[PATCH v2 00/14] namei: clean up retry logic in various do_* functions

[Dmitry Kadashev <dkadashev@gmail.com>]

Suggested by Linus in https://lore.kernel.org/io-uring/CAHk-=wh=cpt_tQCirzFZRPawRpbuFTZ2MxNpXiyUF+eBXF=+sw@mail.gmail.com/

This patchset does all the do_* functions one by one. The idea is to
move the main logic to a helper function and handle stale retries /
struct filename cleanups outside, which makes the logic easier to
follow.

There are a few minor changes in behavior:

1. filename_lookup() / filename_parentat() / filename_create() do their
own retries on ESTALE (regardless of flags), and previously they were
exempt from retries in the do_* functions (but they *were* called on
retry - it's just the return code wasn't checked for ESTALE). And
now the retry is done on the upper level, and so technically it could be
called a behavior change. Hopefully it's an edge case where an
additional check does not matter.

2. Some safety checks like may_mknod() / flags validation are now
repeated on retry. Those are mostly trivial and retry is a slow path, so
that should be OK.

3. retry_estale() is wrapped into unlikely() now

On top of https://lore.kernel.org/io-uring/20210708063447.3556403-1-dkadashev@gmail.com/

v2:

- Split flow changes and code reorganization to different commits;

- Move more checks into the new helpers, to avoid gotos in the touched
  do_* functions completely;

- Add unlikely() around retry_estale();

- Name the new helper functions try_* instead of *_helper;

Dmitry Kadashev (14):
  namei: prepare do_rmdir for refactoring
  namei: clean up do_rmdir retry logic
  namei: prepare do_unlinkat for refactoring
  namei: clean up do_unlinkat retry logic
  namei: prepare do_mkdirat for refactoring
  namei: clean up do_mkdirat retry logic
  namei: prepare do_mknodat for refactoring
  namei: clean up do_mknodat retry logic
  namei: prepare do_symlinkat for refactoring
  namei: clean up do_symlinkat retry logic
  namei: prepare do_linkat for refactoring
  namei: clean up do_linkat retry logic
  namei: prepare do_renameat2 for refactoring
  namei: clean up do_renameat2 retry logic

 fs/namei.c | 252 +++++++++++++++++++++++++++++------------------------
 1 file changed, 140 insertions(+), 112 deletions(-)

-- 
2.30.2