From: Trond Myklebust trond.myklebust@hammerspace.com
[ 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 trond.myklebust@hammerspace.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/nfs/nfs4state.c | 12 ++++++++++++ 1 file changed, 12 insertions(+)
diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c index aa2caba38a01..1d2b81a233bb 100644 --- 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>
@@ -2504,9 +2505,17 @@ static int nfs4_bind_conn_to_session(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 { clear_bit(NFS4CLNT_RUN_MANAGER, &clp->cl_state); @@ -2600,6 +2609,7 @@ 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);
@@ -2616,6 +2626,7 @@ 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;
@@ -2627,6 +2638,7 @@ 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); }