[rds-devel] [External] : Re: [PATCH net] rds: mark snapshot pages dirty in rds_info_getsockopt()

[Allison Henderson]

On Tue, 2026-06-09 at 01:35 -0700, Breno Leitao wrote:
> On Tue, Jun 09, 2026 at 01:02:00AM -0700, Allison Henderson wrote:
> > On Mon, 2026-06-08 at 02:32 -0700, Breno Leitao wrote:
> > > rds_info_getsockopt() pins the destination user pages with FOLL_WRITE and
> > > the RDS_INFO_* producers memcpy the snapshot into them through
> > > kmap_atomic(). Because that copy goes through the kernel direct map, the
> > > dirty bit on the user PTE is never set, so unpin_user_pages() releases the
> > > pages without marking them dirty. A file-backed destination page can then
> > > be reclaimed without writeback, silently discarding the copied data.
> > > 
> > > Use unpin_user_pages_dirty_lock() with make_dirty=true so the modified
> > > pages are marked dirty before they are unpinned.
> > > 
> > > Fixes: a8c879a7ee98 ("RDS: Info and stats")
> > > Signed-off-by: Breno Leitao <leitao at debian.org>
> > 
> > Hi Breno,
> > 
> > Thanks for adding the Fixes tag. One thing though: now that this is
> > standalone, it collides with "[PATCH net-next v3 2/2] rds: convert to
> > getsockopt_iter" since both rewrite the same unpin in the out: block of
> > rds_info_getsockopt().  
> > 
> > Easiest on everyone is to just keep it folded into the net-next series as
> > a three-patch set, rather than splitting the fix out to net.
> 
> I got from the maintainers that they want to continue to split the fixes
> into net and non fixes (features) into net-next.
> 
> 	"So just prepare for net with Fixes tags and we'll route the
> 	patches accordingly." -- Jakub
> 
> https://lore.kernel.org/all/20260527155942.45c43c8d@kernel.org/
> 
> Thanks for the review,
> --breno

I see, ok it's fine to apply my rvb then.

Thanks for working on this,
Allison