xarray: Replace exceptional entries

Introduce xarray value entries and tagged pointers to replace radix
tree exceptional entries.  This is a slight change in encoding to allow
the use of an extra bit (we can now store BITS_PER_LONG - 1 bits in a
value entry).  It is also a change in emphasis; exceptional entries are
intimidating and different.  As the comment explains, you can choose
to store values or pointers in the xarray and they are both first-class
citizens.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Josef Bacik <jbacik@fb.com>
This commit is contained in:
Matthew Wilcox
2017-11-03 13:30:42 -04:00
parent 66ee620f06
commit 3159f943aa
26 changed files with 278 additions and 232 deletions

View File

@@ -4750,7 +4750,7 @@ static struct page *mc_handle_file_pte(struct vm_area_struct *vma,
/* shmem/tmpfs may report page out on swap: account for that too. */
if (shmem_mapping(mapping)) {
page = find_get_entry(mapping, pgoff);
if (radix_tree_exceptional_entry(page)) {
if (xa_is_value(page)) {
swp_entry_t swp = radix_to_swp_entry(page);
if (do_memsw_account())
*entry = swp;