If there is private data attached to THP, the refcount of
THP will be increased and block the THP split. Release
private data attached to THP before split it to increase
the chance of splitting THP successfully.
There was a memory failure issue hit during HW error
injection testing with 5.18 kernel + xfs as rootfs. Test
got killed and system reboot was required to re-run the
test.
The issue was tracked down to THP split failure caused the
memory failure not being handled. The page dump showed:
[ 1785.433075] page:0000000025f9530b refcount:18 mapcount:0 mapping:000000008162eea7 index:0xa10 pfn:0x2f0200
[ 1785.443954] head:0000000025f9530b order:4 compound_mapcount:0 compound_pincount:0
[ 1785.452408] memcg:ff4247f2d28e9000
[ 1785.456304] aops:xfs_address_space_operations ino:8555182 dentry name:"baseos-filenames.solvx"
[ 1785.466612] flags: 0x1000000000012036(referenced|uptodate|lru|active|private|head|node=0|zone=2)
[ 1785.476514] raw: 1000000000012036 ffb9460f8bc07c08 ffb9460f8bc08408 ff4247f22e6299f8
[ 1785.485268] raw: 0000000000000a10 ff4247f194ade900 00000012ffffffff ff4247f2d28e9000
It was like the error was injected to a large folio for xfs
with private data attached.
With private data released before split THP, the test case
could be run successfully many times without reboot system.
Co-developed-by: Qiuxu Zhuo <qiuxu.zhuo@xxxxxxxxx>
Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@xxxxxxxxx>
Signed-off-by: Yin Fengwei <fengwei.yin@xxxxxxxxx>
Suggested-by: Matthew Wilcox <willy@xxxxxxxxxxxxx>
---
Changelog from v2:
- Use safe gfp flags for different callsite of split_huge_page_to_list
per Yang's comment.
- Remove reviewed-by tag from Aaron which was only valid for RFC patch
but keep it by mistake.
Changelog from v1:
- Move private release to split_huge_page_to_list
to cover wider path per Yang's comment.
- Update to commit message.
Changelog from RFC:
- Use new folio API per Mathhew Wilcox's suggestion.
- Add one line comment before re-get folio of page per
Miaohe's comment.
- Remove RFC tag
- Add Co-developed-by of Qiuxu who did a lot of debugging
work to locate where the real issue is.
mm/huge_memory.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 8a7c1b344abe..ae8c4e209e58 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2627,6 +2627,8 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
mapping = NULL;
anon_vma_lock_write(anon_vma);
} else {
+ gfp_t gfp;
+
mapping = head->mapping;
/* Truncated ? */
@@ -2635,8 +2637,16 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
goto out;
}
- xas_split_alloc(&xas, head, compound_order(head),
- mapping_gfp_mask(mapping) & GFP_RECLAIM_MASK);
+ gfp = current_gfp_context(mapping_gfp_mask(mapping) &
+ GFP_RECLAIM_MASK);
+
+ if (folio_test_private(folio) &&
+ !filemap_release_folio(folio, gfp)) {
+ ret = -EBUSY;
+ goto out;
+ }
+
+ xas_split_alloc(&xas, head, compound_order(head), gfp);
if (xas_error(&xas)) {
ret = xas_error(&xas);
goto out;
base-commit: d4252071b97d2027d246f6a82cbee4d52f618b47
--
2.25.1
