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[209.85.208.48]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a9ee0a18539sm792592166b.27.2024.11.12.15.48.27 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 12 Nov 2024 15:48:27 -0800 (PST) Received: by mail-ed1-f48.google.com with SMTP id 4fb4d7f45d1cf-5ceca0ec4e7so7959860a12.0 for ; Tue, 12 Nov 2024 15:48:27 -0800 (PST) X-Forwarded-Encrypted: i=1; AJvYcCWk2Rkju0ZhZy9HZtU5S1wv5pp2+rpyS1ZEWntARexUz7I2feyn4gMpRKZPPpi3Gst86eT1wG74iw==@kvack.org X-Received: by 2002:a17:906:4f96:b0:a9f:168:efdf with SMTP id a640c23a62f3a-a9f0169008dmr1114854566b.6.1731455306729; Tue, 12 Nov 2024 15:48:26 -0800 (PST) MIME-Version: 1.0 References: <141e2cc2dfac8b2f49c1c8d219dd7c20925b2cef.1731433903.git.josef@toxicpanda.com> In-Reply-To: From: Linus Torvalds Date: Tue, 12 Nov 2024 15:48:10 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v7 05/18] fsnotify: introduce pre-content permission events To: Amir Goldstein Cc: Josef Bacik , kernel-team@fb.com, linux-fsdevel@vger.kernel.org, jack@suse.cz, brauner@kernel.org, linux-xfs@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-mm@kvack.org, linux-ext4@vger.kernel.org Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 8745516001A X-Stat-Signature: mtw1gyg63ewb3ptomeyceg6nhkj7gz3d X-Rspam-User: X-Rspamd-Server: rspam05 X-HE-Tag: 1731455282-299398 X-HE-Meta: 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 +aX2CLcc 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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: List-Subscribe: List-Unsubscribe: On Tue, 12 Nov 2024 at 15:06, Amir Goldstein wrote: > > I am fine not optimizing out the legacy FS_ACCESS_PERM event > and just making sure not to add new bad code, if that is what you prefer > and I also am fine with using two FMODE_ flags if that is prefered. So iirc we do have a handful of FMODE flags left. Not many, but I do think a new one would be fine. And if we were to run out (and I'm *not* suggesting we do that now!) we actually have more free bits in "f_flags". That f_flags set of flags is a mess for other reasons: we expose them to user space, and we define the bits using octal numbers for random bad historical reasons, and some architectures specify their own set or bits, etc etc - nasty. But if anybody is really worried about running out of f_mode bits, we could almost certainly turn the existing unsigned int f_flags; into a bitfield, and make it be something like unsigned int f_flags:26, f_special:6; instead, with the rule being that "f_special" only gets set at open time and never any other time (to avoid any data races with fcntl() touching the other 24 bits in the word). [ Bah. I thought we had 8 unused bits in f_flags, but I went and looked. sparc uses 0x2000000 for __O_TMPFILE, so we actually only have 6 bits unused in f_flags. No actual good reason for the sparc choice I think, but it is what it is ] Anyway, I wouldn't begrudge you a bit if that cleans this fsnotify mess up and makes it much simpler and clearer. I really think that if we can do this cleanly, using a bit in f_mode is a good cause. Linus