aufs: copy-up 5/7, simple interface

Because the copy-up operation is big and has many parameters and
functions, consolidate them in this commit.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

fs/aufs/cpup.c

@@ -725,7 +725,6 @@ out:
  * aufs doesn't touch the credential so
  * security_inode_copy_up{,_xattr}() are unnecessary.
  */
-/* re-commit later */ __maybe_unused
 static int au_cpup_single(struct au_cp_generic *cpg, struct dentry *dst_parent)
 {
 	int err, rerr;
@@ -904,6 +903,45 @@ static void au_call_cpup_single(void *args)
 }
 #endif
 
+/*
+ * prevent SIGXFSZ in copy-up.
+ * testing CAP_MKNOD is for generic fs,
+ * but CAP_FSETID is for xfs only, currently.
+ */
+static int au_cpup_sio_test(struct au_pin *pin, umode_t mode)
+{
+	int do_sio;
+	struct super_block *sb;
+	struct inode *h_dir;
+
+	do_sio = 0;
+	sb = au_pinned_parent(pin)->d_sb;
+	if (!au_wkq_test()
+	    && (!au_sbi(sb)->si_plink_maint_pid
+		|| au_plink_maint(sb, AuLock_NOPLM))) {
+		switch (mode & S_IFMT) {
+		case S_IFREG:
+			/* no condition about RLIMIT_FSIZE and the file size */
+			do_sio = 1;
+			break;
+		case S_IFCHR:
+		case S_IFBLK:
+			do_sio = !capable(CAP_MKNOD);
+			break;
+		}
+		if (!do_sio)
+			do_sio = ((mode & (S_ISUID | S_ISGID))
+				  && !capable(CAP_FSETID));
+		/* this workaround may be removed in the future */
+		if (!do_sio) {
+			h_dir = au_pinned_h_dir(pin);
+			do_sio = h_dir->i_mode & S_ISVTX;
+		}
+	}
+
+	return do_sio;
+}
+
 #if 0 /* reserved */
 int au_sio_cpup_single(struct au_cp_generic *cpg, struct dentry *dst_parent)
 {
@@ -927,3 +965,100 @@ int au_sio_cpup_single(struct au_cp_generic *cpg, struct dentry *dst_parent)
 	return err;
 }
 #endif
+
+/*
+ * copyup the @dentry from the first active lower branch to @bdst,
+ * using au_cpup_single().
+ */
+static int au_cpup_simple(struct au_cp_generic *cpg)
+{
+	int err;
+	unsigned int flags_orig;
+	struct dentry *dentry;
+
+	AuDebugOn(cpg->bsrc < 0);
+
+	dentry = cpg->dentry;
+	DiMustWriteLock(dentry);
+
+	err = au_lkup_neg(dentry, cpg->bdst, /*wh*/1);
+	if (!err) {
+		flags_orig = cpg->flags;
+		au_fset_cpup(cpg->flags, RENAME);
+		err = au_cpup_single(cpg, NULL);
+		cpg->flags = flags_orig;
+		if (!err)
+			return 0; /* success */
+
+		/* revert */
+		au_set_h_dptr(dentry, cpg->bdst, NULL);
+		au_set_dbtop(dentry, cpg->bsrc);
+	}
+
+	return err;
+}
+
+struct au_cpup_simple_args {
+	int *errp;
+	struct au_cp_generic *cpg;
+};
+
+static void au_call_cpup_simple(void *args)
+{
+	struct au_cpup_simple_args *a = args;
+
+	au_pin_hdir_acquire_nest(a->cpg->pin);
+	*a->errp = au_cpup_simple(a->cpg);
+	au_pin_hdir_release(a->cpg->pin);
+}
+
+static int au_do_sio_cpup_simple(struct au_cp_generic *cpg)
+{
+	int err, wkq_err;
+	struct dentry *dentry, *parent;
+	struct file *h_file;
+	struct inode *h_dir;
+
+	dentry = cpg->dentry;
+	h_file = NULL;
+	parent = dget_parent(dentry);
+	h_dir = au_h_iptr(d_inode(parent), cpg->bdst);
+	if (!au_test_h_perm_sio(h_dir, MAY_EXEC | MAY_WRITE)
+	    && !au_cpup_sio_test(cpg->pin, d_inode(dentry)->i_mode))
+		err = au_cpup_simple(cpg);
+	else {
+		struct au_cpup_simple_args args = {
+			.errp		= &err,
+			.cpg		= cpg
+		};
+		wkq_err = au_wkq_wait(au_call_cpup_simple, &args);
+		if (unlikely(wkq_err))
+			err = wkq_err;
+	}
+
+	dput(parent);
+
+	return err;
+}
+
+int au_sio_cpup_simple(struct au_cp_generic *cpg)
+{
+	aufs_bindex_t bsrc, bbot;
+	struct dentry *dentry, *h_dentry;
+
+	if (cpg->bsrc < 0) {
+		dentry = cpg->dentry;
+		bbot = au_dbbot(dentry);
+		for (bsrc = cpg->bdst + 1; bsrc <= bbot; bsrc++) {
+			h_dentry = au_h_dptr(dentry, bsrc);
+			if (h_dentry) {
+				AuDebugOn(d_is_negative(h_dentry));
+				break;
+			}
+		}
+		AuDebugOn(bsrc > bbot);
+		cpg->bsrc = bsrc;
+	}
+	AuDebugOn(cpg->bsrc <= cpg->bdst);
+	return au_do_sio_cpup_simple(cpg);
+}

fs/aufs/cpup.h

@@ -47,6 +47,7 @@ struct au_cp_generic {
 	do { (flags) &= ~AuCpup_##name; } while (0)
 
 int au_copy_file(struct file *dst, struct file *src, loff_t len);
+int au_sio_cpup_simple(struct au_cp_generic *cpg);
 
 /* ---------------------------------------------------------------------- */