Re: ceph: fix leaked inode reference on writeback abort at umount

Hi matthew,

NACK for now. Thanks for the patch, but I have some concerns
that need a v2:

  1. [major] commit message: Commit message describes a nonexistent redirty mechanism
     The commit message claims `redirty_page_for_writepage()` calls
     `folio_mark_dirty()`, which re-enters `ceph_dirty_folio()` and
     double-increments `i_wrbuffer_ref`. This doesn't happen. The actual
     chain is `redirty_page_for_writepage()` →
     `folio_redirty_for_writepage()` → `filemap_dirty_folio()`, which
     sets PG_dirty directly — it never dispatches through
     `->dirty_folio`, so `ceph_dirty_folio()` is never re-entered. The
     real bug is simpler: the wrbuffer claim (i_wrbuffer_ref,
     snap_context, ihold) is leaked because `writepages_finish()` — the
     only release path — never runs for writes that were never
     submitted. During umount the osd_stopping_blocker keeps failing, so
     the claim stays leaked and the inode can't be evicted.
     Suggested fix: Drop the double-increment theory. Rewrite around the
     actual failure: unsubmitted writes orphan their wrbuffer claim, and
     releasing it before redirtying lets `i_wrbuffer_ref` reach 0 and
     unblocks inode eviction.
  2. [nit] fs/ceph/addr.c:1429: Helper uses page API instead of folio API
     `ceph_undo_wrbuffer_claim()` takes `struct page *` and uses
     `detach_page_private()`, while `ceph_invalidate_folio()` uses
     `folio_detach_private()`. Functionally identical but folio API is
     preferred for new code.
     Suggested fix: Worth converting if respinning anyway, but not a
     blocker.

Code fix is correct but commit message wrongly claims redirty re-enters ceph_dirty_folio(); needs respin with accurate description of the leaked wrbuffer claim.


-- 
Alex Markuze