![wanglei](/assets/img/avatar_default.png)
Implement the ability for the root directory of a mounted AFS filesystem to accept lookups of arbitrary directory names, to interpet the names as the names of cells, to look the cell names up in the DNS for AFSDB records and to mount the root.cell volume of the nominated cell on the pseudo-directory created by lookup. This facility is requested by passing: -o autocell to the mountpoint for which this is desired, usually the /afs mount. To use this facility, a DNS upcall program is required for AFSDB records. This can be obtained from: http://people.redhat.com/~dhowells/afs/dns.afsdb.c It should be compiled with -lresolv and -lkeyutils and installed as, say: /usr/sbin/dns.afsdb Then the following line needs to be added to /sbin/request-key.conf: create dns_resolver afsdb:* * /usr/sbin/dns.afsdb %k This can be tested by mounting AFS, say: insmod dns_resolver.ko insmod af-rxrpc.ko insmod kafs.ko rootcell=grand.central.org mount -t afs "#grand.central.org:root.cell." /afs -o autocell and doing: ls /afs/grand.central.org/ which should show: archive/ cvs/ doc/ local/ project/ service/ software/ user/ www/ if it works. Signed-off-by: Wang Lei <wang840925@gmail.com> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Steve French <sfrench@us.ibm.com>
315 lines
7.5 KiB
C
315 lines
7.5 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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const struct inode_operations afs_autocell_inode_operations = {
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.follow_link = afs_mntpt_follow_link,
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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 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_cache_page(AFS_VNODE_TO_I(vnode)->i_mapping, 0,
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afs_page_filler, key);
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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 afs_vnode *vnode;
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struct page *page;
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char *devname, *options;
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bool rwpath = false;
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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 = -ENOMEM;
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devname = (char *) get_zeroed_page(GFP_KERNEL);
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if (!devname)
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goto error_no_devname;
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options = (char *) get_zeroed_page(GFP_KERNEL);
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if (!options)
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goto error_no_options;
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vnode = AFS_FS_I(mntpt->d_inode);
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if (test_bit(AFS_VNODE_PSEUDODIR, &vnode->flags)) {
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/* if the directory is a pseudo directory, use the d_name */
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static const char afs_root_cell[] = ":root.cell.";
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unsigned size = mntpt->d_name.len;
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ret = -ENOENT;
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if (size < 2 || size > AFS_MAXCELLNAME)
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goto error_no_page;
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if (mntpt->d_name.name[0] == '.') {
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devname[0] = '#';
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memcpy(devname + 1, mntpt->d_name.name, size - 1);
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memcpy(devname + size, afs_root_cell,
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sizeof(afs_root_cell));
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rwpath = true;
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} else {
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devname[0] = '%';
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memcpy(devname + 1, mntpt->d_name.name, size);
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memcpy(devname + size + 1, afs_root_cell,
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sizeof(afs_root_cell));
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}
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} else {
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/* read the contents of the AFS special symlink */
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loff_t size = i_size_read(mntpt->d_inode);
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char *buf;
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ret = -EINVAL;
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if (size > PAGE_SIZE - 1)
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goto error_no_page;
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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_no_page;
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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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}
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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 || rwpath)
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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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page_cache_release(page);
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error_no_page:
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free_page((unsigned long) options);
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error_no_options:
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free_page((unsigned long) devname);
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error_no_devname:
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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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