Re: [Lsf-pc] [LSF/MM TOPIC] sharing pages between mappings

2017-01-17 Thread Jan Kara
On Wed 11-01-17 15:13:19, Miklos Szeredi wrote: > On Wed, Jan 11, 2017 at 12:51 PM, Jan Kara wrote: > > On Wed 11-01-17 11:29:28, Miklos Szeredi wrote: > >> I know there's work on this for xfs, but could this be done in generic mm > >> code? > >> > >> What are the obstacles?

Re: [LSF/MM TOPIC] sharing pages between mappings

2017-01-11 Thread Andreas Dilger
On Jan 11, 2017, at 3:29 AM, Miklos Szeredi wrote: > > I know there's work on this for xfs, but could this be done in generic mm > code? > > What are the obstacles? page->mapping and page->index are the obvious ones. > > If that's too difficult is it maybe enough to share

Re: [Lsf-pc] [LSF/MM TOPIC] sharing pages between mappings

2017-01-11 Thread Darrick J. Wong
On Wed, Jan 11, 2017 at 12:51:43PM +0100, Jan Kara wrote: > On Wed 11-01-17 11:29:28, Miklos Szeredi wrote: > > I know there's work on this for xfs, but could this be done in generic mm > > code? > > > > What are the obstacles? page->mapping and page->index are the obvious > > ones. > > Yes,

Re: [Lsf-pc] [LSF/MM TOPIC] sharing pages between mappings

2017-01-11 Thread Miklos Szeredi
On Wed, Jan 11, 2017 at 12:51 PM, Jan Kara wrote: > On Wed 11-01-17 11:29:28, Miklos Szeredi wrote: >> I know there's work on this for xfs, but could this be done in generic mm >> code? >> >> What are the obstacles? page->mapping and page->index are the obvious >> ones. > > Yes,

Re: [Lsf-pc] [LSF/MM TOPIC] sharing pages between mappings

2017-01-11 Thread Jan Kara
On Wed 11-01-17 11:29:28, Miklos Szeredi wrote: > I know there's work on this for xfs, but could this be done in generic mm > code? > > What are the obstacles? page->mapping and page->index are the obvious > ones. Yes, these two are the main that come to my mind. Also you'd need to somehow

[LSF/MM TOPIC] sharing pages between mappings

2017-01-11 Thread Miklos Szeredi
I know there's work on this for xfs, but could this be done in generic mm code? What are the obstacles? page->mapping and page->index are the obvious ones. If that's too difficult is it maybe enough to share mappings between files while they are completely identical and clone the mapping when