blob: dac45c92d872b977312372210243ffa318ad08cb [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
David Howells454e2392006-06-23 02:02:57 -070053int foo_get_sb(struct file_system_type *fs_type,
54 int flags, const char *dev_name, void *data, struct vfsmount *mnt)
Linus Torvalds1da177e2005-04-16 15:20:36 -070055{
David Howells454e2392006-06-23 02:02:57 -070056 return get_sb_bdev(fs_type, flags, dev_name, data, foo_fill_super,
57 mnt);
Linus Torvalds1da177e2005-04-16 15:20:36 -070058}
59
60(or similar with s/bdev/nodev/ or s/bdev/single/, depending on the kind of
61filesystem).
62
63Replace DECLARE_FSTYPE... with explicit initializer and have ->get_sb set as
64foo_get_sb.
65
66---
67[mandatory]
68
69Locking change: ->s_vfs_rename_sem is taken only by cross-directory renames.
70Most likely there is no need to change anything, but if you relied on
71global exclusion between renames for some internal purpose - you need to
72change your internal locking. Otherwise exclusion warranties remain the
73same (i.e. parents and victim are locked, etc.).
74
75---
76[informational]
77
78Now we have the exclusion between ->lookup() and directory removal (by
79->rmdir() and ->rename()). If you used to need that exclusion and do
80it by internal locking (most of filesystems couldn't care less) - you
81can relax your locking.
82
83---
84[mandatory]
85
86->lookup(), ->truncate(), ->create(), ->unlink(), ->mknod(), ->mkdir(),
87->rmdir(), ->link(), ->lseek(), ->symlink(), ->rename()
88and ->readdir() are called without BKL now. Grab it on entry, drop upon return
89- that will guarantee the same locking you used to have. If your method or its
90parts do not need BKL - better yet, now you can shift lock_kernel() and
91unlock_kernel() so that they would protect exactly what needs to be
92protected.
93
94---
95[mandatory]
96
97BKL is also moved from around sb operations. ->write_super() Is now called
98without BKL held. BKL should have been shifted into individual fs sb_op
99functions. If you don't need it, remove it.
100
101---
102[informational]
103
104check for ->link() target not being a directory is done by callers. Feel
105free to drop it...
106
107---
108[informational]
109
Josef 'Jeff' Sipekc2b38982007-05-24 12:21:43 -0400110->link() callers hold ->i_mutex on the object we are linking to. Some of your
Linus Torvalds1da177e2005-04-16 15:20:36 -0700111problems might be over...
112
113---
114[mandatory]
115
116new file_system_type method - kill_sb(superblock). If you are converting
117an existing filesystem, set it according to ->fs_flags:
118 FS_REQUIRES_DEV - kill_block_super
119 FS_LITTER - kill_litter_super
120 neither - kill_anon_super
121FS_LITTER is gone - just remove it from fs_flags.
122
123---
124[mandatory]
125
126 FS_SINGLE is gone (actually, that had happened back when ->get_sb()
127went in - and hadn't been documented ;-/). Just remove it from fs_flags
128(and see ->get_sb() entry for other actions).
129
130---
131[mandatory]
132
Josef 'Jeff' Sipekc2b38982007-05-24 12:21:43 -0400133->setattr() is called without BKL now. Caller _always_ holds ->i_mutex, so
134watch for ->i_mutex-grabbing code that might be used by your ->setattr().
135Callers of notify_change() need ->i_mutex now.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700136
137---
138[recommended]
139
140New super_block field "struct export_operations *s_export_op" for
141explicit support for exporting, e.g. via NFS. The structure is fully
142documented at its declaration in include/linux/fs.h, and in
143Documentation/filesystems/Exporting.
144
145Briefly it allows for the definition of decode_fh and encode_fh operations
146to encode and decode filehandles, and allows the filesystem to use
147a standard helper function for decode_fh, and provide file-system specific
148support for this helper, particularly get_parent.
149
150It is planned that this will be required for exporting once the code
151settles down a bit.
152
153[mandatory]
154
155s_export_op is now required for exporting a filesystem.
156isofs, ext2, ext3, resierfs, fat
157can be used as examples of very different filesystems.
158
159---
160[mandatory]
161
162iget4() and the read_inode2 callback have been superseded by iget5_locked()
163which has the following prototype,
164
165 struct inode *iget5_locked(struct super_block *sb, unsigned long ino,
166 int (*test)(struct inode *, void *),
167 int (*set)(struct inode *, void *),
168 void *data);
169
170'test' is an additional function that can be used when the inode
171number is not sufficient to identify the actual file object. 'set'
172should be a non-blocking function that initializes those parts of a
173newly created inode to allow the test function to succeed. 'data' is
174passed as an opaque value to both test and set functions.
175
176When the inode has been created by iget5_locked(), it will be returned with
177the I_NEW flag set and will still be locked. read_inode has not been
178called so the file system still has to finalize the initialization. Once
179the inode is initialized it must be unlocked by calling unlock_new_inode().
180
181The filesystem is responsible for setting (and possibly testing) i_ino
182when appropriate. There is also a simpler iget_locked function that
183just takes the superblock and inode number as arguments and does the
184test and set for you.
185
186e.g.
187 inode = iget_locked(sb, ino);
188 if (inode->i_state & I_NEW) {
189 read_inode_from_disk(inode);
190 unlock_new_inode(inode);
191 }
192
193---
194[recommended]
195
196->getattr() finally getting used. See instances in nfs, minix, etc.
197
198---
199[mandatory]
200
201->revalidate() is gone. If your filesystem had it - provide ->getattr()
202and let it call whatever you had as ->revlidate() + (for symlinks that
203had ->revalidate()) add calls in ->follow_link()/->readlink().
204
205---
206[mandatory]
207
208->d_parent changes are not protected by BKL anymore. Read access is safe
209if at least one of the following is true:
210 * filesystem has no cross-directory rename()
211 * dcache_lock is held
212 * we know that parent had been locked (e.g. we are looking at
213->d_parent of ->lookup() argument).
214 * we are called from ->rename().
215 * the child's ->d_lock is held
216Audit your code and add locking if needed. Notice that any place that is
217not protected by the conditions above is risky even in the old tree - you
218had been relying on BKL and that's prone to screwups. Old tree had quite
219a few holes of that kind - unprotected access to ->d_parent leading to
220anything from oops to silent memory corruption.
221
222---
223[mandatory]
224
225 FS_NOMOUNT is gone. If you use it - just set MS_NOUSER in flags
226(see rootfs for one kind of solution and bdev/socket/pipe for another).
227
228---
229[recommended]
230
231 Use bdev_read_only(bdev) instead of is_read_only(kdev). The latter
232is still alive, but only because of the mess in drivers/s390/block/dasd.c.
233As soon as it gets fixed is_read_only() will die.
234
235---
236[mandatory]
237
238->permission() is called without BKL now. Grab it on entry, drop upon
239return - that will guarantee the same locking you used to have. If
240your method or its parts do not need BKL - better yet, now you can
241shift lock_kernel() and unlock_kernel() so that they would protect
242exactly what needs to be protected.
243
244---
245[mandatory]
246
247->statfs() is now called without BKL held. BKL should have been
248shifted into individual fs sb_op functions where it's not clear that
249it's safe to remove it. If you don't need it, remove it.
250
251---
252[mandatory]
253
254 is_read_only() is gone; use bdev_read_only() instead.
255
256---
257[mandatory]
258
259 destroy_buffers() is gone; use invalidate_bdev().
260
261---
262[mandatory]
263
264 fsync_dev() is gone; use fsync_bdev(). NOTE: lvm breakage is
265deliberate; as soon as struct block_device * is propagated in a reasonable
266way by that code fixing will become trivial; until then nothing can be
267done.