The patch titled
Subject: fs: don't allocate blocks beyond EOF from __mpage_writepage
has been added to the -mm mm-unstable branch. Its filename is
fs-dont-allocate-blocks-beyond-eof-from-__mpage_writepage.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/fs-dont-allocate-blocks-beyond-eof-from-__mpage_writepage.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Jan Kara <jack@xxxxxxx>
Subject: fs: don't allocate blocks beyond EOF from __mpage_writepage
Date: Tue, 3 Jan 2023 11:44:30 +0100
When __mpage_writepage() is called for a page beyond EOF, it will go and
allocate all blocks underlying the page. This is not only unnecessary but
this way blocks can get leaked (e.g. if a page beyond EOF is marked dirty
but in the end write fails and i_size is not extended).
Link: https://lkml.kernel.org/r/20230103104430.27749-1-jack@xxxxxxx
Signed-off-by: Jan Kara <jack@xxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/mpage.c | 6 ++++++
1 file changed, 6 insertions(+)
--- a/fs/mpage.c~fs-dont-allocate-blocks-beyond-eof-from-__mpage_writepage
+++ a/fs/mpage.c
@@ -524,6 +524,12 @@ static int __mpage_writepage(struct page
*/
BUG_ON(!PageUptodate(page));
block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits);
+ /*
+ * Whole page beyond EOF? Skip allocating blocks to avoid leaking
+ * space.
+ */
+ if (block_in_file >= (i_size + (1 << blkbits) - 1) >> blkbits)
+ goto page_is_mapped;
last_block = (i_size - 1) >> blkbits;
map_bh.b_page = page;
for (page_block = 0; page_block < blocks_per_page; ) {
_
Patches currently in -mm which might be from jack@xxxxxxx are
fs-dont-allocate-blocks-beyond-eof-from-__mpage_writepage.patch
