On Fri, Mar 10, 2023 at 03:19:40AM +0000, Al Viro wrote:
> On Thu, Mar 09, 2023 at 11:21:25PM +0800, Yangtao Li wrote:
> > Use i_blockmask() to simplify code.
> >
> > Signed-off-by: Yangtao Li <frank.li@xxxxxxxx>
> > ---
> > v3:
> > -none
> > v2:
> > -convert to i_blockmask()
> > fs/ext4/inode.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> > index d251d705c276..eec36520e5e9 100644
> > --- a/fs/ext4/inode.c
> > +++ b/fs/ext4/inode.c
> > @@ -2218,7 +2218,7 @@ static int mpage_process_page_bufs(struct mpage_da_data *mpd,
> > {
> > struct inode *inode = mpd->inode;
> > int err;
> > - ext4_lblk_t blocks = (i_size_read(inode) + i_blocksize(inode) - 1)
> > + ext4_lblk_t blocks = (i_size_read(inode) + i_blockmask(inode))
> > >> inode->i_blkbits;
>
> Umm... That actually asks for DIV_ROUND_UP(i_size_read_inode(), i_blocksize(inode)) -
> compiler should bloody well be able to figure out that division by (1 << n) is
> shift down by n and it's easier to follow that way...
BTW, here the fact that you are adding the mask is misleading - it's true,
but we are not using it as a mask - it's straight arithmetics.
One can do an equivalent code where it would've been used as a mask, but that
would be harder to read -
(((i_size_read(inode) - 1) | i_blockmask(inode)) + 1) >> inode->i_blkbits
and I doubt anyone wants that kind of puzzles to stumble upon.
