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Linux/fs/afs/mntpt.c

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  1 // SPDX-License-Identifier: GPL-2.0-or-later
  2 /* mountpoint management
  3  *
  4  * Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
  5  * Written by David Howells (dhowells@redhat.com)
  6  */
  7 
  8 #include <linux/kernel.h>
  9 #include <linux/module.h>
 10 #include <linux/init.h>
 11 #include <linux/fs.h>
 12 #include <linux/pagemap.h>
 13 #include <linux/mount.h>
 14 #include <linux/namei.h>
 15 #include <linux/gfp.h>
 16 #include <linux/fs_context.h>
 17 #include "internal.h"
 18 
 19 
 20 static struct dentry *afs_mntpt_lookup(struct inode *dir,
 21                                        struct dentry *dentry,
 22                                        unsigned int flags);
 23 static int afs_mntpt_open(struct inode *inode, struct file *file);
 24 static void afs_mntpt_expiry_timed_out(struct work_struct *work);
 25 
 26 const struct file_operations afs_mntpt_file_operations = {
 27         .open           = afs_mntpt_open,
 28         .llseek         = noop_llseek,
 29 };
 30 
 31 const struct inode_operations afs_mntpt_inode_operations = {
 32         .lookup         = afs_mntpt_lookup,
 33         .readlink       = page_readlink,
 34         .getattr        = afs_getattr,
 35         .listxattr      = afs_listxattr,
 36 };
 37 
 38 const struct inode_operations afs_autocell_inode_operations = {
 39         .getattr        = afs_getattr,
 40 };
 41 
 42 static LIST_HEAD(afs_vfsmounts);
 43 static DECLARE_DELAYED_WORK(afs_mntpt_expiry_timer, afs_mntpt_expiry_timed_out);
 44 
 45 static unsigned long afs_mntpt_expiry_timeout = 10 * 60;
 46 
 47 static const char afs_root_volume[] = "root.cell";
 48 
 49 /*
 50  * no valid lookup procedure on this sort of dir
 51  */
 52 static struct dentry *afs_mntpt_lookup(struct inode *dir,
 53                                        struct dentry *dentry,
 54                                        unsigned int flags)
 55 {
 56         _enter("%p,%p{%pd2}", dir, dentry, dentry);
 57         return ERR_PTR(-EREMOTE);
 58 }
 59 
 60 /*
 61  * no valid open procedure on this sort of dir
 62  */
 63 static int afs_mntpt_open(struct inode *inode, struct file *file)
 64 {
 65         _enter("%p,%p{%pD2}", inode, file, file);
 66         return -EREMOTE;
 67 }
 68 
 69 /*
 70  * Set the parameters for the proposed superblock.
 71  */
 72 static int afs_mntpt_set_params(struct fs_context *fc, struct dentry *mntpt)
 73 {
 74         struct afs_fs_context *ctx = fc->fs_private;
 75         struct afs_super_info *src_as = AFS_FS_S(mntpt->d_sb);
 76         struct afs_vnode *vnode = AFS_FS_I(d_inode(mntpt));
 77         struct afs_cell *cell;
 78         const char *p;
 79         int ret;
 80 
 81         if (fc->net_ns != src_as->net_ns) {
 82                 put_net(fc->net_ns);
 83                 fc->net_ns = get_net(src_as->net_ns);
 84         }
 85 
 86         if (src_as->volume && src_as->volume->type == AFSVL_RWVOL) {
 87                 ctx->type = AFSVL_RWVOL;
 88                 ctx->force = true;
 89         }
 90         if (ctx->cell) {
 91                 afs_put_cell(ctx->net, ctx->cell);
 92                 ctx->cell = NULL;
 93         }
 94         if (test_bit(AFS_VNODE_PSEUDODIR, &vnode->flags)) {
 95                 /* if the directory is a pseudo directory, use the d_name */
 96                 unsigned size = mntpt->d_name.len;
 97 
 98                 if (size < 2)
 99                         return -ENOENT;
100 
101                 p = mntpt->d_name.name;
102                 if (mntpt->d_name.name[0] == '.') {
103                         size--;
104                         p++;
105                         ctx->type = AFSVL_RWVOL;
106                         ctx->force = true;
107                 }
108                 if (size > AFS_MAXCELLNAME)
109                         return -ENAMETOOLONG;
110 
111                 cell = afs_lookup_cell(ctx->net, p, size, NULL, false);
112                 if (IS_ERR(cell)) {
113                         pr_err("kAFS: unable to lookup cell '%pd'\n", mntpt);
114                         return PTR_ERR(cell);
115                 }
116                 ctx->cell = cell;
117 
118                 ctx->volname = afs_root_volume;
119                 ctx->volnamesz = sizeof(afs_root_volume) - 1;
120         } else {
121                 /* read the contents of the AFS special symlink */
122                 struct page *page;
123                 loff_t size = i_size_read(d_inode(mntpt));
124                 char *buf;
125 
126                 if (src_as->cell)
127                         ctx->cell = afs_get_cell(src_as->cell);
128 
129                 if (size > PAGE_SIZE - 1)
130                         return -EINVAL;
131 
132                 page = read_mapping_page(d_inode(mntpt)->i_mapping, 0, NULL);
133                 if (IS_ERR(page))
134                         return PTR_ERR(page);
135 
136                 if (PageError(page)) {
137                         ret = afs_bad(AFS_FS_I(d_inode(mntpt)), afs_file_error_mntpt);
138                         put_page(page);
139                         return ret;
140                 }
141 
142                 buf = kmap(page);
143                 ret = vfs_parse_fs_string(fc, "source", buf, size);
144                 kunmap(page);
145                 put_page(page);
146                 if (ret < 0)
147                         return ret;
148         }
149 
150         return 0;
151 }
152 
153 /*
154  * create a vfsmount to be automounted
155  */
156 static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
157 {
158         struct fs_context *fc;
159         struct vfsmount *mnt;
160         int ret;
161 
162         BUG_ON(!d_inode(mntpt));
163 
164         fc = fs_context_for_submount(&afs_fs_type, mntpt);
165         if (IS_ERR(fc))
166                 return ERR_CAST(fc);
167 
168         ret = afs_mntpt_set_params(fc, mntpt);
169         if (!ret)
170                 mnt = fc_mount(fc);
171         else
172                 mnt = ERR_PTR(ret);
173 
174         put_fs_context(fc);
175         return mnt;
176 }
177 
178 /*
179  * handle an automount point
180  */
181 struct vfsmount *afs_d_automount(struct path *path)
182 {
183         struct vfsmount *newmnt;
184 
185         _enter("{%pd}", path->dentry);
186 
187         newmnt = afs_mntpt_do_automount(path->dentry);
188         if (IS_ERR(newmnt))
189                 return newmnt;
190 
191         mntget(newmnt); /* prevent immediate expiration */
192         mnt_set_expiry(newmnt, &afs_vfsmounts);
193         queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
194                            afs_mntpt_expiry_timeout * HZ);
195         _leave(" = %p", newmnt);
196         return newmnt;
197 }
198 
199 /*
200  * handle mountpoint expiry timer going off
201  */
202 static void afs_mntpt_expiry_timed_out(struct work_struct *work)
203 {
204         _enter("");
205 
206         if (!list_empty(&afs_vfsmounts)) {
207                 mark_mounts_for_expiry(&afs_vfsmounts);
208                 queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
209                                    afs_mntpt_expiry_timeout * HZ);
210         }
211 
212         _leave("");
213 }
214 
215 /*
216  * kill the AFS mountpoint timer if it's still running
217  */
218 void afs_mntpt_kill_timer(void)
219 {
220         _enter("");
221 
222         ASSERT(list_empty(&afs_vfsmounts));
223         cancel_delayed_work_sync(&afs_mntpt_expiry_timer);
224 }
225 

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