aufs: udba=none has no ->getattr() 1/2, inode_operations array

An enhancement for udba=none if possible.
The condition is same to the 'no ->d_revalidate()' patch series.
In this mode, i_op->getattr() is less important, and the default VFS
handler is enough.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

fs/aufs/i_op.c

@@ -1123,7 +1123,9 @@ static int aufs_update_time(struct inode *inode, struct timespec64 *ts,
 
 /* ---------------------------------------------------------------------- */
 
-struct inode_operations aufs_iop[] = {
+/* no getattr version will be set by module.c:aufs_init() */
+struct inode_operations aufs_iop_nogetattr[AuIop_Last],
+	aufs_iop[] = {
 	[AuIop_SYMLINK] = {
 		.permission	= aufs_permission,
 		.setattr	= aufs_setattr,

fs/aufs/inode.c

@@ -173,11 +173,13 @@ static int set_inode(struct inode *inode, struct dentry *dentry)
 	struct dentry *h_dentry;
 	struct inode *h_inode;
 	struct au_iinfo *iinfo;
+	struct inode_operations *iop;
 
 	IiMustWriteLock(inode);
 
 	err = 0;
 	isdir = 0;
+	iop = au_sbi(inode->i_sb)->si_iop_array;
 	btop = au_dbtop(dentry);
 	h_dentry = au_h_dptr(dentry, btop);
 	h_inode = d_inode(h_dentry);
@@ -185,7 +187,7 @@ static int set_inode(struct inode *inode, struct dentry *dentry)
 	switch (mode & S_IFMT) {
 	case S_IFREG:
 		btail = au_dbtail(dentry);
-		inode->i_op = aufs_iop + AuIop_OTHER;
+		inode->i_op = iop + AuIop_OTHER;
 #if 0 /* re-commit later */
 		inode->i_fop = &aufs_file_fop;
 #endif
@@ -196,19 +198,19 @@ static int set_inode(struct inode *inode, struct dentry *dentry)
 	case S_IFDIR:
 		isdir = 1;
 		btail = au_dbtaildir(dentry);
-		inode->i_op = aufs_iop + AuIop_DIR;
+		inode->i_op = iop + AuIop_DIR;
 		inode->i_fop = &simple_dir_operations; /* re-commit later */
 		break;
 	case S_IFLNK:
 		btail = au_dbtail(dentry);
-		inode->i_op = aufs_iop + AuIop_SYMLINK;
+		inode->i_op = iop + AuIop_SYMLINK;
 		break;
 	case S_IFBLK:
 	case S_IFCHR:
 	case S_IFIFO:
 	case S_IFSOCK:
 		btail = au_dbtail(dentry);
-		inode->i_op = aufs_iop + AuIop_OTHER;
+		inode->i_op = iop + AuIop_OTHER;
 		init_special_inode(inode, mode, h_inode->i_rdev);
 		break;
 	default:

fs/aufs/inode.h

@@ -133,7 +133,8 @@ enum {
 	AuIop_OTHER,
 	AuIop_Last
 };
-extern struct inode_operations aufs_iop[AuIop_Last];
+extern struct inode_operations aufs_iop[AuIop_Last],
+	aufs_iop_nogetattr[AuIop_Last];
 
 /* au_wr_dir flags */
 #define AuWrDir_ADD_ENTRY	1

fs/aufs/module.c

@@ -171,6 +171,10 @@ static int __init aufs_init(void)
 
 	au_dir_roflags = au_file_roflags(O_DIRECTORY | O_LARGEFILE);
 
+	memcpy(aufs_iop_nogetattr, aufs_iop, sizeof(aufs_iop));
+	for (i = 0; i < AuIop_Last; i++)
+		aufs_iop_nogetattr[i].getattr = NULL;
+
 	memset(au_cache, 0, sizeof(au_cache));	/* including hnotify */
 
 	au_sbilist_init();

fs/aufs/sbinfo.c

@@ -88,6 +88,9 @@ int au_si_alloc(struct super_block *sb)
 	init_waitqueue_head(&sbinfo->si_plink_wq);
 	spin_lock_init(&sbinfo->si_plink_maint_lock);
 
+	/* with getattr by default */
+	sbinfo->si_iop_array = aufs_iop;
+
 	/* leave other members for sysaufs and si_mnt. */
 	sbinfo->si_sb = sb;
 	sb->s_fs_info = sbinfo;

fs/aufs/super.h

@@ -133,6 +133,9 @@ struct au_sbinfo {
 	spinlock_t		si_plink_maint_lock;
 	pid_t			si_plink_maint_pid;
 
+	/* with/without getattr, brother of sb->s_d_op */
+	struct inode_operations *si_iop_array;
+
 	/*
 	 * sysfs and lifetime management.
 	 * this is not a small structure and it may be a waste of memory in case