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[209.85.208.47]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5dc7204517csm3267578a12.0.2025.01.31.12.00.12 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 31 Jan 2025 12:00:14 -0800 (PST) Received: by mail-ed1-f47.google.com with SMTP id 4fb4d7f45d1cf-5db6890b64eso4378626a12.3 for ; Fri, 31 Jan 2025 12:00:12 -0800 (PST) X-Forwarded-Encrypted: i=1; AJvYcCUbZ0sdH+81xJElcJOyoUL/YQNX8mMB8gD61/l/fm5ISPS6neoue5hJ5KZG/SfSSvWB0hkhOQK7GA==@kvack.org X-Received: by 2002:a05:6402:2709:b0:5da:1448:43f5 with SMTP id 4fb4d7f45d1cf-5dc5effcc33mr12325224a12.31.1738353612239; Fri, 31 Jan 2025 12:00:12 -0800 (PST) MIME-Version: 1.0 References: <9035b82cff08a3801cef3d06bbf2778b2e5a4dba.1731684329.git.josef@toxicpanda.com> <20250131121703.1e4d00a7.alex.williamson@redhat.com> In-Reply-To: <20250131121703.1e4d00a7.alex.williamson@redhat.com> From: Linus Torvalds Date: Fri, 31 Jan 2025 11:59:56 -0800 X-Gmail-Original-Message-ID: X-Gm-Features: AWEUYZmJHVy_un_wj0EXjvnXlSLyiKtpaVCBTRVD7w7Khb3Vui_AFXvwFXKGqO4 Message-ID: Subject: Re: [REGRESSION] Re: [PATCH v8 15/19] mm: don't allow huge faults for files with pre content watches To: Alex Williamson Cc: Josef Bacik , kernel-team@fb.com, linux-fsdevel@vger.kernel.org, jack@suse.cz, amir73il@gmail.com, brauner@kernel.org, viro@zeniv.linux.org.uk, linux-xfs@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-mm@kvack.org, linux-ext4@vger.kernel.org, Peter Xu , "linux-kernel@vger.kernel.org" , "kvm@vger.kernel.org" Content-Type: text/plain; charset="UTF-8" X-Stat-Signature: o8j5qa7wc3e6ojp8ydpr14tt4uwdcqab X-Rspamd-Queue-Id: 6B0F0C0018 X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1738353620-465035 X-HE-Meta: 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 LwFZykUi 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.109027, 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 Fri, 31 Jan 2025 at 11:17, Alex Williamson wrote: > > 20bf82a898b6 ("mm: don't allow huge faults for files with pre content watches") > > This breaks huge_fault support for PFNMAPs that was recently added in > v6.12 and is used by vfio-pci to fault device memory using PMD and PUD > order mappings. Surely only for content watches? Which shouldn't be a valid situation *anyway*. IOW, there must be some unrelated bug somewhere: either somebody is allowed to set a pre-content match on a special device. That should be disabled by the whole /* * If there are permission event watchers but no pre-content event * watchers, set FMODE_NONOTIFY | FMODE_NONOTIFY_PERM to indicate that. */ thing in file_set_fsnotify_mode() which only allows regular files and directories to be notified on. Or, alternatively, that check for huge-fault disabling is just checking the wrong bits. Or - quite possibly - I am missing something obvious? Linus