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/[email protected]
Signed-off-by: Jan Kara <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Al Viro <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
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; ) {
