mirror of https://gitee.com/openkylin/linux.git
285 lines
6.6 KiB
C
285 lines
6.6 KiB
C
/* mountpoint management
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*
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* Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/fs.h>
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#include <linux/pagemap.h>
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#include <linux/mount.h>
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#include <linux/namei.h>
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#include <linux/gfp.h>
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#include "internal.h"
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static struct dentry *afs_mntpt_lookup(struct inode *dir,
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struct dentry *dentry,
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struct nameidata *nd);
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static int afs_mntpt_open(struct inode *inode, struct file *file);
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static void *afs_mntpt_follow_link(struct dentry *dentry, struct nameidata *nd);
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static void afs_mntpt_expiry_timed_out(struct work_struct *work);
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const struct file_operations afs_mntpt_file_operations = {
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.open = afs_mntpt_open,
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};
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const struct inode_operations afs_mntpt_inode_operations = {
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.lookup = afs_mntpt_lookup,
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.follow_link = afs_mntpt_follow_link,
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.readlink = page_readlink,
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.getattr = afs_getattr,
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};
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static LIST_HEAD(afs_vfsmounts);
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static DECLARE_DELAYED_WORK(afs_mntpt_expiry_timer, afs_mntpt_expiry_timed_out);
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static unsigned long afs_mntpt_expiry_timeout = 10 * 60;
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/*
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* check a symbolic link to see whether it actually encodes a mountpoint
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* - sets the AFS_VNODE_MOUNTPOINT flag on the vnode appropriately
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*/
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int afs_mntpt_check_symlink(struct afs_vnode *vnode, struct key *key)
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{
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struct file file = {
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.private_data = key,
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};
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struct page *page;
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size_t size;
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char *buf;
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int ret;
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_enter("{%x:%u,%u}",
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vnode->fid.vid, vnode->fid.vnode, vnode->fid.unique);
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/* read the contents of the symlink into the pagecache */
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page = read_mapping_page(AFS_VNODE_TO_I(vnode)->i_mapping, 0, &file);
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if (IS_ERR(page)) {
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ret = PTR_ERR(page);
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goto out;
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}
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ret = -EIO;
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if (PageError(page))
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goto out_free;
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buf = kmap(page);
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/* examine the symlink's contents */
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size = vnode->status.size;
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_debug("symlink to %*.*s", (int) size, (int) size, buf);
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if (size > 2 &&
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(buf[0] == '%' || buf[0] == '#') &&
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buf[size - 1] == '.'
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) {
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_debug("symlink is a mountpoint");
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spin_lock(&vnode->lock);
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set_bit(AFS_VNODE_MOUNTPOINT, &vnode->flags);
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spin_unlock(&vnode->lock);
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}
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ret = 0;
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kunmap(page);
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out_free:
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page_cache_release(page);
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out:
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_leave(" = %d", ret);
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return ret;
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}
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/*
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* no valid lookup procedure on this sort of dir
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*/
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static struct dentry *afs_mntpt_lookup(struct inode *dir,
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struct dentry *dentry,
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struct nameidata *nd)
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{
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_enter("%p,%p{%p{%s},%s}",
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dir,
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dentry,
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dentry->d_parent,
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dentry->d_parent ?
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dentry->d_parent->d_name.name : (const unsigned char *) "",
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dentry->d_name.name);
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return ERR_PTR(-EREMOTE);
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}
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/*
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* no valid open procedure on this sort of dir
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*/
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static int afs_mntpt_open(struct inode *inode, struct file *file)
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{
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_enter("%p,%p{%p{%s},%s}",
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inode, file,
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file->f_path.dentry->d_parent,
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file->f_path.dentry->d_parent ?
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file->f_path.dentry->d_parent->d_name.name :
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(const unsigned char *) "",
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file->f_path.dentry->d_name.name);
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return -EREMOTE;
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}
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/*
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* create a vfsmount to be automounted
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*/
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static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
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{
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struct afs_super_info *super;
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struct vfsmount *mnt;
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struct page *page = NULL;
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size_t size;
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char *buf, *devname = NULL, *options = NULL;
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int ret;
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_enter("{%s}", mntpt->d_name.name);
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BUG_ON(!mntpt->d_inode);
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ret = -EINVAL;
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size = mntpt->d_inode->i_size;
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if (size > PAGE_SIZE - 1)
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goto error;
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ret = -ENOMEM;
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devname = (char *) get_zeroed_page(GFP_KERNEL);
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if (!devname)
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goto error;
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options = (char *) get_zeroed_page(GFP_KERNEL);
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if (!options)
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goto error;
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/* read the contents of the AFS special symlink */
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page = read_mapping_page(mntpt->d_inode->i_mapping, 0, NULL);
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if (IS_ERR(page)) {
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ret = PTR_ERR(page);
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goto error;
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}
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ret = -EIO;
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if (PageError(page))
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goto error;
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buf = kmap_atomic(page, KM_USER0);
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memcpy(devname, buf, size);
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kunmap_atomic(buf, KM_USER0);
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page_cache_release(page);
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page = NULL;
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/* work out what options we want */
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super = AFS_FS_S(mntpt->d_sb);
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memcpy(options, "cell=", 5);
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strcpy(options + 5, super->volume->cell->name);
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if (super->volume->type == AFSVL_RWVOL)
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strcat(options, ",rwpath");
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/* try and do the mount */
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_debug("--- attempting mount %s -o %s ---", devname, options);
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mnt = vfs_kern_mount(&afs_fs_type, 0, devname, options);
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_debug("--- mount result %p ---", mnt);
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free_page((unsigned long) devname);
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free_page((unsigned long) options);
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_leave(" = %p", mnt);
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return mnt;
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error:
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if (page)
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page_cache_release(page);
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if (devname)
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free_page((unsigned long) devname);
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if (options)
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free_page((unsigned long) options);
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_leave(" = %d", ret);
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return ERR_PTR(ret);
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}
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/*
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* follow a link from a mountpoint directory, thus causing it to be mounted
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*/
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static void *afs_mntpt_follow_link(struct dentry *dentry, struct nameidata *nd)
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{
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struct vfsmount *newmnt;
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int err;
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_enter("%p{%s},{%s:%p{%s},}",
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dentry,
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dentry->d_name.name,
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nd->path.mnt->mnt_devname,
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dentry,
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nd->path.dentry->d_name.name);
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dput(nd->path.dentry);
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nd->path.dentry = dget(dentry);
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newmnt = afs_mntpt_do_automount(nd->path.dentry);
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if (IS_ERR(newmnt)) {
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path_put(&nd->path);
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return (void *)newmnt;
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}
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mntget(newmnt);
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err = do_add_mount(newmnt, &nd->path, MNT_SHRINKABLE, &afs_vfsmounts);
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switch (err) {
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case 0:
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path_put(&nd->path);
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nd->path.mnt = newmnt;
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nd->path.dentry = dget(newmnt->mnt_root);
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schedule_delayed_work(&afs_mntpt_expiry_timer,
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afs_mntpt_expiry_timeout * HZ);
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break;
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case -EBUSY:
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/* someone else made a mount here whilst we were busy */
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while (d_mountpoint(nd->path.dentry) &&
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follow_down(&nd->path))
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;
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err = 0;
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default:
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mntput(newmnt);
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break;
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}
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_leave(" = %d", err);
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return ERR_PTR(err);
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}
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/*
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* handle mountpoint expiry timer going off
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*/
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static void afs_mntpt_expiry_timed_out(struct work_struct *work)
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{
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_enter("");
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if (!list_empty(&afs_vfsmounts)) {
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mark_mounts_for_expiry(&afs_vfsmounts);
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schedule_delayed_work(&afs_mntpt_expiry_timer,
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afs_mntpt_expiry_timeout * HZ);
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}
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_leave("");
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}
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/*
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* kill the AFS mountpoint timer if it's still running
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*/
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void afs_mntpt_kill_timer(void)
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{
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_enter("");
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ASSERT(list_empty(&afs_vfsmounts));
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cancel_delayed_work(&afs_mntpt_expiry_timer);
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flush_scheduled_work();
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}
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