From: Trond Myklebust <trond.myklebust@hammerspace.com>
Date: Sat, 29 Jan 2022 13:32:45 -0500
Subject: [PATCH] NFSv4: Protect the state recovery thread against direct
reclaim
Git-commit: 3e17898aca293a24dae757a440a50aa63ca29671
Patch-mainline: v5.18
References: git-fixes
If memory allocation triggers a direct reclaim from the state recovery
thread, then we can deadlock. Use memalloc_nofs_save/restore to ensure
that doesn't happen.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Acked-by: NeilBrown <neilb@suse.com>
---
fs/nfs/nfs4state.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -49,6 +49,7 @@
#include <linux/workqueue.h>
#include <linux/bitops.h>
#include <linux/jiffies.h>
+#include <linux/sched/mm.h>
#include <linux/sunrpc/clnt.h>
@@ -2576,9 +2577,17 @@ static void nfs4_layoutreturn_any_run(st
static void nfs4_state_manager(struct nfs_client *clp)
{
+ unsigned int memflags;
int status = 0;
const char *section = "", *section_sep = "";
+ /*
+ * State recovery can deadlock if the direct reclaim code tries
+ * start NFS writeback. So ensure memory allocations are all
+ * GFP_NOFS.
+ */
+ memflags = memalloc_nofs_save();
+
/* Ensure exclusive access to NFSv4 state */
do {
trace_nfs4_state_mgr(clp);
@@ -2673,6 +2682,7 @@ static void nfs4_state_manager(struct nf
clear_bit(NFS4CLNT_RECLAIM_NOGRACE, &clp->cl_state);
}
+ memalloc_nofs_restore(memflags);
nfs4_end_drain_session(clp);
nfs4_clear_state_manager_bit(clp);
@@ -2690,6 +2700,7 @@ static void nfs4_state_manager(struct nf
return;
if (test_and_set_bit(NFS4CLNT_MANAGER_RUNNING, &clp->cl_state) != 0)
return;
+ memflags = memalloc_nofs_save();
} while (refcount_read(&clp->cl_count) > 1 && !signalled());
goto out_drain;
@@ -2702,6 +2713,7 @@ out_error:
clp->cl_hostname, -status);
ssleep(1);
out_drain:
+ memalloc_nofs_restore(memflags);
nfs4_end_drain_session(clp);
nfs4_clear_state_manager_bit(clp);
}