btrfs: Replace opencoded sizes with their symbolic constants

Currently btrfs' code uses a mix of opencoded sizes and defines from sizes.h.
Let's unifiy the code base to always use the symbolic constants. No functional
changes
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ctree.h

@@ -523,7 +523,7 @@ struct btrfs_caching_control {
 };
 
 /* Once caching_thread() finds this much free space, it will wake up waiters. */
-#define CACHING_CTL_WAKE_UP (1024 * 1024 * 2)
+#define CACHING_CTL_WAKE_UP SZ_2M
 
 struct btrfs_io_ctl {
 	void *cur, *orig;

fs/btrfs/disk-io.c

@@ -2733,7 +2733,7 @@ int open_ctree(struct super_block *sb,
 	sb->s_bdi->congested_fn = btrfs_congested_fn;
 	sb->s_bdi->congested_data = fs_info;
 	sb->s_bdi->capabilities |= BDI_CAP_CGROUP_WRITEBACK;
-	sb->s_bdi->ra_pages = VM_MAX_READAHEAD * 1024 / PAGE_SIZE;
+	sb->s_bdi->ra_pages = VM_MAX_READAHEAD * SZ_1K / PAGE_SIZE;
 	sb->s_bdi->ra_pages *= btrfs_super_num_devices(disk_super);
 	sb->s_bdi->ra_pages = max(sb->s_bdi->ra_pages, SZ_4M / PAGE_SIZE);
 

fs/btrfs/super.c

@@ -2126,7 +2126,7 @@ static int btrfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 	 * succeed even if the Avail is zero. But this is better than the other
 	 * way around.
 	 */
-	thresh = 4 * 1024 * 1024;
+	thresh = SZ_4M;
 
 	if (!mixed && total_free_meta - thresh < block_rsv->size)
 		buf->f_bavail = 0;

fs/btrfs/tests/inode-tests.c

@@ -770,7 +770,7 @@ static noinline int test_btrfs_get_extent(u32 sectorsize, u32 nodesize)
 	offset = em->start + em->len;
 	free_extent_map(em);
 
-	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, 4096 * 1024, 0);
+	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, SZ_4M, 0);
 	if (IS_ERR(em)) {
 		test_msg("Got an error when we shouldn't have\n");
 		goto out;