From: Huaisheng Ye <[email protected]>
The type of offset within struct iomap is loff_t, which represents
file offset of mapping.
In ext2_iomap_begin, iomap->offset shall be given a type cast as
loff_t instead of u64.
Signed-off-by: Huaisheng Ye <[email protected]>
---
fs/ext2/inode.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index 7163590..ca211bd 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -816,7 +816,7 @@ static int ext2_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
iomap->flags = 0;
iomap->bdev = inode->i_sb->s_bdev;
- iomap->offset = (u64)first_block << blkbits;
+ iomap->offset = (loff_t)first_block << blkbits;
iomap->dax_dev = sbi->s_daxdev;
if (ret == 0) {
--
1.8.3.1
On Sun, Jul 01, 2018 at 02:18:47PM +0800, Huaisheng Ye wrote:
> From: Huaisheng Ye <[email protected]>
>
> The type of offset within struct iomap is loff_t, which represents
> file offset of mapping.
>
> In ext2_iomap_begin, iomap->offset shall be given a type cast as
> loff_t instead of u64.
Why is it an error? loff_t is uniformly typedefed to long long.
In which case the second variant is different from the first one
*and* does not step into nasal demon territory?
> - iomap->offset = (u64)first_block << blkbits;
> + iomap->offset = (loff_t)first_block << blkbits;
---- On Mon, 02 Jul 2018 03:26:00 +0800 Al Viro <[email protected]> wrote ----
> On Sun, Jul 01, 2018 at 02:18:47PM +0800, Huaisheng Ye wrote:
> > From: Huaisheng Ye <[email protected]>
> >
> > The type of offset within struct iomap is loff_t, which represents
> > file offset of mapping.
> >
> > In ext2_iomap_begin, iomap->offset shall be given a type cast as
> > loff_t instead of u64.
>
> Why is it an error? loff_t is uniformly typedefed to long long.
> In which case the second variant is different from the first one
> *and* does not step into nasal demon territory?
Sorry for my inaccuracy.
The type of iomap->offset is loff_t, is it better to cast first_block
to loff_t, then do the left shift operation?
>
> > - iomap->offset = (u64)first_block << blkbits;
> > + iomap->offset = (loff_t)first_block << blkbits;
>
---
Cheers,
Huaisheng
On Mon 02-07-18 14:23:42, Huaisheng Ye wrote:
> ---- On Mon, 02 Jul 2018 03:26:00 +0800 Al Viro <[email protected]> wrote ----
> > On Sun, Jul 01, 2018 at 02:18:47PM +0800, Huaisheng Ye wrote:
> > > From: Huaisheng Ye <[email protected]>
> > >
> > > The type of offset within struct iomap is loff_t, which represents
> > > file offset of mapping.
> > >
> > > In ext2_iomap_begin, iomap->offset shall be given a type cast as
> > > loff_t instead of u64.
> >
> > Why is it an error? loff_t is uniformly typedefed to long long.
> > In which case the second variant is different from the first one
> > *and* does not step into nasal demon territory?
>
> Sorry for my inaccuracy.
> The type of iomap->offset is loff_t, is it better to cast first_block
> to loff_t, then do the left shift operation?
I think what Al meant is that in the kernel loff_t is 64-bit anyway and
furthermore it is signed which means most people have to look up C standard
to remember how right shift is (un)defined if it would overflow ;). So this
does not really make the code any more readable. Rather on contrary...
Honza
>
> >
> > > - iomap->offset = (u64)first_block << blkbits;
> > > + iomap->offset = (loff_t)first_block << blkbits;
> >
>
> ---
> Cheers,
> Huaisheng
>
>
--
Jan Kara <jack-IBi9RG/[email protected]>
SUSE Labs, CR