mm/gup: combine put_compound_head() and unpin_user_page()

These functions accomplish the same thing but have different
implementations.

unpin_user_page() has a bug where it calls mod_node_page_state() after
calling put_page() which creates a risk that the page could have been
hot-uplugged from the system.

Fix this by using put_compound_head() as the only implementation.

__unpin_devmap_managed_user_page() and related can be deleted as well in
favour of the simpler, but slower, version in put_compound_head() that has
an extra atomic page_ref_sub, but always calls put_page() which internally
contains the special devmap code.

Move put_compound_head() to be directly after try_grab_compound_head() so
people can find it in future.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: 1970dc6f5226 ("mm/gup: /proc/vmstat: pin_user_pages (FOLL_PIN) reporting")
Signed-off-by: Jason Gunthorpe <[email protected]>
Reviewed-by: John Hubbard <[email protected]>
Reviewed-by: Ira Weiny <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
CC: Joao Martins <[email protected]>
CC: Jonathan Corbet <[email protected]>
CC: Dan Williams <[email protected]>
CC: Dave Chinner <[email protected]>
CC: Christoph Hellwig <[email protected]>
CC: Jane Chu <[email protected]>
CC: "Kirill A. Shutemov" <[email protected]>
CC: Michal Hocko <[email protected]>
CC: Mike Kravetz <[email protected]>
CC: Shuah Khan <[email protected]>
CC: Muchun Song <[email protected]>
CC: Vlastimil Babka <[email protected]>
CC: Matthew Wilcox <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions