On 2025/10/23 11:05, Zi Yan wrote:
folio split clears PG_has_hwpoisoned, but the flag should be preserved in after-split folios containing pages with PG_hwpoisoned flag if the folio is split to >0 order folios. Scan all pages in a to-be-split folio to determine which after-split folios need the flag.
An alternatives is to change PG_has_hwpoisoned to PG_maybe_hwpoisoned to avoid the scan and set it on all after-split folios, but resulting false positive has undesirable negative impact. To remove false positive, caller of folio_test_has_hwpoisoned() and folio_contain_hwpoisoned_page() needs to do the scan. That might be causing a hassle for current and future callers and more costly than doing the scan in the split code. More details are discussed in [1].
This issue can be exposed via:
- splitting a has_hwpoisoned folio to >0 order from debugfs interface;
- truncating part of a has_hwpoisoned folio in truncate_inode_partial_folio().
And later accesses to a hwpoisoned page could be possible due to the missing has_hwpoisoned folio flag. This will lead to MCE errors.
Link: https://lore.kernel.org/all/CAHbLzkoOZm0PXxE9qwtF4gKR=cpRXrSrJ9V9Pm2DJexs985... [1] Fixes: c010d47f107f ("mm: thp: split huge page to any lower order pages") Cc: stable@vger.kernel.org Signed-off-by: Zi Yan ziy@nvidia.com
LGTM. Reviewed-by: Baolin Wang baolin.wang@linux.alibaba.com