Re: [PATCH 0/2 v8] add ioctl/sysfs to donate file-backed pages

Re: [PATCH 0/2 v8] add ioctl/sysfs to donate file-backed pages

[Christoph Hellwig]

On Fri, Jan 31, 2025 at 10:27:55PM +0000, Jaegeuk Kim wrote:
> Note, let me keep improving this patch set, while trying to get some feedbacks
> from MM and API folks from [1].

Please actually drive it instead of only interacting once after
I told you to.  The feedback is clearly that it is a MM thing, so please
drive it forward instead of going back to the hacky file system version.

> 
> If users clearly know which file-backed pages to reclaim in system view, they
> can use this ioctl() to register in advance and reclaim all at once later.
> 
> I'd like to propose this API in F2FS only, since
> 1) the use-case is quite limited in Android at the moment. Once it's generall
> accepted with more use-cases, happy to propose a generic API such as fadvise.
> Please chime in, if there's any needs.
> 
> 2) it's file-backed pages which requires to maintain the list of inode objects.
> I'm not sure this fits in MM tho, also happy to listen to any feedback.
> 
> [1] https://lore.kernel.org/lkml/Z4qmF2n2pzuHqad_@google.com/
> 
> Change log from v7:
>  - change the sysfs entry to reclaim pages in all f2fs mounts
> 
> Change log from v6:
>  - change sysfs entry name to reclaim_caches_kb
> 
> Jaegeuk Kim (2):
>   f2fs: register inodes which is able to donate pages
>   f2fs: add a sysfs entry to request donate file-backed pages
> 
> Jaegeuk Kim (2):
>   f2fs: register inodes which is able to donate pages
>   f2fs: add a sysfs entry to request donate file-backed pages
> 
>  Documentation/ABI/testing/sysfs-fs-f2fs |  7 ++
>  fs/f2fs/debug.c                         |  3 +
>  fs/f2fs/f2fs.h                          | 14 +++-
>  fs/f2fs/file.c                          | 60 +++++++++++++++++
>  fs/f2fs/inode.c                         | 14 ++++
>  fs/f2fs/shrinker.c                      | 90 +++++++++++++++++++++++++
>  fs/f2fs/super.c                         |  1 +
>  fs/f2fs/sysfs.c                         | 63 +++++++++++++++++
>  include/uapi/linux/f2fs.h               |  7 ++
>  9 files changed, 258 insertions(+), 1 deletion(-)
> 
> -- 
> 2.48.1.362.g079036d154-goog
> 
> 
---end quoted text---

Re: [PATCH 0/2 v8] add ioctl/sysfs to donate file-backed pages

[Jaegeuk Kim]

On 02/03, Christoph Hellwig wrote:
> On Fri, Jan 31, 2025 at 10:27:55PM +0000, Jaegeuk Kim wrote:
> > Note, let me keep improving this patch set, while trying to get some feedbacks
> > from MM and API folks from [1].
> 
> Please actually drive it instead of only interacting once after
> I told you to.  The feedback is clearly that it is a MM thing, so please
> drive it forward instead of going back to the hacky file system version.

I keep saying working in parallel for production. And, no worries, I won't
merge this to -next until I get the feedback from the MM folks. I was
waiting for a couple of weeks before bothering them, so will ping there.

> 
> > 
> > If users clearly know which file-backed pages to reclaim in system view, they
> > can use this ioctl() to register in advance and reclaim all at once later.
> > 
> > I'd like to propose this API in F2FS only, since
> > 1) the use-case is quite limited in Android at the moment. Once it's generall
> > accepted with more use-cases, happy to propose a generic API such as fadvise.
> > Please chime in, if there's any needs.
> > 
> > 2) it's file-backed pages which requires to maintain the list of inode objects.
> > I'm not sure this fits in MM tho, also happy to listen to any feedback.
> > 
> > [1] https://lore.kernel.org/lkml/Z4qmF2n2pzuHqad_@google.com/
> > 
> > Change log from v7:
> >  - change the sysfs entry to reclaim pages in all f2fs mounts
> > 
> > Change log from v6:
> >  - change sysfs entry name to reclaim_caches_kb
> > 
> > Jaegeuk Kim (2):
> >   f2fs: register inodes which is able to donate pages
> >   f2fs: add a sysfs entry to request donate file-backed pages
> > 
> > Jaegeuk Kim (2):
> >   f2fs: register inodes which is able to donate pages
> >   f2fs: add a sysfs entry to request donate file-backed pages
> > 
> >  Documentation/ABI/testing/sysfs-fs-f2fs |  7 ++
> >  fs/f2fs/debug.c                         |  3 +
> >  fs/f2fs/f2fs.h                          | 14 +++-
> >  fs/f2fs/file.c                          | 60 +++++++++++++++++
> >  fs/f2fs/inode.c                         | 14 ++++
> >  fs/f2fs/shrinker.c                      | 90 +++++++++++++++++++++++++
> >  fs/f2fs/super.c                         |  1 +
> >  fs/f2fs/sysfs.c                         | 63 +++++++++++++++++
> >  include/uapi/linux/f2fs.h               |  7 ++
> >  9 files changed, 258 insertions(+), 1 deletion(-)
> > 
> > -- 
> > 2.48.1.362.g079036d154-goog
> > 
> > 
> ---end quoted text---