From 5a0dc7365c240795bf190766eba7a27600be3b3e Mon Sep 17 00:00:00 2001 From: Yongqiang Yang Date: Tue, 13 Dec 2011 22:29:12 -0500 Subject: [PATCH] ext4: handle EOF correctly in ext4_bio_write_page() We need to zero out part of a page which beyond EOF before setting uptodate, otherwise, mapread or write will see non-zero data beyond EOF. Signed-off-by: Yongqiang Yang Signed-off-by: "Theodore Ts'o" Cc: stable@kernel.org --- fs/ext4/page-io.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c index 7ce1d0b19c94..7e106c810c62 100644 --- a/fs/ext4/page-io.c +++ b/fs/ext4/page-io.c @@ -385,6 +385,18 @@ int ext4_bio_write_page(struct ext4_io_submit *io, block_end = block_start + blocksize; if (block_start >= len) { + /* + * Comments copied from block_write_full_page_endio: + * + * The page straddles i_size. It must be zeroed out on + * each and every writepage invocation because it may + * be mmapped. "A file is mapped in multiples of the + * page size. For a file that is not a multiple of + * the page size, the remaining memory is zeroed when + * mapped, and writes to that region are not written + * out to the file." + */ + zero_user_segment(page, block_start, block_end); clear_buffer_dirty(bh); set_buffer_uptodate(bh); continue;