On 26.10.24 07:43, Kefeng Wang wrote:
When clearing gigantic page, it zeros page from the first page to the
last page, if directly passing addr_hint which maybe not the address
of the first page of folio, then some archs could flush the wrong cache
if it does use the addr_hint as a hint. For non-gigantic page, it
calculates the base address inside, even passed the wrong addr_hint, it
only has performance impact as the process_huge_page() wants to process
target page last to keep its cache lines hot), no functional impact.
Let's pass the real accessed address to folio_zero_user() and use the
aligned address in clear_gigantic_page() to fix it.
Fixes: 78fefd04c123 ("mm: memory: convert clear_huge_page() to folio_zero_user()")
Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
---
v2:
- update changelog to clarify the impact, per Andrew
fs/hugetlbfs/inode.c | 2 +-
mm/memory.c | 1 +
2 files changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index a4441fb77f7c..a5ea006f403e 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -825,7 +825,7 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
error = PTR_ERR(folio);
goto out;
}
- folio_zero_user(folio, ALIGN_DOWN(addr, hpage_size));
+ folio_zero_user(folio, addr);
__folio_mark_uptodate(folio);
error = hugetlb_add_to_page_cache(folio, mapping, index);
if (unlikely(error)) {
diff --git a/mm/memory.c b/mm/memory.c
index 75c2dfd04f72..ef47b7ea5ddd 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -6821,6 +6821,7 @@ static void clear_gigantic_page(struct folio *folio, unsigned long addr,
int i;
might_sleep();
+ addr = ALIGN_DOWN(addr, folio_size(folio));
Right, that's what's effectively done in a very bad way in
process_huge_page()
unsigned long addr = addr_hint &
~(((unsigned long)nr_pages << PAGE_SHIFT) - 1);
That should all be cleaned up ... process_huge_page() likely shouldn't
be even consuming "nr_pages".
In clear_gigantic_page(), can you please rename the "unsigned long addr"
parameter to unsigned long "addr_hint" and use an additional "unsigned
long addr" ?
--
Cheers,
David / dhildenb
