From: Joao Martins <joao.m.martins@xxxxxxxxxx> Subject: memory-failure: fetch compound_head after pgmap_pfn_valid() memory_failure_dev_pagemap() at the moment assumes base pages (e.g. dax_lock_page()). For devmap with compound pages fetch the compound_head in case a tail page memory failure is being handled. Currently this is a nop, but in the advent of compound pages in dev_pagemap it allows memory_failure_dev_pagemap() to keep working. Without this fix memory-failure handling (i.e. MCEs on pmem) with device-dax configured namespaces will regress (and crash). Link: https://lkml.kernel.org/r/20211202204422.26777-2-joao.m.martins@xxxxxxxxxx Reported-by: Jane Chu <jane.chu@xxxxxxxxxx> Signed-off-by: Joao Martins <joao.m.martins@xxxxxxxxxx> Reviewed-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx> Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx> Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/memory-failure.c | 6 ++++++ 1 file changed, 6 insertions(+) --- a/mm/memory-failure.c~memory-failure-fetch-compound_head-after-pgmap_pfn_valid +++ a/mm/memory-failure.c @@ -1596,6 +1596,12 @@ static int memory_failure_dev_pagemap(un } /* + * Pages instantiated by device-dax (not filesystem-dax) + * may be compound pages. + */ + page = compound_head(page); + + /* * Prevent the inode from being freed while we are interrogating * the address_space, typically this would be handled by * lock_page(), but dax pages do not use the page lock. This _
