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Mon, 01 May 2023 10:50:32 -0700 (PDT) Date: Mon, 1 May 2023 10:50:24 -0700 In-Reply-To: <20230501175025.36233-1-surenb@google.com> Mime-Version: 1.0 References: <20230501175025.36233-1-surenb@google.com> X-Mailer: git-send-email 2.40.1.495.gc816e09b53d-goog Message-ID: <20230501175025.36233-2-surenb@google.com> Subject: [PATCH 2/3] mm: drop VMA lock before waiting for migration From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: willy@infradead.org, hannes@cmpxchg.org, mhocko@suse.com, josef@toxicpanda.com, jack@suse.cz, ldufour@linux.ibm.com, laurent.dufour@fr.ibm.com, michel@lespinasse.org, liam.howlett@oracle.com, jglisse@google.com, vbabka@suse.cz, minchan@google.com, dave@stgolabs.net, punit.agrawal@bytedance.com, lstoakes@gmail.com, hdanton@sina.com, apopple@nvidia.com, surenb@google.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com X-Rspam-User: X-Rspamd-Queue-Id: 76F411C001C X-Rspamd-Server: rspam01 X-Stat-Signature: 56bht9ypw5hndjc8szjmk81ekn86w1fg X-HE-Tag: 1682963433-403283 X-HE-Meta: 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 qVKEtzpK 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 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: migration_entry_wait does not need VMA lock, therefore it can be dropped before waiting. Introduce VM_FAULT_VMA_UNLOCKED to indicate that VMA lock was dropped while in handle_mm_fault(). Note that once VMA lock is dropped, the VMA reference can't be used as there are no guarantees it was not freed. Signed-off-by: Suren Baghdasaryan --- arch/arm64/mm/fault.c | 3 ++- arch/powerpc/mm/fault.c | 3 ++- arch/s390/mm/fault.c | 3 ++- arch/x86/mm/fault.c | 3 ++- include/linux/mm_types.h | 6 +++++- mm/memory.c | 12 ++++++++++-- 6 files changed, 23 insertions(+), 7 deletions(-) diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index 9e0db5c387e3..8fa281f49d61 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -602,7 +602,8 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr, } fault = handle_mm_fault(vma, addr & PAGE_MASK, mm_flags | FAULT_FLAG_VMA_LOCK, regs); - vma_end_read(vma); + if (!(fault & VM_FAULT_VMA_UNLOCKED)) + vma_end_read(vma); if (!(fault & VM_FAULT_RETRY)) { count_vm_vma_lock_event(VMA_LOCK_SUCCESS); diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c index 531177a4ee08..b27730f07141 100644 --- a/arch/powerpc/mm/fault.c +++ b/arch/powerpc/mm/fault.c @@ -494,7 +494,8 @@ static int ___do_page_fault(struct pt_regs *regs, unsigned long address, } fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs); - vma_end_read(vma); + if (!(fault & VM_FAULT_VMA_UNLOCKED)) + vma_end_read(vma); if (!(fault & VM_FAULT_RETRY)) { count_vm_vma_lock_event(VMA_LOCK_SUCCESS); diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c index b65144c392b0..cc923dbb0821 100644 --- a/arch/s390/mm/fault.c +++ b/arch/s390/mm/fault.c @@ -418,7 +418,8 @@ static inline vm_fault_t do_exception(struct pt_regs *regs, int access) goto lock_mmap; } fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs); - vma_end_read(vma); + if (!(fault & VM_FAULT_VMA_UNLOCKED)) + vma_end_read(vma); if (!(fault & VM_FAULT_RETRY)) { count_vm_vma_lock_event(VMA_LOCK_SUCCESS); goto out; diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index e4399983c50c..ef62ab2fd211 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -1347,7 +1347,8 @@ void do_user_addr_fault(struct pt_regs *regs, goto lock_mmap; } fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs); - vma_end_read(vma); + if (!(fault & VM_FAULT_VMA_UNLOCKED)) + vma_end_read(vma); if (!(fault & VM_FAULT_RETRY)) { count_vm_vma_lock_event(VMA_LOCK_SUCCESS); diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 306a3d1a0fa6..b3b57c6da0e1 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -1030,6 +1030,7 @@ typedef __bitwise unsigned int vm_fault_t; * fsync() to complete (for synchronous page faults * in DAX) * @VM_FAULT_COMPLETED: ->fault completed, meanwhile mmap lock released + * @VM_FAULT_VMA_UNLOCKED: VMA lock was released * @VM_FAULT_HINDEX_MASK: mask HINDEX value * */ @@ -1047,6 +1048,7 @@ enum vm_fault_reason { VM_FAULT_DONE_COW = (__force vm_fault_t)0x001000, VM_FAULT_NEEDDSYNC = (__force vm_fault_t)0x002000, VM_FAULT_COMPLETED = (__force vm_fault_t)0x004000, + VM_FAULT_VMA_UNLOCKED = (__force vm_fault_t)0x008000, VM_FAULT_HINDEX_MASK = (__force vm_fault_t)0x0f0000, }; @@ -1070,7 +1072,9 @@ enum vm_fault_reason { { VM_FAULT_RETRY, "RETRY" }, \ { VM_FAULT_FALLBACK, "FALLBACK" }, \ { VM_FAULT_DONE_COW, "DONE_COW" }, \ - { VM_FAULT_NEEDDSYNC, "NEEDDSYNC" } + { VM_FAULT_NEEDDSYNC, "NEEDDSYNC" }, \ + { VM_FAULT_COMPLETED, "COMPLETED" }, \ + { VM_FAULT_VMA_UNLOCKED, "VMA_UNLOCKED" } struct vm_special_mapping { const char *name; /* The name, e.g. "[vdso]". */ diff --git a/mm/memory.c b/mm/memory.c index 41f45819a923..8222acf74fd3 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3714,8 +3714,16 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) entry = pte_to_swp_entry(vmf->orig_pte); if (unlikely(non_swap_entry(entry))) { if (is_migration_entry(entry)) { - migration_entry_wait(vma->vm_mm, vmf->pmd, - vmf->address); + /* Save mm in case VMA lock is dropped */ + struct mm_struct *mm = vma->vm_mm; + + if (vmf->flags & FAULT_FLAG_VMA_LOCK) { + /* No need to hold VMA lock for migration */ + vma_end_read(vma); + /* CAUTION! VMA can't be used after this */ + ret |= VM_FAULT_VMA_UNLOCKED; + } + migration_entry_wait(mm, vmf->pmd, vmf->address); } else if (is_device_exclusive_entry(entry)) { vmf->page = pfn_swap_entry_to_page(entry); ret = remove_device_exclusive_entry(vmf);