From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> Subject: mm, rmap: fix false positive VM_BUG() in page_add_file_rmap() PageTransCompound() doesn't distinguish THP from from any other type of compound pages. This can lead to false-positive VM_BUG_ON() in page_add_file_rmap() if called on compound page from a driver[1]. I think we can exclude such cases by checking if the page belong to a mapping. The VM_BUG_ON_PAGE() is downgraded to VM_WARN_ON_ONCE(). This path should not cause any harm to non-THP page, but good to know if we step on anything else. [1] http://lkml.kernel.org/r/c711e067-0bff-a6cb-3c37-04dfe77d2db1@xxxxxxxxxx Link: http://lkml.kernel.org/r/20160810161345.GA67522@xxxxxxxxxxxxxxxxxx Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Reported-by: Laura Abbott <labbott@xxxxxxxxxx> Tested-by: Laura Abbott <labbott@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/rmap.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff -puN mm/rmap.c~mm-rmap-fix-false-positive-vm_bug-in-page_add_file_rmap mm/rmap.c --- a/mm/rmap.c~mm-rmap-fix-false-positive-vm_bug-in-page_add_file_rmap +++ a/mm/rmap.c @@ -1284,8 +1284,9 @@ void page_add_file_rmap(struct page *pag VM_BUG_ON_PAGE(!PageSwapBacked(page), page); __inc_node_page_state(page, NR_SHMEM_PMDMAPPED); } else { - if (PageTransCompound(page)) { - VM_BUG_ON_PAGE(!PageLocked(page), page); + if (PageTransCompound(page) && page_mapping(page)) { + VM_WARN_ON_ONCE(!PageLocked(page)); + SetPageDoubleMap(compound_head(page)); if (PageMlocked(page)) clear_page_mlock(compound_head(page)); _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
