bcache: handle cache set verify_ondisk properly for bucket size > 8MB

In bch_btree_cache_alloc() when CONFIG_BCACHE_DEBUG is configured,
allocate memory for c->verify_ondisk may fail if the bucket size > 8MB,
which will require __get_free_pages() to allocate continuous pages
with order > 11 (the default MAX_ORDER of Linux buddy allocator). Such
over size allocation will fail, and cause 2 problems,
- When CONFIG_BCACHE_DEBUG is configured,  bch_btree_verify() does not
  work, because c->verify_ondisk is NULL and bch_btree_verify() returns
  immediately.
- bch_btree_cache_alloc() will fail due to c->verify_ondisk allocation
  failed, then the whole cache device registration fails. And because of
  this failure, the first problem of bch_btree_verify() has no chance to
  be triggered.

This patch fixes the above problem by two means,
1) If pages allocation of c->verify_ondisk fails, set it to NULL and
   returns bch_btree_cache_alloc() with -ENOMEM.
2) When calling __get_free_pages() to allocate c->verify_ondisk pages,
   use ilog2(meta_bucket_pages(&c->sb)) to make sure ilog2() will always
   generate a pages order <= MAX_ORDER (or CONFIG_FORCE_MAX_ZONEORDER).
   Then the buddy system won't directly reject the allocation request.

Signed-off-by: Coly Li <colyli@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index 1e3bd5e..3d8bd06 100644 (file)
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -738,7 +738,7 @@ void bch_btree_cache_free(struct cache_set *c)
        if (c->verify_data)
                list_move(&c->verify_data->list, &c->btree_cache);
 
-       free_pages((unsigned long) c->verify_ondisk, ilog2(bucket_pages(c)));
+       free_pages((unsigned long) c->verify_ondisk, ilog2(meta_bucket_pages(&c->sb)));
 #endif
 
        list_splice(&c->btree_cache_freeable,
@@ -785,7 +785,15 @@ int bch_btree_cache_alloc(struct cache_set *c)
        mutex_init(&c->verify_lock);
 
        c->verify_ondisk = (void *)
-               __get_free_pages(GFP_KERNEL|__GFP_COMP, ilog2(bucket_pages(c)));
+               __get_free_pages(GFP_KERNEL|__GFP_COMP, ilog2(meta_bucket_pages(&c->sb)));
+       if (!c->verify_ondisk) {
+               /*
+                * Don't worry about the mca_rereserve buckets
+                * allocated in previous for-loop, they will be
+                * handled properly in bch_cache_set_unregister().
+                */
+               return -ENOMEM;
+       }
 
        c->verify_data = mca_bucket_alloc(c, &ZERO_KEY, GFP_KERNEL);