Merge tag 'mm-nonmm-stable-2023-02-20-15-29' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull non-MM updates from Andrew Morton:
 "There is no particular theme here - mainly quick hits all over the
  tree.

  Most notable is a set of zlib changes from Mikhail Zaslonko which
  enhances and fixes zlib's use of S390 hardware support: 'lib/zlib: Set
  of s390 DFLTCC related patches for kernel zlib'"

* tag 'mm-nonmm-stable-2023-02-20-15-29' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (55 commits)
  Update CREDITS file entry for Jesper Juhl
  sparc: allow PM configs for sparc32 COMPILE_TEST
  hung_task: print message when hung_task_warnings gets down to zero.
  arch/Kconfig: fix indentation
  scripts/tags.sh: fix the Kconfig tags generation when using latest ctags
  nilfs2: prevent WARNING in nilfs_dat_commit_end()
  lib/zlib: remove redundation assignement of avail_in dfltcc_gdht()
  lib/Kconfig.debug: do not enable DEBUG_PREEMPT by default
  lib/zlib: DFLTCC always switch to software inflate for Z_PACKET_FLUSH option
  lib/zlib: DFLTCC support inflate with small window
  lib/zlib: Split deflate and inflate states for DFLTCC
  lib/zlib: DFLTCC not writing header bits when avail_out == 0
  lib/zlib: fix DFLTCC ignoring flush modes when avail_in == 0
  lib/zlib: fix DFLTCC not flushing EOBS when creating raw streams
  lib/zlib: implement switching between DFLTCC and software
  lib/zlib: adjust offset calculation for dfltcc_state
  nilfs2: replace WARN_ONs for invalid DAT metadata block requests
  scripts/spelling.txt: add "exsits" pattern and fix typo instances
  fs: gracefully handle ->get_block not mapping bh in __mpage_writepage
  cramfs: Kconfig: fix spelling & punctuation
  ...

1 files changed, 65 insertions, 0 deletions

diff --git a/Documentation/fault-injection/fault-injection.rst b/Documentation/fault-injection/fault-injection.rst
index 5f6454b9dbd4..08e420e10973 100644
--- a/Documentation/fault-injection/fault-injection.rst
+++ b/Documentation/fault-injection/fault-injection.rst
@@ -231,6 +231,71 @@ proc entries
 	This feature is intended for systematic testing of faults in a single
 	system call. See an example below.
 
+
+Error Injectable Functions
+--------------------------
+
+This part is for the kenrel developers considering to add a function to
+ALLOW_ERROR_INJECTION() macro.
+
+Requirements for the Error Injectable Functions
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Since the function-level error injection forcibly changes the code path
+and returns an error even if the input and conditions are proper, this can
+cause unexpected kernel crash if you allow error injection on the function
+which is NOT error injectable. Thus, you (and reviewers) must ensure;
+
+- The function returns an error code if it fails, and the callers must check
+  it correctly (need to recover from it).
+
+- The function does not execute any code which can change any state before
+  the first error return. The state includes global or local, or input
+  variable. For example, clear output address storage (e.g. `*ret = NULL`),
+  increments/decrements counter, set a flag, preempt/irq disable or get
+  a lock (if those are recovered before returning error, that will be OK.)
+
+The first requirement is important, and it will result in that the release
+(free objects) functions are usually harder to inject errors than allocate
+functions. If errors of such release functions are not correctly handled
+it will cause a memory leak easily (the caller will confuse that the object
+has been released or corrupted.)
+
+The second one is for the caller which expects the function should always
+does something. Thus if the function error injection skips whole of the
+function, the expectation is betrayed and causes an unexpected error.
+
+Type of the Error Injectable Functions
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Each error injectable functions will have the error type specified by the
+ALLOW_ERROR_INJECTION() macro. You have to choose it carefully if you add
+a new error injectable function. If the wrong error type is chosen, the
+kernel may crash because it may not be able to handle the error.
+There are 4 types of errors defined in include/asm-generic/error-injection.h
+
+EI_ETYPE_NULL
+  This function will return `NULL` if it fails. e.g. return an allocateed
+  object address.
+
+EI_ETYPE_ERRNO
+  This function will return an `-errno` error code if it fails. e.g. return
+  -EINVAL if the input is wrong. This will include the functions which will
+  return an address which encodes `-errno` by ERR_PTR() macro.
+
+EI_ETYPE_ERRNO_NULL
+  This function will return an `-errno` or `NULL` if it fails. If the caller
+  of this function checks the return value with IS_ERR_OR_NULL() macro, this
+  type will be appropriate.
+
+EI_ETYPE_TRUE
+  This function will return `true` (non-zero positive value) if it fails.
+
+If you specifies a wrong type, for example, EI_TYPE_ERRNO for the function
+which returns an allocated object, it may cause a problem because the returned
+value is not an object address and the caller can not access to the address.
+
+
 How to add new fault injection capability
 -----------------------------------------