fs/netfs: Add folio fscache functions

Match the page writeback functions by adding
folio_start_fscache(), folio_end_fscache(), folio_wait_fscache() and
folio_wait_fscache_killable().  Remove set_page_private_2().  Also rewrite
the kernel-doc to describe when to use the function rather than what the
function does, and include the kernel-doc in the appropriate rst file.
Saves 31 bytes of text in netfs_rreq_unlock() due to set_page_fscache()
calling page_folio() once instead of three times.

Signed-off-by: Matthew Wilcox (Oracle) <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Reviewed-by: William Kucharski <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Acked-by: Kirill A. Shutemov <[email protected]>
Acked-by: Mike Rapoport <[email protected]>
Reviewed-by: David Howells <[email protected]>

0 files changed, 0 insertions, 0 deletions