create: Check with OROM limit before setting default chunk size

Make create check with the appropriate meta data handler and see what the
largest chunk size is supported. The current 512K default is not supported
by existing imsm OROM.

[dan.j.williams@intel.com: trim the upper limit to 512k for future oroms]
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Create.c

@@ -235,9 +235,13 @@ int Create(struct supertype *st, char *mddev,
 	case 6:
 	case 0:
 		if (chunk == 0) {
-			chunk = 512;
+			if (st && st->ss->default_chunk)
+				chunk = st->ss->default_chunk(st);
+
+			chunk = chunk ? : 512;
+
 			if (verbose > 0)
-				fprintf(stderr, Name ": chunk size defaults to 512K\n");
+				fprintf(stderr, Name ": chunk size defaults to %dK\n", chunk);
 		}
 		break;
 	case LEVEL_LINEAR:

mdadm.h

@@ -609,6 +609,8 @@ extern struct superswitch {
 	struct mdinfo *(*container_content)(struct supertype *st);
 	/* Allow a metadata handler to override mdadm's default layouts */
 	int (*default_layout)(int level); /* optional */
+	/* query the supertype for default chunk size */
+	int (*default_chunk)(struct supertype *st); /* optional */
 
 /* for mdmon */
 	int (*open_new)(struct supertype *c, struct active_array *a,

platform-intel.h

@@ -115,6 +115,55 @@ static inline int imsm_orom_has_chunk(const struct imsm_orom *orom, int chunk)
 	return !!(orom->sss & (1 << (fs - 1)));
 }
 
+/**
+ * fls - find last (most-significant) bit set
+ * @x: the word to search
+ * The funciton is borrowed from Linux kernel code
+ * include/asm-generic/bitops/fls.h
+ */
+static inline int fls(int x)
+{
+	int r = 32;
+
+	if (!x)
+		return 0;
+	if (!(x & 0xffff0000u)) {
+		x <<= 16;
+		r -= 16;
+	}
+	if (!(x & 0xff000000u)) {
+		x <<= 8;
+		r -= 8;
+	}
+	if (!(x & 0xf0000000u)) {
+		x <<= 4;
+		r -= 4;
+	}
+	if (!(x & 0xc0000000u)) {
+		x <<= 2;
+		r -= 2;
+	}
+	if (!(x & 0x80000000u)) {
+		x <<= 1;
+		r -= 1;
+	}
+	return r;
+}
+
+/**
+ * imsm_orom_default_chunk - return the largest chunk size supported via orom
+ * @orom: orom pointer from find_imsm_orom
+ */
+static inline int imsm_orom_default_chunk(const struct imsm_orom *orom)
+{
+	int fs = fls(orom->sss);
+
+	if (!fs)
+		return 0;
+
+	return min(512, (1 << fs));
+}
+
 struct sys_dev {
 	char *path;
 	struct sys_dev *next;

super-intel.c

@@ -4003,6 +4003,17 @@ static int validate_geometry_imsm(struct supertype *st, int level, int layout,
 	close(cfd);
 	return 0;
 }
+
+static int default_chunk_imsm(struct supertype *st)
+{
+	struct intel_super *super = st->sb;
+
+	if (!super->orom)
+		return 0;
+
+	return imsm_orom_default_chunk(super->orom);
+}
+
 #endif /* MDASSEMBLE */
 
 static int is_rebuilding(struct imsm_dev *dev)
@@ -5240,6 +5251,7 @@ struct superswitch super_imsm = {
 	.brief_detail_super = brief_detail_super_imsm,
 	.write_init_super = write_init_super_imsm,
 	.validate_geometry = validate_geometry_imsm,
+	.default_chunk	= default_chunk_imsm,
 	.add_to_super	= add_to_super_imsm,
 	.detail_platform = detail_platform_imsm,
 #endif