1 files changed, 86 insertions, 1 deletions
diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst
index 26c093969573..df0dc37e6f58 100644
--- a/Documentation/filesystems/porting.rst
+++ b/Documentation/filesystems/porting.rst
@@ -45,6 +45,12 @@ typically between calling iget_locked() and unlocking the inode.
 
 At some point that will become mandatory.
 
+**mandatory**
+
+The foo_inode_info should always be allocated through alloc_inode_sb() rather
+than kmem_cache_alloc() or kmalloc() related to set up the inode reclaim context
+correctly.
+
 ---
 
 **mandatory**
@@ -618,7 +624,7 @@ any symlink that might use page_follow_link_light/page_put_link() must
 have inode_nohighmem(inode) called before anything might start playing with
 its pagecache.  No highmem pages should end up in the pagecache of such
 symlinks.  That includes any preseeding that might be done during symlink
-creation.  __page_symlink() will honour the mapping gfp flags, so once
+creation.  page_symlink() will honour the mapping gfp flags, so once
 you've done inode_nohighmem() it's safe to use, but if you allocate and
 insert the page manually, make sure to use the right gfp flags.
 
@@ -717,6 +723,8 @@ be removed.  Switch while you still can; the old one won't stay.
 **mandatory**
 
 ->setxattr() and xattr_handler.set() get dentry and inode passed separately.
+The xattr_handler.set() gets passed the user namespace of the mount the inode
+is seen from so filesystems can idmap the i_uid and i_gid accordingly.
 dentry might be yet to be attached to inode, so do _not_ use its ->d_inode
 in the instances.  Rationale: !@#!@# security_d_instantiate() needs to be
 called before we attach dentry to inode and !@#!@##!@$!$#!@#$!@$!@$ smack
@@ -858,3 +866,80 @@ be misspelled d_alloc_anon().
 [should've been added in 2016] stale comment in finish_open() nonwithstanding,
 failure exits in ->atomic_open() instances should *NOT* fput() the file,
 no matter what.  Everything is handled by the caller.
+
+---
+
+**mandatory**
+
+clone_private_mount() returns a longterm mount now, so the proper destructor of
+its result is kern_unmount() or kern_unmount_array().
+
+---
+
+**mandatory**
+
+zero-length bvec segments are disallowed, they must be filtered out before
+passed on to an iterator.
+
+---
+
+**mandatory**
+
+For bvec based itererators bio_iov_iter_get_pages() now doesn't copy bvecs but
+uses the one provided. Anyone issuing kiocb-I/O should ensure that the bvec and
+page references stay until I/O has completed, i.e. until ->ki_complete() has
+been called or returned with non -EIOCBQUEUED code.
+
+---
+
+**mandatory**
+
+mnt_want_write_file() can now only be paired with mnt_drop_write_file(),
+whereas previously it could be paired with mnt_drop_write() as well.
+
+---
+
+**mandatory**
+
+iov_iter_copy_from_user_atomic() is gone; use copy_page_from_iter_atomic().
+The difference is copy_page_from_iter_atomic() advances the iterator and
+you don't need iov_iter_advance() after it.  However, if you decide to use
+only a part of obtained data, you should do iov_iter_revert().
+
+---
+
+**mandatory**
+
+Calling conventions for file_open_root() changed; now it takes struct path *
+instead of passing mount and dentry separately.  For callers that used to
+pass <mnt, mnt->mnt_root> pair (i.e. the root of given mount), a new helper
+is provided - file_open_root_mnt().  In-tree users adjusted.
+
+---
+
+**mandatory**
+
+no_llseek is gone; don't set .llseek to that - just leave it NULL instead.
+Checks for "does that file have llseek(2), or should it fail with ESPIPE"
+should be done by looking at FMODE_LSEEK in file->f_mode.
+
+---
+
+*mandatory*
+
+filldir_t (readdir callbacks) calling conventions have changed.  Instead of
+returning 0 or -E... it returns bool now.  false means "no more" (as -E... used
+to) and true - "keep going" (as 0 in old calling conventions).  Rationale:
+callers never looked at specific -E... values anyway.  ->iterate() and
+->iterate_shared() instance require no changes at all, all filldir_t ones in
+the tree converted.
+
+---
+
+**mandatory**
+
+Calling conventions for ->tmpfile() have changed.  It now takes a struct
+file pointer instead of struct dentry pointer.  d_tmpfile() is similarly
+changed to simplify callers.  The passed file is in a non-open state and on
+success must be opened before returning (e.g. by calling
+finish_open_simple()).