Based on kernel version 2.6.26. Page generated on 2008-07-16 21:12 EST.
1 Changes since 2.5.0: 2 3 --- 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 13 --- 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 31 Add foo_alloc_inode() and foo_destroy_inode() - the former should allocate 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 37 Keep in mind that now you need explicit initialization of private data 38 typically between calling iget_locked() and unlocking the inode. 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 53 int foo_get_sb(struct file_system_type *fs_type, 54 int flags, const char *dev_name, void *data, struct vfsmount *mnt) 55 { 56 return get_sb_bdev(fs_type, flags, dev_name, data, foo_fill_super, 57 mnt); 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 97 BKL is also moved from around sb operations. ->write_super() Is now called 98 without BKL held. BKL should have been shifted into individual fs sb_op 99 functions. If you don't need it, remove it. 100 101 --- 102 [informational] 103 104 check for ->link() target not being a directory is done by callers. Feel 105 free to drop it... 106 107 --- 108 [informational] 109 110 ->link() callers hold ->i_mutex on the object we are linking to. Some of your 111 problems might be over... 112 113 --- 114 [mandatory] 115 116 new file_system_type method - kill_sb(superblock). If you are converting 117 an 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 121 FS_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() 127 went 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] 132 133 ->setattr() is called without BKL now. Caller _always_ holds ->i_mutex, so 134 watch for ->i_mutex-grabbing code that might be used by your ->setattr(). 135 Callers of notify_change() need ->i_mutex now. 136 137 --- 138 [recommended] 139 140 New super_block field "struct export_operations *s_export_op" for 141 explicit support for exporting, e.g. via NFS. The structure is fully 142 documented at its declaration in include/linux/fs.h, and in 143 Documentation/filesystems/Exporting. 144 145 Briefly it allows for the definition of decode_fh and encode_fh operations 146 to encode and decode filehandles, and allows the filesystem to use 147 a standard helper function for decode_fh, and provide file-system specific 148 support for this helper, particularly get_parent. 149 150 It is planned that this will be required for exporting once the code 151 settles down a bit. 152 153 [mandatory] 154 155 s_export_op is now required for exporting a filesystem. 156 isofs, ext2, ext3, resierfs, fat 157 can be used as examples of very different filesystems. 158 159 --- 160 [mandatory] 161 162 iget4() and the read_inode2 callback have been superseded by iget5_locked() 163 which 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 171 number is not sufficient to identify the actual file object. 'set' 172 should be a non-blocking function that initializes those parts of a 173 newly created inode to allow the test function to succeed. 'data' is 174 passed as an opaque value to both test and set functions. 175 176 When the inode has been created by iget5_locked(), it will be returned with the 177 I_NEW flag set and will still be locked. The filesystem then needs to finalize 178 the initialization. Once the inode is initialized it must be unlocked by 179 calling unlock_new_inode(). 180 181 The filesystem is responsible for setting (and possibly testing) i_ino 182 when appropriate. There is also a simpler iget_locked function that 183 just takes the superblock and inode number as arguments and does the 184 test and set for you. 185 186 e.g. 187 inode = iget_locked(sb, ino); 188 if (inode->i_state & I_NEW) { 189 err = read_inode_from_disk(inode); 190 if (err < 0) { 191 iget_failed(inode); 192 return err; 193 } 194 unlock_new_inode(inode); 195 } 196 197 Note that if the process of setting up a new inode fails, then iget_failed() 198 should be called on the inode to render it dead, and an appropriate error 199 should be passed back to the caller. 200 201 --- 202 [recommended] 203 204 ->getattr() finally getting used. See instances in nfs, minix, etc. 205 206 --- 207 [mandatory] 208 209 ->revalidate() is gone. If your filesystem had it - provide ->getattr() 210 and let it call whatever you had as ->revlidate() + (for symlinks that 211 had ->revalidate()) add calls in ->follow_link()/->readlink(). 212 213 --- 214 [mandatory] 215 216 ->d_parent changes are not protected by BKL anymore. Read access is safe 217 if at least one of the following is true: 218 * filesystem has no cross-directory rename() 219 * dcache_lock is held 220 * we know that parent had been locked (e.g. we are looking at 221 ->d_parent of ->lookup() argument). 222 * we are called from ->rename(). 223 * the child's ->d_lock is held 224 Audit your code and add locking if needed. Notice that any place that is 225 not protected by the conditions above is risky even in the old tree - you 226 had been relying on BKL and that's prone to screwups. Old tree had quite 227 a few holes of that kind - unprotected access to ->d_parent leading to 228 anything from oops to silent memory corruption. 229 230 --- 231 [mandatory] 232 233 FS_NOMOUNT is gone. If you use it - just set MS_NOUSER in flags 234 (see rootfs for one kind of solution and bdev/socket/pipe for another). 235 236 --- 237 [recommended] 238 239 Use bdev_read_only(bdev) instead of is_read_only(kdev). The latter 240 is still alive, but only because of the mess in drivers/s390/block/dasd.c. 241 As soon as it gets fixed is_read_only() will die. 242 243 --- 244 [mandatory] 245 246 ->permission() is called without BKL now. Grab it on entry, drop upon 247 return - that will guarantee the same locking you used to have. If 248 your method or its parts do not need BKL - better yet, now you can 249 shift lock_kernel() and unlock_kernel() so that they would protect 250 exactly what needs to be protected. 251 252 --- 253 [mandatory] 254 255 ->statfs() is now called without BKL held. BKL should have been 256 shifted into individual fs sb_op functions where it's not clear that 257 it's safe to remove it. If you don't need it, remove it. 258 259 --- 260 [mandatory] 261 262 is_read_only() is gone; use bdev_read_only() instead. 263 264 --- 265 [mandatory] 266 267 destroy_buffers() is gone; use invalidate_bdev(). 268 269 --- 270 [mandatory] 271 272 fsync_dev() is gone; use fsync_bdev(). NOTE: lvm breakage is 273 deliberate; as soon as struct block_device * is propagated in a reasonable 274 way by that code fixing will become trivial; until then nothing can be 275 done.