[PATCH 6.0 0142/1073] nfsd: dont call nfsd_file_put from client states seqfile display

Greg Kroah-Hartman
2022-12-28T15:11:20Z

From: Jeff Layton <jlayton@kernel.org>

[ Upstream commit e0aa651068bfd520afcd357af8ecd2de005fc83d ]

We had a report of this:

BUG: sleeping function called from invalid context at fs/nfsd/filecache.c:440

...with a stack trace showing nfsd_file_put being called from
nfs4_show_open. This code has always tried to call fput while holding a
spinlock, but we recently changed this to use the filecache, and that
started triggering the might_sleep() in nfsd_file_put.

states_start takes and holds the cl_lock while iterating over the
client's states, and we can't sleep with that held.

Have the various nfs4_show_* functions instead hold the fi_lock instead
of taking a nfsd_file reference.

Fixes: 78599c42ae3c ("nfsd4: add file to display list of client's opens")
Link: https://bugzilla.redhat.com/show_bug.cgi?id=2138357
Reported-by: Zhi Li <yieli@redhat.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/nfsd/nfs4state.c | 51 +++++++++++++++++++++++++++++----------------
1 file changed, 33 insertions(+), 18 deletions(-)

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index ddb2bf078fda..94420fad4c41 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -664,15 +664,26 @@ find_any_file(struct nfs4_file *f)
return ret;
}

-static struct nfsd_file *find_deleg_file(struct nfs4_file *f)
+static struct nfsd_file *find_any_file_locked(struct nfs4_file *f)
{
- struct nfsd_file *ret = NULL;
+ lockdep_assert_held(&f->fi_lock);
+
+ if (f->fi_fds[O_RDWR])
+ return f->fi_fds[O_RDWR];
+ if (f->fi_fds[O_WRONLY])
+ return f->fi_fds[O_WRONLY];
+ if (f->fi_fds[O_RDONLY])
+ return f->fi_fds[O_RDONLY];
+ return NULL;
+}
+
+static struct nfsd_file *find_deleg_file_locked(struct nfs4_file *f)
+{
+ lockdep_assert_held(&f->fi_lock);

- spin_lock(&f->fi_lock);
if (f->fi_deleg_file)
- ret = nfsd_file_get(f->fi_deleg_file);
- spin_unlock(&f->fi_lock);
- return ret;
+ return f->fi_deleg_file;
+ return NULL;
}

static atomic_long_t num_delegations;
@@ -2606,9 +2617,11 @@ static int nfs4_show_open(struct seq_file *s, struct nfs4_stid *st)
ols = openlockstateid(st);
oo = ols->st_stateowner;
nf = st->sc_file;
- file = find_any_file(nf);
+
+ spin_lock(&nf->fi_lock);
+ file = find_any_file_locked(nf);
if (!file)
- return 0;
+ goto out;

seq_printf(s, "- ");
nfs4_show_stateid(s, &st->sc_stateid);
@@ -2630,8 +2643,8 @@ static int nfs4_show_open(struct seq_file *s, struct nfs4_stid *st)
seq_printf(s, ", ");
nfs4_show_owner(s, oo);
seq_printf(s, " }\n");
- nfsd_file_put(file);
-
+out:
+ spin_unlock(&nf->fi_lock);
return 0;
}

@@ -2645,9 +2658,10 @@ static int nfs4_show_lock(struct seq_file *s, struct nfs4_stid *st)
ols = openlockstateid(st);
oo = ols->st_stateowner;
nf = st->sc_file;
- file = find_any_file(nf);
+ spin_lock(&nf->fi_lock);
+ file = find_any_file_locked(nf);
if (!file)
- return 0;
+ goto out;

seq_printf(s, "- ");
nfs4_show_stateid(s, &st->sc_stateid);
@@ -2667,8 +2681,8 @@ static int nfs4_show_lock(struct seq_file *s, struct nfs4_stid *st)
seq_printf(s, ", ");
nfs4_show_owner(s, oo);
seq_printf(s, " }\n");
- nfsd_file_put(file);
-
+out:
+ spin_unlock(&nf->fi_lock);
return 0;
}

@@ -2680,9 +2694,10 @@ static int nfs4_show_deleg(struct seq_file *s, struct nfs4_stid *st)

ds = delegstateid(st);
nf = st->sc_file;
- file = find_deleg_file(nf);
+ spin_lock(&nf->fi_lock);
+ file = find_deleg_file_locked(nf);
if (!file)
- return 0;
+ goto out;

seq_printf(s, "- ");
nfs4_show_stateid(s, &st->sc_stateid);
@@ -2698,8 +2713,8 @@ static int nfs4_show_deleg(struct seq_file *s, struct nfs4_stid *st)
seq_printf(s, ", ");
nfs4_show_fname(s, file);
seq_printf(s, " }\n");
- nfsd_file_put(file);
-
+out:
+ spin_unlock(&nf->fi_lock);
return 0;
}

--
2.35.1