The sepcial case in shmem_recalc_inode() is tailored for shmem_writepage().
By raising swapped before nrpages is lowered directly within
shmem_writepage(), we can simplify code of shmem_recalc_inode() and
eliminate the need of executing the special case code for all callers of
shmem_recalc_inode().
Signed-off-by: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
---
mm/shmem.c | 18 ++++++++----------
1 file changed, 8 insertions(+), 10 deletions(-)
diff --git a/mm/shmem.c b/mm/shmem.c
index 2349673b239b..9f5e1eccaacb 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -443,15 +443,6 @@ static void shmem_recalc_inode(struct inode *inode, long alloced, long swapped)
info->swapped += swapped;
freed = info->alloced - info->swapped -
READ_ONCE(inode->i_mapping->nrpages);
- /*
- * Special case: whereas normally shmem_recalc_inode() is called
- * after i_mapping->nrpages has already been adjusted (up or down),
- * shmem_writepage() has to raise swapped before nrpages is lowered -
- * to stop a racing shmem_recalc_inode() from thinking that a page has
- * been freed. Compensate here, to avoid the need for a followup call.
- */
- if (swapped > 0)
- freed += swapped;
if (freed > 0)
info->alloced -= freed;
spin_unlock(&info->lock);
@@ -1694,9 +1685,16 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
list_add(&info->swaplist, &shmem_swaplist);
if (!folio_alloc_swap(folio, __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN)) {
- shmem_recalc_inode(inode, 0, nr_pages);
+ /*
+ * Raise swapped before nrpages is lowered to stop racing
+ * shmem_recalc_inode() from thinking that a page has been freed.
+ */
+ spin_lock(&info->lock);
+ info->swapped += nr_pages;
+ spin_unlock(&info->lock);
swap_shmem_alloc(folio->swap, nr_pages);
shmem_delete_from_page_cache(folio, swp_to_radix_entry(folio->swap));
+ shmem_recalc_inode(inode, 0, 0);
mutex_unlock(&shmem_swaplist_mutex);
BUG_ON(folio_mapped(folio));
--
2.30.0
