Re: [PATCH 18/41] mm/khugepaged: write-lock VMA while collapsing a huge page

2023-01-18 Thread Suren Baghdasaryan
On Wed, Jan 18, 2023 at 1:40 AM Michal Hocko wrote: > > On Tue 17-01-23 21:28:06, Jann Horn wrote: > > On Tue, Jan 17, 2023 at 4:25 PM Michal Hocko wrote: > > > On Mon 09-01-23 12:53:13, Suren Baghdasaryan wrote: > > > > Protect VMA from concurrent page fault handler while collapsing a huge > >

Re: [PATCH 18/41] mm/khugepaged: write-lock VMA while collapsing a huge page

2023-01-18 Thread Jann Horn
On Wed, Jan 18, 2023 at 10:40 AM Michal Hocko wrote: > On Tue 17-01-23 21:28:06, Jann Horn wrote: > > On Tue, Jan 17, 2023 at 4:25 PM Michal Hocko wrote: > > > On Mon 09-01-23 12:53:13, Suren Baghdasaryan wrote: > > > > Protect VMA from concurrent page fault handler while collapsing a huge > > >

Re: [PATCH 18/41] mm/khugepaged: write-lock VMA while collapsing a huge page

2023-01-18 Thread Michal Hocko
On Tue 17-01-23 21:28:06, Jann Horn wrote: > On Tue, Jan 17, 2023 at 4:25 PM Michal Hocko wrote: > > On Mon 09-01-23 12:53:13, Suren Baghdasaryan wrote: > > > Protect VMA from concurrent page fault handler while collapsing a huge > > > page. Page fault handler needs a stable PMD to use PTL and

Re: [PATCH 18/41] mm/khugepaged: write-lock VMA while collapsing a huge page

2023-01-17 Thread Suren Baghdasaryan
On Tue, Jan 17, 2023 at 12:28 PM Jann Horn wrote: > > On Tue, Jan 17, 2023 at 4:25 PM Michal Hocko wrote: > > On Mon 09-01-23 12:53:13, Suren Baghdasaryan wrote: > > > Protect VMA from concurrent page fault handler while collapsing a huge > > > page. Page fault handler needs a stable PMD to use

Re: [PATCH 18/41] mm/khugepaged: write-lock VMA while collapsing a huge page

2023-01-17 Thread Jann Horn
On Tue, Jan 17, 2023 at 4:25 PM Michal Hocko wrote: > On Mon 09-01-23 12:53:13, Suren Baghdasaryan wrote: > > Protect VMA from concurrent page fault handler while collapsing a huge > > page. Page fault handler needs a stable PMD to use PTL and relies on > > per-VMA lock to prevent concurrent PMD

Re: [PATCH 18/41] mm/khugepaged: write-lock VMA while collapsing a huge page

2023-01-17 Thread Michal Hocko
On Mon 09-01-23 12:53:13, Suren Baghdasaryan wrote: > Protect VMA from concurrent page fault handler while collapsing a huge > page. Page fault handler needs a stable PMD to use PTL and relies on > per-VMA lock to prevent concurrent PMD changes. pmdp_collapse_flush(), > set_huge_pmd() and

[PATCH 18/41] mm/khugepaged: write-lock VMA while collapsing a huge page

2023-01-09 Thread Suren Baghdasaryan
Protect VMA from concurrent page fault handler while collapsing a huge page. Page fault handler needs a stable PMD to use PTL and relies on per-VMA lock to prevent concurrent PMD changes. pmdp_collapse_flush(), set_huge_pmd() and collapse_and_free_pmd() can modify a PMD, which will not be detected