mm/hugetlb_cgroup: prepare cftypes based on template

Unlike other cgroup subsystems, the hugetlb cgroup does not provide a
static array of cftype that explicitly displays the properties, handling
functions, etc., of each file.  Instead, it dynamically creates the
attribute of cftypes based on the hstate during the startup procedure. 
This reduces the readability of the code.

To fix this issue, introduce two templates of cftypes, and rebuild the
attributes according to the hstate to make it ready to be added to cgroup
framework.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Xiu Jianfeng <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: Oscar Salvador <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: Xiu Jianfeng

mm/hugetlb_cgroup.c

@@ -27,7 +27,17 @@
 #define MEMFILE_IDX(val)	(((val) >> 16) & 0xffff)
 #define MEMFILE_ATTR(val)	((val) & 0xffff)
 
+/* Use t->m[0] to encode the offset */
+#define MEMFILE_OFFSET(t, m0)	(((offsetof(t, m0) << 16) | sizeof_field(t, m0)))
+#define MEMFILE_OFFSET0(val)	(((val) >> 16) & 0xffff)
+#define MEMFILE_FIELD_SIZE(val)	((val) & 0xffff)
+
+#define DFL_TMPL_SIZE		ARRAY_SIZE(hugetlb_dfl_tmpl)
+#define LEGACY_TMPL_SIZE	ARRAY_SIZE(hugetlb_legacy_tmpl)
+
 static struct hugetlb_cgroup *root_h_cgroup __read_mostly;
+static struct cftype *dfl_files;
+static struct cftype *legacy_files;
 
 static inline struct page_counter *
 __hugetlb_cgroup_counter_from_cgroup(struct hugetlb_cgroup *h_cg, int idx,
@@ -702,12 +712,142 @@ static int hugetlb_events_local_show(struct seq_file *seq, void *v)
 	return __hugetlb_events_show(seq, true);
 }
 
+static struct cftype hugetlb_dfl_tmpl[] = {
+	{
+		.name = "max",
+		.private = RES_LIMIT,
+		.seq_show = hugetlb_cgroup_read_u64_max,
+		.write = hugetlb_cgroup_write_dfl,
+		.flags = CFTYPE_NOT_ON_ROOT,
+	},
+	{
+		.name = "rsvd.max",
+		.private = RES_RSVD_LIMIT,
+		.seq_show = hugetlb_cgroup_read_u64_max,
+		.write = hugetlb_cgroup_write_dfl,
+		.flags = CFTYPE_NOT_ON_ROOT,
+	},
+	{
+		.name = "current",
+		.private = RES_USAGE,
+		.seq_show = hugetlb_cgroup_read_u64_max,
+		.flags = CFTYPE_NOT_ON_ROOT,
+	},
+	{
+		.name = "rsvd.current",
+		.private = RES_RSVD_USAGE,
+		.seq_show = hugetlb_cgroup_read_u64_max,
+		.flags = CFTYPE_NOT_ON_ROOT,
+	},
+	{
+		.name = "events",
+		.seq_show = hugetlb_events_show,
+		.file_offset = MEMFILE_OFFSET(struct hugetlb_cgroup, events_file[0]),
+		.flags = CFTYPE_NOT_ON_ROOT,
+	},
+	{
+		.name = "events.local",
+		.seq_show = hugetlb_events_local_show,
+		.file_offset = MEMFILE_OFFSET(struct hugetlb_cgroup, events_local_file[0]),
+		.flags = CFTYPE_NOT_ON_ROOT,
+	},
+	{
+		.name = "numa_stat",
+		.seq_show = hugetlb_cgroup_read_numa_stat,
+		.flags = CFTYPE_NOT_ON_ROOT,
+	},
+	/* don't need terminator here */
+};
+
+static struct cftype hugetlb_legacy_tmpl[] = {
+	{
+		.name = "limit_in_bytes",
+		.private = RES_LIMIT,
+		.read_u64 = hugetlb_cgroup_read_u64,
+		.write = hugetlb_cgroup_write_legacy,
+	},
+	{
+		.name = "rsvd.limit_in_bytes",
+		.private = RES_RSVD_LIMIT,
+		.read_u64 = hugetlb_cgroup_read_u64,
+		.write = hugetlb_cgroup_write_legacy,
+	},
+	{
+		.name = "usage_in_bytes",
+		.private = RES_USAGE,
+		.read_u64 = hugetlb_cgroup_read_u64,
+	},
+	{
+		.name = "rsvd.usage_in_bytes",
+		.private = RES_RSVD_USAGE,
+		.read_u64 = hugetlb_cgroup_read_u64,
+	},
+	{
+		.name = "max_usage_in_bytes",
+		.private = RES_MAX_USAGE,
+		.write = hugetlb_cgroup_reset,
+		.read_u64 = hugetlb_cgroup_read_u64,
+	},
+	{
+		.name = "rsvd.max_usage_in_bytes",
+		.private = RES_RSVD_MAX_USAGE,
+		.write = hugetlb_cgroup_reset,
+		.read_u64 = hugetlb_cgroup_read_u64,
+	},
+	{
+		.name = "failcnt",
+		.private = RES_FAILCNT,
+		.write = hugetlb_cgroup_reset,
+		.read_u64 = hugetlb_cgroup_read_u64,
+	},
+	{
+		.name = "rsvd.failcnt",
+		.private = RES_RSVD_FAILCNT,
+		.write = hugetlb_cgroup_reset,
+		.read_u64 = hugetlb_cgroup_read_u64,
+	},
+	{
+		.name = "numa_stat",
+		.seq_show = hugetlb_cgroup_read_numa_stat,
+	},
+	/* don't need terminator here */
+};
+
+static void __init
+hugetlb_cgroup_cfttypes_init(struct hstate *h, struct cftype *cft,
+			     struct cftype *tmpl, int tmpl_size)
+{
+	char buf[32];
+	int i, idx = hstate_index(h);
+
+	/* format the size */
+	mem_fmt(buf, sizeof(buf), huge_page_size(h));
+
+	for (i = 0; i < tmpl_size; cft++, tmpl++, i++) {
+		*cft = *tmpl;
+		/* rebuild the name */
+		snprintf(cft->name, MAX_CFTYPE_NAME, "%s.%s", buf, tmpl->name);
+		/* rebuild the private */
+		cft->private = MEMFILE_PRIVATE(idx, tmpl->private);
+		/* rebuild the file_offset */
+		if (tmpl->file_offset) {
+			unsigned int offset = tmpl->file_offset;
+
+			cft->file_offset = MEMFILE_OFFSET0(offset) +
+					   MEMFILE_FIELD_SIZE(offset) * idx;
+		}
+	}
+}
+
 static void __init __hugetlb_cgroup_file_dfl_init(int idx)
 {
 	char buf[32];
 	struct cftype *cft;
 	struct hstate *h = &hstates[idx];
 
+	hugetlb_cgroup_cfttypes_init(h, dfl_files + idx * DFL_TMPL_SIZE,
+				     hugetlb_dfl_tmpl, DFL_TMPL_SIZE);
+
 	/* format the size */
 	mem_fmt(buf, sizeof(buf), huge_page_size(h));
 
@@ -779,6 +919,9 @@ static void __init __hugetlb_cgroup_file_legacy_init(int idx)
 	struct cftype *cft;
 	struct hstate *h = &hstates[idx];
 
+	hugetlb_cgroup_cfttypes_init(h, legacy_files + idx * LEGACY_TMPL_SIZE,
+				     hugetlb_legacy_tmpl, LEGACY_TMPL_SIZE);
+
 	/* format the size */
 	mem_fmt(buf, sizeof(buf), huge_page_size(h));
 
@@ -856,10 +999,23 @@ static void __init __hugetlb_cgroup_file_init(int idx)
 	__hugetlb_cgroup_file_legacy_init(idx);
 }
 
+static void __init __hugetlb_cgroup_file_pre_init(void)
+{
+	int cft_count;
+
+	cft_count = hugetlb_max_hstate * DFL_TMPL_SIZE + 1; /* add terminator */
+	dfl_files = kcalloc(cft_count, sizeof(struct cftype), GFP_KERNEL);
+	BUG_ON(!dfl_files);
+	cft_count = hugetlb_max_hstate * LEGACY_TMPL_SIZE + 1; /* add terminator */
+	legacy_files = kcalloc(cft_count, sizeof(struct cftype), GFP_KERNEL);
+	BUG_ON(!legacy_files);
+}
+
 void __init hugetlb_cgroup_file_init(void)
 {
 	struct hstate *h;
 
+	__hugetlb_cgroup_file_pre_init();
 	for_each_hstate(h)
 		__hugetlb_cgroup_file_init(hstate_index(h));
 }