From a34752aa23975196fb38c5caf98485f258eef3eb Mon Sep 17 00:00:00 2001 From: Trond Myklebust Date: Sat, 29 Jan 2022 13:32:45 -0500 Subject: NFSv4: Protect the state recovery thread against direct reclaim [ Upstream commit 3e17898aca293a24dae757a440a50aa63ca29671 ] 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 Signed-off-by: Sasha Levin --- fs/nfs/nfs4state.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'fs') diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c index 51f5cb41e87a..57ea63e2cdb4 100644 --- a/fs/nfs/nfs4state.c +++ b/fs/nfs/nfs4state.c @@ -49,6 +49,7 @@ #include #include #include +#include #include @@ -2559,9 +2560,17 @@ 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); @@ -2656,6 +2665,7 @@ 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); @@ -2673,6 +2683,7 @@ 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; @@ -2685,6 +2696,7 @@ 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); } -- cgit v1.2.3