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AJvYcCUkp6UmAuwD9U3jcE3Zyl2bxxzAF89HRPPi9D2SPcFKK6KjQzv+lRg9T5yXVuCxctSaMku3conHjA==@kvack.org X-Gm-Message-State: AOJu0YwPQQ+Vx9gzOCz6Ex3gXvVCwsBNnN9dVJ2Bdy51wbUD82dtvZSA jDFtjpspwzrke3MM2aYS0HRmwYvFRjSQeiqdefFDINMSwzYc8eA2Jc16oEav6eLnniJ7KKIvXzC E5C8TAAOBKdZ6B/sC1iiaIwaHLhM= X-Google-Smtp-Source: AGHT+IHwjUZ/D0gPZk+CyMnQLtq/DsFFmkIX1MphMhWMqr5QE96IKENIsI2zKWWf445KGdU4ZCgAOjb0OqPbrvF1gaI= X-Received: by 2002:a17:907:7214:b0:a9a:b9d:bd93 with SMTP id a640c23a62f3a-aa4dd52feb6mr214525666b.4.1732102625052; Wed, 20 Nov 2024 03:37:05 -0800 (PST) MIME-Version: 1.0 References: <141e2cc2dfac8b2f49c1c8d219dd7c20925b2cef.1731433903.git.josef@toxicpanda.com> <20241120-banditen-nimmersatt-e53c268d893a@brauner> In-Reply-To: <20241120-banditen-nimmersatt-e53c268d893a@brauner> From: Amir Goldstein Date: Wed, 20 Nov 2024 12:36:53 +0100 Message-ID: Subject: Re: [PATCH v7 05/18] fsnotify: introduce pre-content permission events To: Christian Brauner Cc: Linus Torvalds , Josef Bacik , kernel-team@fb.com, linux-fsdevel@vger.kernel.org, jack@suse.cz, 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" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 05C1C1C0003 X-Stat-Signature: irjfnfe86ooiizf77rbuw7corqxuguth X-HE-Tag: 1732102603-475800 X-HE-Meta: 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 W4T5hhDH Us4vihYEKDQNibitGGzERIk78voc+EPddeceHfS7HVhix9BR9oiBTKPil3htrUqAIt0TQyyPa/GNapO8s+74qceVj4DOE1o+EkXwLdti00EmqMX6TkyiLRfI1SX98f6C3Pt8HX+9C8r2Xmvf2DPttuX0jwVOMI0QFM+T5n0trZ4OOfA/Mr6D8WTzX1lvT4lFSzm1QijuV6pniJmXPzgkSPW275pNu8tmwDhmqcr/ZmEJPxLmFmvBtWI+Gs+CoHxSR8O23yXrUNO8fdjJEf5LwHag89nOgbkb/vo7EV29I+oW/nsEIuEstuiv2kbUFDOfUDBOcZ2I6KEli+70NJytcMTeuAnjXXOXvggfOWSfcWXenYFgC0XkSUlQrPXa8z6XIgjyHeyyAjNipR5DCRso2QcgsqA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000854, 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 Wed, Nov 20, 2024 at 12:10=E2=80=AFPM Christian Brauner wrote: > > > 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; > > I just saw this now. Two points I would like to keep you to keep mind. > > I've already mentiond that I've freed up 5 fmode bits so it's not that > we're in immediate danger of running out. Especially since I added > f_ops_flags which contains all flags that are static, i.e., never change > and can simply live in the file operations struct and aren't that > performance sensitive. > > I shrunk struct file to three cachelines. And in fact, we have 8 bytes > to use left since I removed f_version. So it really wouldn't be a > problem to simply add a separate u32 f_special member into struct file > without growing it and still leaving a 4 byte hole if it ever comes to > that. That's good to know, but for the record, I ended up using just one extra f_mode bit for fsnotify [1]. Thanks, Amir. [1] https://lore.kernel.org/linux-fsdevel/5ea5f8e283d1edb55aa79c35187bfe344= 056af14.1731684329.git.josef@toxicpanda.com/