aufs: dirren 2/6, branch id as a filename of the info

DIRREN gives an identifier to every branch, and it is used as a part of
the filename of the detailed info file.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

fs/aufs/dirren.c

@@ -318,6 +318,40 @@ out:
 	return err;
 }
 
+/* ---------------------------------------------------------------------- */
+
+static int au_dr_brid_init(struct au_dr_brid *brid, const struct path *path)
+{
+	int err;
+	struct kstatfs kstfs;
+	dev_t dev;
+	struct dentry *dentry;
+	struct super_block *sb;
+
+	err = vfs_statfs((void *)path, &kstfs);
+	AuTraceErr(err);
+	if (unlikely(err))
+		goto out;
+
+	/* todo: support for UUID */
+
+	if (kstfs.f_fsid.val[0] || kstfs.f_fsid.val[1]) {
+		brid->type = AuBrid_FSID;
+		brid->fsid = kstfs.f_fsid;
+	} else {
+		dentry = path->dentry;
+		sb = dentry->d_sb;
+		dev = sb->s_dev;
+		if (dev) {
+			brid->type = AuBrid_DEV;
+			brid->dev = dev;
+		}
+	}
+
+out:
+	return err;
+}
+
 int au_dr_br_init(struct super_block *sb, struct au_branch *br,
 		  const struct path *path)
 {
@@ -330,10 +364,14 @@ int au_dr_br_init(struct super_block *sb, struct au_branch *br,
 	for (i = 0; i < AuDirren_NHASH; i++, hbl++)
 		INIT_HLIST_BL_HEAD(hbl);
 
-	err = 0;
+	err = au_dr_brid_init(&dr->dr_brid, path);
+	if (unlikely(err))
+		goto out;
+
 	if (au_opt_test(au_mntflags(sb), DIRREN))
 		err = au_dr_hino(sb, /*bindex*/-1, br, path);
 
+out:
 	AuTraceErr(err);
 	return err;
 }
@@ -350,3 +388,48 @@ int au_dr_br_fin(struct super_block *sb, struct au_branch *br)
 
 	return err;
 }
+
+/* ---------------------------------------------------------------------- */
+
+/* re-commit later */ __maybe_unused
+static int au_brid_str(struct au_dr_brid *brid, struct inode *h_inode,
+		       char *buf, size_t sz)
+{
+	int err;
+	unsigned int major, minor;
+	char *p;
+
+	p = buf;
+	err = snprintf(p, sz, "%d_", brid->type);
+	AuDebugOn(err > sz);
+	p += err;
+	sz -= err;
+	switch (brid->type) {
+	case AuBrid_Unset:
+		return -EINVAL;
+	case AuBrid_UUID:
+		err = snprintf(p, sz, "%pU", brid->uuid.b);
+		break;
+	case AuBrid_FSID:
+		err = snprintf(p, sz, "%08x-%08x",
+			       brid->fsid.val[0], brid->fsid.val[1]);
+		break;
+	case AuBrid_DEV:
+		major = MAJOR(brid->dev);
+		minor = MINOR(brid->dev);
+		if (major <= 0xff && minor <= 0xff)
+			err = snprintf(p, sz, "%02x%02x", major, minor);
+		else
+			err = snprintf(p, sz, "%03x:%05x", major, minor);
+		break;
+	}
+	AuDebugOn(err > sz);
+	p += err;
+	sz -= err;
+	err = snprintf(p, sz, "_%llu", (unsigned long long)h_inode->i_ino);
+	AuDebugOn(err > sz);
+	p += err;
+	sz -= err;
+
+	return p - buf;
+}

fs/aufs/dirren.h

@@ -12,11 +12,34 @@
 
 #ifdef __KERNEL__
 
+#include <linux/statfs.h>
+#include <linux/uuid.h>
 #include "hbl.h"
 
 #define AuDirren_NHASH 100
 
 #ifdef CONFIG_AUFS_DIRREN
+enum au_brid_type {
+	AuBrid_Unset,
+	AuBrid_UUID,
+	AuBrid_FSID,
+	AuBrid_DEV
+};
+
+struct au_dr_brid {
+	enum au_brid_type	type;
+	union {
+		uuid_t	uuid;	/* unimplemented yet */
+		fsid_t	fsid;
+		dev_t	dev;
+	};
+};
+
+/* 20 is the max digits length of ulong 64 */
+/* brid-type "_" uuid "_" inum */
+#define AUFS_DIRREN_FNAME_SZ	(1 + 1 + UUID_STRING_LEN + 20)
+#define AUFS_DIRREN_ENV_VAL_SZ	(AUFS_DIRREN_FNAME_SZ + 1 + 20)
+
 struct au_dr_hino {
 	struct hlist_bl_node	dr_hnode;
 	ino_t			dr_h_ino;
@@ -24,6 +47,7 @@ struct au_dr_hino {
 
 struct au_dr_br {
 	struct hlist_bl_head	dr_h_ino[AuDirren_NHASH];
+	struct au_dr_brid	dr_brid;
 };
 #else
 struct au_dr_hino;