[PATCH] ocfs2: Alloc at least a page for the DLM hash

The OCFS2 DLM allocates a number of pages for a hash to lookup locks.
There was a bug where a PAGE_SIZE bigger than the hash size (eg, 64K
pages) would result in zero pages allocated.
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

fs/ocfs2/dlm/dlmcommon.h

@@ -37,8 +37,12 @@
 #define DLM_THREAD_SHUFFLE_INTERVAL    5     // flush everything every 5 passes
 #define DLM_THREAD_MS                  200   // flush at least every 200 ms
 
-#define DLM_HASH_SIZE		(1 << 14)
-#define DLM_HASH_PAGES		(DLM_HASH_SIZE / PAGE_SIZE)
+#define DLM_HASH_SIZE_DEFAULT	(1 << 14)
+#if DLM_HASH_SIZE_DEFAULT < PAGE_SIZE
+# define DLM_HASH_PAGES		1
+#else
+# define DLM_HASH_PAGES		(DLM_HASH_SIZE_DEFAULT / PAGE_SIZE)
+#endif
 #define DLM_BUCKETS_PER_PAGE	(PAGE_SIZE / sizeof(struct hlist_head))
 #define DLM_HASH_BUCKETS	(DLM_HASH_PAGES * DLM_BUCKETS_PER_PAGE)
 

fs/ocfs2/dlm/dlmdomain.c

@@ -67,6 +67,9 @@ static void **dlm_alloc_pagevec(int pages)
 	for (i = 0; i < pages; i++)
 		if (!(vec[i] = (void *)__get_free_page(GFP_KERNEL)))
 			goto out_free;
+
+	mlog(0, "Allocated DLM hash pagevec; %d pages (%lu expected), %Zd buckets per page\n",
+	     pages, DLM_HASH_PAGES, DLM_BUCKETS_PER_PAGE);
 	return vec;
 out_free:
 	dlm_free_pagevec(vec, i);