Re: [PATCH] xfs: fix PAGE_MASK usage in xfs_free_file_space

Christoph Hellwig
2018-11-28T18:14:59Z

On Tue, Nov 27, 2018 at 03:43:34PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
>
> In commit e53c4b598, I *tried* to teach xfs to force writeback when we
> fzero/fpunch right up to EOF so that if EOF is in the middle of a page,
> the post-EOF part of the page gets zeroed before we return to userspace.
> Unfortunately, I missed the part where PAGE_MASK is ~(PAGE_SIZE - 1),
> which means that we totally fail to zero if we're fpunching and EOF is
> within the first page. Worse yet, the same PAGE_MASK thinko plagues the
> filemap_write_and_wait_range call, so we'd initiate writeback of the
> entire file, which (mostly) masked the thinko.
>
> Drop the tricky PAGE_MASK and replace it with correct usage of PAGE_SIZE
> and the proper rounding macros.
>
> Fixes: e53c4b598 ("xfs: ensure post-EOF zeroing happens after zeroing part of a file")
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

Thanks. This also happens to be much more readable as well:

Reviewed-by: Christoph Hellwig <hch@lst.de>