[PATCH v2 21/32] mm/madvise: clean up force_shm_swapin_readahead()

Hugh Dickins
2023-06-09T01:35:24Z

Some nearby MADV_WILLNEED cleanup unrelated to pte_offset_map_lock().
shmem_swapin_range() is a better name than force_shm_swapin_readahead().
Fix unimportant off-by-one on end_index. Call the swp_entry_t "entry"
rather than "swap": either is okay, but entry is the name used elsewhere
in mm/madvise.c. Do not assume GFP_HIGHUSER_MOVABLE: that's right for
anon swap, but shmem should take gfp from mapping. Pass the actual vma
and address to read_swap_cache_async(), in case a NUMA mempolicy applies.
lru_add_drain() at outer level, like madvise_willneed()'s other branch.

Signed-off-by: Hugh Dickins <hughd@google.com>
---
mm/madvise.c | 24 +++++++++++++-----------
1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index 0af64c4a8f82..9b3c9610052f 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -235,30 +235,34 @@ static const struct mm_walk_ops swapin_walk_ops = {
.pmd_entry = swapin_walk_pmd_entry,
};

-static void force_shm_swapin_readahead(struct vm_area_struct *vma,
+static void shmem_swapin_range(struct vm_area_struct *vma,
unsigned long start, unsigned long end,
struct address_space *mapping)
{
XA_STATE(xas, &mapping->i_pages, linear_page_index(vma, start));
- pgoff_t end_index = linear_page_index(vma, end + PAGE_SIZE - 1);
+ pgoff_t end_index = linear_page_index(vma, end) - 1;
struct page *page;
struct swap_iocb *splug = NULL;

rcu_read_lock();
xas_for_each(&xas, page, end_index) {
- swp_entry_t swap;
+ unsigned long addr;
+ swp_entry_t entry;

if (!xa_is_value(page))
continue;
- swap = radix_to_swp_entry(page);
+ entry = radix_to_swp_entry(page);
/* There might be swapin error entries in shmem mapping. */
- if (non_swap_entry(swap))
+ if (non_swap_entry(entry))
continue;
+
+ addr = vma->vm_start +
+ ((xas.xa_index - vma->vm_pgoff) << PAGE_SHIFT);
xas_pause(&xas);
rcu_read_unlock();

- page = read_swap_cache_async(swap, GFP_HIGHUSER_MOVABLE,
- NULL, 0, false, &splug);
+ page = read_swap_cache_async(entry, mapping_gfp_mask(mapping),
+ vma, addr, false, &splug);
if (page)
put_page(page);

@@ -266,8 +270,6 @@ static void force_shm_swapin_readahead(struct vm_area_struct *vma,
}
rcu_read_unlock();
swap_read_unplug(splug);
-
- lru_add_drain(); /* Push any new pages onto the LRU now */
}
#endif /* CONFIG_SWAP */

@@ -291,8 +293,8 @@ static long madvise_willneed(struct vm_area_struct *vma,
}

if (shmem_mapping(file->f_mapping)) {
- force_shm_swapin_readahead(vma, start, end,
- file->f_mapping);
+ shmem_swapin_range(vma, start, end, file->f_mapping);
+ lru_add_drain(); /* Push any new pages onto the LRU now */
return 0;
}
#else
--
2.35.3