mm: Split page_has_private() in two to better handle PG_private_2
Split page_has_private() into two functions:
(1) page_needs_cleanup() to find out if a page needs the ->releasepage(),
->invalidatepage(), etc. address space ops calling upon it.
This returns true when either PG_private or PG_private_2 are set.
(2) page_private_count() which returns a count of the number of refs
contributed to a page for attached private data.
This returns 1 if PG_private is set and 0 otherwise.
I think suggestion[1] is that PG_private_2 should just have a ref on the
page, but this isn't accounted in the same way as PG_private's ref.
Notes:
(*) The following:
btrfs_migratepage()
iomap_set_range_uptodate()
iomap_migrate_page()
to_iomap_page()
should probably all use PagePrivate() rather than page_has_private()
since they're interested in what's attached to page->private when
they're doing this, and not PG_private_2.
It may not matter in these cases since page->private is probably NULL
if PG_private is not set.
(*) Should PAGE_FLAGS_CLEANUP (PAGE_FLAGS_PRIVATE as was) just be merged
into page_needs_cleanup() as that's the only user?
(*) Do we actually need PG_private, or is it possible just to see if
page->private is NULL?
(*) There are a lot of "if (page_has_private()) try_to_release_page()"
combinations. Does it make sense to make an inline function that does
this?
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Linus Torvalds <torvalds@linux-foundation.org>
cc: Matthew Wilcox <willy@infradead.org>
cc: Christoph Hellwig <hch@lst.de>
cc: Josef Bacik <josef@toxicpanda.com>
cc: Alexander Viro <viro@zeniv.linux.org.uk>
cc: Andrew Morton <akpm@linux-foundation.org>
cc: linux-mm@kvack.org
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/linux-fsdevel/CAHk-=whWoJhGeMn85LOh9FX-5d2-Upzmv1m2ZmYxvD31TKpUTA@mail.gmail.com/ [1]
15 files changed
