This is a note to let you know that I've just added the patch titled
ext4: fix zeroing of page during writeback
to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ext4-fix-zeroing-of-page-during-writeback.patch
and it can be found in the queue-3.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From eeece469dedadf3918bad50ad80f4616a0064e90 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@xxxxxxx>
Date: Tue, 27 May 2014 12:48:55 -0400
Subject: ext4: fix zeroing of page during writeback
From: Jan Kara <jack@xxxxxxx>
commit eeece469dedadf3918bad50ad80f4616a0064e90 upstream.
Tail of a page straddling inode size must be zeroed when being written
out due to POSIX requirement that modifications of mmaped page beyond
inode size must not be written to the file. ext4_bio_write_page() did
this only for blocks fully beyond inode size but didn't properly zero
blocks partially beyond inode size. Fix this.
The problem has been uncovered by mmap_11-4 test in openposix test suite
(part of LTP).
Reported-by: Xiaoguang Wang <wangxg.fnst@xxxxxxxxxxxxxx>
Fixes: 5a0dc7365c240
Fixes: bd2d0210cf22f
CC: stable@xxxxxxxxxxxxxxx
Signed-off-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/ext4/page-io.c | 24 +++++++++++-------------
1 file changed, 11 insertions(+), 13 deletions(-)
--- a/fs/ext4/page-io.c
+++ b/fs/ext4/page-io.c
@@ -422,6 +422,17 @@ int ext4_bio_write_page(struct ext4_io_s
ClearPageError(page);
/*
+ * 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."
+ */
+ if (len < PAGE_CACHE_SIZE)
+ zero_user_segment(page, len, PAGE_CACHE_SIZE);
+ /*
* In the first loop we prepare and mark buffers to submit. We have to
* mark all buffers in the page before submitting so that
* end_page_writeback() cannot be called from ext4_bio_end_io() when IO
@@ -432,19 +443,6 @@ int ext4_bio_write_page(struct ext4_io_s
do {
block_start = bh_offset(bh);
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_start + blocksize);
clear_buffer_dirty(bh);
set_buffer_uptodate(bh);
continue;
Patches currently in stable-queue which might be from jack@xxxxxxx are
queue-3.14/ext4-fix-zeroing-of-page-during-writeback.patch
queue-3.14/mm-page_alloc-use-word-based-accesses-for-get-set-pageblock-bitmaps.patch
queue-3.14/ext4-fix-data-integrity-sync-in-ordered-mode.patch
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