Commit 4b89a37d authored by Jan Kara's avatar Jan Kara Committed by Andrew Morton
Browse files

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: default avatarJan Kara <jack@suse.cz>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 6c364edc

fs/mpage.c

+6 −0
Original line number Diff line number Diff line
@@ -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; ) {