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NFSv4: Protect the state recovery thread against direct reclaim

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[ Upstream commit 3e17898aca ]

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>
This commit is contained in:
Trond Myklebust 2022-01-29 13:32:45 -05:00 committed by Greg Kroah-Hartman
parent 9b9feec97c
commit 4a2544ce24
1 changed files with 12 additions and 0 deletions
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12
fs/nfs/nfs4state.c
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@ -49,6 +49,7 @@
#include <linux/workqueue.h> #include <linux/workqueue.h>
#include <linux/bitops.h> #include <linux/bitops.h>
#include <linux/jiffies.h> #include <linux/jiffies.h>
#include <linux/sched/mm.h>
#include <linux/sunrpc/clnt.h> #include <linux/sunrpc/clnt.h>
@ -2557,9 +2558,17 @@ static void nfs4_layoutreturn_any_run(struct nfs_client *clp)
static void nfs4_state_manager(struct nfs_client *clp) static void nfs4_state_manager(struct nfs_client *clp)
{ {
unsigned int memflags;
int status = 0; int status = 0;
const char *section = "", *section_sep = ""; 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 */ /* Ensure exclusive access to NFSv4 state */
do { do {
trace_nfs4_state_mgr(clp); trace_nfs4_state_mgr(clp);
@ -2654,6 +2663,7 @@ static void nfs4_state_manager(struct nfs_client *clp)
clear_bit(NFS4CLNT_RECLAIM_NOGRACE, &clp->cl_state); clear_bit(NFS4CLNT_RECLAIM_NOGRACE, &clp->cl_state);
} }
memalloc_nofs_restore(memflags);
nfs4_end_drain_session(clp); nfs4_end_drain_session(clp);
nfs4_clear_state_manager_bit(clp); nfs4_clear_state_manager_bit(clp);
@ -2671,6 +2681,7 @@ static void nfs4_state_manager(struct nfs_client *clp)
return; return;
if (test_and_set_bit(NFS4CLNT_MANAGER_RUNNING, &clp->cl_state) != 0) if (test_and_set_bit(NFS4CLNT_MANAGER_RUNNING, &clp->cl_state) != 0)
return; return;
memflags = memalloc_nofs_save();
} while (refcount_read(&clp->cl_count) > 1 && !signalled()); } while (refcount_read(&clp->cl_count) > 1 && !signalled());
goto out_drain; goto out_drain;
@ -2683,6 +2694,7 @@ static void nfs4_state_manager(struct nfs_client *clp)
clp->cl_hostname, -status); clp->cl_hostname, -status);
ssleep(1); ssleep(1);
out_drain: out_drain:
memalloc_nofs_restore(memflags);
nfs4_end_drain_session(clp); nfs4_end_drain_session(clp);
nfs4_clear_state_manager_bit(clp); nfs4_clear_state_manager_bit(clp);
} }