Linux-libre 4.5.1-gnupck-4.5.1-gnu

1 files changed, 831 insertions, 0 deletions

diff --git a/fs/aufs/file.c b/fs/aufs/file.c
new file mode 100644
index 000000000..6b8a66b4a
--- /dev/null
+++ b/fs/aufs/file.c
@@ -0,0 +1,831 @@
+/*
+ * Copyright (C) 2005-2016 Junjiro R. Okajima
+ */
+
+/*
+ * handling file/dir, and address_space operation
+ */
+
+#ifdef CONFIG_AUFS_DEBUG
+#include <linux/migrate.h>
+#endif
+#include <linux/pagemap.h>
+#include "aufs.h"
+
+/* drop flags for writing */
+unsigned int au_file_roflags(unsigned int flags)
+{
+	flags &= ~(O_WRONLY | O_RDWR | O_APPEND | O_CREAT | O_TRUNC);
+	flags |= O_RDONLY | O_NOATIME;
+	return flags;
+}
+
+/* common functions to regular file and dir */
+struct file *au_h_open(struct dentry *dentry, aufs_bindex_t bindex, int flags,
+		       struct file *file, int force_wr)
+{
+	struct file *h_file;
+	struct dentry *h_dentry;
+	struct inode *h_inode;
+	struct super_block *sb;
+	struct au_branch *br;
+	struct path h_path;
+	int err;
+
+	/* a race condition can happen between open and unlink/rmdir */
+	h_file = ERR_PTR(-ENOENT);
+	h_dentry = au_h_dptr(dentry, bindex);
+	if (au_test_nfsd() && (!h_dentry || d_is_negative(h_dentry)))
+		goto out;
+	h_inode = d_inode(h_dentry);
+	spin_lock(&h_dentry->d_lock);
+	err = (!d_unhashed(dentry) && d_unlinked(h_dentry))
+		/* || !d_inode(dentry)->i_nlink */
+		;
+	spin_unlock(&h_dentry->d_lock);
+	if (unlikely(err))
+		goto out;
+
+	sb = dentry->d_sb;
+	br = au_sbr(sb, bindex);
+	err = au_br_test_oflag(flags, br);
+	h_file = ERR_PTR(err);
+	if (unlikely(err))
+		goto out;
+
+	/* drop flags for writing */
+	if (au_test_ro(sb, bindex, d_inode(dentry))) {
+		if (force_wr && !(flags & O_WRONLY))
+			force_wr = 0;
+		flags = au_file_roflags(flags);
+		if (force_wr) {
+			h_file = ERR_PTR(-EROFS);
+			flags = au_file_roflags(flags);
+			if (unlikely(vfsub_native_ro(h_inode)
+				     || IS_APPEND(h_inode)))
+				goto out;
+			flags &= ~O_ACCMODE;
+			flags |= O_WRONLY;
+		}
+	}
+	flags &= ~O_CREAT;
+	atomic_inc(&br->br_count);
+	h_path.dentry = h_dentry;
+	h_path.mnt = au_br_mnt(br);
+	h_file = vfsub_dentry_open(&h_path, flags);
+	if (IS_ERR(h_file))
+		goto out_br;
+
+	if (flags & __FMODE_EXEC) {
+		err = deny_write_access(h_file);
+		if (unlikely(err)) {
+			fput(h_file);
+			h_file = ERR_PTR(err);
+			goto out_br;
+		}
+	}
+	fsnotify_open(h_file);
+	goto out; /* success */
+
+out_br:
+	atomic_dec(&br->br_count);
+out:
+	return h_file;
+}
+
+static int au_cmoo(struct dentry *dentry)
+{
+	int err, cmoo;
+	unsigned int udba;
+	struct path h_path;
+	struct au_pin pin;
+	struct au_cp_generic cpg = {
+		.dentry	= dentry,
+		.bdst	= -1,
+		.bsrc	= -1,
+		.len	= -1,
+		.pin	= &pin,
+		.flags	= AuCpup_DTIME | AuCpup_HOPEN
+	};
+	struct inode *delegated;
+	struct super_block *sb;
+	struct au_sbinfo *sbinfo;
+	struct au_fhsm *fhsm;
+	pid_t pid;
+	struct au_branch *br;
+	struct dentry *parent;
+	struct au_hinode *hdir;
+
+	DiMustWriteLock(dentry);
+	IiMustWriteLock(d_inode(dentry));
+
+	err = 0;
+	if (IS_ROOT(dentry))
+		goto out;
+	cpg.bsrc = au_dbstart(dentry);
+	if (!cpg.bsrc)
+		goto out;
+
+	sb = dentry->d_sb;
+	sbinfo = au_sbi(sb);
+	fhsm = &sbinfo->si_fhsm;
+	pid = au_fhsm_pid(fhsm);
+	if (pid
+	    && (current->pid == pid
+		|| current->real_parent->pid == pid))
+		goto out;
+
+	br = au_sbr(sb, cpg.bsrc);
+	cmoo = au_br_cmoo(br->br_perm);
+	if (!cmoo)
+		goto out;
+	if (!d_is_reg(dentry))
+		cmoo &= AuBrAttr_COO_ALL;
+	if (!cmoo)
+		goto out;
+
+	parent = dget_parent(dentry);
+	di_write_lock_parent(parent);
+	err = au_wbr_do_copyup_bu(dentry, cpg.bsrc - 1);
+	cpg.bdst = err;
+	if (unlikely(err < 0)) {
+		err = 0;	/* there is no upper writable branch */
+		goto out_dgrade;
+	}
+	AuDbg("bsrc %d, bdst %d\n", cpg.bsrc, cpg.bdst);
+
+	/* do not respect the coo attrib for the target branch */
+	err = au_cpup_dirs(dentry, cpg.bdst);
+	if (unlikely(err))
+		goto out_dgrade;
+
+	di_downgrade_lock(parent, AuLock_IR);
+	udba = au_opt_udba(sb);
+	err = au_pin(&pin, dentry, cpg.bdst, udba,
+		     AuPin_DI_LOCKED | AuPin_MNT_WRITE);
+	if (unlikely(err))
+		goto out_parent;
+
+	err = au_sio_cpup_simple(&cpg);
+	au_unpin(&pin);
+	if (unlikely(err))
+		goto out_parent;
+	if (!(cmoo & AuBrWAttr_MOO))
+		goto out_parent; /* success */
+
+	err = au_pin(&pin, dentry, cpg.bsrc, udba,
+		     AuPin_DI_LOCKED | AuPin_MNT_WRITE);
+	if (unlikely(err))
+		goto out_parent;
+
+	h_path.mnt = au_br_mnt(br);
+	h_path.dentry = au_h_dptr(dentry, cpg.bsrc);
+	hdir = au_hi(d_inode(parent), cpg.bsrc);
+	delegated = NULL;
+	err = vfsub_unlink(hdir->hi_inode, &h_path, &delegated, /*force*/1);
+	au_unpin(&pin);
+	/* todo: keep h_dentry or not? */
+	if (unlikely(err == -EWOULDBLOCK)) {
+		pr_warn("cannot retry for NFSv4 delegation"
+			" for an internal unlink\n");
+		iput(delegated);
+	}
+	if (unlikely(err)) {
+		pr_err("unlink %pd after coo failed (%d), ignored\n",
+		       dentry, err);
+		err = 0;
+	}
+	goto out_parent; /* success */
+
+out_dgrade:
+	di_downgrade_lock(parent, AuLock_IR);
+out_parent:
+	di_read_unlock(parent, AuLock_IR);
+	dput(parent);
+out:
+	AuTraceErr(err);
+	return err;
+}
+
+int au_do_open(struct file *file, struct au_do_open_args *args)
+{
+	int err, no_lock = args->no_lock;
+	struct dentry *dentry;
+	struct au_finfo *finfo;
+
+	if (!no_lock)
+		err = au_finfo_init(file, args->fidir);
+	else {
+		lockdep_off();
+		err = au_finfo_init(file, args->fidir);
+		lockdep_on();
+	}
+	if (unlikely(err))
+		goto out;
+
+	dentry = file->f_path.dentry;
+	AuDebugOn(IS_ERR_OR_NULL(dentry));
+	if (!no_lock) {
+		di_write_lock_child(dentry);
+		err = au_cmoo(dentry);
+		di_downgrade_lock(dentry, AuLock_IR);
+		if (!err)
+			err = args->open(file, vfsub_file_flags(file), NULL);
+		di_read_unlock(dentry, AuLock_IR);
+	} else {
+		err = au_cmoo(dentry);
+		if (!err)
+			err = args->open(file, vfsub_file_flags(file),
+					 args->h_file);
+		if (!err && au_fbstart(file) != au_dbstart(dentry))
+			/*
+			 * cmoo happens after h_file was opened.
+			 * need to refresh file later.
+			 */
+			atomic_dec(&au_fi(file)->fi_generation);
+	}
+
+	finfo = au_fi(file);
+	if (!err) {
+		finfo->fi_file = file;
+		au_sphl_add(&finfo->fi_hlist,
+			    &au_sbi(file->f_path.dentry->d_sb)->si_files);
+	}
+	if (!no_lock)
+		fi_write_unlock(file);
+	else {
+		lockdep_off();
+		fi_write_unlock(file);
+		lockdep_on();
+	}
+	if (unlikely(err)) {
+		finfo->fi_hdir = NULL;
+		au_finfo_fin(file);
+	}
+
+out:
+	return err;
+}
+
+int au_reopen_nondir(struct file *file)
+{
+	int err;
+	aufs_bindex_t bstart;
+	struct dentry *dentry;
+	struct file *h_file, *h_file_tmp;
+
+	dentry = file->f_path.dentry;
+	bstart = au_dbstart(dentry);
+	h_file_tmp = NULL;
+	if (au_fbstart(file) == bstart) {
+		h_file = au_hf_top(file);
+		if (file->f_mode == h_file->f_mode)
+			return 0; /* success */
+		h_file_tmp = h_file;
+		get_file(h_file_tmp);
+		au_set_h_fptr(file, bstart, NULL);
+	}
+	AuDebugOn(au_fi(file)->fi_hdir);
+	/*
+	 * it can happen
+	 * file exists on both of rw and ro
+	 * open --> dbstart and fbstart are both 0
+	 * prepend a branch as rw, "rw" become ro
+	 * remove rw/file
+	 * delete the top branch, "rw" becomes rw again
+	 *	--> dbstart is 1, fbstart is still 0
+	 * write --> fbstart is 0 but dbstart is 1
+	 */
+	/* AuDebugOn(au_fbstart(file) < bstart); */
+
+	h_file = au_h_open(dentry, bstart, vfsub_file_flags(file) & ~O_TRUNC,
+			   file, /*force_wr*/0);
+	err = PTR_ERR(h_file);
+	if (IS_ERR(h_file)) {
+		if (h_file_tmp) {
+			atomic_inc(&au_sbr(dentry->d_sb, bstart)->br_count);
+			au_set_h_fptr(file, bstart, h_file_tmp);
+			h_file_tmp = NULL;
+		}
+		goto out; /* todo: close all? */
+	}
+
+	err = 0;
+	au_set_fbstart(file, bstart);
+	au_set_h_fptr(file, bstart, h_file);
+	au_update_figen(file);
+	/* todo: necessary? */
+	/* file->f_ra = h_file->f_ra; */
+
+out:
+	if (h_file_tmp)
+		fput(h_file_tmp);
+	return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int au_reopen_wh(struct file *file, aufs_bindex_t btgt,
+			struct dentry *hi_wh)
+{
+	int err;
+	aufs_bindex_t bstart;
+	struct au_dinfo *dinfo;
+	struct dentry *h_dentry;
+	struct au_hdentry *hdp;
+
+	dinfo = au_di(file->f_path.dentry);
+	AuRwMustWriteLock(&dinfo->di_rwsem);
+
+	bstart = dinfo->di_bstart;
+	dinfo->di_bstart = btgt;
+	hdp = dinfo->di_hdentry;
+	h_dentry = hdp[0 + btgt].hd_dentry;
+	hdp[0 + btgt].hd_dentry = hi_wh;
+	err = au_reopen_nondir(file);
+	hdp[0 + btgt].hd_dentry = h_dentry;
+	dinfo->di_bstart = bstart;
+
+	return err;
+}
+
+static int au_ready_to_write_wh(struct file *file, loff_t len,
+				aufs_bindex_t bcpup, struct au_pin *pin)
+{
+	int err;
+	struct inode *inode, *h_inode;
+	struct dentry *h_dentry, *hi_wh;
+	struct au_cp_generic cpg = {
+		.dentry	= file->f_path.dentry,
+		.bdst	= bcpup,
+		.bsrc	= -1,
+		.len	= len,
+		.pin	= pin
+	};
+
+	au_update_dbstart(cpg.dentry);
+	inode = d_inode(cpg.dentry);
+	h_inode = NULL;
+	if (au_dbstart(cpg.dentry) <= bcpup
+	    && au_dbend(cpg.dentry) >= bcpup) {
+		h_dentry = au_h_dptr(cpg.dentry, bcpup);
+		if (h_dentry && d_is_positive(h_dentry))
+			h_inode = d_inode(h_dentry);
+	}
+	hi_wh = au_hi_wh(inode, bcpup);
+	if (!hi_wh && !h_inode)
+		err = au_sio_cpup_wh(&cpg, file);
+	else
+		/* already copied-up after unlink */
+		err = au_reopen_wh(file, bcpup, hi_wh);
+
+	if (!err
+	    && (inode->i_nlink > 1
+		|| (inode->i_state & I_LINKABLE))
+	    && au_opt_test(au_mntflags(cpg.dentry->d_sb), PLINK))
+		au_plink_append(inode, bcpup, au_h_dptr(cpg.dentry, bcpup));
+
+	return err;
+}
+
+/*
+ * prepare the @file for writing.
+ */
+int au_ready_to_write(struct file *file, loff_t len, struct au_pin *pin)
+{
+	int err;
+	aufs_bindex_t dbstart;
+	struct dentry *parent;
+	struct inode *inode;
+	struct super_block *sb;
+	struct file *h_file;
+	struct au_cp_generic cpg = {
+		.dentry	= file->f_path.dentry,
+		.bdst	= -1,
+		.bsrc	= -1,
+		.len	= len,
+		.pin	= pin,
+		.flags	= AuCpup_DTIME
+	};
+
+	sb = cpg.dentry->d_sb;
+	inode = d_inode(cpg.dentry);
+	cpg.bsrc = au_fbstart(file);
+	err = au_test_ro(sb, cpg.bsrc, inode);
+	if (!err && (au_hf_top(file)->f_mode & FMODE_WRITE)) {
+		err = au_pin(pin, cpg.dentry, cpg.bsrc, AuOpt_UDBA_NONE,
+			     /*flags*/0);
+		goto out;
+	}
+
+	/* need to cpup or reopen */
+	parent = dget_parent(cpg.dentry);
+	di_write_lock_parent(parent);
+	err = AuWbrCopyup(au_sbi(sb), cpg.dentry);
+	cpg.bdst = err;
+	if (unlikely(err < 0))
+		goto out_dgrade;
+	err = 0;
+
+	if (!d_unhashed(cpg.dentry) && !au_h_dptr(parent, cpg.bdst)) {
+		err = au_cpup_dirs(cpg.dentry, cpg.bdst);
+		if (unlikely(err))
+			goto out_dgrade;
+	}
+
+	err = au_pin(pin, cpg.dentry, cpg.bdst, AuOpt_UDBA_NONE,
+		     AuPin_DI_LOCKED | AuPin_MNT_WRITE);
+	if (unlikely(err))
+		goto out_dgrade;
+
+	dbstart = au_dbstart(cpg.dentry);
+	if (dbstart <= cpg.bdst)
+		cpg.bsrc = cpg.bdst;
+
+	if (dbstart <= cpg.bdst		/* just reopen */
+	    || !d_unhashed(cpg.dentry)	/* copyup and reopen */
+		) {
+		h_file = au_h_open_pre(cpg.dentry, cpg.bsrc, /*force_wr*/0);
+		if (IS_ERR(h_file))
+			err = PTR_ERR(h_file);
+		else {
+			di_downgrade_lock(parent, AuLock_IR);
+			if (dbstart > cpg.bdst)
+				err = au_sio_cpup_simple(&cpg);
+			if (!err)
+				err = au_reopen_nondir(file);
+			au_h_open_post(cpg.dentry, cpg.bsrc, h_file);
+		}
+	} else {			/* copyup as wh and reopen */
+		/*
+		 * since writable hfsplus branch is not supported,
+		 * h_open_pre/post() are unnecessary.
+		 */
+		err = au_ready_to_write_wh(file, len, cpg.bdst, pin);
+		di_downgrade_lock(parent, AuLock_IR);
+	}
+
+	if (!err) {
+		au_pin_set_parent_lflag(pin, /*lflag*/0);
+		goto out_dput; /* success */
+	}
+	au_unpin(pin);
+	goto out_unlock;
+
+out_dgrade:
+	di_downgrade_lock(parent, AuLock_IR);
+out_unlock:
+	di_read_unlock(parent, AuLock_IR);
+out_dput:
+	dput(parent);
+out:
+	return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+int au_do_flush(struct file *file, fl_owner_t id,
+		int (*flush)(struct file *file, fl_owner_t id))
+{
+	int err;
+	struct super_block *sb;
+	struct inode *inode;
+
+	inode = file_inode(file);
+	sb = inode->i_sb;
+	si_noflush_read_lock(sb);
+	fi_read_lock(file);
+	ii_read_lock_child(inode);
+
+	err = flush(file, id);
+	au_cpup_attr_timesizes(inode);
+
+	ii_read_unlock(inode);
+	fi_read_unlock(file);
+	si_read_unlock(sb);
+	return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+static int au_file_refresh_by_inode(struct file *file, int *need_reopen)
+{
+	int err;
+	struct au_pin pin;
+	struct au_finfo *finfo;
+	struct dentry *parent, *hi_wh;
+	struct inode *inode;
+	struct super_block *sb;
+	struct au_cp_generic cpg = {
+		.dentry	= file->f_path.dentry,
+		.bdst	= -1,
+		.bsrc	= -1,
+		.len	= -1,
+		.pin	= &pin,
+		.flags	= AuCpup_DTIME
+	};
+
+	FiMustWriteLock(file);
+
+	err = 0;
+	finfo = au_fi(file);
+	sb = cpg.dentry->d_sb;
+	inode = d_inode(cpg.dentry);
+	cpg.bdst = au_ibstart(inode);
+	if (cpg.bdst == finfo->fi_btop || IS_ROOT(cpg.dentry))
+		goto out;
+
+	parent = dget_parent(cpg.dentry);
+	if (au_test_ro(sb, cpg.bdst, inode)) {
+		di_read_lock_parent(parent, !AuLock_IR);
+		err = AuWbrCopyup(au_sbi(sb), cpg.dentry);
+		cpg.bdst = err;
+		di_read_unlock(parent, !AuLock_IR);
+		if (unlikely(err < 0))
+			goto out_parent;
+		err = 0;
+	}
+
+	di_read_lock_parent(parent, AuLock_IR);
+	hi_wh = au_hi_wh(inode, cpg.bdst);
+	if (!S_ISDIR(inode->i_mode)
+	    && au_opt_test(au_mntflags(sb), PLINK)
+	    && au_plink_test(inode)
+	    && !d_unhashed(cpg.dentry)
+	    && cpg.bdst < au_dbstart(cpg.dentry)) {
+		err = au_test_and_cpup_dirs(cpg.dentry, cpg.bdst);
+		if (unlikely(err))
+			goto out_unlock;
+
+		/* always superio. */
+		err = au_pin(&pin, cpg.dentry, cpg.bdst, AuOpt_UDBA_NONE,
+			     AuPin_DI_LOCKED | AuPin_MNT_WRITE);
+		if (!err) {
+			err = au_sio_cpup_simple(&cpg);
+			au_unpin(&pin);
+		}
+	} else if (hi_wh) {
+		/* already copied-up after unlink */
+		err = au_reopen_wh(file, cpg.bdst, hi_wh);
+		*need_reopen = 0;
+	}
+
+out_unlock:
+	di_read_unlock(parent, AuLock_IR);
+out_parent:
+	dput(parent);
+out:
+	return err;
+}
+
+static void au_do_refresh_dir(struct file *file)
+{
+	aufs_bindex_t bindex, bend, new_bindex, brid;
+	struct au_hfile *p, tmp, *q;
+	struct au_finfo *finfo;
+	struct super_block *sb;
+	struct au_fidir *fidir;
+
+	FiMustWriteLock(file);
+
+	sb = file->f_path.dentry->d_sb;
+	finfo = au_fi(file);
+	fidir = finfo->fi_hdir;
+	AuDebugOn(!fidir);
+	p = fidir->fd_hfile + finfo->fi_btop;
+	brid = p->hf_br->br_id;
+	bend = fidir->fd_bbot;
+	for (bindex = finfo->fi_btop; bindex <= bend; bindex++, p++) {
+		if (!p->hf_file)
+			continue;
+
+		new_bindex = au_br_index(sb, p->hf_br->br_id);
+		if (new_bindex == bindex)
+			continue;
+		if (new_bindex < 0) {
+			au_set_h_fptr(file, bindex, NULL);
+			continue;
+		}
+
+		/* swap two lower inode, and loop again */
+		q = fidir->fd_hfile + new_bindex;
+		tmp = *q;
+		*q = *p;
+		*p = tmp;
+		if (tmp.hf_file) {
+			bindex--;
+			p--;
+		}
+	}
+
+	p = fidir->fd_hfile;
+	if (!au_test_mmapped(file) && !d_unlinked(file->f_path.dentry)) {
+		bend = au_sbend(sb);
+		for (finfo->fi_btop = 0; finfo->fi_btop <= bend;
+		     finfo->fi_btop++, p++)
+			if (p->hf_file) {
+				if (file_inode(p->hf_file))
+					break;
+				au_hfput(p, file);
+			}
+	} else {
+		bend = au_br_index(sb, brid);
+		for (finfo->fi_btop = 0; finfo->fi_btop < bend;
+		     finfo->fi_btop++, p++)
+			if (p->hf_file)
+				au_hfput(p, file);
+		bend = au_sbend(sb);
+	}
+
+	p = fidir->fd_hfile + bend;
+	for (fidir->fd_bbot = bend; fidir->fd_bbot >= finfo->fi_btop;
+	     fidir->fd_bbot--, p--)
+		if (p->hf_file) {
+			if (file_inode(p->hf_file))
+				break;
+			au_hfput(p, file);
+		}
+	AuDebugOn(fidir->fd_bbot < finfo->fi_btop);
+}
+
+/*
+ * after branch manipulating, refresh the file.
+ */
+static int refresh_file(struct file *file, int (*reopen)(struct file *file))
+{
+	int err, need_reopen;
+	aufs_bindex_t bend, bindex;
+	struct dentry *dentry;
+	struct au_finfo *finfo;
+	struct au_hfile *hfile;
+
+	dentry = file->f_path.dentry;
+	finfo = au_fi(file);
+	if (!finfo->fi_hdir) {
+		hfile = &finfo->fi_htop;
+		AuDebugOn(!hfile->hf_file);
+		bindex = au_br_index(dentry->d_sb, hfile->hf_br->br_id);
+		AuDebugOn(bindex < 0);
+		if (bindex != finfo->fi_btop)
+			au_set_fbstart(file, bindex);
+	} else {
+		err = au_fidir_realloc(finfo, au_sbend(dentry->d_sb) + 1);
+		if (unlikely(err))
+			goto out;
+		au_do_refresh_dir(file);
+	}
+
+	err = 0;
+	need_reopen = 1;
+	if (!au_test_mmapped(file))
+		err = au_file_refresh_by_inode(file, &need_reopen);
+	if (!err && need_reopen && !d_unlinked(dentry))
+		err = reopen(file);
+	if (!err) {
+		au_update_figen(file);
+		goto out; /* success */
+	}
+
+	/* error, close all lower files */
+	if (finfo->fi_hdir) {
+		bend = au_fbend_dir(file);
+		for (bindex = au_fbstart(file); bindex <= bend; bindex++)
+			au_set_h_fptr(file, bindex, NULL);
+	}
+
+out:
+	return err;
+}
+
+/* common function to regular file and dir */
+int au_reval_and_lock_fdi(struct file *file, int (*reopen)(struct file *file),
+			  int wlock)
+{
+	int err;
+	unsigned int sigen, figen;
+	aufs_bindex_t bstart;
+	unsigned char pseudo_link;
+	struct dentry *dentry;
+	struct inode *inode;
+
+	err = 0;
+	dentry = file->f_path.dentry;
+	inode = d_inode(dentry);
+	sigen = au_sigen(dentry->d_sb);
+	fi_write_lock(file);
+	figen = au_figen(file);
+	di_write_lock_child(dentry);
+	bstart = au_dbstart(dentry);
+	pseudo_link = (bstart != au_ibstart(inode));
+	if (sigen == figen && !pseudo_link && au_fbstart(file) == bstart) {
+		if (!wlock) {
+			di_downgrade_lock(dentry, AuLock_IR);
+			fi_downgrade_lock(file);
+		}
+		goto out; /* success */
+	}
+
+	AuDbg("sigen %d, figen %d\n", sigen, figen);
+	if (au_digen_test(dentry, sigen)) {
+		err = au_reval_dpath(dentry, sigen);
+		AuDebugOn(!err && au_digen_test(dentry, sigen));
+	}
+
+	if (!err)
+		err = refresh_file(file, reopen);
+	if (!err) {
+		if (!wlock) {
+			di_downgrade_lock(dentry, AuLock_IR);
+			fi_downgrade_lock(file);
+		}
+	} else {
+		di_write_unlock(dentry);
+		fi_write_unlock(file);
+	}
+
+out:
+	return err;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* cf. aufs_nopage() */
+/* for madvise(2) */
+static int aufs_readpage(struct file *file __maybe_unused, struct page *page)
+{
+	unlock_page(page);
+	return 0;
+}
+
+/* it will never be called, but necessary to support O_DIRECT */
+static ssize_t aufs_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
+			      loff_t offset)
+{ BUG(); return 0; }
+
+/* they will never be called. */
+#ifdef CONFIG_AUFS_DEBUG
+static int aufs_write_begin(struct file *file, struct address_space *mapping,
+			    loff_t pos, unsigned len, unsigned flags,
+			    struct page **pagep, void **fsdata)
+{ AuUnsupport(); return 0; }
+static int aufs_write_end(struct file *file, struct address_space *mapping,
+			  loff_t pos, unsigned len, unsigned copied,
+			  struct page *page, void *fsdata)
+{ AuUnsupport(); return 0; }
+static int aufs_writepage(struct page *page, struct writeback_control *wbc)
+{ AuUnsupport(); return 0; }
+
+static int aufs_set_page_dirty(struct page *page)
+{ AuUnsupport(); return 0; }
+static void aufs_invalidatepage(struct page *page, unsigned int offset,
+				unsigned int length)
+{ AuUnsupport(); }
+static int aufs_releasepage(struct page *page, gfp_t gfp)
+{ AuUnsupport(); return 0; }
+#if 0 /* called by memory compaction regardless file */
+static int aufs_migratepage(struct address_space *mapping, struct page *newpage,
+			    struct page *page, enum migrate_mode mode)
+{ AuUnsupport(); return 0; }
+#endif
+static int aufs_launder_page(struct page *page)
+{ AuUnsupport(); return 0; }
+static int aufs_is_partially_uptodate(struct page *page,
+				      unsigned long from,
+				      unsigned long count)
+{ AuUnsupport(); return 0; }
+static void aufs_is_dirty_writeback(struct page *page, bool *dirty,
+				    bool *writeback)
+{ AuUnsupport(); }
+static int aufs_error_remove_page(struct address_space *mapping,
+				  struct page *page)
+{ AuUnsupport(); return 0; }
+static int aufs_swap_activate(struct swap_info_struct *sis, struct file *file,
+			      sector_t *span)
+{ AuUnsupport(); return 0; }
+static void aufs_swap_deactivate(struct file *file)
+{ AuUnsupport(); }
+#endif /* CONFIG_AUFS_DEBUG */
+
+const struct address_space_operations aufs_aop = {
+	.readpage		= aufs_readpage,
+	.direct_IO		= aufs_direct_IO,
+#ifdef CONFIG_AUFS_DEBUG
+	.writepage		= aufs_writepage,
+	/* no writepages, because of writepage */
+	.set_page_dirty		= aufs_set_page_dirty,
+	/* no readpages, because of readpage */
+	.write_begin		= aufs_write_begin,
+	.write_end		= aufs_write_end,
+	/* no bmap, no block device */
+	.invalidatepage		= aufs_invalidatepage,
+	.releasepage		= aufs_releasepage,
+	/* is fallback_migrate_page ok? */
+	/* .migratepage		= aufs_migratepage, */
+	.launder_page		= aufs_launder_page,
+	.is_partially_uptodate	= aufs_is_partially_uptodate,
+	.is_dirty_writeback	= aufs_is_dirty_writeback,
+	.error_remove_page	= aufs_error_remove_page,
+	.swap_activate		= aufs_swap_activate,
+	.swap_deactivate	= aufs_swap_deactivate
+#endif /* CONFIG_AUFS_DEBUG */
+};