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Shutemov" , Maya Gokhale , Johannes Weiner , Marty McFadden , Denis Plotnikov , Hugh Dickins , "Dr . David Alan Gilbert" , Jerome Glisse Subject: [PATCH v6 15/19] userfaultfd: wp: don't wake up when doing write protect Date: Thu, 20 Feb 2020 11:31:08 -0500 Message-Id: <20200220163112.11409-16-peterx@redhat.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200220163112.11409-1-peterx@redhat.com> References: <20200220163112.11409-1-peterx@redhat.com> MIME-Version: 1.0 X-MC-Unique: PG0l8wAtOqexKNHexpmaeQ-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable 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: It does not make sense to try to wake up any waiting thread when we're write-protecting a memory region. Only wake up when resolving a write protected page fault. Reviewed-by: Mike Rapoport Signed-off-by: Peter Xu --- fs/userfaultfd.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 59e9e399fddb..6e878d23547c 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1812,6 +1812,7 @@ static int userfaultfd_writeprotect(struct userfaultf= d_ctx *ctx, =09struct uffdio_writeprotect uffdio_wp; =09struct uffdio_writeprotect __user *user_uffdio_wp; =09struct userfaultfd_wake_range range; +=09bool mode_wp, mode_dontwake; =20 =09if (READ_ONCE(ctx->mmap_changing)) =09=09return -EAGAIN; @@ -1830,18 +1831,20 @@ static int userfaultfd_writeprotect(struct userfaul= tfd_ctx *ctx, =09if (uffdio_wp.mode & ~(UFFDIO_WRITEPROTECT_MODE_DONTWAKE | =09=09=09 UFFDIO_WRITEPROTECT_MODE_WP)) =09=09return -EINVAL; -=09if ((uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_WP) && -=09 (uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_DONTWAKE)) + +=09mode_wp =3D uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_WP; +=09mode_dontwake =3D uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_DONTWAKE; + +=09if (mode_wp && mode_dontwake) =09=09return -EINVAL; =20 =09ret =3D mwriteprotect_range(ctx->mm, uffdio_wp.range.start, -=09=09=09=09 uffdio_wp.range.len, uffdio_wp.mode & -=09=09=09=09 UFFDIO_WRITEPROTECT_MODE_WP, +=09=09=09=09 uffdio_wp.range.len, mode_wp, =09=09=09=09 &ctx->mmap_changing); =09if (ret) =09=09return ret; =20 -=09if (!(uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_DONTWAKE)) { +=09if (!mode_wp && !mode_dontwake) { =09=09range.start =3D uffdio_wp.range.start; =09=09range.len =3D uffdio_wp.range.len; =09=09wake_userfault(ctx, &range); --=20 2.24.1