mm: fix exec activate_mm vs TLB shootdown and lazy tlb switching race

[linux/fpc-iii.git] / fs / xfs / xfs_iops.c

/*
 * Copyright (c) 2000-2005 Silicon Graphics, Inc.
 * All Rights Reserved.
 *
 * This program 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.
 *
 * This program is distributed in the hope that it would 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, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_da_format.h"
#include "xfs_inode.h"
#include "xfs_bmap.h"
#include "xfs_bmap_util.h"
#include "xfs_acl.h"
#include "xfs_quota.h"
#include "xfs_error.h"
#include "xfs_attr.h"
#include "xfs_trans.h"
#include "xfs_trace.h"
#include "xfs_icache.h"
#include "xfs_symlink.h"
#include "xfs_da_btree.h"
#include "xfs_dir2.h"
#include "xfs_trans_space.h"
#include "xfs_pnfs.h"
#include "xfs_iomap.h"

#include <linux/capability.h>
#include <linux/xattr.h>
#include <linux/posix_acl.h>
#include <linux/security.h>
#include <linux/iomap.h>
#include <linux/slab.h>

/*
 * Directories have different lock order w.r.t. mmap_sem compared to regular
 * files. This is due to readdir potentially triggering page faults on a user
 * buffer inside filldir(), and this happens with the ilock on the directory
 * held. For regular files, the lock order is the other way around - the
 * mmap_sem is taken during the page fault, and then we lock the ilock to do
 * block mapping. Hence we need a different class for the directory ilock so
 * that lockdep can tell them apart.
 */
static struct lock_class_key xfs_nondir_ilock_class;
static struct lock_class_key xfs_dir_ilock_class;

static int
xfs_initxattrs(
        struct inode            *inode,
        const struct xattr      *xattr_array,
        void                    *fs_info)
{
        const struct xattr      *xattr;
        struct xfs_inode        *ip = XFS_I(inode);
        int                     error = 0;

        for (xattr = xattr_array; xattr->name != NULL; xattr++) {
                error = xfs_attr_set(ip, xattr->name, xattr->value,
                                      xattr->value_len, ATTR_SECURE);
                if (error < 0)
                        break;
        }
        return error;
}

/*
 * Hook in SELinux.  This is not quite correct yet, what we really need
 * here (as we do for default ACLs) is a mechanism by which creation of
 * these attrs can be journalled at inode creation time (along with the
 * inode, of course, such that log replay can't cause these to be lost).
 */

STATIC int
xfs_init_security(
        struct inode    *inode,
        struct inode    *dir,
        const struct qstr *qstr)
{
        return security_inode_init_security(inode, dir, qstr,
                                             &xfs_initxattrs, NULL);
}

static void
xfs_dentry_to_name(
        struct xfs_name *namep,
        struct dentry   *dentry)
{
        namep->name = dentry->d_name.name;
        namep->len = dentry->d_name.len;
        namep->type = XFS_DIR3_FT_UNKNOWN;
}

static int
xfs_dentry_mode_to_name(
        struct xfs_name *namep,
        struct dentry   *dentry,
        int             mode)
{
        namep->name = dentry->d_name.name;
        namep->len = dentry->d_name.len;
        namep->type = xfs_mode_to_ftype(mode);

        if (unlikely(namep->type == XFS_DIR3_FT_UNKNOWN))
                return -EFSCORRUPTED;

        return 0;
}

STATIC void
xfs_cleanup_inode(
        struct inode    *dir,
        struct inode    *inode,
        struct dentry   *dentry)
{
        struct xfs_name teardown;

        /* Oh, the horror.
         * If we can't add the ACL or we fail in
         * xfs_init_security we must back out.
         * ENOSPC can hit here, among other things.
         */
        xfs_dentry_to_name(&teardown, dentry);

        xfs_remove(XFS_I(dir), &teardown, XFS_I(inode));
}

STATIC int
xfs_generic_create(
        struct inode    *dir,
        struct dentry   *dentry,
        umode_t         mode,
        dev_t           rdev,
        bool            tmpfile)        /* unnamed file */
{
        struct inode    *inode;
        struct xfs_inode *ip = NULL;
        struct posix_acl *default_acl, *acl;
        struct xfs_name name;
        int             error;

        /*
         * Irix uses Missed'em'V split, but doesn't want to see
         * the upper 5 bits of (14bit) major.
         */
        if (S_ISCHR(mode) || S_ISBLK(mode)) {
                if (unlikely(!sysv_valid_dev(rdev) || MAJOR(rdev) & ~0x1ff))
                        return -EINVAL;
                rdev = sysv_encode_dev(rdev);
        } else {
                rdev = 0;
        }

        error = posix_acl_create(dir, &mode, &default_acl, &acl);
        if (error)
                return error;

        /* Verify mode is valid also for tmpfile case */
        error = xfs_dentry_mode_to_name(&name, dentry, mode);
        if (unlikely(error))
                goto out_free_acl;

        if (!tmpfile) {
                error = xfs_create(XFS_I(dir), &name, mode, rdev, &ip);
        } else {
                error = xfs_create_tmpfile(XFS_I(dir), dentry, mode, &ip);
        }
        if (unlikely(error))
                goto out_free_acl;

        inode = VFS_I(ip);

        error = xfs_init_security(inode, dir, &dentry->d_name);
        if (unlikely(error))
                goto out_cleanup_inode;

#ifdef CONFIG_XFS_POSIX_ACL
        if (default_acl) {
                error = __xfs_set_acl(inode, default_acl, ACL_TYPE_DEFAULT);
                if (error)
                        goto out_cleanup_inode;
        }
        if (acl) {
                error = __xfs_set_acl(inode, acl, ACL_TYPE_ACCESS);
                if (error)
                        goto out_cleanup_inode;
        }
#endif

        xfs_setup_iops(ip);

        if (tmpfile)
                d_tmpfile(dentry, inode);
        else
                d_instantiate(dentry, inode);

        xfs_finish_inode_setup(ip);

 out_free_acl:
        if (default_acl)
                posix_acl_release(default_acl);
        if (acl)
                posix_acl_release(acl);
        return error;

 out_cleanup_inode:
        xfs_finish_inode_setup(ip);
        if (!tmpfile)
                xfs_cleanup_inode(dir, inode, dentry);
        iput(inode);
        goto out_free_acl;
}

STATIC int
xfs_vn_mknod(
        struct inode    *dir,
        struct dentry   *dentry,
        umode_t         mode,
        dev_t           rdev)
{
        return xfs_generic_create(dir, dentry, mode, rdev, false);
}

STATIC int
xfs_vn_create(
        struct inode    *dir,
        struct dentry   *dentry,
        umode_t         mode,
        bool            flags)
{
        return xfs_vn_mknod(dir, dentry, mode, 0);
}

STATIC int
xfs_vn_mkdir(
        struct inode    *dir,
        struct dentry   *dentry,
        umode_t         mode)
{
        return xfs_vn_mknod(dir, dentry, mode|S_IFDIR, 0);
}

STATIC struct dentry *
xfs_vn_lookup(
        struct inode    *dir,
        struct dentry   *dentry,
        unsigned int flags)
{
        struct xfs_inode *cip;
        struct xfs_name name;
        int             error;

        if (dentry->d_name.len >= MAXNAMELEN)
                return ERR_PTR(-ENAMETOOLONG);

        xfs_dentry_to_name(&name, dentry);
        error = xfs_lookup(XFS_I(dir), &name, &cip, NULL);
        if (unlikely(error)) {
                if (unlikely(error != -ENOENT))
                        return ERR_PTR(error);
                d_add(dentry, NULL);
                return NULL;
        }

        return d_splice_alias(VFS_I(cip), dentry);
}

STATIC struct dentry *
xfs_vn_ci_lookup(
        struct inode    *dir,
        struct dentry   *dentry,
        unsigned int flags)
{
        struct xfs_inode *ip;
        struct xfs_name xname;
        struct xfs_name ci_name;
        struct qstr     dname;
        int             error;

        if (dentry->d_name.len >= MAXNAMELEN)
                return ERR_PTR(-ENAMETOOLONG);

        xfs_dentry_to_name(&xname, dentry);
        error = xfs_lookup(XFS_I(dir), &xname, &ip, &ci_name);
        if (unlikely(error)) {
                if (unlikely(error != -ENOENT))
                        return ERR_PTR(error);
                /*
                 * call d_add(dentry, NULL) here when d_drop_negative_children
                 * is called in xfs_vn_mknod (ie. allow negative dentries
                 * with CI filesystems).
                 */
                return NULL;
        }

        /* if exact match, just splice and exit */
        if (!ci_name.name)
                return d_splice_alias(VFS_I(ip), dentry);

        /* else case-insensitive match... */
        dname.name = ci_name.name;
        dname.len = ci_name.len;
        dentry = d_add_ci(dentry, VFS_I(ip), &dname);
        kmem_free(ci_name.name);
        return dentry;
}

STATIC int
xfs_vn_link(
        struct dentry   *old_dentry,
        struct inode    *dir,
        struct dentry   *dentry)
{
        struct inode    *inode = d_inode(old_dentry);
        struct xfs_name name;
        int             error;

        error = xfs_dentry_mode_to_name(&name, dentry, inode->i_mode);
        if (unlikely(error))
                return error;

        error = xfs_link(XFS_I(dir), XFS_I(inode), &name);
        if (unlikely(error))
                return error;

        ihold(inode);
        d_instantiate(dentry, inode);
        return 0;
}

STATIC int
xfs_vn_unlink(
        struct inode    *dir,
        struct dentry   *dentry)
{
        struct xfs_name name;
        int             error;

        xfs_dentry_to_name(&name, dentry);

        error = xfs_remove(XFS_I(dir), &name, XFS_I(d_inode(dentry)));
        if (error)
                return error;

        /*
         * With unlink, the VFS makes the dentry "negative": no inode,
         * but still hashed. This is incompatible with case-insensitive
         * mode, so invalidate (unhash) the dentry in CI-mode.
         */
        if (xfs_sb_version_hasasciici(&XFS_M(dir->i_sb)->m_sb))
                d_invalidate(dentry);
        return 0;
}

STATIC int
xfs_vn_symlink(
        struct inode    *dir,
        struct dentry   *dentry,
        const char      *symname)
{
        struct inode    *inode;
        struct xfs_inode *cip = NULL;
        struct xfs_name name;
        int             error;
        umode_t         mode;

        mode = S_IFLNK |
                (irix_symlink_mode ? 0777 & ~current_umask() : S_IRWXUGO);
        error = xfs_dentry_mode_to_name(&name, dentry, mode);
        if (unlikely(error))
                goto out;

        error = xfs_symlink(XFS_I(dir), &name, symname, mode, &cip);
        if (unlikely(error))
                goto out;

        inode = VFS_I(cip);

        error = xfs_init_security(inode, dir, &dentry->d_name);
        if (unlikely(error))
                goto out_cleanup_inode;

        xfs_setup_iops(cip);

        d_instantiate(dentry, inode);
        xfs_finish_inode_setup(cip);
        return 0;

 out_cleanup_inode:
        xfs_finish_inode_setup(cip);
        xfs_cleanup_inode(dir, inode, dentry);
        iput(inode);
 out:
        return error;
}

STATIC int
xfs_vn_rename(
        struct inode    *odir,
        struct dentry   *odentry,
        struct inode    *ndir,
        struct dentry   *ndentry,
        unsigned int    flags)
{
        struct inode    *new_inode = d_inode(ndentry);
        int             omode = 0;
        int             error;
        struct xfs_name oname;
        struct xfs_name nname;

        if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
                return -EINVAL;

        /* if we are exchanging files, we need to set i_mode of both files */
        if (flags & RENAME_EXCHANGE)
                omode = d_inode(ndentry)->i_mode;

        error = xfs_dentry_mode_to_name(&oname, odentry, omode);
        if (omode && unlikely(error))
                return error;

        error = xfs_dentry_mode_to_name(&nname, ndentry,
                                        d_inode(odentry)->i_mode);
        if (unlikely(error))
                return error;

        return xfs_rename(XFS_I(odir), &oname, XFS_I(d_inode(odentry)),
                          XFS_I(ndir), &nname,
                          new_inode ? XFS_I(new_inode) : NULL, flags);
}

/*
 * careful here - this function can get called recursively, so
 * we need to be very careful about how much stack we use.
 * uio is kmalloced for this reason...
 */
STATIC const char *
xfs_vn_get_link(
        struct dentry           *dentry,
        struct inode            *inode,
        struct delayed_call     *done)
{
        char                    *link;
        int                     error = -ENOMEM;

        if (!dentry)
                return ERR_PTR(-ECHILD);

        link = kmalloc(XFS_SYMLINK_MAXLEN+1, GFP_KERNEL);
        if (!link)
                goto out_err;

        error = xfs_readlink(XFS_I(d_inode(dentry)), link);
        if (unlikely(error))
                goto out_kfree;

        set_delayed_call(done, kfree_link, link);
        return link;

 out_kfree:
        kfree(link);
 out_err:
        return ERR_PTR(error);
}

STATIC const char *
xfs_vn_get_link_inline(
        struct dentry           *dentry,
        struct inode            *inode,
        struct delayed_call     *done)
{
        ASSERT(XFS_I(inode)->i_df.if_flags & XFS_IFINLINE);
        return XFS_I(inode)->i_df.if_u1.if_data;
}

STATIC int
xfs_vn_getattr(
        const struct path       *path,
        struct kstat            *stat,
        u32                     request_mask,
        unsigned int            query_flags)
{
        struct inode            *inode = d_inode(path->dentry);
        struct xfs_inode        *ip = XFS_I(inode);
        struct xfs_mount        *mp = ip->i_mount;

        trace_xfs_getattr(ip);

        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;

        stat->size = XFS_ISIZE(ip);
        stat->dev = inode->i_sb->s_dev;
        stat->mode = inode->i_mode;
        stat->nlink = inode->i_nlink;
        stat->uid = inode->i_uid;
        stat->gid = inode->i_gid;
        stat->ino = ip->i_ino;
        stat->atime = inode->i_atime;
        stat->mtime = inode->i_mtime;
        stat->ctime = inode->i_ctime;
        stat->blocks =
                XFS_FSB_TO_BB(mp, ip->i_d.di_nblocks + ip->i_delayed_blks);

        if (ip->i_d.di_version == 3) {
                if (request_mask & STATX_BTIME) {
                        stat->result_mask |= STATX_BTIME;
                        stat->btime.tv_sec = ip->i_d.di_crtime.t_sec;
                        stat->btime.tv_nsec = ip->i_d.di_crtime.t_nsec;
                }
        }

        if (ip->i_d.di_flags & XFS_DIFLAG_IMMUTABLE)
                stat->attributes |= STATX_ATTR_IMMUTABLE;
        if (ip->i_d.di_flags & XFS_DIFLAG_APPEND)
                stat->attributes |= STATX_ATTR_APPEND;
        if (ip->i_d.di_flags & XFS_DIFLAG_NODUMP)
                stat->attributes |= STATX_ATTR_NODUMP;

        switch (inode->i_mode & S_IFMT) {
        case S_IFBLK:
        case S_IFCHR:
                stat->blksize = BLKDEV_IOSIZE;
                stat->rdev = MKDEV(sysv_major(ip->i_df.if_u2.if_rdev) & 0x1ff,
                                   sysv_minor(ip->i_df.if_u2.if_rdev));
                break;
        default:
                if (XFS_IS_REALTIME_INODE(ip)) {
                        /*
                         * If the file blocks are being allocated from a
                         * realtime volume, then return the inode's realtime
                         * extent size or the realtime volume's extent size.
                         */
                        stat->blksize =
                                xfs_get_extsz_hint(ip) << mp->m_sb.sb_blocklog;
                } else
                        stat->blksize = xfs_preferred_iosize(mp);
                stat->rdev = 0;
                break;
        }

        return 0;
}

static void
xfs_setattr_mode(
        struct xfs_inode        *ip,
        struct iattr            *iattr)
{
        struct inode            *inode = VFS_I(ip);
        umode_t                 mode = iattr->ia_mode;

        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));

        inode->i_mode &= S_IFMT;
        inode->i_mode |= mode & ~S_IFMT;
}

void
xfs_setattr_time(
        struct xfs_inode        *ip,
        struct iattr            *iattr)
{
        struct inode            *inode = VFS_I(ip);

        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));

        if (iattr->ia_valid & ATTR_ATIME)
                inode->i_atime = iattr->ia_atime;
        if (iattr->ia_valid & ATTR_CTIME)
                inode->i_ctime = iattr->ia_ctime;
        if (iattr->ia_valid & ATTR_MTIME)
                inode->i_mtime = iattr->ia_mtime;
}

static int
xfs_vn_change_ok(
        struct dentry   *dentry,
        struct iattr    *iattr)
{
        struct xfs_mount        *mp = XFS_I(d_inode(dentry))->i_mount;

        if (mp->m_flags & XFS_MOUNT_RDONLY)
                return -EROFS;

        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;

        return setattr_prepare(dentry, iattr);
}

/*
 * Set non-size attributes of an inode.
 *
 * Caution: The caller of this function is responsible for calling
 * setattr_prepare() or otherwise verifying the change is fine.
 */
int
xfs_setattr_nonsize(
        struct xfs_inode        *ip,
        struct iattr            *iattr,
        int                     flags)
{
        xfs_mount_t             *mp = ip->i_mount;
        struct inode            *inode = VFS_I(ip);
        int                     mask = iattr->ia_valid;
        xfs_trans_t             *tp;
        int                     error;
        kuid_t                  uid = GLOBAL_ROOT_UID, iuid = GLOBAL_ROOT_UID;
        kgid_t                  gid = GLOBAL_ROOT_GID, igid = GLOBAL_ROOT_GID;
        struct xfs_dquot        *udqp = NULL, *gdqp = NULL;
        struct xfs_dquot        *olddquot1 = NULL, *olddquot2 = NULL;

        ASSERT((mask & ATTR_SIZE) == 0);

        /*
         * If disk quotas is on, we make sure that the dquots do exist on disk,
         * before we start any other transactions. Trying to do this later
         * is messy. We don't care to take a readlock to look at the ids
         * in inode here, because we can't hold it across the trans_reserve.
         * If the IDs do change before we take the ilock, we're covered
         * because the i_*dquot fields will get updated anyway.
         */
        if (XFS_IS_QUOTA_ON(mp) && (mask & (ATTR_UID|ATTR_GID))) {
                uint    qflags = 0;

                if ((mask & ATTR_UID) && XFS_IS_UQUOTA_ON(mp)) {
                        uid = iattr->ia_uid;
                        qflags |= XFS_QMOPT_UQUOTA;
                } else {
                        uid = inode->i_uid;
                }
                if ((mask & ATTR_GID) && XFS_IS_GQUOTA_ON(mp)) {
                        gid = iattr->ia_gid;
                        qflags |= XFS_QMOPT_GQUOTA;
                }  else {
                        gid = inode->i_gid;
                }

                /*
                 * We take a reference when we initialize udqp and gdqp,
                 * so it is important that we never blindly double trip on
                 * the same variable. See xfs_create() for an example.
                 */
                ASSERT(udqp == NULL);
                ASSERT(gdqp == NULL);
                error = xfs_qm_vop_dqalloc(ip, xfs_kuid_to_uid(uid),
                                           xfs_kgid_to_gid(gid),
                                           xfs_get_projid(ip),
                                           qflags, &udqp, &gdqp, NULL);
                if (error)
                        return error;
        }

        error = xfs_trans_alloc(mp, &M_RES(mp)->tr_ichange, 0, 0, 0, &tp);
        if (error)
                goto out_dqrele;

        xfs_ilock(ip, XFS_ILOCK_EXCL);
        xfs_trans_ijoin(tp, ip, 0);

        /*
         * Change file ownership.  Must be the owner or privileged.
         */
        if (mask & (ATTR_UID|ATTR_GID)) {
                /*
                 * These IDs could have changed since we last looked at them.
                 * But, we're assured that if the ownership did change
                 * while we didn't have the inode locked, inode's dquot(s)
                 * would have changed also.
                 */
                iuid = inode->i_uid;
                igid = inode->i_gid;
                gid = (mask & ATTR_GID) ? iattr->ia_gid : igid;
                uid = (mask & ATTR_UID) ? iattr->ia_uid : iuid;

                /*
                 * Do a quota reservation only if uid/gid is actually
                 * going to change.
                 */
                if (XFS_IS_QUOTA_RUNNING(mp) &&
                    ((XFS_IS_UQUOTA_ON(mp) && !uid_eq(iuid, uid)) ||
                     (XFS_IS_GQUOTA_ON(mp) && !gid_eq(igid, gid)))) {
                        ASSERT(tp);
                        error = xfs_qm_vop_chown_reserve(tp, ip, udqp, gdqp,
                                                NULL, capable(CAP_FOWNER) ?
                                                XFS_QMOPT_FORCE_RES : 0);
                        if (error)      /* out of quota */
                                goto out_cancel;
                }
        }

        /*
         * Change file ownership.  Must be the owner or privileged.
         */
        if (mask & (ATTR_UID|ATTR_GID)) {
                /*
                 * CAP_FSETID overrides the following restrictions:
                 *
                 * The set-user-ID and set-group-ID bits of a file will be
                 * cleared upon successful return from chown()
                 */
                if ((inode->i_mode & (S_ISUID|S_ISGID)) &&
                    !capable(CAP_FSETID))
                        inode->i_mode &= ~(S_ISUID|S_ISGID);

                /*
                 * Change the ownerships and register quota modifications
                 * in the transaction.
                 */
                if (!uid_eq(iuid, uid)) {
                        if (XFS_IS_QUOTA_RUNNING(mp) && XFS_IS_UQUOTA_ON(mp)) {
                                ASSERT(mask & ATTR_UID);
                                ASSERT(udqp);
                                olddquot1 = xfs_qm_vop_chown(tp, ip,
                                                        &ip->i_udquot, udqp);
                        }
                        ip->i_d.di_uid = xfs_kuid_to_uid(uid);
                        inode->i_uid = uid;
                }
                if (!gid_eq(igid, gid)) {
                        if (XFS_IS_QUOTA_RUNNING(mp) && XFS_IS_GQUOTA_ON(mp)) {
                                ASSERT(xfs_sb_version_has_pquotino(&mp->m_sb) ||
                                       !XFS_IS_PQUOTA_ON(mp));
                                ASSERT(mask & ATTR_GID);
                                ASSERT(gdqp);
                                olddquot2 = xfs_qm_vop_chown(tp, ip,
                                                        &ip->i_gdquot, gdqp);
                        }
                        ip->i_d.di_gid = xfs_kgid_to_gid(gid);
                        inode->i_gid = gid;
                }
        }

        if (mask & ATTR_MODE)
                xfs_setattr_mode(ip, iattr);
        if (mask & (ATTR_ATIME|ATTR_CTIME|ATTR_MTIME))
                xfs_setattr_time(ip, iattr);

        xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);

        XFS_STATS_INC(mp, xs_ig_attrchg);

        if (mp->m_flags & XFS_MOUNT_WSYNC)
                xfs_trans_set_sync(tp);
        error = xfs_trans_commit(tp);

        xfs_iunlock(ip, XFS_ILOCK_EXCL);

        /*
         * Release any dquot(s) the inode had kept before chown.
         */
        xfs_qm_dqrele(olddquot1);
        xfs_qm_dqrele(olddquot2);
        xfs_qm_dqrele(udqp);
        xfs_qm_dqrele(gdqp);

        if (error)
                return error;

        /*
         * XXX(hch): Updating the ACL entries is not atomic vs the i_mode
         *           update.  We could avoid this with linked transactions
         *           and passing down the transaction pointer all the way
         *           to attr_set.  No previous user of the generic
         *           Posix ACL code seems to care about this issue either.
         */
        if ((mask & ATTR_MODE) && !(flags & XFS_ATTR_NOACL)) {
                error = posix_acl_chmod(inode, inode->i_mode);
                if (error)
                        return error;
        }

        return 0;

out_cancel:
        xfs_trans_cancel(tp);
        xfs_iunlock(ip, XFS_ILOCK_EXCL);
out_dqrele:
        xfs_qm_dqrele(udqp);
        xfs_qm_dqrele(gdqp);
        return error;
}

int
xfs_vn_setattr_nonsize(
        struct dentry           *dentry,
        struct iattr            *iattr)
{
        struct xfs_inode        *ip = XFS_I(d_inode(dentry));
        int error;

        trace_xfs_setattr(ip);

        error = xfs_vn_change_ok(dentry, iattr);
        if (error)
                return error;
        return xfs_setattr_nonsize(ip, iattr, 0);
}

/*
 * Truncate file.  Must have write permission and not be a directory.
 *
 * Caution: The caller of this function is responsible for calling
 * setattr_prepare() or otherwise verifying the change is fine.
 */
STATIC int
xfs_setattr_size(
        struct xfs_inode        *ip,
        struct iattr            *iattr)
{
        struct xfs_mount        *mp = ip->i_mount;
        struct inode            *inode = VFS_I(ip);
        xfs_off_t               oldsize, newsize;
        struct xfs_trans        *tp;
        int                     error;
        uint                    lock_flags = 0;
        bool                    did_zeroing = false;

        ASSERT(xfs_isilocked(ip, XFS_IOLOCK_EXCL));
        ASSERT(xfs_isilocked(ip, XFS_MMAPLOCK_EXCL));
        ASSERT(S_ISREG(inode->i_mode));
        ASSERT((iattr->ia_valid & (ATTR_UID|ATTR_GID|ATTR_ATIME|ATTR_ATIME_SET|
                ATTR_MTIME_SET|ATTR_KILL_PRIV|ATTR_TIMES_SET)) == 0);

        oldsize = inode->i_size;
        newsize = iattr->ia_size;

        /*
         * Short circuit the truncate case for zero length files.
         */
        if (newsize == 0 && oldsize == 0 && ip->i_d.di_nextents == 0) {
                if (!(iattr->ia_valid & (ATTR_CTIME|ATTR_MTIME)))
                        return 0;

                /*
                 * Use the regular setattr path to update the timestamps.
                 */
                iattr->ia_valid &= ~ATTR_SIZE;
                return xfs_setattr_nonsize(ip, iattr, 0);
        }

        /*
         * Make sure that the dquots are attached to the inode.
         */
        error = xfs_qm_dqattach(ip, 0);
        if (error)
                return error;

        /*
         * Wait for all direct I/O to complete.
         */
        inode_dio_wait(inode);

        /*
         * File data changes must be complete before we start the transaction to
         * modify the inode.  This needs to be done before joining the inode to
         * the transaction because the inode cannot be unlocked once it is a
         * part of the transaction.
         *
         * Start with zeroing any data beyond EOF that we may expose on file
         * extension, or zeroing out the rest of the block on a downward
         * truncate.
         */
        if (newsize > oldsize) {
                error = xfs_zero_eof(ip, newsize, oldsize, &did_zeroing);
        } else {
                /*
                 * iomap won't detect a dirty page over an unwritten block (or a
                 * cow block over a hole) and subsequently skips zeroing the
                 * newly post-EOF portion of the page. Flush the new EOF to
                 * convert the block before the pagecache truncate.
                 */
                error = filemap_write_and_wait_range(inode->i_mapping, newsize,
                                                     newsize);
                if (error)
                        return error;
                error = iomap_truncate_page(inode, newsize, &did_zeroing,
                                &xfs_iomap_ops);
        }

        if (error)
                return error;

        /*
         * We've already locked out new page faults, so now we can safely remove
         * pages from the page cache knowing they won't get refaulted until we
         * drop the XFS_MMAP_EXCL lock after the extent manipulations are
         * complete. The truncate_setsize() call also cleans partial EOF page
         * PTEs on extending truncates and hence ensures sub-page block size
         * filesystems are correctly handled, too.
         *
         * We have to do all the page cache truncate work outside the
         * transaction context as the "lock" order is page lock->log space
         * reservation as defined by extent allocation in the writeback path.
         * Hence a truncate can fail with ENOMEM from xfs_trans_alloc(), but
         * having already truncated the in-memory version of the file (i.e. made
         * user visible changes). There's not much we can do about this, except
         * to hope that the caller sees ENOMEM and retries the truncate
         * operation.
         *
         * And we update in-core i_size and truncate page cache beyond newsize
         * before writeback the [di_size, newsize] range, so we're guaranteed
         * not to write stale data past the new EOF on truncate down.
         */
        truncate_setsize(inode, newsize);

        /*
         * We are going to log the inode size change in this transaction so
         * any previous writes that are beyond the on disk EOF and the new
         * EOF that have not been written out need to be written here.  If we
         * do not write the data out, we expose ourselves to the null files
         * problem. Note that this includes any block zeroing we did above;
         * otherwise those blocks may not be zeroed after a crash.
         */
        if (did_zeroing ||
            (newsize > ip->i_d.di_size && oldsize != ip->i_d.di_size)) {
                error = filemap_write_and_wait_range(VFS_I(ip)->i_mapping,
                                                ip->i_d.di_size, newsize - 1);
                if (error)
                        return error;
        }

        error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, 0, 0, 0, &tp);
        if (error)
                return error;

        lock_flags |= XFS_ILOCK_EXCL;
        xfs_ilock(ip, XFS_ILOCK_EXCL);
        xfs_trans_ijoin(tp, ip, 0);

        /*
         * Only change the c/mtime if we are changing the size or we are
         * explicitly asked to change it.  This handles the semantic difference
         * between truncate() and ftruncate() as implemented in the VFS.
         *
         * The regular truncate() case without ATTR_CTIME and ATTR_MTIME is a
         * special case where we need to update the times despite not having
         * these flags set.  For all other operations the VFS set these flags
         * explicitly if it wants a timestamp update.
         */
        if (newsize != oldsize &&
            !(iattr->ia_valid & (ATTR_CTIME | ATTR_MTIME))) {
                iattr->ia_ctime = iattr->ia_mtime =
                        current_time(inode);
                iattr->ia_valid |= ATTR_CTIME | ATTR_MTIME;
        }

        /*
         * The first thing we do is set the size to new_size permanently on
         * disk.  This way we don't have to worry about anyone ever being able
         * to look at the data being freed even in the face of a crash.
         * What we're getting around here is the case where we free a block, it
         * is allocated to another file, it is written to, and then we crash.
         * If the new data gets written to the file but the log buffers
         * containing the free and reallocation don't, then we'd end up with
         * garbage in the blocks being freed.  As long as we make the new size
         * permanent before actually freeing any blocks it doesn't matter if
         * they get written to.
         */
        ip->i_d.di_size = newsize;
        xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);

        if (newsize <= oldsize) {
                error = xfs_itruncate_extents(&tp, ip, XFS_DATA_FORK, newsize);
                if (error)
                        goto out_trans_cancel;

                /*
                 * Truncated "down", so we're removing references to old data
                 * here - if we delay flushing for a long time, we expose
                 * ourselves unduly to the notorious NULL files problem.  So,
                 * we mark this inode and flush it when the file is closed,
                 * and do not wait the usual (long) time for writeout.
                 */
                xfs_iflags_set(ip, XFS_ITRUNCATED);

                /* A truncate down always removes post-EOF blocks. */
                xfs_inode_clear_eofblocks_tag(ip);
        }

        if (iattr->ia_valid & ATTR_MODE)
                xfs_setattr_mode(ip, iattr);
        if (iattr->ia_valid & (ATTR_ATIME|ATTR_CTIME|ATTR_MTIME))
                xfs_setattr_time(ip, iattr);

        xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);

        XFS_STATS_INC(mp, xs_ig_attrchg);

        if (mp->m_flags & XFS_MOUNT_WSYNC)
                xfs_trans_set_sync(tp);

        error = xfs_trans_commit(tp);
out_unlock:
        if (lock_flags)
                xfs_iunlock(ip, lock_flags);
        return error;

out_trans_cancel:
        xfs_trans_cancel(tp);
        goto out_unlock;
}

int
xfs_vn_setattr_size(
        struct dentry           *dentry,
        struct iattr            *iattr)
{
        struct xfs_inode        *ip = XFS_I(d_inode(dentry));
        int error;

        trace_xfs_setattr(ip);

        error = xfs_vn_change_ok(dentry, iattr);
        if (error)
                return error;
        return xfs_setattr_size(ip, iattr);
}

STATIC int
xfs_vn_setattr(
        struct dentry           *dentry,
        struct iattr            *iattr)
{
        int                     error;

        if (iattr->ia_valid & ATTR_SIZE) {
                struct xfs_inode        *ip = XFS_I(d_inode(dentry));
                uint                    iolock = XFS_IOLOCK_EXCL;

                error = xfs_break_layouts(d_inode(dentry), &iolock);
                if (error)
                        return error;

                xfs_ilock(ip, XFS_MMAPLOCK_EXCL);
                error = xfs_vn_setattr_size(dentry, iattr);
                xfs_iunlock(ip, XFS_MMAPLOCK_EXCL);
        } else {
                error = xfs_vn_setattr_nonsize(dentry, iattr);
        }

        return error;
}

STATIC int
xfs_vn_update_time(
        struct inode            *inode,
        struct timespec         *now,
        int                     flags)
{
        struct xfs_inode        *ip = XFS_I(inode);
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_trans        *tp;
        int                     error;

        trace_xfs_update_time(ip);

        error = xfs_trans_alloc(mp, &M_RES(mp)->tr_fsyncts, 0, 0, 0, &tp);
        if (error)
                return error;

        xfs_ilock(ip, XFS_ILOCK_EXCL);
        if (flags & S_CTIME)
                inode->i_ctime = *now;
        if (flags & S_MTIME)
                inode->i_mtime = *now;
        if (flags & S_ATIME)
                inode->i_atime = *now;

        xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
        xfs_trans_log_inode(tp, ip, XFS_ILOG_TIMESTAMP);
        return xfs_trans_commit(tp);
}

STATIC int
xfs_vn_fiemap(
        struct inode            *inode,
        struct fiemap_extent_info *fieinfo,
        u64                     start,
        u64                     length)
{
        int                     error;

        xfs_ilock(XFS_I(inode), XFS_IOLOCK_SHARED);
        if (fieinfo->fi_flags & FIEMAP_FLAG_XATTR) {
                fieinfo->fi_flags &= ~FIEMAP_FLAG_XATTR;
                error = iomap_fiemap(inode, fieinfo, start, length,
                                &xfs_xattr_iomap_ops);
        } else {
                error = iomap_fiemap(inode, fieinfo, start, length,
                                &xfs_iomap_ops);
        }
        xfs_iunlock(XFS_I(inode), XFS_IOLOCK_SHARED);

        return error;
}

STATIC int
xfs_vn_tmpfile(
        struct inode    *dir,
        struct dentry   *dentry,
        umode_t         mode)
{
        return xfs_generic_create(dir, dentry, mode, 0, true);
}

static const struct inode_operations xfs_inode_operations = {
        .get_acl                = xfs_get_acl,
        .set_acl                = xfs_set_acl,
        .getattr                = xfs_vn_getattr,
        .setattr                = xfs_vn_setattr,
        .listxattr              = xfs_vn_listxattr,
        .fiemap                 = xfs_vn_fiemap,
        .update_time            = xfs_vn_update_time,
};

static const struct inode_operations xfs_dir_inode_operations = {
        .create                 = xfs_vn_create,
        .lookup                 = xfs_vn_lookup,
        .link                   = xfs_vn_link,
        .unlink                 = xfs_vn_unlink,
        .symlink                = xfs_vn_symlink,
        .mkdir                  = xfs_vn_mkdir,
        /*
         * Yes, XFS uses the same method for rmdir and unlink.
         *
         * There are some subtile differences deeper in the code,
         * but we use S_ISDIR to check for those.
         */
        .rmdir                  = xfs_vn_unlink,
        .mknod                  = xfs_vn_mknod,
        .rename                 = xfs_vn_rename,
        .get_acl                = xfs_get_acl,
        .set_acl                = xfs_set_acl,
        .getattr                = xfs_vn_getattr,
        .setattr                = xfs_vn_setattr,
        .listxattr              = xfs_vn_listxattr,
        .update_time            = xfs_vn_update_time,
        .tmpfile                = xfs_vn_tmpfile,
};

static const struct inode_operations xfs_dir_ci_inode_operations = {
        .create                 = xfs_vn_create,
        .lookup                 = xfs_vn_ci_lookup,
        .link                   = xfs_vn_link,
        .unlink                 = xfs_vn_unlink,
        .symlink                = xfs_vn_symlink,
        .mkdir                  = xfs_vn_mkdir,
        /*
         * Yes, XFS uses the same method for rmdir and unlink.
         *
         * There are some subtile differences deeper in the code,
         * but we use S_ISDIR to check for those.
         */
        .rmdir                  = xfs_vn_unlink,
        .mknod                  = xfs_vn_mknod,
        .rename                 = xfs_vn_rename,
        .get_acl                = xfs_get_acl,
        .set_acl                = xfs_set_acl,
        .getattr                = xfs_vn_getattr,
        .setattr                = xfs_vn_setattr,
        .listxattr              = xfs_vn_listxattr,
        .update_time            = xfs_vn_update_time,
        .tmpfile                = xfs_vn_tmpfile,
};

static const struct inode_operations xfs_symlink_inode_operations = {
        .get_link               = xfs_vn_get_link,
        .getattr                = xfs_vn_getattr,
        .setattr                = xfs_vn_setattr,
        .listxattr              = xfs_vn_listxattr,
        .update_time            = xfs_vn_update_time,
};

static const struct inode_operations xfs_inline_symlink_inode_operations = {
        .get_link               = xfs_vn_get_link_inline,
        .getattr                = xfs_vn_getattr,
        .setattr                = xfs_vn_setattr,
        .listxattr              = xfs_vn_listxattr,
        .update_time            = xfs_vn_update_time,
};

/* Figure out if this file actually supports DAX. */
static bool
xfs_inode_supports_dax(
        struct xfs_inode        *ip)
{
        struct xfs_mount        *mp = ip->i_mount;

        /* Only supported on non-reflinked files. */
        if (!S_ISREG(VFS_I(ip)->i_mode) || xfs_is_reflink_inode(ip))
                return false;

        /* DAX mount option or DAX iflag must be set. */
        if (!(mp->m_flags & XFS_MOUNT_DAX) &&
            !(ip->i_d.di_flags2 & XFS_DIFLAG2_DAX))
                return false;

        /* Block size must match page size */
        if (mp->m_sb.sb_blocksize != PAGE_SIZE)
                return false;

        /* Device has to support DAX too. */
        return xfs_find_daxdev_for_inode(VFS_I(ip)) != NULL;
}

STATIC void
xfs_diflags_to_iflags(
        struct inode            *inode,
        struct xfs_inode        *ip)
{
        uint16_t                flags = ip->i_d.di_flags;

        inode->i_flags &= ~(S_IMMUTABLE | S_APPEND | S_SYNC |
                            S_NOATIME | S_DAX);

        if (flags & XFS_DIFLAG_IMMUTABLE)
                inode->i_flags |= S_IMMUTABLE;
        if (flags & XFS_DIFLAG_APPEND)
                inode->i_flags |= S_APPEND;
        if (flags & XFS_DIFLAG_SYNC)
                inode->i_flags |= S_SYNC;
        if (flags & XFS_DIFLAG_NOATIME)
                inode->i_flags |= S_NOATIME;
        if (xfs_inode_supports_dax(ip))
                inode->i_flags |= S_DAX;
}

/*
 * Initialize the Linux inode.
 *
 * When reading existing inodes from disk this is called directly from xfs_iget,
 * when creating a new inode it is called from xfs_ialloc after setting up the
 * inode. These callers have different criteria for clearing XFS_INEW, so leave
 * it up to the caller to deal with unlocking the inode appropriately.
 */
void
xfs_setup_inode(
        struct xfs_inode        *ip)
{
        struct inode            *inode = &ip->i_vnode;
        gfp_t                   gfp_mask;

        inode->i_ino = ip->i_ino;
        inode->i_state = I_NEW;

        inode_sb_list_add(inode);
        /* make the inode look hashed for the writeback code */
        hlist_add_fake(&inode->i_hash);

        inode->i_uid    = xfs_uid_to_kuid(ip->i_d.di_uid);
        inode->i_gid    = xfs_gid_to_kgid(ip->i_d.di_gid);

        switch (inode->i_mode & S_IFMT) {
        case S_IFBLK:
        case S_IFCHR:
                inode->i_rdev =
                        MKDEV(sysv_major(ip->i_df.if_u2.if_rdev) & 0x1ff,
                              sysv_minor(ip->i_df.if_u2.if_rdev));
                break;
        default:
                inode->i_rdev = 0;
                break;
        }

        i_size_write(inode, ip->i_d.di_size);
        xfs_diflags_to_iflags(inode, ip);

        if (S_ISDIR(inode->i_mode)) {
                lockdep_set_class(&ip->i_lock.mr_lock, &xfs_dir_ilock_class);
                ip->d_ops = ip->i_mount->m_dir_inode_ops;
        } else {
                ip->d_ops = ip->i_mount->m_nondir_inode_ops;
                lockdep_set_class(&ip->i_lock.mr_lock, &xfs_nondir_ilock_class);
        }

        /*
         * Ensure all page cache allocations are done from GFP_NOFS context to
         * prevent direct reclaim recursion back into the filesystem and blowing
         * stacks or deadlocking.
         */
        gfp_mask = mapping_gfp_mask(inode->i_mapping);
        mapping_set_gfp_mask(inode->i_mapping, (gfp_mask & ~(__GFP_FS)));

        /*
         * If there is no attribute fork no ACL can exist on this inode,
         * and it can't have any file capabilities attached to it either.
         */
        if (!XFS_IFORK_Q(ip)) {
                inode_has_no_xattr(inode);
                cache_no_acl(inode);
        }
}

void
xfs_setup_iops(
        struct xfs_inode        *ip)
{
        struct inode            *inode = &ip->i_vnode;

        switch (inode->i_mode & S_IFMT) {
        case S_IFREG:
                inode->i_op = &xfs_inode_operations;
                inode->i_fop = &xfs_file_operations;
                inode->i_mapping->a_ops = &xfs_address_space_operations;
                break;
        case S_IFDIR:
                if (xfs_sb_version_hasasciici(&XFS_M(inode->i_sb)->m_sb))
                        inode->i_op = &xfs_dir_ci_inode_operations;
                else
                        inode->i_op = &xfs_dir_inode_operations;
                inode->i_fop = &xfs_dir_file_operations;
                break;
        case S_IFLNK:
                if (ip->i_df.if_flags & XFS_IFINLINE)
                        inode->i_op = &xfs_inline_symlink_inode_operations;
                else
                        inode->i_op = &xfs_symlink_inode_operations;
                break;
        default:
                inode->i_op = &xfs_inode_operations;
                init_special_inode(inode, inode->i_mode, inode->i_rdev);
                break;
        }
}