[38/45] ext4: handle EOF correctly in ext4_bio_write_page()
From: Greg KH <gregkh@suse.de>
Date: 2011-12-16 19:56:00
Also in:
lkml
3.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yongqiang Yang <redacted> commit 5a0dc7365c240795bf190766eba7a27600be3b3e upstream. 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 <redacted> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> --- fs/ext4/page-io.c | 12 ++++++++++++ 1 file changed, 12 insertions(+)
--- a/fs/ext4/page-io.c
+++ b/fs/ext4/page-io.c@@ -405,6 +405,18 @@ int ext4_bio_write_page(struct ext4_io_s 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;