blob: 2f388460cbe72865be75b43b96f58e231b00e379 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001Changes since 2.5.0:
2
3---
4[recommended]
5
6New helpers: sb_bread(), sb_getblk(), sb_find_get_block(), set_bh(),
7 sb_set_blocksize() and sb_min_blocksize().
8
9Use them.
10
11(sb_find_get_block() replaces 2.4's get_hash_table())
12
13---
14[recommended]
15
16New methods: ->alloc_inode() and ->destroy_inode().
17
18Remove inode->u.foo_inode_i
19Declare
20 struct foo_inode_info {
21 /* fs-private stuff */
22 struct inode vfs_inode;
23 };
24 static inline struct foo_inode_info *FOO_I(struct inode *inode)
25 {
26 return list_entry(inode, struct foo_inode_info, vfs_inode);
27 }
28
29Use FOO_I(inode) instead of &inode->u.foo_inode_i;
30
31Add foo_alloc_inode() and foo_destory_inode() - the former should allocate
32foo_inode_info and return the address of ->vfs_inode, the latter should free
33FOO_I(inode) (see in-tree filesystems for examples).
34
35Make them ->alloc_inode and ->destroy_inode in your super_operations.
36
37Keep in mind that now you need explicit initialization of private data -
38typically in ->read_inode() and after getting an inode from new_inode().
39
40At some point that will become mandatory.
41
42---
43[mandatory]
44
45Change of file_system_type method (->read_super to ->get_sb)
46
47->read_super() is no more. Ditto for DECLARE_FSTYPE and DECLARE_FSTYPE_DEV.
48
49Turn your foo_read_super() into a function that would return 0 in case of
50success and negative number in case of error (-EINVAL unless you have more
51informative error value to report). Call it foo_fill_super(). Now declare
52
53struct super_block foo_get_sb(struct file_system_type *fs_type,
54 int flags, const char *dev_name, void *data)
55{
56 return get_sb_bdev(fs_type, flags, dev_name, data, ext2_fill_super);
57}
58
59(or similar with s/bdev/nodev/ or s/bdev/single/, depending on the kind of
60filesystem).
61
62Replace DECLARE_FSTYPE... with explicit initializer and have ->get_sb set as
63foo_get_sb.
64
65---
66[mandatory]
67
68Locking change: ->s_vfs_rename_sem is taken only by cross-directory renames.
69Most likely there is no need to change anything, but if you relied on
70global exclusion between renames for some internal purpose - you need to
71change your internal locking. Otherwise exclusion warranties remain the
72same (i.e. parents and victim are locked, etc.).
73
74---
75[informational]
76
77Now we have the exclusion between ->lookup() and directory removal (by
78->rmdir() and ->rename()). If you used to need that exclusion and do
79it by internal locking (most of filesystems couldn't care less) - you
80can relax your locking.
81
82---
83[mandatory]
84
85->lookup(), ->truncate(), ->create(), ->unlink(), ->mknod(), ->mkdir(),
86->rmdir(), ->link(), ->lseek(), ->symlink(), ->rename()
87and ->readdir() are called without BKL now. Grab it on entry, drop upon return
88- that will guarantee the same locking you used to have. If your method or its
89parts do not need BKL - better yet, now you can shift lock_kernel() and
90unlock_kernel() so that they would protect exactly what needs to be
91protected.
92
93---
94[mandatory]
95
96BKL is also moved from around sb operations. ->write_super() Is now called
97without BKL held. BKL should have been shifted into individual fs sb_op
98functions. If you don't need it, remove it.
99
100---
101[informational]
102
103check for ->link() target not being a directory is done by callers. Feel
104free to drop it...
105
106---
107[informational]
108
109->link() callers hold ->i_sem on the object we are linking to. Some of your
110problems might be over...
111
112---
113[mandatory]
114
115new file_system_type method - kill_sb(superblock). If you are converting
116an existing filesystem, set it according to ->fs_flags:
117 FS_REQUIRES_DEV - kill_block_super
118 FS_LITTER - kill_litter_super
119 neither - kill_anon_super
120FS_LITTER is gone - just remove it from fs_flags.
121
122---
123[mandatory]
124
125 FS_SINGLE is gone (actually, that had happened back when ->get_sb()
126went in - and hadn't been documented ;-/). Just remove it from fs_flags
127(and see ->get_sb() entry for other actions).
128
129---
130[mandatory]
131
132->setattr() is called without BKL now. Caller _always_ holds ->i_sem, so
133watch for ->i_sem-grabbing code that might be used by your ->setattr().
134Callers of notify_change() need ->i_sem now.
135
136---
137[recommended]
138
139New super_block field "struct export_operations *s_export_op" for
140explicit support for exporting, e.g. via NFS. The structure is fully
141documented at its declaration in include/linux/fs.h, and in
142Documentation/filesystems/Exporting.
143
144Briefly it allows for the definition of decode_fh and encode_fh operations
145to encode and decode filehandles, and allows the filesystem to use
146a standard helper function for decode_fh, and provide file-system specific
147support for this helper, particularly get_parent.
148
149It is planned that this will be required for exporting once the code
150settles down a bit.
151
152[mandatory]
153
154s_export_op is now required for exporting a filesystem.
155isofs, ext2, ext3, resierfs, fat
156can be used as examples of very different filesystems.
157
158---
159[mandatory]
160
161iget4() and the read_inode2 callback have been superseded by iget5_locked()
162which has the following prototype,
163
164 struct inode *iget5_locked(struct super_block *sb, unsigned long ino,
165 int (*test)(struct inode *, void *),
166 int (*set)(struct inode *, void *),
167 void *data);
168
169'test' is an additional function that can be used when the inode
170number is not sufficient to identify the actual file object. 'set'
171should be a non-blocking function that initializes those parts of a
172newly created inode to allow the test function to succeed. 'data' is
173passed as an opaque value to both test and set functions.
174
175When the inode has been created by iget5_locked(), it will be returned with
176the I_NEW flag set and will still be locked. read_inode has not been
177called so the file system still has to finalize the initialization. Once
178the inode is initialized it must be unlocked by calling unlock_new_inode().
179
180The filesystem is responsible for setting (and possibly testing) i_ino
181when appropriate. There is also a simpler iget_locked function that
182just takes the superblock and inode number as arguments and does the
183test and set for you.
184
185e.g.
186 inode = iget_locked(sb, ino);
187 if (inode->i_state & I_NEW) {
188 read_inode_from_disk(inode);
189 unlock_new_inode(inode);
190 }
191
192---
193[recommended]
194
195->getattr() finally getting used. See instances in nfs, minix, etc.
196
197---
198[mandatory]
199
200->revalidate() is gone. If your filesystem had it - provide ->getattr()
201and let it call whatever you had as ->revlidate() + (for symlinks that
202had ->revalidate()) add calls in ->follow_link()/->readlink().
203
204---
205[mandatory]
206
207->d_parent changes are not protected by BKL anymore. Read access is safe
208if at least one of the following is true:
209 * filesystem has no cross-directory rename()
210 * dcache_lock is held
211 * we know that parent had been locked (e.g. we are looking at
212->d_parent of ->lookup() argument).
213 * we are called from ->rename().
214 * the child's ->d_lock is held
215Audit your code and add locking if needed. Notice that any place that is
216not protected by the conditions above is risky even in the old tree - you
217had been relying on BKL and that's prone to screwups. Old tree had quite
218a few holes of that kind - unprotected access to ->d_parent leading to
219anything from oops to silent memory corruption.
220
221---
222[mandatory]
223
224 FS_NOMOUNT is gone. If you use it - just set MS_NOUSER in flags
225(see rootfs for one kind of solution and bdev/socket/pipe for another).
226
227---
228[recommended]
229
230 Use bdev_read_only(bdev) instead of is_read_only(kdev). The latter
231is still alive, but only because of the mess in drivers/s390/block/dasd.c.
232As soon as it gets fixed is_read_only() will die.
233
234---
235[mandatory]
236
237->permission() is called without BKL now. Grab it on entry, drop upon
238return - that will guarantee the same locking you used to have. If
239your method or its parts do not need BKL - better yet, now you can
240shift lock_kernel() and unlock_kernel() so that they would protect
241exactly what needs to be protected.
242
243---
244[mandatory]
245
246->statfs() is now called without BKL held. BKL should have been
247shifted into individual fs sb_op functions where it's not clear that
248it's safe to remove it. If you don't need it, remove it.
249
250---
251[mandatory]
252
253 is_read_only() is gone; use bdev_read_only() instead.
254
255---
256[mandatory]
257
258 destroy_buffers() is gone; use invalidate_bdev().
259
260---
261[mandatory]
262
263 fsync_dev() is gone; use fsync_bdev(). NOTE: lvm breakage is
264deliberate; as soon as struct block_device * is propagated in a reasonable
265way by that code fixing will become trivial; until then nothing can be
266done.