1Changes 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 53int 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 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] 109 110->link() callers hold ->i_mutex on the object we are linking to. Some of your 111problems 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] 132 133->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. 136 137--- 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. 268