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Wed, 6 Mar 2024 10:42:03 +0000 (UTC) Received: from x1n.redhat.com (unknown [10.72.116.8]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3C2C5112131D; Wed, 6 Mar 2024 10:41:56 +0000 (UTC) From: peterx@redhat.com To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org, Andrew Morton , Muchun Song , Jason Gunthorpe , peterx@redhat.com, Matthew Wilcox , Mike Rapoport , Christophe Leroy , x86@kernel.org, sparclinux@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Alistair Popple Subject: [PATCH RFC 01/13] mm/hmm: Process pud swap entry without pud_huge() Date: Wed, 6 Mar 2024 18:41:35 +0800 Message-ID: <20240306104147.193052-2-peterx@redhat.com> In-Reply-To: <20240306104147.193052-1-peterx@redhat.com> References: <20240306104147.193052-1-peterx@redhat.com> Precedence: bulk X-Mailing-List: sparclinux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.3 From: Peter Xu Swap pud entries do not always return true for pud_huge() for all archs. x86 and sparc (so far) allow it, but all the rest do not accept a swap entry to be reported as pud_huge(). So it's not safe to check swap entries within pud_huge(). Check swap entries before pud_huge(), so it should be always safe. This is the only place in the kernel that (IMHO, wrongly) relies on pud_huge() to return true on pud swap entries. The plan is to cleanup pXd_huge() to only report non-swap mappings for all archs. Cc: Alistair Popple Signed-off-by: Peter Xu Reviewed-by: Jason Gunthorpe --- mm/hmm.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) diff --git a/mm/hmm.c b/mm/hmm.c index 277ddcab4947..c44391a0246e 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -424,7 +424,7 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end, walk->action = ACTION_CONTINUE; pud = READ_ONCE(*pudp); - if (pud_none(pud)) { + if (pud_none(pud) || !pud_present(pud)) { spin_unlock(ptl); return hmm_vma_walk_hole(start, end, -1, walk); } @@ -435,11 +435,6 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end, unsigned long *hmm_pfns; unsigned long cpu_flags; - if (!pud_present(pud)) { - spin_unlock(ptl); - return hmm_vma_walk_hole(start, end, -1, walk); - } - i = (addr - range->start) >> PAGE_SHIFT; npages = (end - addr) >> PAGE_SHIFT; hmm_pfns = &range->hmm_pfns[i];