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Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1rwQuS-0000000GEKe-3pmn; Mon, 15 Apr 2024 18:18:29 +0000 Date: Mon, 15 Apr 2024 19:18:28 +0100 From: Matthew Wilcox To: Suren Baghdasaryan Cc: linux-mm@kvack.org Subject: Re: [RFC] Trylock the mmap_lock in vmf_anon_prepare() Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 9AE461C0008 X-Rspam-User: X-Stat-Signature: rwfj5subnawmu78i6rimbxwxbqp7fcr9 X-Rspamd-Server: rspam01 X-HE-Tag: 1713205111-595986 X-HE-Meta: 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 wbuSeGZJ BuUXIx8PymytnIvtxuV0HHBoKSyzzdrNJ37BbdSxWOPBD8osgBQ5704vrEZUlioLrldnfqc114M8TD7XBW6d8JRrnWGiimp3TpgLslRf11D9Ud/iDN9k3p/K8jAyvYQtI0/DBS7LaEJNzOk8PGghgoaDua7KfBtNx4oiTdAXsaCJ5TqobyFRdVN0SU0tZMx58rNjF54+MwqmZvP+D06Jjwh+bbwZmMUY13CARwxXFzvkV9zk= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000018, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Apr 15, 2024 at 09:14:10AM -0700, Suren Baghdasaryan wrote: > > if (vmf->flags & FAULT_FLAG_VMA_LOCK) { > > - vma_end_read(vma); > > - return VM_FAULT_RETRY; > > + if (!mmap_read_trylock(vma->vm_mm)) { > > + vma_end_read(vma); > > + return VM_FAULT_RETRY; > > + } > > } > > if (__anon_vma_prepare(vma)) > > return VM_FAULT_OOM; > > You should drop mmap_lock when returning VM_FAULT_OOM as well. > > > + if (vmf->flags & FAULT_FLAG_VMA_LOCK) > > + mmap_read_unlock(vma->vm_mm); > > return 0; > > } Thanks. Fixed and pushed to git://git.infradead.org/users/willy/pagecache.git vma-lock +++ b/mm/memory.c @@ -3224,16 +3224,21 @@ static inline vm_fault_t vmf_can_call_fault(const struct vm_fault *vmf) vm_fault_t vmf_anon_prepare(struct vm_fault *vmf) { struct vm_area_struct *vma = vmf->vma; + vm_fault_t ret = 0; if (likely(vma->anon_vma)) return 0; if (vmf->flags & FAULT_FLAG_VMA_LOCK) { - vma_end_read(vma); - return VM_FAULT_RETRY; + if (!mmap_read_trylock(vma->vm_mm)) { + vma_end_read(vma); + return VM_FAULT_RETRY; + } } if (__anon_vma_prepare(vma)) - return VM_FAULT_OOM; - return 0; + ret = VM_FAULT_OOM; + if (vmf->flags & FAULT_FLAG_VMA_LOCK) + mmap_read_unlock(vma->vm_mm); + return ret; } /*