1 | /* |
2 | * Copyright (c) 2016 Apple Inc. All rights reserved. |
3 | * |
4 | * @APPLE_LICENSE_HEADER_START@ |
5 | * |
6 | * This file contains Original Code and/or Modifications of Original Code |
7 | * as defined in and that are subject to the Apple Public Source License |
8 | * Version 2.0 (the 'License'). You may not use this file except in |
9 | * compliance with the License. Please obtain a copy of the License at |
10 | * http://www.opensource.apple.com/apsl/ and read it before using this |
11 | * file. |
12 | * |
13 | * The Original Code and all software distributed under the License are |
14 | * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER |
15 | * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, |
16 | * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, |
17 | * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. |
18 | * Please see the License for the specific language governing rights and |
19 | * limitations under the License. |
20 | * |
21 | * @APPLE_LICENSE_HEADER_END@ |
22 | */ |
23 | |
24 | /*- |
25 | * Portions Copyright (c) 1992, 1993 |
26 | * The Regents of the University of California. All rights reserved. |
27 | * |
28 | * This code is derived from software donated to Berkeley by |
29 | * Jan-Simon Pendry. |
30 | * |
31 | * Redistribution and use in source and binary forms, with or without |
32 | * modification, are permitted provided that the following conditions |
33 | * are met: |
34 | * 1. Redistributions of source code must retain the above copyright |
35 | * notice, this list of conditions and the following disclaimer. |
36 | * 2. Redistributions in binary form must reproduce the above copyright |
37 | * notice, this list of conditions and the following disclaimer in the |
38 | * documentation and/or other materials provided with the distribution. |
39 | * 4. Neither the name of the University nor the names of its contributors |
40 | * may be used to endorse or promote products derived from this software |
41 | * without specific prior written permission. |
42 | * |
43 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND |
44 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
45 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
46 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE |
47 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
48 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
49 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
50 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
51 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
52 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
53 | * SUCH DAMAGE. |
54 | * |
55 | * @(#)null_subr.c 8.7 (Berkeley) 5/14/95 |
56 | * |
57 | * $FreeBSD$ |
58 | */ |
59 | #include <sys/param.h> |
60 | #include <sys/systm.h> |
61 | #include <sys/kernel.h> |
62 | #include <sys/lock.h> |
63 | #include <sys/malloc.h> |
64 | #include <sys/mount.h> |
65 | #include <sys/proc.h> |
66 | #include <sys/vnode.h> |
67 | |
68 | #include "nullfs.h" |
69 | |
70 | /* |
71 | * Null layer cache: |
72 | * Each cache entry holds a reference to the lower vnode |
73 | * along with a pointer to the alias vnode. When an |
74 | * entry is added the lower vnode is VREF'd. When the |
75 | * alias is removed the lower vnode is vrele'd. |
76 | */ |
77 | |
78 | #define NULL_HASH_SIZE (desiredvnodes / 10) |
79 | |
80 | /* osx doesn't really have the functionality freebsd uses here..gonna try this |
81 | * hacked hash...*/ |
82 | #define NULL_NHASH(vp) (&null_node_hashtbl[((((uintptr_t)vp) >> vnsz2log) + (uintptr_t)vnode_mount(vp)) & null_hash_mask]) |
83 | |
84 | static LIST_HEAD(null_node_hashhead, null_node) * null_node_hashtbl; |
85 | static LCK_GRP_DECLARE(null_hashlck_grp, "com.apple.filesystems.nullfs" ); |
86 | static LCK_MTX_DECLARE(null_hashmtx, &null_hashlck_grp); |
87 | static u_long null_hash_mask; |
88 | |
89 | /* os x doesn't have hashes built into vnode. gonna try doing what freebsd does |
90 | * anyway |
91 | * Don't want to create a dependency on vnode_internal.h and the real struct |
92 | * vnode. |
93 | * 9 is an eyeball of the log 2 size of vnode */ |
94 | static int vnsz2log = 9; |
95 | |
96 | static int null_hashins(struct mount *, struct null_node *, struct vnode **); |
97 | |
98 | void |
99 | nullfs_init_lck(lck_mtx_t * lck) |
100 | { |
101 | lck_mtx_init(lck, grp: &null_hashlck_grp, LCK_ATTR_NULL); |
102 | } |
103 | |
104 | void |
105 | nullfs_destroy_lck(lck_mtx_t * lck) |
106 | { |
107 | lck_mtx_destroy(lck, grp: &null_hashlck_grp); |
108 | } |
109 | |
110 | /* |
111 | * Initialise cache headers |
112 | */ |
113 | int |
114 | nullfs_init(__unused struct vfsconf * vfsp) |
115 | { |
116 | NULLFSDEBUG("%s\n" , __FUNCTION__); |
117 | null_node_hashtbl = hashinit(NULL_HASH_SIZE, M_TEMP, hashmask: &null_hash_mask); |
118 | NULLFSDEBUG("%s finished\n" , __FUNCTION__); |
119 | return 0; |
120 | } |
121 | |
122 | int |
123 | nullfs_uninit(void) |
124 | { |
125 | /* This gets called when the fs is uninstalled, there wasn't an exact |
126 | * equivalent in vfsops */ |
127 | hashdestroy(null_node_hashtbl, M_TEMP, hashmask: null_hash_mask); |
128 | return 0; |
129 | } |
130 | |
131 | /* |
132 | * Find the nullfs vnode mapped to lowervp. Return it in *vpp with an iocount if found. |
133 | * Return 0 on success. On failure *vpp will be null and a non-zero error code will be returned. |
134 | */ |
135 | int |
136 | null_hashget(struct mount * mp, struct vnode * lowervp, struct vnode ** vpp) |
137 | { |
138 | struct null_node_hashhead * hd = NULL; |
139 | struct null_node * a = NULL; |
140 | struct vnode * vp = NULL; |
141 | uint32_t vp_vid = 0; |
142 | int error = ENOENT; |
143 | |
144 | /* |
145 | * Find hash base, and then search the (two-way) linked |
146 | * list looking for a null_node structure which is referencing |
147 | * the lower vnode. We only give up our reference at reclaim so |
148 | * just check whether the lowervp has gotten pulled from under us |
149 | */ |
150 | hd = NULL_NHASH(lowervp); |
151 | // In the future we should consider using a per bucket lock |
152 | lck_mtx_lock(lck: &null_hashmtx); |
153 | LIST_FOREACH(a, hd, null_hash) |
154 | { |
155 | if (a->null_lowervp == lowervp && vnode_mount(NULLTOV(a)) == mp) { |
156 | vp = NULLTOV(a); |
157 | if (a->null_lowervid != vnode_vid(vp: lowervp)) { |
158 | /*lowervp has reved */ |
159 | error = EIO; |
160 | vp = NULL; |
161 | } else { |
162 | vp_vid = a->null_myvid; |
163 | } |
164 | // In the case of a succesful look-up we should consider moving the object to the top of the head |
165 | break; |
166 | } |
167 | } |
168 | if (vp != NULL) { |
169 | vnode_hold(vp); |
170 | } |
171 | lck_mtx_unlock(lck: &null_hashmtx); |
172 | if (vp != NULL) { |
173 | error = vnode_getwithvid(vp, vp_vid); |
174 | if (error == 0) { |
175 | *vpp = vp; |
176 | } |
177 | vnode_drop(vp); |
178 | } |
179 | return error; |
180 | } |
181 | |
182 | /* |
183 | * Act like null_hashget, but add passed null_node to hash if no existing |
184 | * node found. |
185 | */ |
186 | static int |
187 | null_hashins(struct mount * mp, struct null_node * xp, struct vnode ** vpp) |
188 | { |
189 | struct null_node_hashhead * hd = NULL; |
190 | struct null_node * oxp = NULL; |
191 | struct vnode * ovp = NULL; |
192 | uint32_t oxp_vid = 0; |
193 | int error = 0; |
194 | |
195 | hd = NULL_NHASH(xp->null_lowervp); |
196 | lck_mtx_lock(lck: &null_hashmtx); |
197 | LIST_FOREACH(oxp, hd, null_hash) |
198 | { |
199 | if (oxp->null_lowervp == xp->null_lowervp && vnode_mount(NULLTOV(oxp)) == mp) { |
200 | /* |
201 | * See null_hashget for a description of this |
202 | * operation. |
203 | */ |
204 | ovp = NULLTOV(oxp); |
205 | if (oxp->null_lowervid != vnode_vid(vp: oxp->null_lowervp)) { |
206 | /*vp doesn't exist so return null (not sure we are actually gonna catch |
207 | * recycle right now |
208 | * This is an exceptional case right now, it suggests the vnode we are |
209 | * trying to add has been recycled |
210 | * don't add it.*/ |
211 | error = EIO; |
212 | ovp = NULL; |
213 | } else { |
214 | oxp_vid = oxp->null_myvid; |
215 | } |
216 | goto end; |
217 | } |
218 | } |
219 | /* if it wasn't in the hash map then the vnode pointed to by xp already has a |
220 | * iocount so don't bother */ |
221 | LIST_INSERT_HEAD(hd, xp, null_hash); |
222 | xp->null_flags |= NULL_FLAG_HASHED; |
223 | end: |
224 | if (ovp != NULL) { |
225 | vnode_hold(vp: ovp); |
226 | } |
227 | lck_mtx_unlock(lck: &null_hashmtx); |
228 | if (ovp != NULL) { |
229 | /* if we found something in the hash map then grab an iocount */ |
230 | error = vnode_getwithvid(ovp, oxp_vid); |
231 | if (error == 0) { |
232 | *vpp = ovp; |
233 | } |
234 | vnode_drop(vp: ovp); |
235 | } |
236 | return error; |
237 | } |
238 | |
239 | /* |
240 | * Remove node from hash. |
241 | */ |
242 | void |
243 | null_hashrem(struct null_node * xp) |
244 | { |
245 | lck_mtx_lock(lck: &null_hashmtx); |
246 | LIST_REMOVE(xp, null_hash); |
247 | lck_mtx_unlock(lck: &null_hashmtx); |
248 | } |
249 | |
250 | static struct null_node * |
251 | null_nodecreate(struct vnode * lowervp) |
252 | { |
253 | struct null_node * xp; |
254 | |
255 | xp = kalloc_type(struct null_node, Z_WAITOK | Z_ZERO | Z_NOFAIL); |
256 | if (lowervp) { |
257 | xp->null_lowervp = lowervp; |
258 | xp->null_lowervid = vnode_vid(vp: lowervp); |
259 | } |
260 | return xp; |
261 | } |
262 | |
263 | /* assumption is that vnode has iocount on it after vnode create */ |
264 | int |
265 | null_getnewvnode( |
266 | struct mount * mp, struct vnode * lowervp, struct vnode * dvp, struct vnode ** vpp, struct componentname * cnp, int root) |
267 | { |
268 | struct vnode_fsparam vnfs_param; |
269 | int error = 0; |
270 | enum vtype type = VDIR; |
271 | struct null_node * xp = null_nodecreate(lowervp); |
272 | |
273 | if (xp == NULL) { |
274 | return ENOMEM; |
275 | } |
276 | |
277 | if (lowervp) { |
278 | type = vnode_vtype(vp: lowervp); |
279 | } |
280 | |
281 | vnfs_param.vnfs_mp = mp; |
282 | vnfs_param.vnfs_vtype = type; |
283 | vnfs_param.vnfs_str = "nullfs" ; |
284 | vnfs_param.vnfs_dvp = dvp; |
285 | vnfs_param.vnfs_fsnode = (void *)xp; |
286 | vnfs_param.vnfs_vops = nullfs_vnodeop_p; |
287 | vnfs_param.vnfs_markroot = root; |
288 | vnfs_param.vnfs_marksystem = 0; |
289 | vnfs_param.vnfs_rdev = 0; |
290 | vnfs_param.vnfs_filesize = 0; // set this to 0 since we should only be shadowing non-regular files |
291 | vnfs_param.vnfs_cnp = cnp; |
292 | vnfs_param.vnfs_flags = VNFS_ADDFSREF; |
293 | |
294 | error = vnode_create_ext(VNCREATE_FLAVOR, VCREATESIZE, data: &vnfs_param, vpp, VNODE_CREATE_DEFAULT); |
295 | if (error == 0) { |
296 | xp->null_vnode = *vpp; |
297 | xp->null_myvid = vnode_vid(vp: *vpp); |
298 | vnode_settag(vp: *vpp, tag: VT_NULL); |
299 | } else { |
300 | kfree_type(struct null_node, xp); |
301 | } |
302 | return error; |
303 | } |
304 | |
305 | /* |
306 | * Make a new or get existing nullfs node. |
307 | * Vp is the alias vnode, lowervp is the lower vnode. |
308 | * |
309 | * lowervp is assumed to have an iocount on it from the caller |
310 | */ |
311 | int |
312 | null_nodeget( |
313 | struct mount * mp, struct vnode * lowervp, struct vnode * dvp, struct vnode ** vpp, struct componentname * cnp, int root) |
314 | { |
315 | struct vnode * vp; |
316 | int error; |
317 | |
318 | /* Lookup the hash firstly. */ |
319 | error = null_hashget(mp, lowervp, vpp); |
320 | /* ENOENT means it wasn't found, EIO is a failure we should bail from, 0 is it |
321 | * was found */ |
322 | if (error != ENOENT) { |
323 | /* null_hashget checked the vid, so if we got something here its legit to |
324 | * the best of our knowledge*/ |
325 | /* if we found something then there is an iocount on vpp, |
326 | * if we didn't find something then vpp shouldn't be used by the caller */ |
327 | return error; |
328 | } |
329 | |
330 | /* |
331 | * We do not serialize vnode creation, instead we will check for |
332 | * duplicates later, when adding new vnode to hash. |
333 | */ |
334 | error = vnode_ref(vp: lowervp); // take a ref on lowervp so we let the system know we care about it |
335 | if (error) { |
336 | // Failed to get a reference on the lower vp so bail. Lowervp may be gone already. |
337 | return error; |
338 | } |
339 | |
340 | error = null_getnewvnode(mp, lowervp, dvp, vpp: &vp, cnp, root); |
341 | |
342 | if (error) { |
343 | vnode_rele(vp: lowervp); |
344 | return error; |
345 | } |
346 | |
347 | /* |
348 | * Atomically insert our new node into the hash or vget existing |
349 | * if someone else has beaten us to it. |
350 | */ |
351 | error = null_hashins(mp, VTONULL(vp), vpp); |
352 | if (error || *vpp != NULL) { |
353 | /* recycle will call reclaim which will get rid of the internals */ |
354 | vnode_recycle(vp); |
355 | vnode_put(vp); |
356 | /* if we found vpp, then null_hashins put an iocount on it */ |
357 | return error; |
358 | } |
359 | |
360 | /* vp has an iocount from null_getnewvnode */ |
361 | *vpp = vp; |
362 | |
363 | return 0; |
364 | } |
365 | |