On Tue, Jan 03, 2023 at 11:44:30AM +0100, Jan Kara wrote: > 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). > > Signed-off-by: Jan Kara <jack@xxxxxxx> > --- > fs/mpage.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/fs/mpage.c b/fs/mpage.c > index 0f8ae954a579..9f040c1d5912 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; Why not simply if (block_in_file > last_block) goto page_is_mapped; after last_block has been calculated?
