diff mbox series

[v3,4/6] ext4: convert to use i_blockmask()

Message ID 20230309152127.41427-4-frank.li@vivo.com
State New
Headers
Series [v3,1/6] fs: add i_blockmask() |

Commit Message

李扬韬 March 9, 2023, 3:21 p.m. UTC 
  Use i_blockmask() to simplify code.

Signed-off-by: Yangtao Li <frank.li@vivo.com>
---
v3:
-none
v2:
-convert to i_blockmask()
 fs/ext4/inode.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Al Viro March 10, 2023, 3:19 a.m. UTC | #1 
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@vivo.com>
> ---
> 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...
Al Viro March 10, 2023, 3:32 a.m. UTC | #2 
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@vivo.com>
> > ---
> > 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.
diff mbox series

Patch

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;
 
 	if (ext4_verity_in_progress(inode))