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[209.85.208.43]) by smtp.gmail.com with ESMTPSA id c9-20020a509f89000000b0055eb53aae03sm2256123edf.94.2024.01.28.17.42.47 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 28 Jan 2024 17:42:47 -0800 (PST) Received: by mail-ed1-f43.google.com with SMTP id 4fb4d7f45d1cf-55f13b682d4so4282a12.1 for ; Sun, 28 Jan 2024 17:42:47 -0800 (PST) X-Received: by 2002:aa7:c70f:0:b0:55e:c2d9:3750 with SMTP id i15-20020aa7c70f000000b0055ec2d93750mr2555420edq.5.1706492567478; Sun, 28 Jan 2024 17:42:47 -0800 (PST) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20240126150209.367ff402@gandalf.local.home> <20240126162626.31d90da9@gandalf.local.home> <20240128175111.69f8b973@rorschach.local.home> <20240128185943.6920388b@rorschach.local.home> <20240128192108.6875ecf4@rorschach.local.home> In-Reply-To: From: Linus Torvalds Date: Sun, 28 Jan 2024 17:42:30 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] eventfs: Have inodes have unique inode numbers To: Steven Rostedt Cc: Masami Hiramatsu , Mathieu Desnoyers , LKML , Linux Trace Devel , Christian Brauner , Ajay Kaher , Geert Uytterhoeven , linux-fsdevel Content-Type: text/plain; charset="UTF-8" On Sun, 28 Jan 2024 at 17:00, Linus Torvalds wrote: > > mkdir dummy > cd dummy > echo "Hello" > hello > ( sleep 10; cat ) < hello & > rm hello > cd .. > rmdir dummy Note that it's worth repeating that simple_recursive_removal() wouldn't change any of the above. It only unhashes things and makes them *look* gone, doing things like clearing i_nlink etc. But those VFS data structures would still exist, and the files that had them open would still continue to be open. So if you thought that simple_recursive_removal() would make the above kind of thing not able to happen, and that eventfs wouldn't have to deal with dentries that point to event_inodes that are dead, you were always wrong. simple_recursive_removal() is mostly just lipstick on a pig. It does cause the cached dentries that have no active use be removed earlier, so it has that "memory pressure" kind of effect, but it has no real fundamental semantic effect. Of course, for a filesystem where the dentry tree *is* the underlying data (ie the 'tmpfs' kind, but also things like debugfs or ipathfs, for example), then things are different. There the dentries are the primary thing, and not just a cache in front of the backing store. But you didn't want that, and those days are long gone as far as tracefs is concerned. Linus