fuse: drop usage of folio_index

fuse: drop usage of folio_index

Patch series "mm, swap: clean up swap cache mapping helper", v3.

This series removes usage of folio_index usage in fs/, and remove swap
cache checking in folio_contains.

Currently, the swap cache is already no longer directly exposed to fs, and
swap cache will be more different from page cache.  Clean up the helpers
first to simplify the code and eliminate the helpers used for resolving
circular header dependency issue between filemap and swap headers, and
prepare for further changes.

This patch (of 6):

folio_index is only needed for mixed usage of page cache and swap cache,
for pure page cache usage, the caller can just use folio->index instead.

It can't be a swap cache folio here.  Swap mapping may only call into fs
through `swap_rw` but fuse does not use that method for SWAP.

Link: https://lkml.kernel.org/r/20250430181052.55698-1-ryncsn@gmail.com
Link: https://lkml.kernel.org/r/20250430181052.55698-2-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Joanne Koong <joannelkoong@gmail.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Chao Yu <chao@kernel.org>
Cc: Chris Mason <clm@fb.com>
Cc: David Sterba <dsterba@suse.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Qu Wenruo <wqu@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>