Re: [PATCH v2 23/26] userfaultfd: wp: don't wake up when doing write protect
From: Mike Rapoport <hidden>
Date: 2019-02-26 08:00:58
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On Tue, Feb 12, 2019 at 10:56:29AM +0800, Peter Xu wrote:
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. Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Mike Rapoport <redacted>
quoted hunk ↗ jump to hunk
--- fs/userfaultfd.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-)diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 81962d62520c..f1f61a0278c2 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c@@ -1771,6 +1771,7 @@ static int userfaultfd_writeprotect(struct userfaultfd_ctx *ctx, struct uffdio_writeprotect uffdio_wp; struct uffdio_writeprotect __user *user_uffdio_wp; struct userfaultfd_wake_range range; + bool mode_wp, mode_dontwake; if (READ_ONCE(ctx->mmap_changing)) return -EAGAIN;@@ -1789,18 +1790,20 @@ static int userfaultfd_writeprotect(struct userfaultfd_ctx *ctx, if (uffdio_wp.mode & ~(UFFDIO_WRITEPROTECT_MODE_DONTWAKE | UFFDIO_WRITEPROTECT_MODE_WP)) return -EINVAL; - if ((uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_WP) && - (uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_DONTWAKE)) + + mode_wp = uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_WP; + mode_dontwake = uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_DONTWAKE; + + if (mode_wp && mode_dontwake) return -EINVAL; ret = mwriteprotect_range(ctx->mm, uffdio_wp.range.start, - uffdio_wp.range.len, uffdio_wp.mode & - UFFDIO_WRITEPROTECT_MODE_WP, + uffdio_wp.range.len, mode_wp, &ctx->mmap_changing); if (ret) return ret; - if (!(uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_DONTWAKE)) { + if (!mode_wp && !mode_dontwake) { range.start = uffdio_wp.range.start; range.len = uffdio_wp.range.len; wake_userfault(ctx, &range);-- 2.17.1
-- Sincerely yours, Mike.