From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ralph Campbell Subject: Re: [PATCH 1/9] mm: Allow the [page|pfn]_mkwrite callbacks to drop the mmap_sem Date: Fri, 12 Apr 2019 11:52:18 -0700 Message-ID: References: <20190412160338.64994-1-thellstrom@vmware.com> <20190412160338.64994-2-thellstrom@vmware.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <20190412160338.64994-2-thellstrom@vmware.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Thomas Hellstrom , "dri-devel@lists.freedesktop.org" , Linux-graphics-maintainer , "linux-kernel@vger.kernel.org" Cc: Andrew Morton , Matthew Wilcox , Will Deacon , Peter Zijlstra , Rik van Riel , Minchan Kim , Michal Hocko , Huang Ying , Souptick Joarder , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , "linux-mm@kvack.org" List-Id: dri-devel@lists.freedesktop.org On 4/12/19 9:04 AM, Thomas Hellstrom wrote: > Driver fault callbacks are allowed to drop the mmap_sem when expecting > long hardware waits to avoid blocking other mm users. Allow the mkwrite > callbacks to do the same by returning early on VM_FAULT_RETRY. >=20 > In particular we want to be able to drop the mmap_sem when waiting for > a reservation object lock on a GPU buffer object. These locks may be > held while waiting for the GPU. >=20 > Cc: Andrew Morton > Cc: Matthew Wilcox > Cc: Will Deacon > Cc: Peter Zijlstra > Cc: Rik van Riel > Cc: Minchan Kim > Cc: Michal Hocko > Cc: Huang Ying > Cc: Souptick Joarder > Cc: "J=C3=A9r=C3=B4me Glisse" > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org >=20 > Signed-off-by: Thomas Hellstrom Reviewed-by: Ralph Campbell > --- > mm/memory.c | 10 ++++++---- > 1 file changed, 6 insertions(+), 4 deletions(-) >=20 > diff --git a/mm/memory.c b/mm/memory.c > index e11ca9dd823f..a95b4a3b1ae2 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -2144,7 +2144,7 @@ static vm_fault_t do_page_mkwrite(struct vm_fault *= vmf) > ret =3D vmf->vma->vm_ops->page_mkwrite(vmf); > /* Restore original flags so that caller is not surprised */ > vmf->flags =3D old_flags; > - if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) > + if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_RETRY | VM_FAULT_NOPAGE))= ) A very minor nit, for consistency elsewhere in mm/memory.c, could you make this be: (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY) > return ret; > if (unlikely(!(ret & VM_FAULT_LOCKED))) { > lock_page(page); > @@ -2419,7 +2419,7 @@ static vm_fault_t wp_pfn_shared(struct vm_fault *vm= f) > pte_unmap_unlock(vmf->pte, vmf->ptl); > vmf->flags |=3D FAULT_FLAG_MKWRITE; > ret =3D vma->vm_ops->pfn_mkwrite(vmf); > - if (ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)) > + if (ret & (VM_FAULT_ERROR | VM_FAULT_RETRY | VM_FAULT_NOPAGE)) > return ret; > return finish_mkwrite_fault(vmf); > } > @@ -2440,7 +2440,8 @@ static vm_fault_t wp_page_shared(struct vm_fault *v= mf) > pte_unmap_unlock(vmf->pte, vmf->ptl); > tmp =3D do_page_mkwrite(vmf); > if (unlikely(!tmp || (tmp & > - (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) { > + (VM_FAULT_ERROR | VM_FAULT_RETRY | > + VM_FAULT_NOPAGE)))) { > put_page(vmf->page); > return tmp; > } > @@ -3494,7 +3495,8 @@ static vm_fault_t do_shared_fault(struct vm_fault *= vmf) > unlock_page(vmf->page); > tmp =3D do_page_mkwrite(vmf); > if (unlikely(!tmp || > - (tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) { > + (tmp & (VM_FAULT_ERROR | VM_FAULT_RETRY | > + VM_FAULT_NOPAGE)))) { > put_page(vmf->page); > return tmp; > } >=20