GFS2: Clean up quota slot allocation

Quota slot allocation has historically used a vector of pages and a set of homegrown find/test/set/clear bit functions. Since the size of the bitmap is likely to be based on the default qc file size, thats a couple of pages at most. So we ought to be able to allocate that as a single chunk, with a vmalloc fallback, just in case of memory fragmentation.

We are then able to use the kernel's own find/test/set/clear bit functions, rather than rolling our own.

index 59d99ec..4b9aa5b 100644
@@ -733,8 +733,7 @@ struct gfs2_sbd {
 	spinlock_t sd_trunc_lock;
 
 	unsigned int sd_quota_slots;
-	unsigned int sd_quota_chunks;
-	unsigned char **sd_quota_bitmap;
+	unsigned long *sd_quota_bitmap;
 
 	u64 sd_quota_sync_gen;
 

1.8.3.1