12debc4248
Remove the old iget() call and the read_inode() superblock operation it uses
as these are really obsolete, and the use of read_inode() does not produce
proper error handling (no distinction between ENOMEM and EIO when marking an
inode bad).
Furthermore, this removes the temptation to use iget() to find an inode by
number in a filesystem from code outside that filesystem.
iget_locked() should be used instead. A new function is added in an earlier
patch (iget_failed) that is to be called to mark an inode as bad, unlock it
and release it should the get routine fail. Mark iget() and read_inode() as
being obsolete and remove references to them from the documentation.
Typically a filesystem will be modified such that the read_inode function
becomes an internal iget function, for example the following:
void thingyfs_read_inode(struct inode *inode)
{
...
}
would be changed into something like:
struct inode *thingyfs_iget(struct super_block *sp, unsigned long ino)
{
struct inode *inode;
int ret;
inode = iget_locked(sb, ino);
if (!inode)
return ERR_PTR(-ENOMEM);
if (!(inode->i_state & I_NEW))
return inode;
...
unlock_new_inode(inode);
return inode;
error:
iget_failed(inode);
return ERR_PTR(ret);
}
and then thingyfs_iget() would be called rather than iget(), for example:
ret = -EINVAL;
inode = iget(sb, ino);
if (!inode || is_bad_inode(inode))
goto error;
becomes:
inode = thingyfs_iget(sb, ino);
if (IS_ERR(inode)) {
ret = PTR_ERR(inode);
goto error;
}
Note that is_bad_inode() does not need to be called. The error returned by
thingyfs_iget() should render it unnecessary.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
276 lines
8.4 KiB
Plaintext
276 lines
8.4 KiB
Plaintext
Changes since 2.5.0:
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---
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[recommended]
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New helpers: sb_bread(), sb_getblk(), sb_find_get_block(), set_bh(),
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sb_set_blocksize() and sb_min_blocksize().
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Use them.
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(sb_find_get_block() replaces 2.4's get_hash_table())
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---
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[recommended]
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New methods: ->alloc_inode() and ->destroy_inode().
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Remove inode->u.foo_inode_i
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Declare
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struct foo_inode_info {
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/* fs-private stuff */
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struct inode vfs_inode;
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};
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static inline struct foo_inode_info *FOO_I(struct inode *inode)
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{
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return list_entry(inode, struct foo_inode_info, vfs_inode);
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}
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Use FOO_I(inode) instead of &inode->u.foo_inode_i;
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Add foo_alloc_inode() and foo_destroy_inode() - the former should allocate
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foo_inode_info and return the address of ->vfs_inode, the latter should free
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FOO_I(inode) (see in-tree filesystems for examples).
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Make them ->alloc_inode and ->destroy_inode in your super_operations.
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Keep in mind that now you need explicit initialization of private data
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typically between calling iget_locked() and unlocking the inode.
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At some point that will become mandatory.
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---
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[mandatory]
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Change of file_system_type method (->read_super to ->get_sb)
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->read_super() is no more. Ditto for DECLARE_FSTYPE and DECLARE_FSTYPE_DEV.
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Turn your foo_read_super() into a function that would return 0 in case of
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success and negative number in case of error (-EINVAL unless you have more
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informative error value to report). Call it foo_fill_super(). Now declare
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int foo_get_sb(struct file_system_type *fs_type,
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int flags, const char *dev_name, void *data, struct vfsmount *mnt)
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{
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return get_sb_bdev(fs_type, flags, dev_name, data, foo_fill_super,
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mnt);
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}
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(or similar with s/bdev/nodev/ or s/bdev/single/, depending on the kind of
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filesystem).
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Replace DECLARE_FSTYPE... with explicit initializer and have ->get_sb set as
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foo_get_sb.
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---
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[mandatory]
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Locking change: ->s_vfs_rename_sem is taken only by cross-directory renames.
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Most likely there is no need to change anything, but if you relied on
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global exclusion between renames for some internal purpose - you need to
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change your internal locking. Otherwise exclusion warranties remain the
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same (i.e. parents and victim are locked, etc.).
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---
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[informational]
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Now we have the exclusion between ->lookup() and directory removal (by
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->rmdir() and ->rename()). If you used to need that exclusion and do
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it by internal locking (most of filesystems couldn't care less) - you
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can relax your locking.
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---
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[mandatory]
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->lookup(), ->truncate(), ->create(), ->unlink(), ->mknod(), ->mkdir(),
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->rmdir(), ->link(), ->lseek(), ->symlink(), ->rename()
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and ->readdir() are called without BKL now. Grab it on entry, drop upon return
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- that will guarantee the same locking you used to have. If your method or its
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parts do not need BKL - better yet, now you can shift lock_kernel() and
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unlock_kernel() so that they would protect exactly what needs to be
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protected.
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---
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[mandatory]
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BKL is also moved from around sb operations. ->write_super() Is now called
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without BKL held. BKL should have been shifted into individual fs sb_op
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functions. If you don't need it, remove it.
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---
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[informational]
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check for ->link() target not being a directory is done by callers. Feel
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free to drop it...
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---
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[informational]
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->link() callers hold ->i_mutex on the object we are linking to. Some of your
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problems might be over...
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---
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[mandatory]
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new file_system_type method - kill_sb(superblock). If you are converting
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an existing filesystem, set it according to ->fs_flags:
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FS_REQUIRES_DEV - kill_block_super
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FS_LITTER - kill_litter_super
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neither - kill_anon_super
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FS_LITTER is gone - just remove it from fs_flags.
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---
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[mandatory]
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FS_SINGLE is gone (actually, that had happened back when ->get_sb()
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went in - and hadn't been documented ;-/). Just remove it from fs_flags
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(and see ->get_sb() entry for other actions).
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---
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[mandatory]
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->setattr() is called without BKL now. Caller _always_ holds ->i_mutex, so
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watch for ->i_mutex-grabbing code that might be used by your ->setattr().
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Callers of notify_change() need ->i_mutex now.
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---
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[recommended]
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New super_block field "struct export_operations *s_export_op" for
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explicit support for exporting, e.g. via NFS. The structure is fully
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documented at its declaration in include/linux/fs.h, and in
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Documentation/filesystems/Exporting.
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Briefly it allows for the definition of decode_fh and encode_fh operations
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to encode and decode filehandles, and allows the filesystem to use
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a standard helper function for decode_fh, and provide file-system specific
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support for this helper, particularly get_parent.
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It is planned that this will be required for exporting once the code
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settles down a bit.
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[mandatory]
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s_export_op is now required for exporting a filesystem.
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isofs, ext2, ext3, resierfs, fat
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can be used as examples of very different filesystems.
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---
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[mandatory]
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iget4() and the read_inode2 callback have been superseded by iget5_locked()
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which has the following prototype,
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struct inode *iget5_locked(struct super_block *sb, unsigned long ino,
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int (*test)(struct inode *, void *),
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int (*set)(struct inode *, void *),
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void *data);
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'test' is an additional function that can be used when the inode
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number is not sufficient to identify the actual file object. 'set'
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should be a non-blocking function that initializes those parts of a
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newly created inode to allow the test function to succeed. 'data' is
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passed as an opaque value to both test and set functions.
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When the inode has been created by iget5_locked(), it will be returned with the
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I_NEW flag set and will still be locked. The filesystem then needs to finalize
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the initialization. Once the inode is initialized it must be unlocked by
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calling unlock_new_inode().
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The filesystem is responsible for setting (and possibly testing) i_ino
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when appropriate. There is also a simpler iget_locked function that
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just takes the superblock and inode number as arguments and does the
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test and set for you.
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e.g.
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inode = iget_locked(sb, ino);
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if (inode->i_state & I_NEW) {
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err = read_inode_from_disk(inode);
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if (err < 0) {
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iget_failed(inode);
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return err;
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}
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unlock_new_inode(inode);
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}
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Note that if the process of setting up a new inode fails, then iget_failed()
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should be called on the inode to render it dead, and an appropriate error
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should be passed back to the caller.
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---
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[recommended]
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->getattr() finally getting used. See instances in nfs, minix, etc.
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---
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[mandatory]
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->revalidate() is gone. If your filesystem had it - provide ->getattr()
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and let it call whatever you had as ->revlidate() + (for symlinks that
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had ->revalidate()) add calls in ->follow_link()/->readlink().
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---
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[mandatory]
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->d_parent changes are not protected by BKL anymore. Read access is safe
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if at least one of the following is true:
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* filesystem has no cross-directory rename()
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* dcache_lock is held
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* we know that parent had been locked (e.g. we are looking at
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->d_parent of ->lookup() argument).
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* we are called from ->rename().
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* the child's ->d_lock is held
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Audit your code and add locking if needed. Notice that any place that is
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not protected by the conditions above is risky even in the old tree - you
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had been relying on BKL and that's prone to screwups. Old tree had quite
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a few holes of that kind - unprotected access to ->d_parent leading to
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anything from oops to silent memory corruption.
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---
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[mandatory]
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FS_NOMOUNT is gone. If you use it - just set MS_NOUSER in flags
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(see rootfs for one kind of solution and bdev/socket/pipe for another).
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---
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[recommended]
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Use bdev_read_only(bdev) instead of is_read_only(kdev). The latter
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is still alive, but only because of the mess in drivers/s390/block/dasd.c.
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As soon as it gets fixed is_read_only() will die.
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---
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[mandatory]
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->permission() is called without BKL now. Grab it on entry, drop upon
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return - that will guarantee the same locking you used to have. If
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your method or its parts do not need BKL - better yet, now you can
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shift lock_kernel() and unlock_kernel() so that they would protect
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exactly what needs to be protected.
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---
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[mandatory]
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->statfs() is now called without BKL held. BKL should have been
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shifted into individual fs sb_op functions where it's not clear that
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it's safe to remove it. If you don't need it, remove it.
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---
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[mandatory]
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is_read_only() is gone; use bdev_read_only() instead.
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---
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[mandatory]
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destroy_buffers() is gone; use invalidate_bdev().
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---
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[mandatory]
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fsync_dev() is gone; use fsync_bdev(). NOTE: lvm breakage is
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deliberate; as soon as struct block_device * is propagated in a reasonable
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way by that code fixing will become trivial; until then nothing can be
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done.
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