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2024-09-20 cf4ce59b3b70238352c7f1729f0f7223214828ad 
 kernel/fs/kernfs/mount.c
....@@ -1,11 +1,10 @@
1
+// SPDX-License-Identifier: GPL-2.0-only
12 /*
23  * fs/kernfs/mount.c - kernfs mount implementation
34  *
45  * Copyright (c) 2001-3 Patrick Mochel
56  * Copyright (c) 2007 SUSE Linux Products GmbH
67  * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
7
- *
8
- * This file is released under the GPLv2.
98  */
109 
1110 #include <linux/fs.h>
....@@ -20,17 +19,7 @@
2019 
2120 #include "kernfs-internal.h"
2221 
23
-struct kmem_cache *kernfs_node_cache;
24
-
25
-static int kernfs_sop_remount_fs(struct super_block *sb, int *flags, char *data)
26
-{
27
-	struct kernfs_root *root = kernfs_info(sb)->root;
28
-	struct kernfs_syscall_ops *scops = root->syscall_ops;
29
-
30
-	if (scops && scops->remount_fs)
31
-		return scops->remount_fs(root, flags, data);
32
-	return 0;
33
-}
22
+struct kmem_cache *kernfs_node_cache, *kernfs_iattrs_cache;
3423 
3524 static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry)
3625 {
....@@ -60,68 +49,89 @@
6049 	.drop_inode	= generic_delete_inode,
6150 	.evict_inode	= kernfs_evict_inode,
6251 
63
-	.remount_fs	= kernfs_sop_remount_fs,
6452 	.show_options	= kernfs_sop_show_options,
6553 	.show_path	= kernfs_sop_show_path,
6654 };
6755 
68
-/*
69
- * Similar to kernfs_fh_get_inode, this one gets kernfs node from inode
70
- * number and generation
71
- */
72
-struct kernfs_node *kernfs_get_node_by_id(struct kernfs_root *root,
73
-	const union kernfs_node_id *id)
56
+static int kernfs_encode_fh(struct inode *inode, __u32 *fh, int *max_len,
57
+			    struct inode *parent)
7458 {
75
-	struct kernfs_node *kn;
59
+	struct kernfs_node *kn = inode->i_private;
7660 
77
-	kn = kernfs_find_and_get_node_by_ino(root, id->ino);
78
-	if (!kn)
79
-		return NULL;
80
-	if (kn->id.generation != id->generation) {
81
-		kernfs_put(kn);
82
-		return NULL;
61
+	if (*max_len < 2) {
62
+		*max_len = 2;
63
+		return FILEID_INVALID;
8364 	}
84
-	return kn;
65
+
66
+	*max_len = 2;
67
+	*(u64 *)fh = kn->id;
68
+	return FILEID_KERNFS;
8569 }
8670 
87
-static struct inode *kernfs_fh_get_inode(struct super_block *sb,
88
-		u64 ino, u32 generation)
71
+static struct dentry *__kernfs_fh_to_dentry(struct super_block *sb,
72
+					    struct fid *fid, int fh_len,
73
+					    int fh_type, bool get_parent)
8974 {
9075 	struct kernfs_super_info *info = kernfs_info(sb);
91
-	struct inode *inode;
9276 	struct kernfs_node *kn;
77
+	struct inode *inode;
78
+	u64 id;
9379 
94
-	if (ino == 0)
95
-		return ERR_PTR(-ESTALE);
80
+	if (fh_len < 2)
81
+		return NULL;
9682 
97
-	kn = kernfs_find_and_get_node_by_ino(info->root, ino);
83
+	switch (fh_type) {
84
+	case FILEID_KERNFS:
85
+		id = *(u64 *)fid;
86
+		break;
87
+	case FILEID_INO32_GEN:
88
+	case FILEID_INO32_GEN_PARENT:
89
+		/*
90
+		 * blk_log_action() exposes "LOW32,HIGH32" pair without
91
+		 * type and userland can call us with generic fid
92
+		 * constructed from them.  Combine it back to ID.  See
93
+		 * blk_log_action().
94
+		 */
95
+		id = ((u64)fid->i32.gen << 32) | fid->i32.ino;
96
+		break;
97
+	default:
98
+		return NULL;
99
+	}
100
+
101
+	kn = kernfs_find_and_get_node_by_id(info->root, id);
98102 	if (!kn)
99103 		return ERR_PTR(-ESTALE);
104
+
105
+	if (get_parent) {
106
+		struct kernfs_node *parent;
107
+
108
+		parent = kernfs_get_parent(kn);
109
+		kernfs_put(kn);
110
+		kn = parent;
111
+		if (!kn)
112
+			return ERR_PTR(-ESTALE);
113
+	}
114
+
100115 	inode = kernfs_get_inode(sb, kn);
101116 	kernfs_put(kn);
102117 	if (!inode)
103118 		return ERR_PTR(-ESTALE);
104119 
105
-	if (generation && inode->i_generation != generation) {
106
-		/* we didn't find the right inode.. */
107
-		iput(inode);
108
-		return ERR_PTR(-ESTALE);
109
-	}
110
-	return inode;
120
+	return d_obtain_alias(inode);
111121 }
112122 
113
-static struct dentry *kernfs_fh_to_dentry(struct super_block *sb, struct fid *fid,
114
-		int fh_len, int fh_type)
123
+static struct dentry *kernfs_fh_to_dentry(struct super_block *sb,
124
+					  struct fid *fid, int fh_len,
125
+					  int fh_type)
115126 {
116
-	return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
117
-				    kernfs_fh_get_inode);
127
+	return __kernfs_fh_to_dentry(sb, fid, fh_len, fh_type, false);
118128 }
119129 
120
-static struct dentry *kernfs_fh_to_parent(struct super_block *sb, struct fid *fid,
121
-		int fh_len, int fh_type)
130
+static struct dentry *kernfs_fh_to_parent(struct super_block *sb,
131
+					  struct fid *fid, int fh_len,
132
+					  int fh_type)
122133 {
123
-	return generic_fh_to_parent(sb, fid, fh_len, fh_type,
124
-				    kernfs_fh_get_inode);
134
+	return __kernfs_fh_to_dentry(sb, fid, fh_len, fh_type, true);
125135 }
126136 
127137 static struct dentry *kernfs_get_parent_dentry(struct dentry *child)
....@@ -132,6 +142,7 @@
132142 }
133143 
134144 static const struct export_operations kernfs_export_ops = {
145
+	.encode_fh	= kernfs_encode_fh,
135146 	.fh_to_dentry	= kernfs_fh_to_dentry,
136147 	.fh_to_parent	= kernfs_fh_to_parent,
137148 	.get_parent	= kernfs_get_parent_dentry,
....@@ -212,7 +223,7 @@
212223 			dput(dentry);
213224 			return ERR_PTR(-EINVAL);
214225 		}
215
-		dtmp = lookup_one_len_unlocked(kntmp->name, dentry,
226
+		dtmp = lookup_positive_unlocked(kntmp->name, dentry,
216227 					       strlen(kntmp->name));
217228 		dput(dentry);
218229 		if (IS_ERR(dtmp))
....@@ -222,7 +233,7 @@
222233 	} while (true);
223234 }
224235 
225
-static int kernfs_fill_super(struct super_block *sb, unsigned long magic)
236
+static int kernfs_fill_super(struct super_block *sb, struct kernfs_fs_context *kfc)
226237 {
227238 	struct kernfs_super_info *info = kernfs_info(sb);
228239 	struct inode *inode;
....@@ -233,12 +244,15 @@
233244 	sb->s_iflags |= SB_I_NOEXEC | SB_I_NODEV;
234245 	sb->s_blocksize = PAGE_SIZE;
235246 	sb->s_blocksize_bits = PAGE_SHIFT;
236
-	sb->s_magic = magic;
247
+	sb->s_magic = kfc->magic;
237248 	sb->s_op = &kernfs_sops;
238249 	sb->s_xattr = kernfs_xattr_handlers;
239250 	if (info->root->flags & KERNFS_ROOT_SUPPORT_EXPORTOP)
240251 		sb->s_export_op = &kernfs_export_ops;
241252 	sb->s_time_gran = 1;
253
+
254
+	/* sysfs dentries and inodes don't require IO to create */
255
+	sb->s_shrink.seeks = 0;
242256 
243257 	/* get root inode, initialize and unlock it */
244258 	mutex_lock(&kernfs_mutex);
....@@ -260,21 +274,20 @@
260274 	return 0;
261275 }
262276 
263
-static int kernfs_test_super(struct super_block *sb, void *data)
277
+static int kernfs_test_super(struct super_block *sb, struct fs_context *fc)
264278 {
265279 	struct kernfs_super_info *sb_info = kernfs_info(sb);
266
-	struct kernfs_super_info *info = data;
280
+	struct kernfs_super_info *info = fc->s_fs_info;
267281 
268282 	return sb_info->root == info->root && sb_info->ns == info->ns;
269283 }
270284 
271
-static int kernfs_set_super(struct super_block *sb, void *data)
285
+static int kernfs_set_super(struct super_block *sb, struct fs_context *fc)
272286 {
273
-	int error;
274
-	error = set_anon_super(sb, data);
275
-	if (!error)
276
-		sb->s_fs_info = data;
277
-	return error;
287
+	struct kernfs_fs_context *kfc = fc->fs_private;
288
+
289
+	kfc->ns_tag = NULL;
290
+	return set_anon_super_fc(sb, fc);
278291 }
279292 
280293 /**
....@@ -291,63 +304,60 @@
291304 }
292305 
293306 /**
294
- * kernfs_mount_ns - kernfs mount helper
295
- * @fs_type: file_system_type of the fs being mounted
296
- * @flags: mount flags specified for the mount
297
- * @root: kernfs_root of the hierarchy being mounted
298
- * @magic: file system specific magic number
299
- * @new_sb_created: tell the caller if we allocated a new superblock
300
- * @ns: optional namespace tag of the mount
307
+ * kernfs_get_tree - kernfs filesystem access/retrieval helper
308
+ * @fc: The filesystem context.
301309  *
302
- * This is to be called from each kernfs user's file_system_type->mount()
303
- * implementation, which should pass through the specified @fs_type and
304
- * @flags, and specify the hierarchy and namespace tag to mount via @root
305
- * and @ns, respectively.
306
- *
307
- * The return value can be passed to the vfs layer verbatim.
310
+ * This is to be called from each kernfs user's fs_context->ops->get_tree()
311
+ * implementation, which should set the specified ->@fs_type and ->@flags, and
312
+ * specify the hierarchy and namespace tag to mount via ->@root and ->@ns,
313
+ * respectively.
308314  */
309
-struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
310
-				struct kernfs_root *root, unsigned long magic,
311
-				bool *new_sb_created, const void *ns)
315
+int kernfs_get_tree(struct fs_context *fc)
312316 {
317
+	struct kernfs_fs_context *kfc = fc->fs_private;
313318 	struct super_block *sb;
314319 	struct kernfs_super_info *info;
315320 	int error;
316321 
317322 	info = kzalloc(sizeof(*info), GFP_KERNEL);
318323 	if (!info)
319
-		return ERR_PTR(-ENOMEM);
324
+		return -ENOMEM;
320325 
321
-	info->root = root;
322
-	info->ns = ns;
326
+	info->root = kfc->root;
327
+	info->ns = kfc->ns_tag;
323328 	INIT_LIST_HEAD(&info->node);
324329 
325
-	sb = sget_userns(fs_type, kernfs_test_super, kernfs_set_super, flags,
326
-			 &init_user_ns, info);
327
-	if (IS_ERR(sb) || sb->s_fs_info != info)
328
-		kfree(info);
330
+	fc->s_fs_info = info;
331
+	sb = sget_fc(fc, kernfs_test_super, kernfs_set_super);
329332 	if (IS_ERR(sb))
330
-		return ERR_CAST(sb);
331
-
332
-	if (new_sb_created)
333
-		*new_sb_created = !sb->s_root;
333
+		return PTR_ERR(sb);
334334 
335335 	if (!sb->s_root) {
336336 		struct kernfs_super_info *info = kernfs_info(sb);
337337 
338
-		error = kernfs_fill_super(sb, magic);
338
+		kfc->new_sb_created = true;
339
+
340
+		error = kernfs_fill_super(sb, kfc);
339341 		if (error) {
340342 			deactivate_locked_super(sb);
341
-			return ERR_PTR(error);
343
+			return error;
342344 		}
343345 		sb->s_flags |= SB_ACTIVE;
344346 
345347 		mutex_lock(&kernfs_mutex);
346
-		list_add(&info->node, &root->supers);
348
+		list_add(&info->node, &info->root->supers);
347349 		mutex_unlock(&kernfs_mutex);
348350 	}
349351 
350
-	return dget(sb->s_root);
352
+	fc->root = dget(sb->s_root);
353
+	return 0;
354
+}
355
+
356
+void kernfs_free_fs_context(struct fs_context *fc)
357
+{
358
+	/* Note that we don't deal with kfc->ns_tag here. */
359
+	kfree(fc->s_fs_info);
360
+	fc->s_fs_info = NULL;
351361 }
352362 
353363 /**
....@@ -374,48 +384,14 @@
374384 	kfree(info);
375385 }
376386 
377
-/**
378
- * kernfs_pin_sb: try to pin the superblock associated with a kernfs_root
379
- * @kernfs_root: the kernfs_root in question
380
- * @ns: the namespace tag
381
- *
382
- * Pin the superblock so the superblock won't be destroyed in subsequent
383
- * operations.  This can be used to block ->kill_sb() which may be useful
384
- * for kernfs users which dynamically manage superblocks.
385
- *
386
- * Returns NULL if there's no superblock associated to this kernfs_root, or
387
- * -EINVAL if the superblock is being freed.
388
- */
389
-struct super_block *kernfs_pin_sb(struct kernfs_root *root, const void *ns)
390
-{
391
-	struct kernfs_super_info *info;
392
-	struct super_block *sb = NULL;
393
-
394
-	mutex_lock(&kernfs_mutex);
395
-	list_for_each_entry(info, &root->supers, node) {
396
-		if (info->ns == ns) {
397
-			sb = info->sb;
398
-			if (!atomic_inc_not_zero(&info->sb->s_active))
399
-				sb = ERR_PTR(-EINVAL);
400
-			break;
401
-		}
402
-	}
403
-	mutex_unlock(&kernfs_mutex);
404
-	return sb;
405
-}
406
-
407387 void __init kernfs_init(void)
408388 {
409
-
410
-	/*
411
-	 * the slab is freed in RCU context, so kernfs_find_and_get_node_by_ino
412
-	 * can access the slab lock free. This could introduce stale nodes,
413
-	 * please see how kernfs_find_and_get_node_by_ino filters out stale
414
-	 * nodes.
415
-	 */
416389 	kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
417390 					      sizeof(struct kernfs_node),
418
-					      0,
419
-					      SLAB_PANIC | SLAB_TYPESAFE_BY_RCU,
420
-					      NULL);
391
+					      0, SLAB_PANIC, NULL);
392
+
393
+	/* Creates slab cache for kernfs inode attributes */
394
+	kernfs_iattrs_cache  = kmem_cache_create("kernfs_iattrs_cache",
395
+					      sizeof(struct kernfs_iattrs),
396
+					      0, SLAB_PANIC, NULL);
421397 }