aufs: branch attributes, copy/move-up on open

When these attributes are specified and aufs tries opening a file on that
branch, aufs copies/moves it up.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

fs/aufs/file.c

@@ -94,6 +94,111 @@ out:
 	return h_file;
 }
 
+static int au_cmoo(struct dentry *dentry)
+{
+	int err, cmoo;
+	unsigned int udba;
+	struct path h_path;
+	struct au_pin pin;
+	struct au_cp_generic cpg = {
+		.dentry	= dentry,
+		.bdst	= -1,
+		.bsrc	= -1,
+		.len	= -1,
+		.pin	= &pin,
+		.flags	= AuCpup_DTIME
+	};
+	struct inode *delegated;
+	struct super_block *sb;
+	struct au_sbinfo *sbinfo;
+	struct au_branch *br;
+	struct dentry *parent;
+	struct au_hinode *hdir;
+
+	DiMustWriteLock(dentry);
+	IiMustWriteLock(d_inode(dentry));
+
+	err = 0;
+	if (IS_ROOT(dentry))
+		goto out;
+	cpg.bsrc = au_dbtop(dentry);
+	if (!cpg.bsrc)
+		goto out;
+
+	sb = dentry->d_sb;
+	sbinfo = au_sbi(sb);
+	br = au_sbr(sb, cpg.bsrc);
+	cmoo = au_br_cmoo(br->br_perm);
+	if (!cmoo)
+		goto out;
+	if (!d_is_reg(dentry))
+		cmoo &= AuBrAttr_COO_ALL;
+	if (!cmoo)
+		goto out;
+
+	parent = dget_parent(dentry);
+	di_write_lock_parent(parent);
+	err = au_wbr_do_copyup_bu(dentry, cpg.bsrc - 1);
+	cpg.bdst = err;
+	if (unlikely(err < 0)) {
+		err = 0;	/* there is no upper writable branch */
+		goto out_dgrade;
+	}
+	AuDbg("bsrc %d, bdst %d\n", cpg.bsrc, cpg.bdst);
+
+	/* do not respect the coo attrib for the target branch */
+	err = au_cpup_dirs(dentry, cpg.bdst);
+	if (unlikely(err))
+		goto out_dgrade;
+
+	di_downgrade_lock(parent, AuLock_IR);
+	udba = au_opt_udba(sb);
+	err = au_pin(&pin, dentry, cpg.bdst, udba,
+		     AuPin_DI_LOCKED | AuPin_MNT_WRITE);
+	if (unlikely(err))
+		goto out_parent;
+
+	err = au_sio_cpup_simple(&cpg);
+	au_unpin(&pin);
+	if (unlikely(err))
+		goto out_parent;
+	if (!(cmoo & AuBrWAttr_MOO))
+		goto out_parent; /* success */
+
+	err = au_pin(&pin, dentry, cpg.bsrc, udba,
+		     AuPin_DI_LOCKED | AuPin_MNT_WRITE);
+	if (unlikely(err))
+		goto out_parent;
+
+	h_path.mnt = au_br_mnt(br);
+	h_path.dentry = au_h_dptr(dentry, cpg.bsrc);
+	hdir = au_hi(d_inode(parent), cpg.bsrc);
+	delegated = NULL;
+	err = vfsub_unlink(hdir->hi_inode, &h_path, &delegated, /*force*/1);
+	au_unpin(&pin);
+	/* todo: keep h_dentry or not? */
+	if (unlikely(err == -EWOULDBLOCK)) {
+		pr_warn("cannot retry for NFSv4 delegation"
+			" for an internal unlink\n");
+		iput(delegated);
+	}
+	if (unlikely(err)) {
+		pr_err("unlink %pd after coo failed (%d), ignored\n",
+		       dentry, err);
+		err = 0;
+	}
+	goto out_parent; /* success */
+
+out_dgrade:
+	di_downgrade_lock(parent, AuLock_IR);
+out_parent:
+	di_read_unlock(parent, AuLock_IR);
+	dput(parent);
+out:
+	AuTraceErr(err);
+	return err;
+}
+
 int au_do_open(struct file *file, struct au_do_open_args *args)
 {
 	int err, aopen = args->aopen;
@@ -112,14 +217,18 @@ int au_do_open(struct file *file, struct au_do_open_args *args)
 
 	dentry = file->f_path.dentry;
 	AuDebugOn(IS_ERR_OR_NULL(dentry));
-	di_read_lock_child(dentry, AuLock_IR);
-	if (!aopen)
-		err = args->open(file, vfsub_file_flags(file), NULL);
-	else {
-		lockdep_off();
+	di_write_lock_child(dentry);
+	err = au_cmoo(dentry);
+	di_downgrade_lock(dentry, AuLock_IR);
+	if (!err) {
+		if (!aopen)
+			err = args->open(file, vfsub_file_flags(file), NULL);
+		else {
+			lockdep_off();
 			err = args->open(file, vfsub_file_flags(file),
 					 args->h_file);
-		lockdep_on();
+			lockdep_on();
+		}
 	}
 	di_read_unlock(dentry, AuLock_IR);
 

fs/aufs/opts.c

@@ -202,6 +202,9 @@ static match_table_t brperm = {
 };
 
 static match_table_t brattr = {
+	/* general */
+	{AuBrAttr_COO_REG, AUFS_BRATTR_COO_REG},
+	{AuBrAttr_COO_ALL, AUFS_BRATTR_COO_ALL},
 #ifdef CONFIG_AUFS_XATTR
 	{AuBrAttr_ICEX, AUFS_BRATTR_ICEX},
 	{AuBrAttr_ICEX_SEC, AUFS_BRATTR_ICEX_SEC},
@@ -215,9 +218,9 @@ static match_table_t brattr = {
 	{AuBrRAttr_WH, AUFS_BRRATTR_WH},
 
 	/* rw branch */
+	{AuBrWAttr_MOO, AUFS_BRWATTR_MOO},
 	{AuBrWAttr_NoLinkWH, AUFS_BRWATTR_NLWH},
 
-	/* add more later */
 	{0, NULL}
 };
 
@@ -232,9 +235,11 @@ static int br_attr_val(char *str, match_table_t table, substring_t args[])
 		if (p)
 			*p = 0;
 		v = match_token(str, table, args);
-		if (v)
+		if (v) {
+			if (v & AuBrAttr_CMOO_Mask)
+				attr &= ~AuBrAttr_CMOO_Mask;
 			attr |= v;
-		else {
+		} else {
 			if (p)
 				*p = '+';
 			pr_warn("ignored branch attribute %s\n", str);

include/uapi/linux/aufs_type.h

@@ -111,6 +111,8 @@ typedef int16_t aufs_bindex_t;
 #define AUFS_BRPERM_RW		"rw"
 #define AUFS_BRPERM_RO		"ro"
 #define AUFS_BRPERM_RR		"rr"
+#define AUFS_BRATTR_COO_REG	"coo_reg"
+#define AUFS_BRATTR_COO_ALL	"coo_all"
 #define AUFS_BRATTR_ICEX	"icex"
 #define AUFS_BRATTR_ICEX_SEC	"icexsec"
 #define AUFS_BRATTR_ICEX_SYS	"icexsys"
@@ -119,12 +121,17 @@ typedef int16_t aufs_bindex_t;
 #define AUFS_BRATTR_ICEX_OTH	"icexoth"
 #define AUFS_BRRATTR_WH		"wh"
 #define AUFS_BRWATTR_NLWH	"nolwh"
+#define AUFS_BRWATTR_MOO	"moo"
 
 #define AuBrPerm_RW		1		/* writable, hardlinkable wh */
 #define AuBrPerm_RO		(1 << 1)	/* readonly */
 #define AuBrPerm_RR		(1 << 2)	/* natively readonly */
 #define AuBrPerm_Mask		(AuBrPerm_RW | AuBrPerm_RO | AuBrPerm_RR)
 
+#define AuBrAttr_COO_REG	(1 << 3)	/* copy-up on open */
+#define AuBrAttr_COO_ALL	(1 << 4)
+#define AuBrAttr_COO_Mask	(AuBrAttr_COO_REG | AuBrAttr_COO_ALL)
+
 /* ignore error in copying XATTR */
 #define AuBrAttr_ICEX_SEC	(1 << 7)
 #define AuBrAttr_ICEX_SYS	(1 << 8)
@@ -141,7 +148,10 @@ typedef int16_t aufs_bindex_t;
 #define AuBrRAttr_Mask		AuBrRAttr_WH
 
 #define AuBrWAttr_NoLinkWH	(1 << 13)	/* un-hardlinkable whiteouts */
-#define AuBrWAttr_Mask		AuBrWAttr_NoLinkWH
+#define AuBrWAttr_MOO		(1 << 14)	/* move-up on open */
+#define AuBrWAttr_Mask		(AuBrWAttr_NoLinkWH | AuBrWAttr_MOO)
+
+#define AuBrAttr_CMOO_Mask	(AuBrAttr_COO_Mask | AuBrWAttr_MOO)
 
 /* #warning test userspace */
 #ifdef __KERNEL__
@@ -189,6 +199,11 @@ static inline int au_br_wh_linkable(int brperm)
 	return !(brperm & AuBrWAttr_NoLinkWH);
 }
 
+static inline int au_br_cmoo(int brperm)
+{
+	return brperm & AuBrAttr_CMOO_Mask;
+}
+
 /* ---------------------------------------------------------------------- */
 
 /* ioctl */