dm raid1: keep retrying alloc if mempool_alloc failed

If the code can't handle allocation failures, use __GFP_NOFAIL so that
in case of memory pressure the allocator will retry indefinitely and
won't return NULL which would cause a crash in the function.

This is still not a correct fix, it may cause a classic deadlock when
memory manager waits for I/O being done and I/O waits for some free memory.
I/O code shouldn't allocate any memory. But in this case it probably
doesn't matter much in practice, people usually do not swap on RAID.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

diff --git a/drivers/md/dm-region-hash.c b/drivers/md/dm-region-hash.c
index 7b899be..36dbe29 100644 (file)
--- a/drivers/md/dm-region-hash.c
+++ b/drivers/md/dm-region-hash.c
@@ -283,7 +283,7 @@ static struct dm_region *__rh_alloc(struct dm_region_hash *rh, region_t region)
 
        nreg = mempool_alloc(rh->region_pool, GFP_ATOMIC);
        if (unlikely(!nreg))
-               nreg = kmalloc(sizeof(*nreg), GFP_NOIO);
+               nreg = kmalloc(sizeof(*nreg), GFP_NOIO | __GFP_NOFAIL);
 
        nreg->state = rh->log->type->in_sync(rh->log, region, 1) ?
                      DM_RH_CLEAN : DM_RH_NOSYNC;