aufs: users' direct branch access

Aufs allows users' direct branch access (UDBA), ie. by-passing aufs.
Of course it will make aufs inode/dentry-caches obsolete. In order to
detect such change by the several tests, "udba=" option is introduced.

For details, see lookup.txt in later commit.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

fs/aufs/cpup.c

@@ -659,7 +659,8 @@ int cpup_entry(struct au_cp_generic *cpg, struct dentry *dst_parent,
 	}
 
 	mnt_flags = au_mntflags(sb);
-	if (!isdir
+	if (!au_opt_test(mnt_flags, UDBA_NONE)
+	    && !isdir
 	    && au_opt_test(mnt_flags, XINO)
 	    && (h_inode->i_nlink == 1
 		|| (h_inode->i_state & I_LINKABLE))
@@ -1208,7 +1209,7 @@ int au_sio_cpup_wh(struct au_cp_generic *cpg, struct file *file)
 
 		pin_orig = cpg->pin;
 		au_pin_init(&wh_pin, dentry, bdst, AuLsc_DI_PARENT,
-			    AuLsc_I_PARENT3, AuPin_DI_LOCKED);
+			    AuLsc_I_PARENT3, cpg->pin->udba, AuPin_DI_LOCKED);
 		cpg->pin = &wh_pin;
 	}
 
@@ -1261,7 +1262,7 @@ int au_cp_dirs(struct dentry *dentry, aufs_bindex_t bdst,
 		goto out;
 
 	au_pin_init(&pin, dentry, bdst, AuLsc_DI_PARENT2, AuLsc_I_PARENT2,
-		    AuPin_MNT_WRITE);
+		    au_opt_udba(dentry->d_sb), AuPin_MNT_WRITE);
 
 	/* do not use au_dpage */
 	real_parent = parent;

fs/aufs/dentry.c

@@ -171,7 +171,8 @@ int au_lkup_dentry(struct dentry *dentry, aufs_bindex_t btop,
 		au_update_dbtop(dentry);
 	}
 	err = npositive;
-	if (unlikely(au_dbtop(dentry) < 0)) {
+	if (unlikely(!au_opt_test(au_mntflags(sb), UDBA_NONE)
+		     && au_dbtop(dentry) < 0)) {
 		err = -EIO;
 		AuIOErr("both of real entry and whiteout found, %pd, err %d\n",
 			dentry, err);
@@ -326,16 +327,17 @@ out:
 	return err;
 }
 
-int au_h_verify(struct dentry *h_dentry, struct inode *h_dir,
+int au_h_verify(struct dentry *h_dentry, unsigned int udba, struct inode *h_dir,
 		struct dentry *h_parent, struct au_branch *br)
 {
 	int err;
 
 	err = 0;
-	if (!au_test_fs_remote(h_dentry->d_sb)) {
+	if (udba == AuOpt_UDBA_REVAL
+	    && !au_test_fs_remote(h_dentry->d_sb)) {
 		IMustLock(h_dir);
 		err = (d_inode(h_dentry->d_parent) != h_dir);
-	} else
+	} else if (udba != AuOpt_UDBA_NONE)
 		err = au_h_verify_dentry(h_dentry, h_parent, br);
 
 	return err;

fs/aufs/dentry.h

@@ -51,7 +51,7 @@ struct au_do_lookup_args {
 /* dentry.c */
 struct au_branch;
 struct dentry *au_sio_lkup_one(struct qstr *name, struct dentry *parent);
-int au_h_verify(struct dentry *h_dentry, struct inode *h_dir,
+int au_h_verify(struct dentry *h_dentry, unsigned int udba, struct inode *h_dir,
 		struct dentry *h_parent, struct au_branch *br);
 
 int au_lkup_dentry(struct dentry *dentry, aufs_bindex_t btop,

fs/aufs/i_op.c

@@ -32,8 +32,8 @@ int au_pin_hdir_lock(struct au_pin *p)
 
 	err = 0;
 	if (p->h_dentry)
-		err = au_h_verify(p->h_dentry, p->hdir->hi_inode, p->h_parent,
-				  p->br);
+		err = au_h_verify(p->h_dentry, p->udba, p->hdir->hi_inode,
+				  p->h_parent, p->br);
 
 out:
 	return err;
@@ -193,9 +193,10 @@ out:
 
 void au_pin_init(struct au_pin *p, struct dentry *dentry,
 		 aufs_bindex_t bindex, int lsc_di, int lsc_hi,
-		 unsigned char flags)
+		 unsigned int udba, unsigned char flags)
 {
 	p->dentry = dentry;
+	p->udba = udba;
 	p->lsc_di = lsc_di;
 	p->lsc_hi = lsc_hi;
 	p->flags = flags;
@@ -212,9 +213,9 @@ void au_pin_init(struct au_pin *p, struct dentry *dentry,
 }
 
 int au_pin(struct au_pin *pin, struct dentry *dentry, aufs_bindex_t bindex,
-	   unsigned char flags)
+	   unsigned int udba, unsigned char flags)
 {
 	au_pin_init(pin, dentry, bindex, AuLsc_DI_PARENT, AuLsc_I_PARENT2,
-		    flags);
+		    udba, flags);
 	return au_do_pin(pin);
 }

fs/aufs/inode.h

@@ -59,6 +59,7 @@ struct au_icntnr {
 struct au_pin {
 	/* input */
 	struct dentry *dentry;
+	unsigned int udba;
 	unsigned char lsc_di, lsc_hi, flags;
 	aufs_bindex_t bindex;
 
@@ -100,9 +101,9 @@ int au_test_h_perm_sio(struct inode *h_inode, int mask);
 struct dentry *au_pinned_h_parent(struct au_pin *pin);
 void au_pin_init(struct au_pin *pin, struct dentry *dentry,
 		 aufs_bindex_t bindex, int lsc_di, int lsc_hi,
-		 unsigned char flags);
+		 unsigned int udba, unsigned char flags);
 int au_pin(struct au_pin *pin, struct dentry *dentry, aufs_bindex_t bindex,
-	   unsigned char flags) __must_check;
+	   unsigned int udba, unsigned char flags) __must_check;
 int au_do_pin(struct au_pin *pin) __must_check;
 void au_unpin(struct au_pin *pin);
 

fs/aufs/opts.c

@@ -252,6 +252,27 @@ void au_optstr_br_perm(au_br_perm_str_t *str, int perm)
 
 /* ---------------------------------------------------------------------- */
 
+static match_table_t udbalevel = {
+	{AuOpt_UDBA_REVAL, "reval"},
+	{AuOpt_UDBA_NONE, "none"},
+	{-1, NULL}
+};
+
+/* re-commit later */ __maybe_unused
+static int noinline_for_stack udba_val(char *str)
+{
+	substring_t args[MAX_OPT_ARGS];
+
+	return match_token(str, udbalevel, args);
+}
+
+const char *au_optstr_udba(int udba)
+{
+	return au_parser_pattern(udba, udbalevel);
+}
+
+/* ---------------------------------------------------------------------- */
+
 static match_table_t au_wbr_create_policy = {
 	{AuWbrCreate_TDP, "tdp"},
 	{AuWbrCreate_TDP, "top-down-parent"},
@@ -1063,3 +1084,10 @@ int au_opts_mount(struct super_block *sb, struct au_opts *opts)
 out:
 	return err;
 }
+
+/* ---------------------------------------------------------------------- */
+
+unsigned int au_opt_udba(struct super_block *sb)
+{
+	return au_mntflags(sb) & AuOptMask_UDBA;
+}

fs/aufs/opts.h

@@ -22,13 +22,23 @@ struct file;
 #define AuOpt_XINO		1		/* external inode number bitmap
 						   and translation table */
 #define AuOpt_TRUNC_XINO	(1 << 1)	/* truncate xino files */
+#define AuOpt_UDBA_NONE		(1 << 2)	/* users direct branch access */
+#define AuOpt_UDBA_REVAL	(1 << 3)
 #define AuOpt_PLINK		(1 << 6)	/* pseudo-link */
 
 #define AuOpt_Def	(AuOpt_XINO \
+			 | AuOpt_UDBA_REVAL \
 			 | AuOpt_PLINK)
+#define AuOptMask_UDBA	(AuOpt_UDBA_NONE \
+			 | AuOpt_UDBA_REVAL)
 
 #define au_opt_test(flags, name)	(flags & AuOpt_##name)
 #define au_opt_set(flags, name) do { \
+	BUILD_BUG_ON(AuOpt_##name & AuOptMask_UDBA); \
+	((flags) |= AuOpt_##name); \
+} while (0)
+#define au_opt_set_udba(flags, name) do { \
+	(flags) &= ~AuOptMask_UDBA; \
 	((flags) |= AuOpt_##name); \
 } while (0)
 #define au_opt_clr(flags, name) do { \
@@ -128,6 +138,7 @@ struct au_opts {
 
 /* opts.c */
 void au_optstr_br_perm(au_br_perm_str_t *str, int perm);
+const char *au_optstr_udba(int udba);
 const char *au_optstr_wbr_copyup(int wbr_copyup);
 const char *au_optstr_wbr_create(int wbr_create);
 
@@ -138,5 +149,7 @@ int au_opts_verify(struct super_block *sb, unsigned long sb_flags,
 		   unsigned int pending);
 int au_opts_mount(struct super_block *sb, struct au_opts *opts);
 
+unsigned int au_opt_udba(struct super_block *sb);
+
 #endif /* __KERNEL__ */
 #endif /* __AUFS_OPTS_H__ */

fs/aufs/whout.c

@@ -499,7 +499,8 @@ static void reinit_br_wh(void *arg)
 
 	inode_lock_nested(hdir->hi_inode, AuLsc_I_PARENT);
 	wbr_wh_write_lock(wbr);
-	err = au_h_verify(wbr->wbr_whbase, hdir->hi_inode, h_root, a->br);
+	err = au_h_verify(wbr->wbr_whbase, au_opt_udba(a->sb), hdir->hi_inode,
+			  h_root, a->br);
 	if (!err) {
 		h_path.dentry = wbr->wbr_whbase;
 		h_path.mnt = au_br_mnt(a->br);