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charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: CF6244001B X-Rspam-User: X-Stat-Signature: 1qncftuoqufzm7s8g6hzbe1iefjhutbz X-HE-Tag: 1681852285-155836 X-HE-Meta: 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 ZrRBO7DN 6L0INnVXJF5FsDAb1Ey0GfRin5sA3HLTgnTlCPO2YXKz6vY/7b1U9AlkJ+8rDU2nDZh3j1cYW6FcF553228CKlDQOrn7harltWdtGclsFkFIso7NVrktD7HRXZMydGxtNNDMIvhDVUt1lkWKoa44Ul/ZWPrG3PvZtMyspgRga/q8ZEDx7OdO7cMH62SEC7HTExTIvBrvrm6dn76lxQSvPrkzy2Zqp0yuYGIMagmFXsxtqL6T3hHZjsKIhog3wyVH3dO8yPKHqNHXKl9amcGKBHT2xdw76NfZ+e5iEuPoUbhJKrHQiDL5QnWUgBrX9QzGfmVZ32G4gqin05SUvTJn8OOeGJGRC8hbL3S8jzUqt1rTFJx4pr3Rqq1qi0gTVdahDJX7tz0Akdx0SnyhlTSPwmtH4Gw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Apr 17, 2023 at 09:41:41PM -0700, Hugh Dickins wrote: > On Thu, 9 Mar 2023, Luis Chamberlain wrote: > > > In theory when info->flags & VM_LOCKED we should not be getting > > shem_writepage() called so we should be verifying this with a > > WARN_ON_ONCE(). Since we should not be swapping then best to ensure > > we also don't do the folio split earlier too. So just move the check > > early to avoid folio splits in case its a dubious call. > > > > We also have a similar early bail when !total_swap_pages so just move > > that earlier to avoid the possible folio split in the same situation. > > > > Acked-by: David Hildenbrand > > Reviewed-by: Christian Brauner > > Signed-off-by: Luis Chamberlain > > --- > > mm/shmem.c | 10 ++++++---- > > 1 file changed, 6 insertions(+), 4 deletions(-) > > > > diff --git a/mm/shmem.c b/mm/shmem.c > > index 68e9970baf1e..dfd995da77b4 100644 > > --- a/mm/shmem.c > > +++ b/mm/shmem.c > > @@ -1350,6 +1350,12 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc) > > if (WARN_ON_ONCE(!wbc->for_reclaim)) > > goto redirty; > > > > + if (WARN_ON_ONCE(info->flags & VM_LOCKED)) > > + goto redirty; > > Well, okay, I don't mind that. But shall we take bets on how soon syzbot > (hope it's not watching) will try flipping SHM_LOCK on while swapping out > pages from a SHM segment, and hit that warning? Perhaps I'm wrong, but I > don't think any serialization prevents that. I though that may be the case. Would such serialization be welcomed? Luis