aufs: statfs sum options

Since aufs can have multiple writable branches, these options are
useful.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

fs/aufs/opts.c

@@ -29,6 +29,7 @@ enum {
 	Opt_dio, Opt_nodio,
 	Opt_wbr_copyup, Opt_wbr_create,
 	Opt_verbose, Opt_noverbose,
+	Opt_sum, Opt_nosum, Opt_wsum,
 	Opt_dirperm1, Opt_nodirperm1,
 	Opt_acl, Opt_noacl,
 	Opt_tail, Opt_ignore, Opt_ignore_silent, Opt_err
@@ -94,6 +95,10 @@ static match_table_t options = {
 	{Opt_noverbose, "q"},
 	{Opt_noverbose, "silent"},
 
+	{Opt_sum, "sum"},
+	{Opt_nosum, "nosum"},
+	{Opt_wsum, "wsum"},
+
 	{Opt_rdcache, "rdcache=%d"},
 	{Opt_rdblk, "rdblk=%d"},
 	{Opt_rdblk_def, "rdblk=def"},
@@ -593,6 +598,15 @@ static void dump_opts(struct au_opts *opts)
 		case Opt_noverbose:
 			AuLabel(noverbose);
 			break;
+		case Opt_sum:
+			AuLabel(sum);
+			break;
+		case Opt_nosum:
+			AuLabel(nosum);
+			break;
+		case Opt_wsum:
+			AuLabel(wsum);
+			break;
 		case Opt_wbr_create:
 			u.create = &opt->wbr_create;
 			AuDbg("create %d, %s\n", u.create->wbr_create,
@@ -1059,6 +1073,9 @@ int au_opts_parse(struct super_block *sb, char *str, struct au_opts *opts)
 		case Opt_nodio:
 		case Opt_verbose:
 		case Opt_noverbose:
+		case Opt_sum:
+		case Opt_nosum:
+		case Opt_wsum:
 		case Opt_rdblk_def:
 		case Opt_rdhash_def:
 		case Opt_acl:
@@ -1220,6 +1237,17 @@ static int au_opt_simple(struct super_block *sb, struct au_opt *opt,
 		au_opt_clr(sbinfo->si_mntflags, VERBOSE);
 		break;
 
+	case Opt_sum:
+		au_opt_set(sbinfo->si_mntflags, SUM);
+		break;
+	case Opt_wsum:
+		au_opt_clr(sbinfo->si_mntflags, SUM);
+		au_opt_set(sbinfo->si_mntflags, SUM_W);
+	case Opt_nosum:
+		au_opt_clr(sbinfo->si_mntflags, SUM);
+		au_opt_clr(sbinfo->si_mntflags, SUM_W);
+		break;
+
 	case Opt_wbr_create:
 		err = au_opt_wbr_create(sb, &opt->wbr_create);
 		break;

fs/aufs/opts.h

@@ -28,6 +28,8 @@ struct file;
 #define AuOpt_PLINK		(1 << 6)	/* pseudo-link */
 #define AuOpt_DIRPERM1		(1 << 7)	/* ignore the lower dir's perm
 						   bits */
+#define AuOpt_SUM		(1 << 10)	/* summation for statfs(2) */
+#define AuOpt_SUM_W		(1 << 11)	/* unimplemented */
 #define AuOpt_VERBOSE		(1 << 13)	/* print the cause of error */
 #define AuOpt_DIO		(1 << 14)	/* direct io */
 

fs/aufs/super.c

@@ -276,6 +276,8 @@ static int aufs_show_options(struct seq_file *m, struct dentry *dentry)
 	AuUInt(RDBLK, rdblk, sbinfo->si_rdblk);
 	AuUInt(RDHASH, rdhash, sbinfo->si_rdhash);
 
+	AuBool(SUM, sum);
+	/* AuBool(SUM_W, wsum); */
 	AuBool(VERBOSE, verbose);
 
 out:
@@ -294,6 +296,98 @@ out:
 
 /* ---------------------------------------------------------------------- */
 
+/* sum mode which returns the summation for statfs(2) */
+
+static u64 au_add_till_max(u64 a, u64 b)
+{
+	u64 old;
+
+	old = a;
+	a += b;
+	if (old <= a)
+		return a;
+	return ULLONG_MAX;
+}
+
+static u64 au_mul_till_max(u64 a, long mul)
+{
+	u64 old;
+
+	old = a;
+	a *= mul;
+	if (old <= a)
+		return a;
+	return ULLONG_MAX;
+}
+
+static int au_statfs_sum(struct super_block *sb, struct kstatfs *buf)
+{
+	int err;
+	long bsize, factor;
+	u64 blocks, bfree, bavail, files, ffree;
+	aufs_bindex_t bbot, bindex, i;
+	unsigned char shared;
+	struct path h_path;
+	struct super_block *h_sb;
+
+	err = 0;
+	bsize = LONG_MAX;
+	files = 0;
+	ffree = 0;
+	blocks = 0;
+	bfree = 0;
+	bavail = 0;
+	bbot = au_sbbot(sb);
+	for (bindex = 0; bindex <= bbot; bindex++) {
+		h_path.mnt = au_sbr_mnt(sb, bindex);
+		h_sb = h_path.mnt->mnt_sb;
+		shared = 0;
+		for (i = 0; !shared && i < bindex; i++)
+			shared = (au_sbr_sb(sb, i) == h_sb);
+		if (shared)
+			continue;
+
+		/* sb->s_root for NFS is unreliable */
+		h_path.dentry = h_path.mnt->mnt_root;
+		err = vfs_statfs(&h_path, buf);
+		if (unlikely(err))
+			goto out;
+
+		if (bsize > buf->f_bsize) {
+			/*
+			 * we will reduce bsize, so we have to expand blocks
+			 * etc. to match them again
+			 */
+			factor = (bsize / buf->f_bsize);
+			blocks = au_mul_till_max(blocks, factor);
+			bfree = au_mul_till_max(bfree, factor);
+			bavail = au_mul_till_max(bavail, factor);
+			bsize = buf->f_bsize;
+		}
+
+		factor = (buf->f_bsize / bsize);
+		blocks = au_add_till_max(blocks,
+				au_mul_till_max(buf->f_blocks, factor));
+		bfree = au_add_till_max(bfree,
+				au_mul_till_max(buf->f_bfree, factor));
+		bavail = au_add_till_max(bavail,
+				au_mul_till_max(buf->f_bavail, factor));
+		files = au_add_till_max(files, buf->f_files);
+		ffree = au_add_till_max(ffree, buf->f_ffree);
+	}
+
+	buf->f_bsize = bsize;
+	buf->f_blocks = blocks;
+	buf->f_bfree = bfree;
+	buf->f_bavail = bavail;
+	buf->f_files = files;
+	buf->f_ffree = ffree;
+	buf->f_frsize = 0;
+
+out:
+	return err;
+}
+
 static int aufs_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
 	int err;
@@ -303,10 +397,13 @@ static int aufs_statfs(struct dentry *dentry, struct kstatfs *buf)
 	/* lock free root dinfo */
 	sb = dentry->d_sb;
 	si_noflush_read_lock(sb);
-	/* sb->s_root for NFS is unreliable */
-	h_path.mnt = au_sbr_mnt(sb, 0);
-	h_path.dentry = h_path.mnt->mnt_root;
-	err = vfs_statfs(&h_path, buf);
+	if (!au_opt_test(au_mntflags(sb), SUM)) {
+		/* sb->s_root for NFS is unreliable */
+		h_path.mnt = au_sbr_mnt(sb, 0);
+		h_path.dentry = h_path.mnt->mnt_root;
+		err = vfs_statfs(&h_path, buf);
+	} else
+		err = au_statfs_sum(sb, buf);
 	si_read_unlock(sb);
 
 	if (!err) {