Switching to iterate_shared

[Matthew Wilcox <willy@infradead.org>]

On Tue, Aug 16, 2022 at 11:58:36AM -0700, Linus Torvalds wrote:
> That said, our filldir code is still confusing as hell. And I would
> really like to see that "shared vs non-shared" iterator thing go away,
> with everybody using the shared one - and filesystems that can't deal
> with it using their own lock.
> 
> But that's a completely independent wart in our complicated filldir saga.
> 
> But if somebody were to look at that iterate-vs-iterate_shared, that
> would be lovely. A quick grep shows that we don't have *that* many of
> the non-shared cases left:
> 
>       git grep '\.iterate\>.*='
> 
> seems to imply that converting them to a "use my own load" wouldn't be
> _too_ bad.
> 
> And some of them might actually be perfectly ok with the shared
> semantics (ie inode->i_rwsem held just for reading) and they just were
> never converted originally.

What's depressing is that some of these are newly added.  It'd be
great if we could attach something _like_ __deprecated to things
that checkpatch could pick up on.

fs/adfs/dir_f.c:        .iterate        = adfs_f_iterate,
fs/adfs/dir_fplus.c:    .iterate        = adfs_fplus_iterate,

ADFS is read-only, so must be safe?

fs/ceph/dir.c:  .iterate = ceph_readdir,
fs/ceph/dir.c:  .iterate = ceph_readdir,

At least CEPH has active maintainers, cc'd

fs/coda/dir.c:  .iterate        = coda_readdir,

Would anyone notice if we broke CODA?  Maintainers cc'd anyway.

fs/exfat/dir.c: .iterate        = exfat_iterate,

Exfat is a new addition, but has active maintainers.

fs/jfs/namei.c: .iterate        = jfs_readdir,

Maintainer cc'd

fs/ntfs/dir.c:  .iterate        = ntfs_readdir,         /* Read directory contents. */

Maybe we can get rid of ntfs soon.

fs/ocfs2/file.c:        .iterate        = ocfs2_readdir,
fs/ocfs2/file.c:        .iterate        = ocfs2_readdir,

maintainers cc'd

fs/orangefs/dir.c:      .iterate = orangefs_dir_iterate,

New; maintainer cc'd

fs/overlayfs/readdir.c: .iterate        = ovl_iterate,

Active maintainer, cc'd

fs/proc/base.c: .iterate        = proc_##LSM##_attr_dir_iterate, \

Hmm.  We need both SMACK and Apparmor to agree to this ... cc's added.

fs/vboxsf/dir.c:        .iterate = vboxsf_dir_iterate,

Also newly added.  Maintainer cc'd.