NFS: Fix a delegation callback race
[linux-3.10.git] / fs / nfs / nfs4super.c
1 /*
2  * Copyright (c) 2012 Bryan Schumaker <bjschuma@netapp.com>
3  */
4 #include <linux/init.h>
5 #include <linux/module.h>
6 #include <linux/nfs_idmap.h>
7 #include <linux/nfs4_mount.h>
8 #include <linux/nfs_fs.h>
9 #include "delegation.h"
10 #include "internal.h"
11 #include "nfs4_fs.h"
12 #include "pnfs.h"
13 #include "nfs.h"
14
15 #define NFSDBG_FACILITY         NFSDBG_VFS
16
17 static int nfs4_write_inode(struct inode *inode, struct writeback_control *wbc);
18 static void nfs4_evict_inode(struct inode *inode);
19 static struct dentry *nfs4_remote_mount(struct file_system_type *fs_type,
20         int flags, const char *dev_name, void *raw_data);
21 static struct dentry *nfs4_referral_mount(struct file_system_type *fs_type,
22         int flags, const char *dev_name, void *raw_data);
23 static struct dentry *nfs4_remote_referral_mount(struct file_system_type *fs_type,
24         int flags, const char *dev_name, void *raw_data);
25
26 static struct file_system_type nfs4_remote_fs_type = {
27         .owner          = THIS_MODULE,
28         .name           = "nfs4",
29         .mount          = nfs4_remote_mount,
30         .kill_sb        = nfs_kill_super,
31         .fs_flags       = FS_RENAME_DOES_D_MOVE|FS_BINARY_MOUNTDATA,
32 };
33
34 static struct file_system_type nfs4_remote_referral_fs_type = {
35         .owner          = THIS_MODULE,
36         .name           = "nfs4",
37         .mount          = nfs4_remote_referral_mount,
38         .kill_sb        = nfs_kill_super,
39         .fs_flags       = FS_RENAME_DOES_D_MOVE|FS_BINARY_MOUNTDATA,
40 };
41
42 struct file_system_type nfs4_referral_fs_type = {
43         .owner          = THIS_MODULE,
44         .name           = "nfs4",
45         .mount          = nfs4_referral_mount,
46         .kill_sb        = nfs_kill_super,
47         .fs_flags       = FS_RENAME_DOES_D_MOVE|FS_BINARY_MOUNTDATA,
48 };
49
50 static const struct super_operations nfs4_sops = {
51         .alloc_inode    = nfs_alloc_inode,
52         .destroy_inode  = nfs_destroy_inode,
53         .write_inode    = nfs4_write_inode,
54         .drop_inode     = nfs_drop_inode,
55         .put_super      = nfs_put_super,
56         .statfs         = nfs_statfs,
57         .evict_inode    = nfs4_evict_inode,
58         .umount_begin   = nfs_umount_begin,
59         .show_options   = nfs_show_options,
60         .show_devname   = nfs_show_devname,
61         .show_path      = nfs_show_path,
62         .show_stats     = nfs_show_stats,
63         .remount_fs     = nfs_remount,
64 };
65
66 struct nfs_subversion nfs_v4 = {
67         .owner = THIS_MODULE,
68         .nfs_fs   = &nfs4_fs_type,
69         .rpc_vers = &nfs_version4,
70         .rpc_ops  = &nfs_v4_clientops,
71         .sops     = &nfs4_sops,
72         .xattr    = nfs4_xattr_handlers,
73 };
74
75 static int nfs4_write_inode(struct inode *inode, struct writeback_control *wbc)
76 {
77         int ret = nfs_write_inode(inode, wbc);
78
79         if (ret >= 0 && test_bit(NFS_INO_LAYOUTCOMMIT, &NFS_I(inode)->flags)) {
80                 int status;
81                 bool sync = true;
82
83                 if (wbc->sync_mode == WB_SYNC_NONE)
84                         sync = false;
85
86                 status = pnfs_layoutcommit_inode(inode, sync);
87                 if (status < 0)
88                         return status;
89         }
90         return ret;
91 }
92
93 /*
94  * Clean out any remaining NFSv4 state that might be left over due
95  * to open() calls that passed nfs_atomic_lookup, but failed to call
96  * nfs_open().
97  */
98 static void nfs4_evict_inode(struct inode *inode)
99 {
100         truncate_inode_pages(&inode->i_data, 0);
101         clear_inode(inode);
102         pnfs_return_layout(inode);
103         pnfs_destroy_layout(NFS_I(inode));
104         /* If we are holding a delegation, return it! */
105         nfs_inode_return_delegation_noreclaim(inode);
106         /* First call standard NFS clear_inode() code */
107         nfs_clear_inode(inode);
108 }
109
110 /*
111  * Get the superblock for the NFS4 root partition
112  */
113 static struct dentry *
114 nfs4_remote_mount(struct file_system_type *fs_type, int flags,
115                   const char *dev_name, void *info)
116 {
117         struct nfs_mount_info *mount_info = info;
118         struct nfs_server *server;
119         struct dentry *mntroot = ERR_PTR(-ENOMEM);
120
121         mount_info->set_security = nfs_set_sb_security;
122
123         /* Get a volume representation */
124         server = nfs4_create_server(mount_info, &nfs_v4);
125         if (IS_ERR(server)) {
126                 mntroot = ERR_CAST(server);
127                 goto out;
128         }
129
130         mntroot = nfs_fs_mount_common(server, flags, dev_name, mount_info, &nfs_v4);
131
132 out:
133         return mntroot;
134 }
135
136 static struct vfsmount *nfs_do_root_mount(struct file_system_type *fs_type,
137                 int flags, void *data, const char *hostname)
138 {
139         struct vfsmount *root_mnt;
140         char *root_devname;
141         size_t len;
142
143         len = strlen(hostname) + 5;
144         root_devname = kmalloc(len, GFP_KERNEL);
145         if (root_devname == NULL)
146                 return ERR_PTR(-ENOMEM);
147         /* Does hostname needs to be enclosed in brackets? */
148         if (strchr(hostname, ':'))
149                 snprintf(root_devname, len, "[%s]:/", hostname);
150         else
151                 snprintf(root_devname, len, "%s:/", hostname);
152         root_mnt = vfs_kern_mount(fs_type, flags, root_devname, data);
153         kfree(root_devname);
154         return root_mnt;
155 }
156
157 struct nfs_referral_count {
158         struct list_head list;
159         const struct task_struct *task;
160         unsigned int referral_count;
161 };
162
163 static LIST_HEAD(nfs_referral_count_list);
164 static DEFINE_SPINLOCK(nfs_referral_count_list_lock);
165
166 static struct nfs_referral_count *nfs_find_referral_count(void)
167 {
168         struct nfs_referral_count *p;
169
170         list_for_each_entry(p, &nfs_referral_count_list, list) {
171                 if (p->task == current)
172                         return p;
173         }
174         return NULL;
175 }
176
177 #define NFS_MAX_NESTED_REFERRALS 2
178
179 static int nfs_referral_loop_protect(void)
180 {
181         struct nfs_referral_count *p, *new;
182         int ret = -ENOMEM;
183
184         new = kmalloc(sizeof(*new), GFP_KERNEL);
185         if (!new)
186                 goto out;
187         new->task = current;
188         new->referral_count = 1;
189
190         ret = 0;
191         spin_lock(&nfs_referral_count_list_lock);
192         p = nfs_find_referral_count();
193         if (p != NULL) {
194                 if (p->referral_count >= NFS_MAX_NESTED_REFERRALS)
195                         ret = -ELOOP;
196                 else
197                         p->referral_count++;
198         } else {
199                 list_add(&new->list, &nfs_referral_count_list);
200                 new = NULL;
201         }
202         spin_unlock(&nfs_referral_count_list_lock);
203         kfree(new);
204 out:
205         return ret;
206 }
207
208 static void nfs_referral_loop_unprotect(void)
209 {
210         struct nfs_referral_count *p;
211
212         spin_lock(&nfs_referral_count_list_lock);
213         p = nfs_find_referral_count();
214         p->referral_count--;
215         if (p->referral_count == 0)
216                 list_del(&p->list);
217         else
218                 p = NULL;
219         spin_unlock(&nfs_referral_count_list_lock);
220         kfree(p);
221 }
222
223 static struct dentry *nfs_follow_remote_path(struct vfsmount *root_mnt,
224                 const char *export_path)
225 {
226         struct dentry *dentry;
227         int err;
228
229         if (IS_ERR(root_mnt))
230                 return ERR_CAST(root_mnt);
231
232         err = nfs_referral_loop_protect();
233         if (err) {
234                 mntput(root_mnt);
235                 return ERR_PTR(err);
236         }
237
238         dentry = mount_subtree(root_mnt, export_path);
239         nfs_referral_loop_unprotect();
240
241         return dentry;
242 }
243
244 struct dentry *nfs4_try_mount(int flags, const char *dev_name,
245                               struct nfs_mount_info *mount_info,
246                               struct nfs_subversion *nfs_mod)
247 {
248         char *export_path;
249         struct vfsmount *root_mnt;
250         struct dentry *res;
251         struct nfs_parsed_mount_data *data = mount_info->parsed;
252
253         dfprintk(MOUNT, "--> nfs4_try_mount()\n");
254
255         if (data->auth_flavors[0] == RPC_AUTH_MAXFLAVOR)
256                 data->auth_flavors[0] = RPC_AUTH_UNIX;
257         export_path = data->nfs_server.export_path;
258         data->nfs_server.export_path = "/";
259         root_mnt = nfs_do_root_mount(&nfs4_remote_fs_type, flags, mount_info,
260                         data->nfs_server.hostname);
261         data->nfs_server.export_path = export_path;
262
263         res = nfs_follow_remote_path(root_mnt, export_path);
264
265         dfprintk(MOUNT, "<-- nfs4_try_mount() = %ld%s\n",
266                         IS_ERR(res) ? PTR_ERR(res) : 0,
267                         IS_ERR(res) ? " [error]" : "");
268         return res;
269 }
270
271 static struct dentry *
272 nfs4_remote_referral_mount(struct file_system_type *fs_type, int flags,
273                            const char *dev_name, void *raw_data)
274 {
275         struct nfs_mount_info mount_info = {
276                 .fill_super = nfs_fill_super,
277                 .set_security = nfs_clone_sb_security,
278                 .cloned = raw_data,
279         };
280         struct nfs_server *server;
281         struct dentry *mntroot = ERR_PTR(-ENOMEM);
282
283         dprintk("--> nfs4_referral_get_sb()\n");
284
285         mount_info.mntfh = nfs_alloc_fhandle();
286         if (mount_info.cloned == NULL || mount_info.mntfh == NULL)
287                 goto out;
288
289         /* create a new volume representation */
290         server = nfs4_create_referral_server(mount_info.cloned, mount_info.mntfh);
291         if (IS_ERR(server)) {
292                 mntroot = ERR_CAST(server);
293                 goto out;
294         }
295
296         mntroot = nfs_fs_mount_common(server, flags, dev_name, &mount_info, &nfs_v4);
297 out:
298         nfs_free_fhandle(mount_info.mntfh);
299         return mntroot;
300 }
301
302 /*
303  * Create an NFS4 server record on referral traversal
304  */
305 static struct dentry *nfs4_referral_mount(struct file_system_type *fs_type,
306                 int flags, const char *dev_name, void *raw_data)
307 {
308         struct nfs_clone_mount *data = raw_data;
309         char *export_path;
310         struct vfsmount *root_mnt;
311         struct dentry *res;
312
313         dprintk("--> nfs4_referral_mount()\n");
314
315         export_path = data->mnt_path;
316         data->mnt_path = "/";
317
318         root_mnt = nfs_do_root_mount(&nfs4_remote_referral_fs_type,
319                         flags, data, data->hostname);
320         data->mnt_path = export_path;
321
322         res = nfs_follow_remote_path(root_mnt, export_path);
323         dprintk("<-- nfs4_referral_mount() = %ld%s\n",
324                         IS_ERR(res) ? PTR_ERR(res) : 0,
325                         IS_ERR(res) ? " [error]" : "");
326         return res;
327 }
328
329
330 static int __init init_nfs_v4(void)
331 {
332         int err;
333
334         err = nfs_idmap_init();
335         if (err)
336                 goto out;
337
338         err = nfs4_register_sysctl();
339         if (err)
340                 goto out1;
341
342         register_nfs_version(&nfs_v4);
343         return 0;
344 out1:
345         nfs_idmap_quit();
346 out:
347         return err;
348 }
349
350 static void __exit exit_nfs_v4(void)
351 {
352         unregister_nfs_version(&nfs_v4);
353         nfs4_unregister_sysctl();
354         nfs_idmap_quit();
355 }
356
357 MODULE_LICENSE("GPL");
358
359 module_init(init_nfs_v4);
360 module_exit(exit_nfs_v4);