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NFSv4: Protect the state recovery thread against direct reclaim

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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>
This commit is contained in:
Trond Myklebust 2022-01-29 13:32:45 -05:00
parent ab22e2cbbc
commit 3e17898aca
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/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 @@ 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);
}