4: Fix a deadlock between nfs4_open_recover_helper() and delegreturn

Greg Kroah-Hartman
2022-12-28T15:00:03Z

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

[ Upstream commit 51069e4aef6257b0454057359faed0ab0c9af083 ]

If we're asked to recover open state while a delegation return is
outstanding, then the state manager thread cannot use a cached open, so
if the server returns a delegation, we can end up deadlocked behind the
pending delegreturn.
To avoid this problem, let's just ask the server not to give us a
delegation unless we're explicitly reclaiming one.

Fixes: be36e185bd26 ("NFSv4: nfs4_open_recover_helper() must set share access")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/nfs/nfs4proc.c | 19 ++++++++++++-------
1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 3c9ed63710a9..b6b1fad031c7 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -2144,18 +2144,18 @@ static struct nfs4_opendata *nfs4_open_recoverdata_alloc(struct nfs_open_context
}

static int nfs4_open_recover_helper(struct nfs4_opendata *opendata,
- fmode_t fmode)
+ fmode_t fmode)
{
struct nfs4_state *newstate;
+ struct nfs_server *server = NFS_SB(opendata->dentry->d_sb);
+ int openflags = opendata->o_arg.open_flags;
int ret;

if (!nfs4_mode_match_open_stateid(opendata->state, fmode))
return 0;
- opendata->o_arg.open_flags = 0;
opendata->o_arg.fmode = fmode;
- opendata->o_arg.share_access = nfs4_map_atomic_open_share(
- NFS_SB(opendata->dentry->d_sb),
- fmode, 0);
+ opendata->o_arg.share_access =
+ nfs4_map_atomic_open_share(server, fmode, openflags);
memset(&opendata->o_res, 0, sizeof(opendata->o_res));
memset(&opendata->c_res, 0, sizeof(opendata->c_res));
nfs4_init_opendata_res(opendata);
@@ -2735,10 +2735,15 @@ static int _nfs4_open_expired(struct nfs_open_context *ctx, struct nfs4_state *s
struct nfs4_opendata *opendata;
int ret;

- opendata = nfs4_open_recoverdata_alloc(ctx, state,
- NFS4_OPEN_CLAIM_FH);
+ opendata = nfs4_open_recoverdata_alloc(ctx, state, NFS4_OPEN_CLAIM_FH);
if (IS_ERR(opendata))
return PTR_ERR(opendata);
+ /*
+ * We're not recovering a delegation, so ask for no delegation.
+ * Otherwise the recovery thread could deadlock with an outstanding
+ * delegation return.
+ */
+ opendata->o_arg.open_flags = O_DIRECT;
ret = nfs4_open_recover(opendata, state);
if (ret == -ESTALE)
d_drop(ctx->dentry);
--
2.35.1