[RFC v2 3/8] shmem: account for high order folios

Luis Chamberlain
2023-05-26T07:56:38Z

shmem uses the shem_info_inode alloced, swapped to account
for allocated pages and swapped pages. In preparation for high
order folios adjust the accounting to use folio_nr_pages().

This should produce no functional changes yet as higher order
folios are not yet used or supported in shmem.

Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
---
mm/shmem.c | 34 ++++++++++++++++++++--------------
1 file changed, 20 insertions(+), 14 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index a947f2678a39..7bea4c5cb83a 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -803,15 +803,15 @@ unsigned long shmem_partial_swap_usage(struct address_space *mapping,
pgoff_t start, pgoff_t end)
{
XA_STATE(xas, &mapping->i_pages, start);
- struct page *page;
+ struct folio *folio;
unsigned long swapped = 0;

rcu_read_lock();
- xas_for_each(&xas, page, end - 1) {
- if (xas_retry(&xas, page))
+ xas_for_each(&xas, folio, end - 1) {
+ if (xas_retry(&xas, folio))
continue;
- if (xa_is_value(page))
- swapped++;
+ if (xa_is_value(folio))
+ swapped += (folio_nr_pages(folio));

if (need_resched()) {
xas_pause(&xas);
@@ -938,10 +938,12 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
folio = fbatch.folios[i];

if (xa_is_value(folio)) {
+ long swaps_freed;
if (unfalloc)
continue;
- nr_swaps_freed += !shmem_free_swap(mapping,
- indices[i], folio);
+ swaps_freed = folio_nr_pages(folio);
+ if (!shmem_free_swap(mapping, indices[i], folio))
+ nr_swaps_freed += swaps_freed;
continue;
}

@@ -1007,14 +1009,16 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
folio = fbatch.folios[i];

if (xa_is_value(folio)) {
+ long swaps_freed;
if (unfalloc)
continue;
+ swaps_freed = folio_nr_pages(folio);
if (shmem_free_swap(mapping, indices[i], folio)) {
/* Swap was replaced by page: retry */
index = indices[i];
break;
}
- nr_swaps_freed++;
+ nr_swaps_freed += swaps_freed;
continue;
}

@@ -1445,7 +1449,7 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
NULL) == 0) {
spin_lock_irq(&info->lock);
shmem_recalc_inode(inode);
- info->swapped++;
+ info->swapped += folio_nr_pages(folio);
spin_unlock_irq(&info->lock);

swap_shmem_alloc(swap);
@@ -1720,6 +1724,7 @@ static void shmem_set_folio_swapin_error(struct inode *inode, pgoff_t index,
struct shmem_inode_info *info = SHMEM_I(inode);
swp_entry_t swapin_error;
void *old;
+ long num_swap_pages;

swapin_error = make_swapin_error_entry();
old = xa_cmpxchg_irq(&mapping->i_pages, index,
@@ -1729,6 +1734,7 @@ static void shmem_set_folio_swapin_error(struct inode *inode, pgoff_t index,
return;

folio_wait_writeback(folio);
+ num_swap_pages = folio_nr_pages(folio);
delete_from_swap_cache(folio);
spin_lock_irq(&info->lock);
/*
@@ -1736,8 +1742,8 @@ static void shmem_set_folio_swapin_error(struct inode *inode, pgoff_t index,
* be 0 when inode is released and thus trigger WARN_ON(inode->i_blocks) in
* shmem_evict_inode.
*/
- info->alloced--;
- info->swapped--;
+ info->alloced -= num_swap_pages;
+ info->swapped -= num_swap_pages;
shmem_recalc_inode(inode);
spin_unlock_irq(&info->lock);
swap_free(swap);
@@ -1827,7 +1833,7 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
goto failed;

spin_lock_irq(&info->lock);
- info->swapped--;
+ info->swapped -= folio_nr_pages(folio);
shmem_recalc_inode(inode);
spin_unlock_irq(&info->lock);

@@ -2542,8 +2548,8 @@ int shmem_mfill_atomic_pte(pmd_t *dst_pmd,
goto out_delete_from_cache;

spin_lock_irq(&info->lock);
- info->alloced++;
- inode->i_blocks += PAGE_SECTORS;
+ info->alloced += folio_nr_pages(folio);
+ inode->i_blocks += PAGE_SECTORS << folio_order(folio);
shmem_recalc_inode(inode);
spin_unlock_irq(&info->lock);

--
2.39.2