From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> Subject: mm/thp: allow dropping THP from page cache Once a THP is added to the page cache, it cannot be dropped via /proc/sys/vm/drop_caches. Fix this issue with proper handling in invalidate_mapping_pages(). Link: http://lkml.kernel.org/r/20191017164223.2762148-5-songliubraving@xxxxxx Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS") Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Signed-off-by: Song Liu <songliubraving@xxxxxx> Tested-by: Song Liu <songliubraving@xxxxxx> Acked-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx> Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Cc: Oleg Nesterov <oleg@xxxxxxxxxx> Cc: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx> Cc: William Kucharski <william.kucharski@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/truncate.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) --- a/mm/truncate.c~mm-thp-allow-drop-thp-from-page-cache +++ a/mm/truncate.c @@ -592,6 +592,16 @@ unsigned long invalidate_mapping_pages(s unlock_page(page); continue; } + + /* Take a pin outside pagevec */ + get_page(page); + + /* + * Drop extra pins before trying to invalidate + * the huge page. + */ + pagevec_remove_exceptionals(&pvec); + pagevec_release(&pvec); } ret = invalidate_inode_page(page); @@ -602,6 +612,8 @@ unsigned long invalidate_mapping_pages(s */ if (!ret) deactivate_file_page(page); + if (PageTransHuge(page)) + put_page(page); count += ret; } pagevec_remove_exceptionals(&pvec); _
