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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Qi Zheng Subject: [PATCH v1 2/2] mm/memory: handle non-split locks correctly in zap_empty_pte_table() Date: Mon, 19 Jan 2026 23:07:08 +0100 Message-ID: <20260119220708.3438514-3-david@kernel.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260119220708.3438514-1-david@kernel.org> References: <20260119220708.3438514-1-david@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: nh4euc99dkh6gx5ek4bkgakxjemnuft4 X-Rspam-User: X-Rspamd-Queue-Id: 43A382000A X-Rspamd-Server: rspam08 X-HE-Tag: 1768860441-695650 X-HE-Meta: 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 4+nZyvz6 dmXqsG9UgA6UuWA1h/j0tNCNrOsQAS7mGaVGg5EV7C5V3riLlYxjS5UAU0p3Dv/6iOO6fULYKYvfcuL0NH4qlnG9rYT6O0dyKafBvTz8yobrZ7GP7OX526BT27lNerB+2DD8Nsl63z0UM5GQHwSerwA0oN1Bb/bnKXQKSQDrp7+JPlFEqvUSs/4/MlmOL3WmtWhwpUc99SDapHLl/7xEskBYq0oFFJ7H/ZYyIaSIBnvk71XqAlu/RiTzhYAjRDEvt837lrgtigxuoj2d3Ixtvw9134pNRKSRrJEBB6EglaKESGDhbkhZ0PO3LNFzsSxbZwJVb 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: List-Subscribe: List-Unsubscribe: While we handle pte_lockptr() == pmd_lockptr() correctly in zap_pte_table_if_empty(), we don't handle it in zap_empty_pte_table(), making the spin_trylock() always fail and forcing us onto the slow path. So let's handle the scenario where pte_lockptr() == pmd_lockptr() better, which can only happen if CONFIG_SPLIT_PTE_PTLOCKS is not set. This is only relevant once we unlock CONFIG_PT_RECLAIM on architectures that are not x86-64. Signed-off-by: David Hildenbrand (Red Hat) --- mm/memory.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index c3055b2577c27..3852075ea62d4 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1833,16 +1833,18 @@ static bool pte_table_reclaim_possible(unsigned long start, unsigned long end, return details && details->reclaim_pt && (end - start >= PMD_SIZE); } -static bool zap_empty_pte_table(struct mm_struct *mm, pmd_t *pmd, pmd_t *pmdval) +static bool zap_empty_pte_table(struct mm_struct *mm, pmd_t *pmd, + spinlock_t *ptl, pmd_t *pmdval) { spinlock_t *pml = pmd_lockptr(mm, pmd); - if (!spin_trylock(pml)) + if (ptl != pml && !spin_trylock(pml)) return false; *pmdval = pmdp_get(pmd); pmd_clear(pmd); - spin_unlock(pml); + if (ptl != pml) + spin_unlock(pml); return true; } @@ -1934,7 +1936,7 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb, * from being repopulated by another thread. */ if (can_reclaim_pt && direct_reclaim && addr == end) - direct_reclaim = zap_empty_pte_table(mm, pmd, &pmdval); + direct_reclaim = zap_empty_pte_table(mm, pmd, ptl, &pmdval); add_mm_rss_vec(mm, rss); lazy_mmu_mode_disable(); -- 2.52.0