Re: [PATCH 2/7] btrfs: subpagesize-blocksize: Use a global alignment for size

[Chandra Seetharaman <sekharan@us.ibm.com>]

On Mon, 2013-12-16 at 15:48 +0100, David Sterba wrote:
> On Mon, Dec 16, 2013 at 02:33:11PM +0200, saeed bishara wrote:
> > On Thu, Dec 12, 2013 at 1:38 AM, Chandra Seetharaman
> > <sekharan@us.ibm.com> wrote:
> > > In order to handle a blocksize that is smaller than the
> > > PAGE_SIZE, we need align all IOs to PAGE_SIZE.
> > >
> > > This patch defines a new macro btrfs_align_size() that
> > > calculates the alignment size based on the sectorsize
> > > and uses it at appropriate places.
> > >
> > > Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
> > > ---
> > >  fs/btrfs/btrfs_inode.h  |  7 +++++++
> > >  fs/btrfs/compression.c  |  3 ++-
> > >  fs/btrfs/extent-tree.c  | 12 ++++++------
> > >  fs/btrfs/extent_io.c    | 17 ++++++-----------
> > >  fs/btrfs/file.c         | 15 +++++++--------
> > >  fs/btrfs/inode.c        | 41 ++++++++++++++++++++++-------------------
> > >  fs/btrfs/ioctl.c        |  6 +++---
> > >  fs/btrfs/ordered-data.c |  2 +-
> > >  fs/btrfs/tree-log.c     |  2 +-
> > >  9 files changed, 55 insertions(+), 50 deletions(-)
> > >
> > > diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
> > > index ac0b39d..eee994f 100644
> > > --- a/fs/btrfs/btrfs_inode.h
> > > +++ b/fs/btrfs/btrfs_inode.h
> > > @@ -280,4 +280,11 @@ static inline void btrfs_inode_resume_unlocked_dio(struct inode *inode)
> > >                   &BTRFS_I(inode)->runtime_flags);
> > >  }
> > >
> > > +static inline u64 btrfs_align_size(struct inode *inode)
> > > +{
> > > +       if (BTRFS_I(inode)->root->sectorsize < PAGE_CACHE_SIZE)
> > > +               return (u64)PAGE_CACHE_SIZE;
> > > +       else
> > > +               return (u64)BTRFS_I(inode)->root->sectorsize;
> > > +}
> > for performance, isn't it worth to store this value instead of
> > calculating it each time?

Good suggestion Saeed. will do
> 
> I agree, would be better to add the corresponding item into fs_info,
> initialized as proposed above.

Godd idea David. will do.
>