1 files changed, 367 insertions, 0 deletions
diff --git a/fs/aufs/dynop.c b/fs/aufs/dynop.c
new file mode 100644
index 000000000000..837f94d49f74
--- /dev/null
+++ b/fs/aufs/dynop.c
@@ -0,0 +1,367 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2010-2020 Junjiro R. Okajima
+ *
+ * This program, aufs is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * dynamically customizable operations for regular files
+ */
+
+#include "aufs.h"
+
+#define DyPrSym(key)	AuDbgSym(key->dk_op.dy_hop)
+
+/*
+ * How large will these lists be?
+ * Usually just a few elements, 20-30 at most for each, I guess.
+ */
+static struct hlist_bl_head dynop[AuDyLast];
+
+static struct au_dykey *dy_gfind_get(struct hlist_bl_head *hbl,
+				     const void *h_op)
+{
+	struct au_dykey *key, *tmp;
+	struct hlist_bl_node *pos;
+
+	key = NULL;
+	hlist_bl_lock(hbl);
+	hlist_bl_for_each_entry(tmp, pos, hbl, dk_hnode)
+		if (tmp->dk_op.dy_hop == h_op) {
+			if (kref_get_unless_zero(&tmp->dk_kref))
+				key = tmp;
+			break;
+		}
+	hlist_bl_unlock(hbl);
+
+	return key;
+}
+
+static struct au_dykey *dy_bradd(struct au_branch *br, struct au_dykey *key)
+{
+	struct au_dykey **k, *found;
+	const void *h_op = key->dk_op.dy_hop;
+	int i;
+
+	found = NULL;
+	k = br->br_dykey;
+	for (i = 0; i < AuBrDynOp; i++)
+		if (k[i]) {
+			if (k[i]->dk_op.dy_hop == h_op) {
+				found = k[i];
+				break;
+			}
+		} else
+			break;
+	if (!found) {
+		spin_lock(&br->br_dykey_lock);
+		for (; i < AuBrDynOp; i++)
+			if (k[i]) {
+				if (k[i]->dk_op.dy_hop == h_op) {
+					found = k[i];
+					break;
+				}
+			} else {
+				k[i] = key;
+				break;
+			}
+		spin_unlock(&br->br_dykey_lock);
+		BUG_ON(i == AuBrDynOp); /* expand the array */
+	}
+
+	return found;
+}
+
+/* kref_get() if @key is already added */
+static struct au_dykey *dy_gadd(struct hlist_bl_head *hbl, struct au_dykey *key)
+{
+	struct au_dykey *tmp, *found;
+	struct hlist_bl_node *pos;
+	const void *h_op = key->dk_op.dy_hop;
+
+	found = NULL;
+	hlist_bl_lock(hbl);
+	hlist_bl_for_each_entry(tmp, pos, hbl, dk_hnode)
+		if (tmp->dk_op.dy_hop == h_op) {
+			if (kref_get_unless_zero(&tmp->dk_kref))
+				found = tmp;
+			break;
+		}
+	if (!found)
+		hlist_bl_add_head(&key->dk_hnode, hbl);
+	hlist_bl_unlock(hbl);
+
+	if (!found)
+		DyPrSym(key);
+	return found;
+}
+
+static void dy_free_rcu(struct rcu_head *rcu)
+{
+	struct au_dykey *key;
+
+	key = container_of(rcu, struct au_dykey, dk_rcu);
+	DyPrSym(key);
+	kfree(key);
+}
+
+static void dy_free(struct kref *kref)
+{
+	struct au_dykey *key;
+	struct hlist_bl_head *hbl;
+
+	key = container_of(kref, struct au_dykey, dk_kref);
+	hbl = dynop + key->dk_op.dy_type;
+	au_hbl_del(&key->dk_hnode, hbl);
+	call_rcu(&key->dk_rcu, dy_free_rcu);
+}
+
+void au_dy_put(struct au_dykey *key)
+{
+	kref_put(&key->dk_kref, dy_free);
+}
+
+/* ---------------------------------------------------------------------- */
+
+#define DyDbgSize(cnt, op)	AuDebugOn(cnt != sizeof(op)/sizeof(void *))
+
+#ifdef CONFIG_AUFS_DEBUG
+#define DyDbgDeclare(cnt)	unsigned int cnt = 0
+#define DyDbgInc(cnt)		do { cnt++; } while (0)
+#else
+#define DyDbgDeclare(cnt)	do {} while (0)
+#define DyDbgInc(cnt)		do {} while (0)
+#endif
+
+#define DySet(func, dst, src, h_op, h_sb) do {				\
+	DyDbgInc(cnt);							\
+	if (h_op->func) {						\
+		if (src.func)						\
+			dst.func = src.func;				\
+		else							\
+			AuDbg("%s %s\n", au_sbtype(h_sb), #func);	\
+	}								\
+} while (0)
+
+#define DySetForce(func, dst, src) do {		\
+	AuDebugOn(!src.func);			\
+	DyDbgInc(cnt);				\
+	dst.func = src.func;			\
+} while (0)
+
+#define DySetAop(func) \
+	DySet(func, dyaop->da_op, aufs_aop, h_aop, h_sb)
+#define DySetAopForce(func) \
+	DySetForce(func, dyaop->da_op, aufs_aop)
+
+static void dy_aop(struct au_dykey *key, const void *h_op,
+		   struct super_block *h_sb __maybe_unused)
+{
+	struct au_dyaop *dyaop = (void *)key;
+	const struct address_space_operations *h_aop = h_op;
+	DyDbgDeclare(cnt);
+
+	AuDbg("%s\n", au_sbtype(h_sb));
+
+	DySetAop(writepage);
+	DySetAopForce(readpage);	/* force */
+	DySetAop(writepages);
+	DySetAop(set_page_dirty);
+	DySetAop(readpages);
+	DySetAop(write_begin);
+	DySetAop(write_end);
+	DySetAop(bmap);
+	DySetAop(invalidatepage);
+	DySetAop(releasepage);
+	DySetAop(freepage);
+	/* this one will be changed according to an aufs mount option */
+	DySetAop(direct_IO);
+	DySetAop(migratepage);
+	DySetAop(isolate_page);
+	DySetAop(putback_page);
+	DySetAop(launder_page);
+	DySetAop(is_partially_uptodate);
+	DySetAop(is_dirty_writeback);
+	DySetAop(error_remove_page);
+	DySetAop(swap_activate);
+	DySetAop(swap_deactivate);
+
+	DyDbgSize(cnt, *h_aop);
+}
+
+/* ---------------------------------------------------------------------- */
+
+static void dy_bug(struct kref *kref)
+{
+	BUG();
+}
+
+static struct au_dykey *dy_get(struct au_dynop *op, struct au_branch *br)
+{
+	struct au_dykey *key, *old;
+	struct hlist_bl_head *hbl;
+	struct op {
+		unsigned int sz;
+		void (*set)(struct au_dykey *key, const void *h_op,
+			    struct super_block *h_sb __maybe_unused);
+	};
+	static const struct op a[] = {
+		[AuDy_AOP] = {
+			.sz	= sizeof(struct au_dyaop),
+			.set	= dy_aop
+		}
+	};
+	const struct op *p;
+
+	hbl = dynop + op->dy_type;
+	key = dy_gfind_get(hbl, op->dy_hop);
+	if (key)
+		goto out_add; /* success */
+
+	p = a + op->dy_type;
+	key = kzalloc(p->sz, GFP_NOFS);
+	if (unlikely(!key)) {
+		key = ERR_PTR(-ENOMEM);
+		goto out;
+	}
+
+	key->dk_op.dy_hop = op->dy_hop;
+	kref_init(&key->dk_kref);
+	p->set(key, op->dy_hop, au_br_sb(br));
+	old = dy_gadd(hbl, key);
+	if (old) {
+		au_kfree_rcu(key);
+		key = old;
+	}
+
+out_add:
+	old = dy_bradd(br, key);
+	if (old)
+		/* its ref-count should never be zero here */
+		kref_put(&key->dk_kref, dy_bug);
+out:
+	return key;
+}
+
+/* ---------------------------------------------------------------------- */
+/*
+ * Aufs prohibits O_DIRECT by default even if the branch supports it.
+ * This behaviour is necessary to return an error from open(O_DIRECT) instead
+ * of the succeeding I/O. The dio mount option enables O_DIRECT and makes
+ * open(O_DIRECT) always succeed, but the succeeding I/O may return an error.
+ * See the aufs manual in detail.
+ */
+static void dy_adx(struct au_dyaop *dyaop, int do_dx)
+{
+	if (!do_dx)
+		dyaop->da_op.direct_IO = NULL;
+	else
+		dyaop->da_op.direct_IO = aufs_aop.direct_IO;
+}
+
+static struct au_dyaop *dy_aget(struct au_branch *br,
+				const struct address_space_operations *h_aop,
+				int do_dx)
+{
+	struct au_dyaop *dyaop;
+	struct au_dynop op;
+
+	op.dy_type = AuDy_AOP;
+	op.dy_haop = h_aop;
+	dyaop = (void *)dy_get(&op, br);
+	if (IS_ERR(dyaop))
+		goto out;
+	dy_adx(dyaop, do_dx);
+
+out:
+	return dyaop;
+}
+
+int au_dy_iaop(struct inode *inode, aufs_bindex_t bindex,
+		struct inode *h_inode)
+{
+	int err, do_dx;
+	struct super_block *sb;
+	struct au_branch *br;
+	struct au_dyaop *dyaop;
+
+	AuDebugOn(!S_ISREG(h_inode->i_mode));
+	IiMustWriteLock(inode);
+
+	sb = inode->i_sb;
+	br = au_sbr(sb, bindex);
+	do_dx = !!au_opt_test(au_mntflags(sb), DIO);
+	dyaop = dy_aget(br, h_inode->i_mapping->a_ops, do_dx);
+	err = PTR_ERR(dyaop);
+	if (IS_ERR(dyaop))
+		/* unnecessary to call dy_fput() */
+		goto out;
+
+	err = 0;
+	inode->i_mapping->a_ops = &dyaop->da_op;
+
+out:
+	return err;
+}
+
+/*
+ * Is it safe to replace a_ops during the inode/file is in operation?
+ * Yes, I hope so.
+ */
+int au_dy_irefresh(struct inode *inode)
+{
+	int err;
+	aufs_bindex_t btop;
+	struct inode *h_inode;
+
+	err = 0;
+	if (S_ISREG(inode->i_mode)) {
+		btop = au_ibtop(inode);
+		h_inode = au_h_iptr(inode, btop);
+		err = au_dy_iaop(inode, btop, h_inode);
+	}
+	return err;
+}
+
+void au_dy_arefresh(int do_dx)
+{
+	struct hlist_bl_head *hbl;
+	struct hlist_bl_node *pos;
+	struct au_dykey *key;
+
+	hbl = dynop + AuDy_AOP;
+	hlist_bl_lock(hbl);
+	hlist_bl_for_each_entry(key, pos, hbl, dk_hnode)
+		dy_adx((void *)key, do_dx);
+	hlist_bl_unlock(hbl);
+}
+
+/* ---------------------------------------------------------------------- */
+
+void __init au_dy_init(void)
+{
+	int i;
+
+	for (i = 0; i < AuDyLast; i++)
+		INIT_HLIST_BL_HEAD(dynop + i);
+}
+
+void au_dy_fin(void)
+{
+	int i;
+
+	for (i = 0; i < AuDyLast; i++)
+		WARN_ON(!hlist_bl_empty(dynop + i));
+}