Revert "UBUNTU: SAUCE: aufs -- Convert to use xattr handlers"

[mirror_ubuntu-zesty-kernel.git] / fs / aufs / whout.c

/*
 * Copyright (C) 2005-2016 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/>.
 */

/*
 * whiteout for logical deletion and opaque directory
 */

#include "aufs.h"

#define WH_MASK                 S_IRUGO

/*
 * If a directory contains this file, then it is opaque.  We start with the
 * .wh. flag so that it is blocked by lookup.
 */
static struct qstr diropq_name = QSTR_INIT(AUFS_WH_DIROPQ,
                                           sizeof(AUFS_WH_DIROPQ) - 1);

/*
 * generate whiteout name, which is NOT terminated by NULL.
 * @name: original d_name.name
 * @len: original d_name.len
 * @wh: whiteout qstr
 * returns zero when succeeds, otherwise error.
 * succeeded value as wh->name should be freed by kfree().
 */
int au_wh_name_alloc(struct qstr *wh, const struct qstr *name)
{
        char *p;

        if (unlikely(name->len > PATH_MAX - AUFS_WH_PFX_LEN))
                return -ENAMETOOLONG;

        wh->len = name->len + AUFS_WH_PFX_LEN;
        p = kmalloc(wh->len, GFP_NOFS);
        wh->name = p;
        if (p) {
                memcpy(p, AUFS_WH_PFX, AUFS_WH_PFX_LEN);
                memcpy(p + AUFS_WH_PFX_LEN, name->name, name->len);
                /* smp_mb(); */
                return 0;
        }
        return -ENOMEM;
}

/* ---------------------------------------------------------------------- */

/*
 * test if the @wh_name exists under @h_parent.
 * @try_sio specifies the necessary of super-io.
 */
int au_wh_test(struct dentry *h_parent, struct qstr *wh_name, int try_sio)
{
        int err;
        struct dentry *wh_dentry;

        if (!try_sio)
                wh_dentry = vfsub_lkup_one(wh_name, h_parent);
        else
                wh_dentry = au_sio_lkup_one(wh_name, h_parent);
        err = PTR_ERR(wh_dentry);
        if (IS_ERR(wh_dentry)) {
                if (err == -ENAMETOOLONG)
                        err = 0;
                goto out;
        }

        err = 0;
        if (d_is_negative(wh_dentry))
                goto out_wh; /* success */

        err = 1;
        if (d_is_reg(wh_dentry))
                goto out_wh; /* success */

        err = -EIO;
        AuIOErr("%pd Invalid whiteout entry type 0%o.\n",
                wh_dentry, d_inode(wh_dentry)->i_mode);

out_wh:
        dput(wh_dentry);
out:
        return err;
}

/*
 * test if the @h_dentry sets opaque or not.
 */
int au_diropq_test(struct dentry *h_dentry)
{
        int err;
        struct inode *h_dir;

        h_dir = d_inode(h_dentry);
        err = au_wh_test(h_dentry, &diropq_name,
                         au_test_h_perm_sio(h_dir, MAY_EXEC));
        return err;
}

/*
 * returns a negative dentry whose name is unique and temporary.
 */
struct dentry *au_whtmp_lkup(struct dentry *h_parent, struct au_branch *br,
                             struct qstr *prefix)
{
        struct dentry *dentry;
        int i;
        char defname[NAME_MAX - AUFS_MAX_NAMELEN + DNAME_INLINE_LEN + 1],
                *name, *p;
        /* strict atomic_t is unnecessary here */
        static unsigned short cnt;
        struct qstr qs;

        BUILD_BUG_ON(sizeof(cnt) * 2 > AUFS_WH_TMP_LEN);

        name = defname;
        qs.len = sizeof(defname) - DNAME_INLINE_LEN + prefix->len - 1;
        if (unlikely(prefix->len > DNAME_INLINE_LEN)) {
                dentry = ERR_PTR(-ENAMETOOLONG);
                if (unlikely(qs.len > NAME_MAX))
                        goto out;
                dentry = ERR_PTR(-ENOMEM);
                name = kmalloc(qs.len + 1, GFP_NOFS);
                if (unlikely(!name))
                        goto out;
        }

        /* doubly whiteout-ed */
        memcpy(name, AUFS_WH_PFX AUFS_WH_PFX, AUFS_WH_PFX_LEN * 2);
        p = name + AUFS_WH_PFX_LEN * 2;
        memcpy(p, prefix->name, prefix->len);
        p += prefix->len;
        *p++ = '.';
        AuDebugOn(name + qs.len + 1 - p <= AUFS_WH_TMP_LEN);

        qs.name = name;
        for (i = 0; i < 3; i++) {
                sprintf(p, "%.*x", AUFS_WH_TMP_LEN, cnt++);
                dentry = au_sio_lkup_one(&qs, h_parent);
                if (IS_ERR(dentry) || d_is_negative(dentry))
                        goto out_name;
                dput(dentry);
        }
        /* pr_warn("could not get random name\n"); */
        dentry = ERR_PTR(-EEXIST);
        AuDbg("%.*s\n", AuLNPair(&qs));
        BUG();

out_name:
        if (name != defname)
                au_delayed_kfree(name);
out:
        AuTraceErrPtr(dentry);
        return dentry;
}

/*
 * rename the @h_dentry on @br to the whiteouted temporary name.
 */
int au_whtmp_ren(struct dentry *h_dentry, struct au_branch *br)
{
        int err;
        struct path h_path = {
                .mnt = au_br_mnt(br)
        };
        struct inode *h_dir, *delegated;
        struct dentry *h_parent;

        h_parent = h_dentry->d_parent; /* dir inode is locked */
        h_dir = d_inode(h_parent);
        IMustLock(h_dir);

        h_path.dentry = au_whtmp_lkup(h_parent, br, &h_dentry->d_name);
        err = PTR_ERR(h_path.dentry);
        if (IS_ERR(h_path.dentry))
                goto out;

        /* under the same dir, no need to lock_rename() */
        delegated = NULL;
        err = vfsub_rename(h_dir, h_dentry, h_dir, &h_path, &delegated);
        AuTraceErr(err);
        if (unlikely(err == -EWOULDBLOCK)) {
                pr_warn("cannot retry for NFSv4 delegation"
                        " for an internal rename\n");
                iput(delegated);
        }
        dput(h_path.dentry);

out:
        AuTraceErr(err);
        return err;
}

/* ---------------------------------------------------------------------- */
/*
 * functions for removing a whiteout
 */

static int do_unlink_wh(struct inode *h_dir, struct path *h_path)
{
        int err, force;
        struct inode *delegated;

        /*
         * forces superio when the dir has a sticky bit.
         * this may be a violation of unix fs semantics.
         */
        force = (h_dir->i_mode & S_ISVTX)
                && !uid_eq(current_fsuid(), d_inode(h_path->dentry)->i_uid);
        delegated = NULL;
        err = vfsub_unlink(h_dir, h_path, &delegated, force);
        if (unlikely(err == -EWOULDBLOCK)) {
                pr_warn("cannot retry for NFSv4 delegation"
                        " for an internal unlink\n");
                iput(delegated);
        }
        return err;
}

int au_wh_unlink_dentry(struct inode *h_dir, struct path *h_path,
                        struct dentry *dentry)
{
        int err;

        err = do_unlink_wh(h_dir, h_path);
        if (!err && dentry)
                au_set_dbwh(dentry, -1);

        return err;
}

static int unlink_wh_name(struct dentry *h_parent, struct qstr *wh,
                          struct au_branch *br)
{
        int err;
        struct path h_path = {
                .mnt = au_br_mnt(br)
        };

        err = 0;
        h_path.dentry = vfsub_lkup_one(wh, h_parent);
        if (IS_ERR(h_path.dentry))
                err = PTR_ERR(h_path.dentry);
        else {
                if (d_is_reg(h_path.dentry))
                        err = do_unlink_wh(d_inode(h_parent), &h_path);
                dput(h_path.dentry);
        }

        return err;
}

/* ---------------------------------------------------------------------- */
/*
 * initialize/clean whiteout for a branch
 */

static void au_wh_clean(struct inode *h_dir, struct path *whpath,
                        const int isdir)
{
        int err;
        struct inode *delegated;

        if (d_is_negative(whpath->dentry))
                return;

        if (isdir)
                err = vfsub_rmdir(h_dir, whpath);
        else {
                delegated = NULL;
                err = vfsub_unlink(h_dir, whpath, &delegated, /*force*/0);
                if (unlikely(err == -EWOULDBLOCK)) {
                        pr_warn("cannot retry for NFSv4 delegation"
                                " for an internal unlink\n");
                        iput(delegated);
                }
        }
        if (unlikely(err))
                pr_warn("failed removing %pd (%d), ignored.\n",
                        whpath->dentry, err);
}

static int test_linkable(struct dentry *h_root)
{
        struct inode *h_dir = d_inode(h_root);

        if (h_dir->i_op->link)
                return 0;

        pr_err("%pd (%s) doesn't support link(2), use noplink and rw+nolwh\n",
               h_root, au_sbtype(h_root->d_sb));
        return -ENOSYS;
}

/* todo: should this mkdir be done in /sbin/mount.aufs helper? */
static int au_whdir(struct inode *h_dir, struct path *path)
{
        int err;

        err = -EEXIST;
        if (d_is_negative(path->dentry)) {
                int mode = S_IRWXU;

                if (au_test_nfs(path->dentry->d_sb))
                        mode |= S_IXUGO;
                err = vfsub_mkdir(h_dir, path, mode);
        } else if (d_is_dir(path->dentry))
                err = 0;
        else
                pr_err("unknown %pd exists\n", path->dentry);

        return err;
}

struct au_wh_base {
        const struct qstr *name;
        struct dentry *dentry;
};

static void au_wh_init_ro(struct inode *h_dir, struct au_wh_base base[],
                          struct path *h_path)
{
        h_path->dentry = base[AuBrWh_BASE].dentry;
        au_wh_clean(h_dir, h_path, /*isdir*/0);
        h_path->dentry = base[AuBrWh_PLINK].dentry;
        au_wh_clean(h_dir, h_path, /*isdir*/1);
        h_path->dentry = base[AuBrWh_ORPH].dentry;
        au_wh_clean(h_dir, h_path, /*isdir*/1);
}

/*
 * returns tri-state,
 * minus: error, caller should print the message
 * zero: succuess
 * plus: error, caller should NOT print the message
 */
static int au_wh_init_rw_nolink(struct dentry *h_root, struct au_wbr *wbr,
                                int do_plink, struct au_wh_base base[],
                                struct path *h_path)
{
        int err;
        struct inode *h_dir;

        h_dir = d_inode(h_root);
        h_path->dentry = base[AuBrWh_BASE].dentry;
        au_wh_clean(h_dir, h_path, /*isdir*/0);
        h_path->dentry = base[AuBrWh_PLINK].dentry;
        if (do_plink) {
                err = test_linkable(h_root);
                if (unlikely(err)) {
                        err = 1;
                        goto out;
                }

                err = au_whdir(h_dir, h_path);
                if (unlikely(err))
                        goto out;
                wbr->wbr_plink = dget(base[AuBrWh_PLINK].dentry);
        } else
                au_wh_clean(h_dir, h_path, /*isdir*/1);
        h_path->dentry = base[AuBrWh_ORPH].dentry;
        err = au_whdir(h_dir, h_path);
        if (unlikely(err))
                goto out;
        wbr->wbr_orph = dget(base[AuBrWh_ORPH].dentry);

out:
        return err;
}

/*
 * for the moment, aufs supports the branch filesystem which does not support
 * link(2). testing on FAT which does not support i_op->setattr() fully either,
 * copyup failed. finally, such filesystem will not be used as the writable
 * branch.
 *
 * returns tri-state, see above.
 */
static int au_wh_init_rw(struct dentry *h_root, struct au_wbr *wbr,
                         int do_plink, struct au_wh_base base[],
                         struct path *h_path)
{
        int err;
        struct inode *h_dir;

        WbrWhMustWriteLock(wbr);

        err = test_linkable(h_root);
        if (unlikely(err)) {
                err = 1;
                goto out;
        }

        /*
         * todo: should this create be done in /sbin/mount.aufs helper?
         */
        err = -EEXIST;
        h_dir = d_inode(h_root);
        if (d_is_negative(base[AuBrWh_BASE].dentry)) {
                h_path->dentry = base[AuBrWh_BASE].dentry;
                err = vfsub_create(h_dir, h_path, WH_MASK, /*want_excl*/true);
        } else if (d_is_reg(base[AuBrWh_BASE].dentry))
                err = 0;
        else
                pr_err("unknown %pd2 exists\n", base[AuBrWh_BASE].dentry);
        if (unlikely(err))
                goto out;

        h_path->dentry = base[AuBrWh_PLINK].dentry;
        if (do_plink) {
                err = au_whdir(h_dir, h_path);
                if (unlikely(err))
                        goto out;
                wbr->wbr_plink = dget(base[AuBrWh_PLINK].dentry);
        } else
                au_wh_clean(h_dir, h_path, /*isdir*/1);
        wbr->wbr_whbase = dget(base[AuBrWh_BASE].dentry);

        h_path->dentry = base[AuBrWh_ORPH].dentry;
        err = au_whdir(h_dir, h_path);
        if (unlikely(err))
                goto out;
        wbr->wbr_orph = dget(base[AuBrWh_ORPH].dentry);

out:
        return err;
}

/*
 * initialize the whiteout base file/dir for @br.
 */
int au_wh_init(struct au_branch *br, struct super_block *sb)
{
        int err, i;
        const unsigned char do_plink
                = !!au_opt_test(au_mntflags(sb), PLINK);
        struct inode *h_dir;
        struct path path = br->br_path;
        struct dentry *h_root = path.dentry;
        struct au_wbr *wbr = br->br_wbr;
        static const struct qstr base_name[] = {
                [AuBrWh_BASE] = QSTR_INIT(AUFS_BASE_NAME,
                                          sizeof(AUFS_BASE_NAME) - 1),
                [AuBrWh_PLINK] = QSTR_INIT(AUFS_PLINKDIR_NAME,
                                           sizeof(AUFS_PLINKDIR_NAME) - 1),
                [AuBrWh_ORPH] = QSTR_INIT(AUFS_ORPHDIR_NAME,
                                          sizeof(AUFS_ORPHDIR_NAME) - 1)
        };
        struct au_wh_base base[] = {
                [AuBrWh_BASE] = {
                        .name   = base_name + AuBrWh_BASE,
                        .dentry = NULL
                },
                [AuBrWh_PLINK] = {
                        .name   = base_name + AuBrWh_PLINK,
                        .dentry = NULL
                },
                [AuBrWh_ORPH] = {
                        .name   = base_name + AuBrWh_ORPH,
                        .dentry = NULL
                }
        };

        if (wbr)
                WbrWhMustWriteLock(wbr);

        for (i = 0; i < AuBrWh_Last; i++) {
                /* doubly whiteouted */
                struct dentry *d;

                d = au_wh_lkup(h_root, (void *)base[i].name, br);
                err = PTR_ERR(d);
                if (IS_ERR(d))
                        goto out;

                base[i].dentry = d;
                AuDebugOn(wbr
                          && wbr->wbr_wh[i]
                          && wbr->wbr_wh[i] != base[i].dentry);
        }

        if (wbr)
                for (i = 0; i < AuBrWh_Last; i++) {
                        dput(wbr->wbr_wh[i]);
                        wbr->wbr_wh[i] = NULL;
                }

        err = 0;
        if (!au_br_writable(br->br_perm)) {
                h_dir = d_inode(h_root);
                au_wh_init_ro(h_dir, base, &path);
        } else if (!au_br_wh_linkable(br->br_perm)) {
                err = au_wh_init_rw_nolink(h_root, wbr, do_plink, base, &path);
                if (err > 0)
                        goto out;
                else if (err)
                        goto out_err;
        } else {
                err = au_wh_init_rw(h_root, wbr, do_plink, base, &path);
                if (err > 0)
                        goto out;
                else if (err)
                        goto out_err;
        }
        goto out; /* success */

out_err:
        pr_err("an error(%d) on the writable branch %pd(%s)\n",
               err, h_root, au_sbtype(h_root->d_sb));
out:
        for (i = 0; i < AuBrWh_Last; i++)
                dput(base[i].dentry);
        return err;
}

/* ---------------------------------------------------------------------- */
/*
 * whiteouts are all hard-linked usually.
 * when its link count reaches a ceiling, we create a new whiteout base
 * asynchronously.
 */

struct reinit_br_wh {
        struct super_block *sb;
        struct au_branch *br;
};

static void reinit_br_wh(void *arg)
{
        int err;
        aufs_bindex_t bindex;
        struct path h_path;
        struct reinit_br_wh *a = arg;
        struct au_wbr *wbr;
        struct inode *dir, *delegated;
        struct dentry *h_root;
        struct au_hinode *hdir;

        err = 0;
        wbr = a->br->br_wbr;
        /* big aufs lock */
        si_noflush_write_lock(a->sb);
        if (!au_br_writable(a->br->br_perm))
                goto out;
        bindex = au_br_index(a->sb, a->br->br_id);
        if (unlikely(bindex < 0))
                goto out;

        di_read_lock_parent(a->sb->s_root, AuLock_IR);
        dir = d_inode(a->sb->s_root);
        hdir = au_hi(dir, bindex);
        h_root = au_h_dptr(a->sb->s_root, bindex);
        AuDebugOn(h_root != au_br_dentry(a->br));

        au_hn_inode_lock_nested(hdir, AuLsc_I_PARENT);
        wbr_wh_write_lock(wbr);
        err = au_h_verify(wbr->wbr_whbase, au_opt_udba(a->sb), hdir->hi_inode,
                          h_root, a->br);
        if (!err) {
                h_path.dentry = wbr->wbr_whbase;
                h_path.mnt = au_br_mnt(a->br);
                delegated = NULL;
                err = vfsub_unlink(hdir->hi_inode, &h_path, &delegated,
                                   /*force*/0);
                if (unlikely(err == -EWOULDBLOCK)) {
                        pr_warn("cannot retry for NFSv4 delegation"
                                " for an internal unlink\n");
                        iput(delegated);
                }
        } else {
                pr_warn("%pd is moved, ignored\n", wbr->wbr_whbase);
                err = 0;
        }
        dput(wbr->wbr_whbase);
        wbr->wbr_whbase = NULL;
        if (!err)
                err = au_wh_init(a->br, a->sb);
        wbr_wh_write_unlock(wbr);
        au_hn_inode_unlock(hdir);
        di_read_unlock(a->sb->s_root, AuLock_IR);
        if (!err)
                au_fhsm_wrote(a->sb, bindex, /*force*/0);

out:
        if (wbr)
                atomic_dec(&wbr->wbr_wh_running);
        au_br_put(a->br);
        si_write_unlock(a->sb);
        au_nwt_done(&au_sbi(a->sb)->si_nowait);
        au_delayed_kfree(arg);
        if (unlikely(err))
                AuIOErr("err %d\n", err);
}

static void kick_reinit_br_wh(struct super_block *sb, struct au_branch *br)
{
        int do_dec, wkq_err;
        struct reinit_br_wh *arg;

        do_dec = 1;
        if (atomic_inc_return(&br->br_wbr->wbr_wh_running) != 1)
                goto out;

        /* ignore ENOMEM */
        arg = kmalloc(sizeof(*arg), GFP_NOFS);
        if (arg) {
                /*
                 * dec(wh_running), kfree(arg) and dec(br_count)
                 * in reinit function
                 */
                arg->sb = sb;
                arg->br = br;
                au_br_get(br);
                wkq_err = au_wkq_nowait(reinit_br_wh, arg, sb, /*flags*/0);
                if (unlikely(wkq_err)) {
                        atomic_dec(&br->br_wbr->wbr_wh_running);
                        au_br_put(br);
                        au_delayed_kfree(arg);
                }
                do_dec = 0;
        }

out:
        if (do_dec)
                atomic_dec(&br->br_wbr->wbr_wh_running);
}

/* ---------------------------------------------------------------------- */

/*
 * create the whiteout @wh.
 */
static int link_or_create_wh(struct super_block *sb, aufs_bindex_t bindex,
                             struct dentry *wh)
{
        int err;
        struct path h_path = {
                .dentry = wh
        };
        struct au_branch *br;
        struct au_wbr *wbr;
        struct dentry *h_parent;
        struct inode *h_dir, *delegated;

        h_parent = wh->d_parent; /* dir inode is locked */
        h_dir = d_inode(h_parent);
        IMustLock(h_dir);

        br = au_sbr(sb, bindex);
        h_path.mnt = au_br_mnt(br);
        wbr = br->br_wbr;
        wbr_wh_read_lock(wbr);
        if (wbr->wbr_whbase) {
                delegated = NULL;
                err = vfsub_link(wbr->wbr_whbase, h_dir, &h_path, &delegated);
                if (unlikely(err == -EWOULDBLOCK)) {
                        pr_warn("cannot retry for NFSv4 delegation"
                                " for an internal link\n");
                        iput(delegated);
                }
                if (!err || err != -EMLINK)
                        goto out;

                /* link count full. re-initialize br_whbase. */
                kick_reinit_br_wh(sb, br);
        }

        /* return this error in this context */
        err = vfsub_create(h_dir, &h_path, WH_MASK, /*want_excl*/true);
        if (!err)
                au_fhsm_wrote(sb, bindex, /*force*/0);

out:
        wbr_wh_read_unlock(wbr);
        return err;
}

/* ---------------------------------------------------------------------- */

/*
 * create or remove the diropq.
 */
static struct dentry *do_diropq(struct dentry *dentry, aufs_bindex_t bindex,
                                unsigned int flags)
{
        struct dentry *opq_dentry, *h_dentry;
        struct super_block *sb;
        struct au_branch *br;
        int err;

        sb = dentry->d_sb;
        br = au_sbr(sb, bindex);
        h_dentry = au_h_dptr(dentry, bindex);
        opq_dentry = vfsub_lkup_one(&diropq_name, h_dentry);
        if (IS_ERR(opq_dentry))
                goto out;

        if (au_ftest_diropq(flags, CREATE)) {
                err = link_or_create_wh(sb, bindex, opq_dentry);
                if (!err) {
                        au_set_dbdiropq(dentry, bindex);
                        goto out; /* success */
                }
        } else {
                struct path tmp = {
                        .dentry = opq_dentry,
                        .mnt    = au_br_mnt(br)
                };
                err = do_unlink_wh(au_h_iptr(d_inode(dentry), bindex), &tmp);
                if (!err)
                        au_set_dbdiropq(dentry, -1);
        }
        dput(opq_dentry);
        opq_dentry = ERR_PTR(err);

out:
        return opq_dentry;
}

struct do_diropq_args {
        struct dentry **errp;
        struct dentry *dentry;
        aufs_bindex_t bindex;
        unsigned int flags;
};

static void call_do_diropq(void *args)
{
        struct do_diropq_args *a = args;
        *a->errp = do_diropq(a->dentry, a->bindex, a->flags);
}

struct dentry *au_diropq_sio(struct dentry *dentry, aufs_bindex_t bindex,
                             unsigned int flags)
{
        struct dentry *diropq, *h_dentry;

        h_dentry = au_h_dptr(dentry, bindex);
        if (!au_test_h_perm_sio(d_inode(h_dentry), MAY_EXEC | MAY_WRITE))
                diropq = do_diropq(dentry, bindex, flags);
        else {
                int wkq_err;
                struct do_diropq_args args = {
                        .errp           = &diropq,
                        .dentry         = dentry,
                        .bindex         = bindex,
                        .flags          = flags
                };

                wkq_err = au_wkq_wait(call_do_diropq, &args);
                if (unlikely(wkq_err))
                        diropq = ERR_PTR(wkq_err);
        }

        return diropq;
}

/* ---------------------------------------------------------------------- */

/*
 * lookup whiteout dentry.
 * @h_parent: lower parent dentry which must exist and be locked
 * @base_name: name of dentry which will be whiteouted
 * returns dentry for whiteout.
 */
struct dentry *au_wh_lkup(struct dentry *h_parent, struct qstr *base_name,
                          struct au_branch *br)
{
        int err;
        struct qstr wh_name;
        struct dentry *wh_dentry;

        err = au_wh_name_alloc(&wh_name, base_name);
        wh_dentry = ERR_PTR(err);
        if (!err) {
                wh_dentry = vfsub_lkup_one(&wh_name, h_parent);
                au_delayed_kfree(wh_name.name);
        }
        return wh_dentry;
}

/*
 * link/create a whiteout for @dentry on @bindex.
 */
struct dentry *au_wh_create(struct dentry *dentry, aufs_bindex_t bindex,
                            struct dentry *h_parent)
{
        struct dentry *wh_dentry;
        struct super_block *sb;
        int err;

        sb = dentry->d_sb;
        wh_dentry = au_wh_lkup(h_parent, &dentry->d_name, au_sbr(sb, bindex));
        if (!IS_ERR(wh_dentry) && d_is_negative(wh_dentry)) {
                err = link_or_create_wh(sb, bindex, wh_dentry);
                if (!err) {
                        au_set_dbwh(dentry, bindex);
                        au_fhsm_wrote(sb, bindex, /*force*/0);
                } else {
                        dput(wh_dentry);
                        wh_dentry = ERR_PTR(err);
                }
        }

        return wh_dentry;
}

/* ---------------------------------------------------------------------- */

/* Delete all whiteouts in this directory on branch bindex. */
static int del_wh_children(struct dentry *h_dentry, struct au_nhash *whlist,
                           aufs_bindex_t bindex, struct au_branch *br)
{
        int err;
        unsigned long ul, n;
        struct qstr wh_name;
        char *p;
        struct hlist_head *head;
        struct au_vdir_wh *pos;
        struct au_vdir_destr *str;

        err = -ENOMEM;
        p = (void *)__get_free_page(GFP_NOFS);
        wh_name.name = p;
        if (unlikely(!wh_name.name))
                goto out;

        err = 0;
        memcpy(p, AUFS_WH_PFX, AUFS_WH_PFX_LEN);
        p += AUFS_WH_PFX_LEN;
        n = whlist->nh_num;
        head = whlist->nh_head;
        for (ul = 0; !err && ul < n; ul++, head++) {
                hlist_for_each_entry(pos, head, wh_hash) {
                        if (pos->wh_bindex != bindex)
                                continue;

                        str = &pos->wh_str;
                        if (str->len + AUFS_WH_PFX_LEN <= PATH_MAX) {
                                memcpy(p, str->name, str->len);
                                wh_name.len = AUFS_WH_PFX_LEN + str->len;
                                err = unlink_wh_name(h_dentry, &wh_name, br);
                                if (!err)
                                        continue;
                                break;
                        }
                        AuIOErr("whiteout name too long %.*s\n",
                                str->len, str->name);
                        err = -EIO;
                        break;
                }
        }
        au_delayed_free_page((unsigned long)wh_name.name);

out:
        return err;
}

struct del_wh_children_args {
        int *errp;
        struct dentry *h_dentry;
        struct au_nhash *whlist;
        aufs_bindex_t bindex;
        struct au_branch *br;
};

static void call_del_wh_children(void *args)
{
        struct del_wh_children_args *a = args;
        *a->errp = del_wh_children(a->h_dentry, a->whlist, a->bindex, a->br);
}

/* ---------------------------------------------------------------------- */

struct au_whtmp_rmdir *au_whtmp_rmdir_alloc(struct super_block *sb, gfp_t gfp)
{
        struct au_whtmp_rmdir *whtmp;
        int err;
        unsigned int rdhash;

        SiMustAnyLock(sb);

        whtmp = kzalloc(sizeof(*whtmp), gfp);
        if (unlikely(!whtmp)) {
                whtmp = ERR_PTR(-ENOMEM);
                goto out;
        }

        /* no estimation for dir size */
        rdhash = au_sbi(sb)->si_rdhash;
        if (!rdhash)
                rdhash = AUFS_RDHASH_DEF;
        err = au_nhash_alloc(&whtmp->whlist, rdhash, gfp);
        if (unlikely(err)) {
                au_delayed_kfree(whtmp);
                whtmp = ERR_PTR(err);
        }

out:
        return whtmp;
}

void au_whtmp_rmdir_free(struct au_whtmp_rmdir *whtmp)
{
        if (whtmp->br)
                au_br_put(whtmp->br);
        dput(whtmp->wh_dentry);
        iput(whtmp->dir);
        au_nhash_wh_free(&whtmp->whlist);
        au_delayed_kfree(whtmp);
}

/*
 * rmdir the whiteouted temporary named dir @h_dentry.
 * @whlist: whiteouted children.
 */
int au_whtmp_rmdir(struct inode *dir, aufs_bindex_t bindex,
                   struct dentry *wh_dentry, struct au_nhash *whlist)
{
        int err;
        unsigned int h_nlink;
        struct path h_tmp;
        struct inode *wh_inode, *h_dir;
        struct au_branch *br;

        h_dir = d_inode(wh_dentry->d_parent); /* dir inode is locked */
        IMustLock(h_dir);

        br = au_sbr(dir->i_sb, bindex);
        wh_inode = d_inode(wh_dentry);
        inode_lock_nested(wh_inode, AuLsc_I_CHILD);

        /*
         * someone else might change some whiteouts while we were sleeping.
         * it means this whlist may have an obsoleted entry.
         */
        if (!au_test_h_perm_sio(wh_inode, MAY_EXEC | MAY_WRITE))
                err = del_wh_children(wh_dentry, whlist, bindex, br);
        else {
                int wkq_err;
                struct del_wh_children_args args = {
                        .errp           = &err,
                        .h_dentry       = wh_dentry,
                        .whlist         = whlist,
                        .bindex         = bindex,
                        .br             = br
                };

                wkq_err = au_wkq_wait(call_del_wh_children, &args);
                if (unlikely(wkq_err))
                        err = wkq_err;
        }
        inode_unlock(wh_inode);

        if (!err) {
                h_tmp.dentry = wh_dentry;
                h_tmp.mnt = au_br_mnt(br);
                h_nlink = h_dir->i_nlink;
                err = vfsub_rmdir(h_dir, &h_tmp);
                /* some fs doesn't change the parent nlink in some cases */
                h_nlink -= h_dir->i_nlink;
        }

        if (!err) {
                if (au_ibtop(dir) == bindex) {
                        /* todo: dir->i_mutex is necessary */
                        au_cpup_attr_timesizes(dir);
                        if (h_nlink)
                                vfsub_drop_nlink(dir);
                }
                return 0; /* success */
        }

        pr_warn("failed removing %pd(%d), ignored\n", wh_dentry, err);
        return err;
}

static void call_rmdir_whtmp(void *args)
{
        int err;
        aufs_bindex_t bindex;
        struct au_whtmp_rmdir *a = args;
        struct super_block *sb;
        struct dentry *h_parent;
        struct inode *h_dir;
        struct au_hinode *hdir;

        /* rmdir by nfsd may cause deadlock with this i_mutex */
        /* inode_lock(a->dir); */
        err = -EROFS;
        sb = a->dir->i_sb;
        si_read_lock(sb, !AuLock_FLUSH);
        if (!au_br_writable(a->br->br_perm))
                goto out;
        bindex = au_br_index(sb, a->br->br_id);
        if (unlikely(bindex < 0))
                goto out;

        err = -EIO;
        ii_write_lock_parent(a->dir);
        h_parent = dget_parent(a->wh_dentry);
        h_dir = d_inode(h_parent);
        hdir = au_hi(a->dir, bindex);
        err = vfsub_mnt_want_write(au_br_mnt(a->br));
        if (unlikely(err))
                goto out_mnt;
        au_hn_inode_lock_nested(hdir, AuLsc_I_PARENT);
        err = au_h_verify(a->wh_dentry, au_opt_udba(sb), h_dir, h_parent,
                          a->br);
        if (!err)
                err = au_whtmp_rmdir(a->dir, bindex, a->wh_dentry, &a->whlist);
        au_hn_inode_unlock(hdir);
        vfsub_mnt_drop_write(au_br_mnt(a->br));

out_mnt:
        dput(h_parent);
        ii_write_unlock(a->dir);
out:
        /* inode_unlock(a->dir); */
        au_whtmp_rmdir_free(a);
        si_read_unlock(sb);
        au_nwt_done(&au_sbi(sb)->si_nowait);
        if (unlikely(err))
                AuIOErr("err %d\n", err);
}

void au_whtmp_kick_rmdir(struct inode *dir, aufs_bindex_t bindex,
                         struct dentry *wh_dentry, struct au_whtmp_rmdir *args)
{
        int wkq_err;
        struct super_block *sb;

        IMustLock(dir);

        /* all post-process will be done in do_rmdir_whtmp(). */
        sb = dir->i_sb;
        args->dir = au_igrab(dir);
        args->br = au_sbr(sb, bindex);
        au_br_get(args->br);
        args->wh_dentry = dget(wh_dentry);
        wkq_err = au_wkq_nowait(call_rmdir_whtmp, args, sb, /*flags*/0);
        if (unlikely(wkq_err)) {
                pr_warn("rmdir error %pd (%d), ignored\n", wh_dentry, wkq_err);
                au_whtmp_rmdir_free(args);
        }
}