1 files changed, 144 insertions, 0 deletions
diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst
index c1c121055204..85f590254f07 100644
--- a/Documentation/filesystems/porting.rst
+++ b/Documentation/filesystems/porting.rst
@@ -1141,3 +1141,147 @@ pointer are gone.
 
 set_blocksize() takes opened struct file instead of struct block_device now
 and it *must* be opened exclusive.
+
+---
+
+**mandatory**
+
+->d_revalidate() gets two extra arguments - inode of parent directory and
+name our dentry is expected to have.  Both are stable (dir is pinned in
+non-RCU case and will stay around during the call in RCU case, and name
+is guaranteed to stay unchanging).  Your instance doesn't have to use
+either, but it often helps to avoid a lot of painful boilerplate.
+Note that while name->name is stable and NUL-terminated, it may (and
+often will) have name->name[name->len] equal to '/' rather than '\0' -
+in normal case it points into the pathname being looked up.
+NOTE: if you need something like full path from the root of filesystem,
+you are still on your own - this assists with simple cases, but it's not
+magic.
+
+---
+
+**recommended**
+
+kern_path_locked() and user_path_locked() no longer return a negative
+dentry so this doesn't need to be checked.  If the name cannot be found,
+ERR_PTR(-ENOENT) is returned.
+
+---
+
+**recommended**
+
+lookup_one_qstr_excl() is changed to return errors in more cases, so
+these conditions don't require explicit checks:
+
+ - if LOOKUP_CREATE is NOT given, then the dentry won't be negative,
+   ERR_PTR(-ENOENT) is returned instead
+ - if LOOKUP_EXCL IS given, then the dentry won't be positive,
+   ERR_PTR(-EEXIST) is rreturned instread
+
+LOOKUP_EXCL now means "target must not exist".  It can be combined with
+LOOK_CREATE or LOOKUP_RENAME_TARGET.
+
+---
+
+**mandatory**
+invalidate_inodes() is gone use evict_inodes() instead.
+
+---
+
+**mandatory**
+
+->mkdir() now returns a dentry.  If the created inode is found to
+already be in cache and have a dentry (often IS_ROOT()), it will need to
+be spliced into the given name in place of the given dentry. That dentry
+now needs to be returned.  If the original dentry is used, NULL should
+be returned.  Any error should be returned with ERR_PTR().
+
+In general, filesystems which use d_instantiate_new() to install the new
+inode can safely return NULL.  Filesystems which may not have an I_NEW inode
+should use d_drop();d_splice_alias() and return the result of the latter.
+
+If a positive dentry cannot be returned for some reason, in-kernel
+clients such as cachefiles, nfsd, smb/server may not perform ideally but
+will fail-safe.
+
+---
+
+** mandatory**
+
+lookup_one(), lookup_one_unlocked(), lookup_one_positive_unlocked() now
+take a qstr instead of a name and len.  These, not the "one_len"
+versions, should be used whenever accessing a filesystem from outside
+that filesysmtem, through a mount point - which will have a mnt_idmap.
+
+---
+
+** mandatory**
+
+Functions try_lookup_one_len(), lookup_one_len(),
+lookup_one_len_unlocked() and lookup_positive_unlocked() have been
+renamed to try_lookup_noperm(), lookup_noperm(),
+lookup_noperm_unlocked(), lookup_noperm_positive_unlocked().  They now
+take a qstr instead of separate name and length.  QSTR() can be used
+when strlen() is needed for the length.
+
+These function no longer do any permission checking - they previously
+checked that the caller has 'X' permission on the parent.  They must
+ONLY be used internally by a filesystem on itself when it knows that
+permissions are irrelevant or in a context where permission checks have
+already been performed such as after vfs_path_parent_lookup()
+
+---
+
+** mandatory**
+
+d_hash_and_lookup() is no longer exported or available outside the VFS.
+Use try_lookup_noperm() instead.  This adds name validation and takes
+arguments in the opposite order but is otherwise identical.
+
+Using try_lookup_noperm() will require linux/namei.h to be included.
+
+---
+
+**mandatory**
+
+Calling conventions for ->d_automount() have changed; we should *not* grab
+an extra reference to new mount - it should be returned with refcount 1.
+
+---
+
+collect_mounts()/drop_collected_mounts()/iterate_mounts() are gone now.
+Replacement is collect_paths()/drop_collected_path(), with no special
+iterator needed.  Instead of a cloned mount tree, the new interface returns
+an array of struct path, one for each mount collect_mounts() would've
+created.  These struct path point to locations in the caller's namespace
+that would be roots of the cloned mounts.
+
+---
+
+**mandatory**
+
+If your filesystem sets the default dentry_operations, use set_default_d_op()
+rather than manually setting sb->s_d_op.
+
+---
+
+**mandatory**
+
+d_set_d_op() is no longer exported (or public, for that matter); _if_
+your filesystem really needed that, make use of d_splice_alias_ops()
+to have them set.  Better yet, think hard whether you need different
+->d_op for different dentries - if not, just use set_default_d_op()
+at mount time and be done with that.  Currently procfs is the only
+thing that really needs ->d_op varying between dentries.
+
+---
+
+**highly recommended**
+
+The file operations mmap() callback is deprecated in favour of
+mmap_prepare(). This passes a pointer to a vm_area_desc to the callback
+rather than a VMA, as the VMA at this stage is not yet valid.
+
+The vm_area_desc provides the minimum required information for a filesystem
+to initialise state upon memory mapping of a file-backed region, and output
+parameters for the file system to set this state.