Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | Changes since 2.5.0: |
| 2 | |
Oliver Pinter | 3eb43f6 | 2008-02-03 17:59:17 +0200 | [diff] [blame] | 3 | --- |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 4 | [recommended] |
| 5 | |
| 6 | New helpers: sb_bread(), sb_getblk(), sb_find_get_block(), set_bh(), |
| 7 | sb_set_blocksize() and sb_min_blocksize(). |
| 8 | |
| 9 | Use them. |
| 10 | |
| 11 | (sb_find_get_block() replaces 2.4's get_hash_table()) |
| 12 | |
Oliver Pinter | 3eb43f6 | 2008-02-03 17:59:17 +0200 | [diff] [blame] | 13 | --- |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 14 | [recommended] |
| 15 | |
| 16 | New methods: ->alloc_inode() and ->destroy_inode(). |
| 17 | |
| 18 | Remove inode->u.foo_inode_i |
| 19 | Declare |
| 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 | |
| 29 | Use FOO_I(inode) instead of &inode->u.foo_inode_i; |
| 30 | |
Oliver Pinter | 3eb43f6 | 2008-02-03 17:59:17 +0200 | [diff] [blame] | 31 | Add foo_alloc_inode() and foo_destroy_inode() - the former should allocate |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 32 | foo_inode_info and return the address of ->vfs_inode, the latter should free |
| 33 | FOO_I(inode) (see in-tree filesystems for examples). |
| 34 | |
| 35 | Make them ->alloc_inode and ->destroy_inode in your super_operations. |
| 36 | |
David Howells | 12debc4 | 2008-02-07 00:15:52 -0800 | [diff] [blame] | 37 | Keep in mind that now you need explicit initialization of private data |
| 38 | typically between calling iget_locked() and unlocking the inode. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 39 | |
| 40 | At some point that will become mandatory. |
| 41 | |
| 42 | --- |
| 43 | [mandatory] |
| 44 | |
| 45 | Change 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 | |
| 49 | Turn your foo_read_super() into a function that would return 0 in case of |
| 50 | success and negative number in case of error (-EINVAL unless you have more |
| 51 | informative error value to report). Call it foo_fill_super(). Now declare |
| 52 | |
David Howells | 454e239 | 2006-06-23 02:02:57 -0700 | [diff] [blame] | 53 | int foo_get_sb(struct file_system_type *fs_type, |
| 54 | int flags, const char *dev_name, void *data, struct vfsmount *mnt) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 55 | { |
David Howells | 454e239 | 2006-06-23 02:02:57 -0700 | [diff] [blame] | 56 | return get_sb_bdev(fs_type, flags, dev_name, data, foo_fill_super, |
| 57 | mnt); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 58 | } |
| 59 | |
| 60 | (or similar with s/bdev/nodev/ or s/bdev/single/, depending on the kind of |
| 61 | filesystem). |
| 62 | |
| 63 | Replace DECLARE_FSTYPE... with explicit initializer and have ->get_sb set as |
| 64 | foo_get_sb. |
| 65 | |
| 66 | --- |
| 67 | [mandatory] |
| 68 | |
| 69 | Locking change: ->s_vfs_rename_sem is taken only by cross-directory renames. |
| 70 | Most likely there is no need to change anything, but if you relied on |
| 71 | global exclusion between renames for some internal purpose - you need to |
| 72 | change your internal locking. Otherwise exclusion warranties remain the |
| 73 | same (i.e. parents and victim are locked, etc.). |
| 74 | |
| 75 | --- |
| 76 | [informational] |
| 77 | |
| 78 | Now we have the exclusion between ->lookup() and directory removal (by |
| 79 | ->rmdir() and ->rename()). If you used to need that exclusion and do |
| 80 | it by internal locking (most of filesystems couldn't care less) - you |
| 81 | can relax your locking. |
| 82 | |
| 83 | --- |
| 84 | [mandatory] |
| 85 | |
| 86 | ->lookup(), ->truncate(), ->create(), ->unlink(), ->mknod(), ->mkdir(), |
| 87 | ->rmdir(), ->link(), ->lseek(), ->symlink(), ->rename() |
| 88 | and ->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 |
| 90 | parts do not need BKL - better yet, now you can shift lock_kernel() and |
| 91 | unlock_kernel() so that they would protect exactly what needs to be |
| 92 | protected. |
| 93 | |
| 94 | --- |
| 95 | [mandatory] |
| 96 | |
Artem Bityutskiy | 34e5053 | 2012-07-25 18:12:00 +0300 | [diff] [blame] | 97 | BKL is also moved from around sb operations. BKL should have been shifted into |
| 98 | individual fs sb_op functions. If you don't need it, remove it. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 99 | |
| 100 | --- |
| 101 | [informational] |
| 102 | |
| 103 | check for ->link() target not being a directory is done by callers. Feel |
| 104 | free to drop it... |
| 105 | |
| 106 | --- |
| 107 | [informational] |
| 108 | |
Josef 'Jeff' Sipek | c2b3898 | 2007-05-24 12:21:43 -0400 | [diff] [blame] | 109 | ->link() callers hold ->i_mutex on the object we are linking to. Some of your |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 110 | problems might be over... |
| 111 | |
| 112 | --- |
| 113 | [mandatory] |
| 114 | |
| 115 | new file_system_type method - kill_sb(superblock). If you are converting |
| 116 | an 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 |
| 120 | FS_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() |
| 126 | went 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 | |
Josef 'Jeff' Sipek | c2b3898 | 2007-05-24 12:21:43 -0400 | [diff] [blame] | 132 | ->setattr() is called without BKL now. Caller _always_ holds ->i_mutex, so |
| 133 | watch for ->i_mutex-grabbing code that might be used by your ->setattr(). |
| 134 | Callers of notify_change() need ->i_mutex now. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 135 | |
| 136 | --- |
| 137 | [recommended] |
| 138 | |
| 139 | New super_block field "struct export_operations *s_export_op" for |
| 140 | explicit support for exporting, e.g. via NFS. The structure is fully |
| 141 | documented at its declaration in include/linux/fs.h, and in |
J. Bruce Fields | dc7a081 | 2009-10-27 14:41:35 -0400 | [diff] [blame] | 142 | Documentation/filesystems/nfs/Exporting. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 143 | |
| 144 | Briefly it allows for the definition of decode_fh and encode_fh operations |
| 145 | to encode and decode filehandles, and allows the filesystem to use |
| 146 | a standard helper function for decode_fh, and provide file-system specific |
| 147 | support for this helper, particularly get_parent. |
| 148 | |
| 149 | It is planned that this will be required for exporting once the code |
| 150 | settles down a bit. |
| 151 | |
| 152 | [mandatory] |
| 153 | |
| 154 | s_export_op is now required for exporting a filesystem. |
| 155 | isofs, ext2, ext3, resierfs, fat |
| 156 | can be used as examples of very different filesystems. |
| 157 | |
| 158 | --- |
| 159 | [mandatory] |
| 160 | |
| 161 | iget4() and the read_inode2 callback have been superseded by iget5_locked() |
| 162 | which 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 |
| 170 | number is not sufficient to identify the actual file object. 'set' |
| 171 | should be a non-blocking function that initializes those parts of a |
| 172 | newly created inode to allow the test function to succeed. 'data' is |
| 173 | passed as an opaque value to both test and set functions. |
| 174 | |
David Howells | 12debc4 | 2008-02-07 00:15:52 -0800 | [diff] [blame] | 175 | When the inode has been created by iget5_locked(), it will be returned with the |
| 176 | I_NEW flag set and will still be locked. The filesystem then needs to finalize |
| 177 | the initialization. Once the inode is initialized it must be unlocked by |
| 178 | calling unlock_new_inode(). |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 179 | |
| 180 | The filesystem is responsible for setting (and possibly testing) i_ino |
| 181 | when appropriate. There is also a simpler iget_locked function that |
| 182 | just takes the superblock and inode number as arguments and does the |
| 183 | test and set for you. |
| 184 | |
| 185 | e.g. |
David Howells | b46980f | 2008-02-07 00:15:27 -0800 | [diff] [blame] | 186 | inode = iget_locked(sb, ino); |
| 187 | if (inode->i_state & I_NEW) { |
| 188 | err = read_inode_from_disk(inode); |
| 189 | if (err < 0) { |
| 190 | iget_failed(inode); |
| 191 | return err; |
| 192 | } |
| 193 | unlock_new_inode(inode); |
| 194 | } |
| 195 | |
| 196 | Note that if the process of setting up a new inode fails, then iget_failed() |
| 197 | should be called on the inode to render it dead, and an appropriate error |
| 198 | should be passed back to the caller. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 199 | |
| 200 | --- |
| 201 | [recommended] |
| 202 | |
| 203 | ->getattr() finally getting used. See instances in nfs, minix, etc. |
| 204 | |
| 205 | --- |
| 206 | [mandatory] |
| 207 | |
| 208 | ->revalidate() is gone. If your filesystem had it - provide ->getattr() |
| 209 | and let it call whatever you had as ->revlidate() + (for symlinks that |
| 210 | had ->revalidate()) add calls in ->follow_link()/->readlink(). |
| 211 | |
| 212 | --- |
| 213 | [mandatory] |
| 214 | |
| 215 | ->d_parent changes are not protected by BKL anymore. Read access is safe |
| 216 | if at least one of the following is true: |
| 217 | * filesystem has no cross-directory rename() |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 218 | * we know that parent had been locked (e.g. we are looking at |
| 219 | ->d_parent of ->lookup() argument). |
| 220 | * we are called from ->rename(). |
| 221 | * the child's ->d_lock is held |
| 222 | Audit your code and add locking if needed. Notice that any place that is |
| 223 | not protected by the conditions above is risky even in the old tree - you |
| 224 | had been relying on BKL and that's prone to screwups. Old tree had quite |
| 225 | a few holes of that kind - unprotected access to ->d_parent leading to |
| 226 | anything from oops to silent memory corruption. |
| 227 | |
| 228 | --- |
| 229 | [mandatory] |
| 230 | |
| 231 | FS_NOMOUNT is gone. If you use it - just set MS_NOUSER in flags |
| 232 | (see rootfs for one kind of solution and bdev/socket/pipe for another). |
| 233 | |
| 234 | --- |
| 235 | [recommended] |
| 236 | |
| 237 | Use bdev_read_only(bdev) instead of is_read_only(kdev). The latter |
| 238 | is still alive, but only because of the mess in drivers/s390/block/dasd.c. |
| 239 | As soon as it gets fixed is_read_only() will die. |
| 240 | |
| 241 | --- |
| 242 | [mandatory] |
| 243 | |
| 244 | ->permission() is called without BKL now. Grab it on entry, drop upon |
| 245 | return - that will guarantee the same locking you used to have. If |
| 246 | your method or its parts do not need BKL - better yet, now you can |
| 247 | shift lock_kernel() and unlock_kernel() so that they would protect |
| 248 | exactly what needs to be protected. |
| 249 | |
| 250 | --- |
| 251 | [mandatory] |
| 252 | |
| 253 | ->statfs() is now called without BKL held. BKL should have been |
| 254 | shifted into individual fs sb_op functions where it's not clear that |
| 255 | it's safe to remove it. If you don't need it, remove it. |
| 256 | |
| 257 | --- |
| 258 | [mandatory] |
| 259 | |
| 260 | is_read_only() is gone; use bdev_read_only() instead. |
| 261 | |
| 262 | --- |
| 263 | [mandatory] |
| 264 | |
| 265 | destroy_buffers() is gone; use invalidate_bdev(). |
| 266 | |
| 267 | --- |
| 268 | [mandatory] |
| 269 | |
| 270 | fsync_dev() is gone; use fsync_bdev(). NOTE: lvm breakage is |
| 271 | deliberate; as soon as struct block_device * is propagated in a reasonable |
| 272 | way by that code fixing will become trivial; until then nothing can be |
| 273 | done. |
Christoph Hellwig | 1e23173 | 2010-06-07 09:29:20 +0200 | [diff] [blame] | 274 | |
| 275 | [mandatory] |
| 276 | |
| 277 | block truncatation on error exit from ->write_begin, and ->direct_IO |
| 278 | moved from generic methods (block_write_begin, cont_write_begin, |
| 279 | nobh_write_begin, blockdev_direct_IO*) to callers. Take a look at |
| 280 | ext2_write_failed and callers for an example. |
| 281 | |
| 282 | [mandatory] |
| 283 | |
Marco Stornelli | b9f61c3 | 2012-12-15 12:00:38 +0100 | [diff] [blame] | 284 | ->truncate is gone. The whole truncate sequence needs to be |
Christoph Hellwig | 1e23173 | 2010-06-07 09:29:20 +0200 | [diff] [blame] | 285 | implemented in ->setattr, which is now mandatory for filesystems |
| 286 | implementing on-disk size changes. Start with a copy of the old inode_setattr |
| 287 | and vmtruncate, and the reorder the vmtruncate + foofs_vmtruncate sequence to |
| 288 | be in order of zeroing blocks using block_truncate_page or similar helpers, |
| 289 | size update and on finally on-disk truncation which should not fail. |
Jan Kara | 31051c8 | 2016-05-26 16:55:18 +0200 | [diff] [blame] | 290 | setattr_prepare (which used to be inode_change_ok) now includes the size checks |
| 291 | for ATTR_SIZE and must be called in the beginning of ->setattr unconditionally. |
Al Viro | 336fb3b | 2010-06-08 00:37:12 -0400 | [diff] [blame] | 292 | |
| 293 | [mandatory] |
| 294 | |
| 295 | ->clear_inode() and ->delete_inode() are gone; ->evict_inode() should |
| 296 | be used instead. It gets called whenever the inode is evicted, whether it has |
| 297 | remaining links or not. Caller does *not* evict the pagecache or inode-associated |
Johannes Weiner | 91b0abe | 2014-04-03 14:47:49 -0700 | [diff] [blame] | 298 | metadata buffers; the method has to use truncate_inode_pages_final() to get rid |
| 299 | of those. Caller makes sure async writeback cannot be running for the inode while |
| 300 | (or after) ->evict_inode() is called. |
Dave Chinner | f283c86 | 2011-03-22 22:23:39 +1100 | [diff] [blame] | 301 | |
| 302 | ->drop_inode() returns int now; it's called on final iput() with |
| 303 | inode->i_lock held and it returns true if filesystems wants the inode to be |
| 304 | dropped. As before, generic_drop_inode() is still the default and it's been |
| 305 | updated appropriately. generic_delete_inode() is also alive and it consists |
| 306 | simply of return 1. Note that all actual eviction work is done by caller after |
| 307 | ->drop_inode() returns. |
| 308 | |
Jan Kara | dbd5768 | 2012-05-03 14:48:02 +0200 | [diff] [blame] | 309 | As before, clear_inode() must be called exactly once on each call of |
| 310 | ->evict_inode() (as it used to be for each call of ->delete_inode()). Unlike |
| 311 | before, if you are using inode-associated metadata buffers (i.e. |
| 312 | mark_buffer_dirty_inode()), it's your responsibility to call |
| 313 | invalidate_inode_buffers() before clear_inode(). |
Al Viro | 336fb3b | 2010-06-08 00:37:12 -0400 | [diff] [blame] | 314 | |
| 315 | NOTE: checking i_nlink in the beginning of ->write_inode() and bailing out |
| 316 | if it's zero is not *and* *never* *had* *been* enough. Final unlink() and iput() |
| 317 | may happen while the inode is in the middle of ->write_inode(); e.g. if you blindly |
| 318 | free the on-disk inode, you may end up doing that while ->write_inode() is writing |
| 319 | to it. |
Nick Piggin | fe15ce4 | 2011-01-07 17:49:23 +1100 | [diff] [blame] | 320 | |
| 321 | --- |
| 322 | [mandatory] |
| 323 | |
| 324 | .d_delete() now only advises the dcache as to whether or not to cache |
| 325 | unreferenced dentries, and is now only called when the dentry refcount goes to |
| 326 | 0. Even on 0 refcount transition, it must be able to tolerate being called 0, |
| 327 | 1, or more times (eg. constant, idempotent). |
Nick Piggin | 621e155 | 2011-01-07 17:49:27 +1100 | [diff] [blame] | 328 | |
| 329 | --- |
| 330 | [mandatory] |
| 331 | |
| 332 | .d_compare() calling convention and locking rules are significantly |
| 333 | changed. Read updated documentation in Documentation/filesystems/vfs.txt (and |
| 334 | look at examples of other filesystems) for guidance. |
Nick Piggin | b1e6a01 | 2011-01-07 17:49:28 +1100 | [diff] [blame] | 335 | |
| 336 | --- |
| 337 | [mandatory] |
| 338 | |
| 339 | .d_hash() calling convention and locking rules are significantly |
| 340 | changed. Read updated documentation in Documentation/filesystems/vfs.txt (and |
| 341 | look at examples of other filesystems) for guidance. |
Nick Piggin | b5c84bf | 2011-01-07 17:49:38 +1100 | [diff] [blame] | 342 | |
| 343 | --- |
| 344 | [mandatory] |
| 345 | dcache_lock is gone, replaced by fine grained locks. See fs/dcache.c |
| 346 | for details of what locks to replace dcache_lock with in order to protect |
| 347 | particular things. Most of the time, a filesystem only needs ->d_lock, which |
| 348 | protects *all* the dcache state of a given dentry. |
Nick Piggin | fa0d7e3d | 2011-01-07 17:49:49 +1100 | [diff] [blame] | 349 | |
| 350 | -- |
| 351 | [mandatory] |
| 352 | |
| 353 | Filesystems must RCU-free their inodes, if they can have been accessed |
| 354 | via rcu-walk path walk (basically, if the file can have had a path name in the |
| 355 | vfs namespace). |
| 356 | |
Al Viro | 049b3c1 | 2012-06-09 11:55:20 -0400 | [diff] [blame] | 357 | Even though i_dentry and i_rcu share storage in a union, we will |
| 358 | initialize the former in inode_init_always(), so just leave it alone in |
| 359 | the callback. It used to be necessary to clean it there, but not anymore |
| 360 | (starting at 3.2). |
Nick Piggin | 34286d6 | 2011-01-07 17:49:57 +1100 | [diff] [blame] | 361 | |
| 362 | -- |
| 363 | [recommended] |
| 364 | vfs now tries to do path walking in "rcu-walk mode", which avoids |
| 365 | atomic operations and scalability hazards on dentries and inodes (see |
Nick Piggin | a82416d | 2011-01-14 02:26:53 +0000 | [diff] [blame] | 366 | Documentation/filesystems/path-lookup.txt). d_hash and d_compare changes |
| 367 | (above) are examples of the changes required to support this. For more complex |
Nick Piggin | 34286d6 | 2011-01-07 17:49:57 +1100 | [diff] [blame] | 368 | filesystem callbacks, the vfs drops out of rcu-walk mode before the fs call, so |
| 369 | no changes are required to the filesystem. However, this is costly and loses |
| 370 | the benefits of rcu-walk mode. We will begin to add filesystem callbacks that |
| 371 | are rcu-walk aware, shown below. Filesystems should take advantage of this |
| 372 | where possible. |
| 373 | |
| 374 | -- |
| 375 | [mandatory] |
| 376 | d_revalidate is a callback that is made on every path element (if |
| 377 | the filesystem provides it), which requires dropping out of rcu-walk mode. This |
| 378 | may now be called in rcu-walk mode (nd->flags & LOOKUP_RCU). -ECHILD should be |
| 379 | returned if the filesystem cannot handle rcu-walk. See |
| 380 | Documentation/filesystems/vfs.txt for more details. |
Nick Piggin | b74c79e | 2011-01-07 17:49:58 +1100 | [diff] [blame] | 381 | |
Andreas Gruenbacher | 4701607 | 2015-06-05 01:11:22 +0200 | [diff] [blame] | 382 | permission is an inode permission check that is called on many or all |
| 383 | directory inodes on the way down a path walk (to check for exec permission). It |
| 384 | must now be rcu-walk aware (mask & MAY_NOT_BLOCK). See |
| 385 | Documentation/filesystems/vfs.txt for more details. |
Josef Bacik | 9242415 | 2011-01-05 15:00:07 -0500 | [diff] [blame] | 386 | |
| 387 | -- |
| 388 | [mandatory] |
| 389 | In ->fallocate() you must check the mode option passed in. If your |
| 390 | filesystem does not support hole punching (deallocating space in the middle of a |
| 391 | file) you must return -EOPNOTSUPP if FALLOC_FL_PUNCH_HOLE is set in mode. |
| 392 | Currently you can only have FALLOC_FL_PUNCH_HOLE with FALLOC_FL_KEEP_SIZE set, |
| 393 | so the i_size should not change when hole punching, even when puching the end of |
| 394 | a file off. |
Al Viro | 1a102ff | 2011-03-16 09:07:58 -0400 | [diff] [blame] | 395 | |
| 396 | -- |
| 397 | [mandatory] |
| 398 | ->get_sb() is gone. Switch to use of ->mount(). Typically it's just |
| 399 | a matter of switching from calling get_sb_... to mount_... and changing the |
| 400 | function type. If you were doing it manually, just switch from setting ->mnt_root |
| 401 | to some pointer to returning that pointer. On errors return ERR_PTR(...). |
Al Viro | 76fe327 | 2011-06-20 21:56:31 -0400 | [diff] [blame] | 402 | |
| 403 | -- |
| 404 | [mandatory] |
Christoph Hellwig | 4e34e71 | 2011-07-23 17:37:31 +0200 | [diff] [blame] | 405 | ->permission() and generic_permission()have lost flags |
Al Viro | 76fe327 | 2011-06-20 21:56:31 -0400 | [diff] [blame] | 406 | argument; instead of passing IPERM_FLAG_RCU we add MAY_NOT_BLOCK into mask. |
Christoph Hellwig | 4e34e71 | 2011-07-23 17:37:31 +0200 | [diff] [blame] | 407 | generic_permission() has also lost the check_acl argument; ACL checking |
| 408 | has been taken to VFS and filesystems need to provide a non-NULL ->i_op->get_acl |
| 409 | to read an ACL from disk. |
Josef Bacik | 982d816 | 2011-07-18 13:21:35 -0400 | [diff] [blame] | 410 | |
| 411 | -- |
| 412 | [mandatory] |
| 413 | If you implement your own ->llseek() you must handle SEEK_HOLE and |
| 414 | SEEK_DATA. You can hanle this by returning -EINVAL, but it would be nicer to |
| 415 | support it in some way. The generic handler assumes that the entire file is |
| 416 | data and there is a virtual hole at the end of the file. So if the provided |
| 417 | offset is less than i_size and SEEK_DATA is specified, return the same offset. |
| 418 | If the above is true for the offset and you are given SEEK_HOLE, return the end |
| 419 | of the file. If the offset is i_size or greater return -ENXIO in either case. |
Josef Bacik | 02c24a8 | 2011-07-16 20:44:56 -0400 | [diff] [blame] | 420 | |
| 421 | [mandatory] |
| 422 | If you have your own ->fsync() you must make sure to call |
| 423 | filemap_write_and_wait_range() so that all dirty pages are synced out properly. |
| 424 | You must also keep in mind that ->fsync() is not called with i_mutex held |
| 425 | anymore, so if you require i_mutex locking you must make sure to take it and |
| 426 | release it yourself. |
Al Viro | 32991ab | 2012-02-12 22:15:47 -0500 | [diff] [blame] | 427 | |
| 428 | -- |
| 429 | [mandatory] |
| 430 | d_alloc_root() is gone, along with a lot of bugs caused by code |
| 431 | misusing it. Replacement: d_make_root(inode). The difference is, |
| 432 | d_make_root() drops the reference to inode if dentry allocation fails. |
Al Viro | 0b728e1 | 2012-06-10 16:03:43 -0400 | [diff] [blame] | 433 | |
| 434 | -- |
| 435 | [mandatory] |
Al Viro | 00cd8dd | 2012-06-10 17:13:09 -0400 | [diff] [blame] | 436 | The witch is dead! Well, 2/3 of it, anyway. ->d_revalidate() and |
| 437 | ->lookup() do *not* take struct nameidata anymore; just the flags. |
Al Viro | ebfc3b4 | 2012-06-10 18:05:36 -0400 | [diff] [blame] | 438 | -- |
| 439 | [mandatory] |
| 440 | ->create() doesn't take struct nameidata *; unlike the previous |
| 441 | two, it gets "is it an O_EXCL or equivalent?" boolean argument. Note that |
| 442 | local filesystems can ignore tha argument - they are guaranteed that the |
| 443 | object doesn't exist. It's remote/distributed ones that might care... |
Jeff Layton | ecf3d1f | 2013-02-20 11:19:05 -0500 | [diff] [blame] | 444 | -- |
| 445 | [mandatory] |
| 446 | FS_REVAL_DOT is gone; if you used to have it, add ->d_weak_revalidate() |
| 447 | in your dentry operations instead. |
Al Viro | 5c0ba4e | 2013-05-15 13:52:59 -0400 | [diff] [blame] | 448 | -- |
| 449 | [mandatory] |
| 450 | vfs_readdir() is gone; switch to iterate_dir() instead |
Al Viro | 2233f31 | 2013-05-22 21:44:23 -0400 | [diff] [blame] | 451 | -- |
| 452 | [mandatory] |
| 453 | ->readdir() is gone now; switch to ->iterate() |
Christoph Hellwig | 4aa3289 | 2013-09-09 07:16:41 -0700 | [diff] [blame] | 454 | [mandatory] |
| 455 | vfs_follow_link has been removed. Filesystems must use nd_set_link |
| 456 | from ->follow_link for normal symlinks, or nd_jump_link for magic |
| 457 | /proc/<pid> style links. |
Al Viro | 5a3cd9928 | 2013-11-06 09:54:52 -0500 | [diff] [blame] | 458 | -- |
| 459 | [mandatory] |
| 460 | iget5_locked()/ilookup5()/ilookup5_nowait() test() callback used to be |
| 461 | called with both ->i_lock and inode_hash_lock held; the former is *not* |
| 462 | taken anymore, so verify that your callbacks do not rely on it (none |
| 463 | of the in-tree instances did). inode_hash_lock is still held, |
| 464 | of course, so they are still serialized wrt removal from inode hash, |
| 465 | as well as wrt set() callback of iget5_locked(). |
Al Viro | 41d28bc | 2014-10-12 22:24:21 -0400 | [diff] [blame] | 466 | -- |
| 467 | [mandatory] |
| 468 | d_materialise_unique() is gone; d_splice_alias() does everything you |
| 469 | need now. Remember that they have opposite orders of arguments ;-/ |
Al Viro | 78d28e6 | 2014-10-31 01:22:04 -0400 | [diff] [blame] | 470 | -- |
| 471 | [mandatory] |
| 472 | f_dentry is gone; use f_path.dentry, or, better yet, see if you can avoid |
| 473 | it entirely. |
Al Viro | 5d5d568 | 2015-04-03 15:41:18 -0400 | [diff] [blame] | 474 | -- |
| 475 | [mandatory] |
| 476 | never call ->read() and ->write() directly; use __vfs_{read,write} or |
| 477 | wrappers; instead of checking for ->write or ->read being NULL, look for |
| 478 | FMODE_CAN_{WRITE,READ} in file->f_mode. |
| 479 | -- |
| 480 | [mandatory] |
| 481 | do _not_ use new_sync_{read,write} for ->read/->write; leave it NULL |
| 482 | instead. |
Al Viro | 8436318 | 2015-04-04 01:14:53 -0400 | [diff] [blame] | 483 | -- |
| 484 | [mandatory] |
| 485 | ->aio_read/->aio_write are gone. Use ->read_iter/->write_iter. |
Al Viro | 203bc64 | 2015-05-11 08:29:30 -0400 | [diff] [blame] | 486 | --- |
| 487 | [recommended] |
| 488 | for embedded ("fast") symlinks just set inode->i_link to wherever the |
| 489 | symlink body is and use simple_follow_link() as ->follow_link(). |
| 490 | -- |
| 491 | [mandatory] |
| 492 | calling conventions for ->follow_link() have changed. Instead of returning |
| 493 | cookie and using nd_set_link() to store the body to traverse, we return |
| 494 | the body to traverse and store the cookie using explicit void ** argument. |
| 495 | nameidata isn't passed at all - nd_jump_link() doesn't need it and |
| 496 | nd_[gs]et_link() is gone. |
| 497 | -- |
| 498 | [mandatory] |
| 499 | calling conventions for ->put_link() have changed. It gets inode instead of |
| 500 | dentry, it does not get nameidata at all and it gets called only when cookie |
| 501 | is non-NULL. Note that link body isn't available anymore, so if you need it, |
| 502 | store it as cookie. |
Eric Dumazet | 8a81252 | 2015-06-30 15:54:08 +0200 | [diff] [blame] | 503 | -- |
| 504 | [mandatory] |
| 505 | __fd_install() & fd_install() can now sleep. Callers should not |
| 506 | hold a spinlock or other resources that do not allow a schedule. |
Al Viro | 21fc61c | 2015-11-17 01:07:57 -0500 | [diff] [blame] | 507 | -- |
| 508 | [mandatory] |
| 509 | any symlink that might use page_follow_link_light/page_put_link() must |
| 510 | have inode_nohighmem(inode) called before anything might start playing with |
Al Viro | e8ecde2 | 2016-01-14 17:52:59 -0500 | [diff] [blame] | 511 | its pagecache. No highmem pages should end up in the pagecache of such |
| 512 | symlinks. That includes any preseeding that might be done during symlink |
| 513 | creation. __page_symlink() will honour the mapping gfp flags, so once |
| 514 | you've done inode_nohighmem() it's safe to use, but if you allocate and |
| 515 | insert the page manually, make sure to use the right gfp flags. |
Al Viro | 6b25539 | 2015-11-17 10:20:54 -0500 | [diff] [blame] | 516 | -- |
| 517 | [mandatory] |
| 518 | ->follow_link() is replaced with ->get_link(); same API, except that |
| 519 | * ->get_link() gets inode as a separate argument |
| 520 | * ->get_link() may be called in RCU mode - in that case NULL |
| 521 | dentry is passed |
Al Viro | fceef39 | 2015-12-29 15:58:39 -0500 | [diff] [blame] | 522 | -- |
| 523 | [mandatory] |
| 524 | ->get_link() gets struct delayed_call *done now, and should do |
| 525 | set_delayed_call() where it used to set *cookie. |
| 526 | ->put_link() is gone - just give the destructor to set_delayed_call() |
| 527 | in ->get_link(). |
Al Viro | ce23e64 | 2016-04-11 00:48:00 -0400 | [diff] [blame] | 528 | -- |
| 529 | [mandatory] |
| 530 | ->getxattr() and xattr_handler.get() get dentry and inode passed separately. |
| 531 | dentry might be yet to be attached to inode, so do _not_ use its ->d_inode |
| 532 | in the instances. Rationale: !@#!@# security_d_instantiate() needs to be |
| 533 | called before we attach dentry to inode. |
Al Viro | 84e710d | 2016-04-15 00:58:55 -0400 | [diff] [blame] | 534 | -- |
| 535 | [mandatory] |
| 536 | symlinks are no longer the only inodes that do *not* have i_bdev/i_cdev/ |
| 537 | i_pipe/i_link union zeroed out at inode eviction. As the result, you can't |
| 538 | assume that non-NULL value in ->i_nlink at ->destroy_inode() implies that |
| 539 | it's a symlink. Checking ->i_mode is really needed now. In-tree we had |
| 540 | to fix shmem_destroy_callback() that used to take that kind of shortcut; |
| 541 | watch out, since that shortcut is no longer valid. |
Al Viro | 9902af7 | 2016-04-15 15:08:36 -0400 | [diff] [blame] | 542 | -- |
| 543 | [mandatory] |
| 544 | ->i_mutex is replaced with ->i_rwsem now. inode_lock() et.al. work as |
| 545 | they used to - they just take it exclusive. However, ->lookup() may be |
| 546 | called with parent locked shared. Its instances must not |
| 547 | * use d_instantiate) and d_rehash() separately - use d_add() or |
| 548 | d_splice_alias() instead. |
| 549 | * use d_rehash() alone - call d_add(new_dentry, NULL) instead. |
| 550 | * in the unlikely case when (read-only) access to filesystem |
| 551 | data structures needs exclusion for some reason, arrange it |
| 552 | yourself. None of the in-tree filesystems needed that. |
| 553 | * rely on ->d_parent and ->d_name not changing after dentry has |
| 554 | been fed to d_add() or d_splice_alias(). Again, none of the |
| 555 | in-tree instances relied upon that. |
| 556 | We are guaranteed that lookups of the same name in the same directory |
| 557 | will not happen in parallel ("same" in the sense of your ->d_compare()). |
| 558 | Lookups on different names in the same directory can and do happen in |
| 559 | parallel now. |
Al Viro | 6192269 | 2016-04-20 23:08:32 -0400 | [diff] [blame] | 560 | -- |
| 561 | [recommended] |
| 562 | ->iterate_shared() is added; it's a parallel variant of ->iterate(). |
| 563 | Exclusion on struct file level is still provided (as well as that |
| 564 | between it and lseek on the same struct file), but if your directory |
| 565 | has been opened several times, you can get these called in parallel. |
| 566 | Exclusion between that method and all directory-modifying ones is |
| 567 | still provided, of course. |
| 568 | |
| 569 | Often enough ->iterate() can serve as ->iterate_shared() without any |
| 570 | changes - it is a read-only operation, after all. If you have any |
| 571 | per-inode or per-dentry in-core data structures modified by ->iterate(), |
| 572 | you might need something to serialize the access to them. If you |
| 573 | do dcache pre-seeding, you'll need to switch to d_alloc_parallel() for |
| 574 | that; look for in-tree examples. |
| 575 | |
| 576 | Old method is only used if the new one is absent; eventually it will |
| 577 | be removed. Switch while you still can; the old one won't stay. |
Al Viro | 9cf843e | 2016-04-28 19:35:16 -0400 | [diff] [blame] | 578 | -- |
| 579 | [mandatory] |
| 580 | ->atomic_open() calls without O_CREAT may happen in parallel. |
Al Viro | 3767e25 | 2016-05-27 11:06:05 -0400 | [diff] [blame] | 581 | -- |
| 582 | [mandatory] |
| 583 | ->setxattr() and xattr_handler.set() get dentry and inode passed separately. |
| 584 | dentry might be yet to be attached to inode, so do _not_ use its ->d_inode |
| 585 | in the instances. Rationale: !@#!@# security_d_instantiate() needs to be |
| 586 | called before we attach dentry to inode and !@#!@##!@$!$#!@#$!@$!@$ smack |
| 587 | ->d_instantiate() uses not just ->getxattr() but ->setxattr() as well. |
Al Viro | 6fa67e7 | 2016-07-31 16:37:25 -0400 | [diff] [blame] | 588 | -- |
| 589 | [mandatory] |
| 590 | ->d_compare() doesn't get parent as a separate argument anymore. If you |
| 591 | used it for finding the struct super_block involved, dentry->d_sb will |
| 592 | work just as well; if it's something more complicated, use dentry->d_parent. |
| 593 | Just be careful not to assume that fetching it more than once will yield |
| 594 | the same value - in RCU mode it could change under you. |
Miklos Szeredi | aadfa80 | 2016-09-27 11:03:58 +0200 | [diff] [blame] | 595 | -- |
| 596 | [mandatory] |
| 597 | ->rename() has an added flags argument. Any flags not handled by the |
| 598 | filesystem should result in EINVAL being returned. |