folio_file_pos is only needed for mixed usage of page cache and swap
cache, for pure page cache usage, the caller can just use folio_pos
instead.

After commit e1209d3a ("mm: introduce ->swap_rw and use it for reads
from SWP_FS_OPS swap-space"), swap cache should never be exposed to nfs.

So remove the usage of folio_file_pos in following NFS functions / helpers:

- nfs_vm_page_mkwrite

  It's only used by nfs_file_vm_ops.page_mkwrite

- trace event helper: nfs_folio_event
- trace event helper: nfs_folio_event_done

  These two are used through DEFINE_NFS_FOLIO_EVENT and
  DEFINE_NFS_FOLIO_EVENT_DONE, which defined following events:

  - trace_nfs_aop_readpage{_done}: only called by nfs_read_folio
  - trace_nfs_writeback_folio: only called by nfs_wb_folio
  - trace_nfs_invalidate_folio: only called by nfs_invalidate_folio
  - trace_nfs_launder_folio_done: only called by nfs_launder_folio

  None of them could possibly be used on swap cache folio,
  nfs_read_folio only called by:
  .write_begin -> nfs_read_folio
  .read_folio

  nfs_wb_folio only called by nfs mapping:
  .release_folio -> nfs_wb_folio
  .launder_folio -> nfs_wb_folio
  .write_begin -> nfs_read_folio -> nfs_wb_folio
  .read_folio -> nfs_wb_folio
  .write_end -> nfs_update_folio -> nfs_writepage_setup -> nfs_setup_write_request -> nfs_try_to_update_request -> nfs_wb_folio
  .page_mkwrite -> nfs_update_folio -> nfs_writepage_setup -> nfs_setup_write_request -> nfs_try_to_update_request -> nfs_wb_folio
  .write_begin -> nfs_flush_incompatible -> nfs_wb_folio
  .page_mkwrite -> nfs_vm_page_mkwrite -> nfs_flush_incompatible -> nfs_wb_folio

  nfs_invalidate_folio is only called by .invalidate_folio.
  nfs_launder_folio is only called by .launder_folio

- nfs_grow_file
- nfs_update_folio

  nfs_grow_file is only called by nfs_update_folio, and all
  possible callers of them are:

  .write_end -> nfs_update_folio
  .page_mkwrite -> nfs_update_folio

- nfs_wb_folio_cancel

  .invalidate_folio -> nfs_wb_folio_cancel

Also, seeing from the swap side, swap_rw is now the only interface calling
into fs, the offset info is always in iocb.ki_pos now.

So we can remove all these folio_file_pos call safely.

Link: https://lkml.kernel.org/r/20240521175854.96038-8-ryncsn@gmail.comSigned-off-by: Kairui Song <kasong@tencent.com>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Anna Schumaker <anna@kernel.org>
Cc: Barry Song <v-songbaohua@oppo.com>
Cc: Chao Yu <chao@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Marc Dionne <marc.dionne@auristor.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: NeilBrown <neilb@suse.de>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: Xiubo Li <xiubli@redhat.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>