Commit 3e17898a authored by Trond Myklebust's avatar Trond Myklebust
Browse files

NFSv4: Protect the state recovery thread against direct reclaim 



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: default avatarTrond Myklebust <trond.myklebust@hammerspace.com>
parent ab22e2cb

fs/nfs/nfs4state.c

+12 −0
Original line number Diff line number Diff line
@@ -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>
@@ -2560,9 +2561,17 @@ static void nfs4_layoutreturn_any_run(struct nfs_client *clp) 


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);
@@ -2657,6 +2666,7 @@ static void nfs4_state_manager(struct nfs_client *clp) 
			clear_bit(NFS4CLNT_RECLAIM_NOGRACE, &clp->cl_state);

		}



		memalloc_nofs_restore(memflags);

		nfs4_end_drain_session(clp);

		nfs4_clear_state_manager_bit(clp);
@@ -2674,6 +2684,7 @@ static void nfs4_state_manager(struct nfs_client *clp) 
			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;
@@ -2686,6 +2697,7 @@ static void nfs4_state_manager(struct nfs_client *clp) 
			clp->cl_hostname, -status);

	ssleep(1);

out_drain:

	memalloc_nofs_restore(memflags);

	nfs4_end_drain_session(clp);

	nfs4_clear_state_manager_bit(clp);

}