The patch titled Subject: mm/thp: flush file for !is_shmem PageDirty() case in collapse_file() has been removed from the -mm tree. Its filename was mmthp-recheck-each-page-before-collapsing-file-thp-fix.patch This patch was dropped because it was folded into mmthp-recheck-each-page-before-collapsing-file-thp.patch ------------------------------------------------------ From: Song Liu <songliubraving@xxxxxx> Subject: mm/thp: flush file for !is_shmem PageDirty() case in collapse_file() For non-shmem file THPs, khugepaged only collapses read only .text mapping (VM_DENYWRITE). These pages should not be dirty except the case where the file hasn't been flushed since first write. Call filemap_flush() in collapse_file() to accelerate the write back in such cases. Also add warning if PageDirty() triggered for pages from readahead path. Link: http://lkml.kernel.org/r/20191030200736.3455046-1-songliubraving@xxxxxx Signed-off-by: Song Liu <songliubraving@xxxxxx> Reported-by: syzbot+efb9e48b9fbdc49bb34a@xxxxxxxxxxxxxxxxxxxxxxxxx Tested-by: syzbot+efb9e48b9fbdc49bb34a@xxxxxxxxxxxxxxxxxxxxxxxxx Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: William Kucharski <william.kucharski@xxxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/khugepaged.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) --- a/mm/khugepaged.c~mmthp-recheck-each-page-before-collapsing-file-thp-fix +++ a/mm/khugepaged.c @@ -1601,6 +1601,33 @@ static void collapse_file(struct mm_stru result = SCAN_FAIL; goto xa_unlocked; } + if (WARN_ON_ONCE(PageDirty(page))) { + /* + * page from readahead should not + * be dirty. Show warning if this + * somehow happens. + */ + result = SCAN_FAIL; + goto out_unlock; + } + } else if (PageDirty(page)) { + /* + * khugepaged only works on read-only fd, + * so this page is dirty because it hasn't + * been flushed since first write. There + * won't be new dirty pages. + * + * Trigger async flush here and hope the + * writeback is done when khugepaged + * revisits this page. + * + * This is a one-off situation. We are not + * forcing writeback in loop. + */ + xas_unlock_irq(&xas); + filemap_flush(mapping); + result = SCAN_FAIL; + goto xa_unlocked; } else if (trylock_page(page)) { get_page(page); xas_unlock_irq(&xas); _ Patches currently in -mm which might be from songliubraving@xxxxxx are mmthp-recheck-each-page-before-collapsing-file-thp.patch maintainers-update-information-for-memory-management.patch