aufs: sbinfo core

The structure is very similar to inode and dentry infos (in previous
commits), but the internal array is for 'struct au_branch' instead of
'superblock.' Additionally the lifetime of 'struct au_sbinfo' is managed
by kobject since it will be connected to sysfs by later commit.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

fs/aufs/Makefile

@@ -9,7 +9,7 @@ ccflags-y += -DDEBUG
 ccflags-y += -include ${srctree}/include/uapi/linux/aufs_type.h
 
 obj-$(CONFIG_AUFS_FS) += aufs.o
-aufs-y := module.o super.o \
+aufs-y := module.o sbinfo.o super.o \
 	dinfo.o \
 	iinfo.o
 

fs/aufs/debug.h

@@ -52,6 +52,16 @@ AuStubInt0(au_debug_test, void)
 } while (0)
 #define AuLabel(l)		AuDbg(#l "\n")
 
+#define AuTraceErr(e) do { \
+	if (unlikely((e) < 0)) \
+		AuDbg("err %d\n", (int)(e)); \
+} while (0)
+
+#define AuTraceErrPtr(p) do { \
+	if (IS_ERR(p)) \
+		AuDbg("err %ld\n", PTR_ERR(p)); \
+} while (0)
+
 /* ---------------------------------------------------------------------- */
 
 struct dentry;

fs/aufs/sbinfo.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2005-2019 Junjiro R. Okajima
+ */
+
+/*
+ * superblock private data
+ */
+
+#include "aufs.h"
+
+/*
+ * they are necessary regardless sysfs is disabled.
+ */
+void au_si_free(struct kobject *kobj)
+{
+	struct au_sbinfo *sbinfo;
+
+	sbinfo = container_of(kobj, struct au_sbinfo, si_kobj);
+	au_kfree_try_rcu(sbinfo->si_branch);
+	AuRwDestroy(&sbinfo->si_rwsem);
+
+	au_kfree_rcu(sbinfo);
+}
+
+int au_si_alloc(struct super_block *sb)
+{
+	int err;
+	struct au_sbinfo *sbinfo;
+
+	err = -ENOMEM;
+	sbinfo = kzalloc(sizeof(*sbinfo), GFP_NOFS);
+	if (unlikely(!sbinfo))
+		goto out;
+
+	/* will be reallocated separately */
+	sbinfo->si_branch = kzalloc(sizeof(*sbinfo->si_branch), GFP_NOFS);
+	if (unlikely(!sbinfo->si_branch))
+		goto out_sbinfo;
+
+	au_rw_init_wlock(&sbinfo->si_rwsem);
+
+	sbinfo->si_bbot = -1;
+
+	/* leave other members for sysaufs and si_mnt. */
+	sb->s_fs_info = sbinfo;
+	return 0; /* success */
+
+	au_kfree_try_rcu(sbinfo->si_branch);
+out_sbinfo:
+	au_kfree_rcu(sbinfo);
+out:
+	return err;
+}

fs/aufs/super.c

@@ -65,14 +65,28 @@ struct inode *au_iget_locked(struct super_block *sb, ino_t ino)
 out:
 	/* never return NULL */
 	AuDebugOn(!inode);
+	AuTraceErrPtr(inode);
 	return inode;
 }
 
 /* ---------------------------------------------------------------------- */
 
+/* final actions when unmounting a file system */
+static void aufs_put_super(struct super_block *sb)
+{
+	struct au_sbinfo *sbinfo;
+
+	sbinfo = au_sbi(sb);
+	if (sbinfo)
+		kobject_put(&sbinfo->si_kobj);
+}
+
+/* ---------------------------------------------------------------------- */
+
 static const struct super_operations aufs_sop = {
 	.alloc_inode	= aufs_alloc_inode,
 	.destroy_inode	= aufs_destroy_inode,
 	/* always deleting, no clearing */
-	.drop_inode	= generic_delete_inode
+	.drop_inode	= generic_delete_inode,
+	.put_super	= aufs_put_super
 };

fs/aufs/super.h

@@ -12,6 +12,33 @@
 
 #ifdef __KERNEL__
 
+#include <linux/fs.h>
+#include <linux/kobject.h>
+#include "rwsem.h"
+
+struct au_branch;
+struct au_sbinfo {
+	/*
+	 * tried sb->s_umount, but failed due to the dependency between i_mutex.
+	 * rwsem for au_sbinfo is necessary.
+	 */
+	struct au_rwsem		si_rwsem;
+
+	/* branch management */
+	aufs_bindex_t		si_bbot;
+	struct au_branch	**si_branch;
+
+	/*
+	 * sysfs and lifetime management.
+	 * this is not a small structure and it may be a waste of memory in case
+	 * of sysfs is disabled, particularly when many aufs-es are mounted.
+	 * but using sysfs is majority.
+	 */
+	struct kobject		si_kobj;
+};
+
+/* ---------------------------------------------------------------------- */
+
 /* flags for __si_read_lock()/aufs_read_lock()/di_read_lock() */
 #define AuLock_DW		1		/* write-lock dentry */
 #define AuLock_IR		(1 << 1)	/* read-lock inode */
@@ -25,8 +52,48 @@
 /* ---------------------------------------------------------------------- */
 
 /* super.c */
-struct super_block;
 struct inode *au_iget_locked(struct super_block *sb, ino_t ino);
 
+/* sbinfo.c */
+void au_si_free(struct kobject *kobj);
+int au_si_alloc(struct super_block *sb);
+
+/* ---------------------------------------------------------------------- */
+
+static inline struct au_sbinfo *au_sbi(struct super_block *sb)
+{
+	return sb->s_fs_info;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* lock superblock. mainly for entry point functions */
+#define __si_read_lock(sb)	au_rw_read_lock(&au_sbi(sb)->si_rwsem)
+#define __si_write_lock(sb)	au_rw_write_lock(&au_sbi(sb)->si_rwsem)
+#define __si_read_trylock(sb)	au_rw_read_trylock(&au_sbi(sb)->si_rwsem)
+#define __si_write_trylock(sb)	au_rw_write_trylock(&au_sbi(sb)->si_rwsem)
+/*
+#define __si_read_trylock_nested(sb) \
+	au_rw_read_trylock_nested(&au_sbi(sb)->si_rwsem)
+#define __si_write_trylock_nested(sb) \
+	au_rw_write_trylock_nested(&au_sbi(sb)->si_rwsem)
+*/
+
+#define __si_read_unlock(sb)	au_rw_read_unlock(&au_sbi(sb)->si_rwsem)
+#define __si_write_unlock(sb)	au_rw_write_unlock(&au_sbi(sb)->si_rwsem)
+#define __si_downgrade_lock(sb)	au_rw_dgrade_lock(&au_sbi(sb)->si_rwsem)
+
+#define SiMustNoWaiters(sb)	AuRwMustNoWaiters(&au_sbi(sb)->si_rwsem)
+#define SiMustAnyLock(sb)	AuRwMustAnyLock(&au_sbi(sb)->si_rwsem)
+#define SiMustWriteLock(sb)	AuRwMustWriteLock(&au_sbi(sb)->si_rwsem)
+
+/* ---------------------------------------------------------------------- */
+
+static inline aufs_bindex_t au_sbbot(struct super_block *sb)
+{
+	SiMustAnyLock(sb);
+	return au_sbi(sb)->si_bbot;
+}
+
 #endif /* __KERNEL__ */
 #endif /* __AUFS_SUPER_H__ */