From 4b89a37d54a0b5ed6b2e5a9afc44a15a22e563f5 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Tue, 3 Jan 2023 11:44:30 +0100 Subject: [PATCH] fs: don't allocate blocks beyond EOF from __mpage_writepage 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@suse.cz Signed-off-by: Jan Kara Reviewed-by: Christoph Hellwig Cc: Matthew Wilcox Cc: Al Viro Signed-off-by: Andrew Morton --- fs/mpage.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/mpage.c b/fs/mpage.c index d36a954..b8e7975 100644 --- a/fs/mpage.c +++ b/fs/mpage.c @@ -524,6 +524,12 @@ static int __mpage_writepage(struct page *page, struct writeback_control *wbc, */ 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; ) { -- 2.7.4