1 files changed, 63 insertions, 1 deletions
diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst
index 9ab2a3d6f2b4..767b2927c762 100644
--- a/Documentation/filesystems/porting.rst
+++ b/Documentation/filesystems/porting.rst
@@ -313,7 +313,7 @@ done.
 
 **mandatory**
 
-block truncatation on error exit from ->write_begin, and ->direct_IO
+block truncation on error exit from ->write_begin, and ->direct_IO
 moved from generic methods (block_write_begin, cont_write_begin,
 nobh_write_begin, blockdev_direct_IO*) to callers.  Take a look at
 ext2_write_failed and callers for an example.
@@ -1141,3 +1141,65 @@ 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.