On Tue, Nov 21, 2023 at 07:36:34PM +0800, Yu Kuai wrote:
> Hi,
>
> 在 2023/11/21 19:21, Ming Lei 写道:
> > On Tue, Nov 21, 2023 at 07:12:44PM +0800, Yu Kuai wrote:
> > > Hi,
> > >
> > > 在 2023/11/21 18:11, Ming Lei 写道:
> > > > The .bd_inode field of block_device is used in IO fast path of
> > > > blkdev_write_iter() and blkdev_llseek(), so it is more efficient to keep
> > > > it into the 1st cacheline.
> > > >
> > > > .bd_openers is only touched in open()/close(), and .bd_size_lock is only
> > > > for updating bdev capacity, which is in slow path too.
> > > >
> > > > So swap .bd_inode layout with .bd_openers & .bd_size_lock to move
> > > > .bd_inode into the 1st cache line.
> > >
> > > This patch looks good, do you want me do take it for a v3 for the
> > > other patchset?
> >
> > Yeah, please take it.
>
> Ok
> >
> > >
> > > And by the way, can we also move 'int bd_writers' to near 'atomic_t
> > > bd_fsfreeze_count' to save 8 bytes(int 64bit platform)?
> > >
> > > diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> > > index 07abd0165226..a47ab9249bdd 100644
> > > --- a/include/linux/blk_types.h
> > > +++ b/include/linux/blk_types.h
> > > @@ -63,11 +63,11 @@ struct block_device {
> > > int bd_holders;
> > > struct kobject *bd_holder_dir;
> > >
> > > + int bd_writers;
> > > atomic_t bd_fsfreeze_count; /* number of freeze
> > > requests */
> > > struct mutex bd_fsfreeze_mutex; /* serialize freeze/thaw
> > > */
> > >
> > > struct partition_meta_info *bd_meta_info;
> > > - int bd_writers;
> >
> > Which tree are you talking about? I don't see 'bd_writers' in both
> > linus tree and block-6.7, and for-6.8/block isn't open yet.
>
> This is introduced from commit dc85fbc92365 ("block: Add config option
> to not allow writing to mounted devices") from linux-next by Jan.
Patch isn't supposed to be against linux-next, and either you need to base the
change against maintainer tree(fs) or block tree when Jan's change lands linus
tree.
Thanks,
Ming
