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([2a0b:e7c0:0:107::aaaa:69]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a5a1789240asm845725066b.48.2024.05.15.04.10.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 15 May 2024 04:10:50 -0700 (PDT) Message-ID: <210098f9-1e71-48c9-be08-7e8074ec33c1@kernel.org> Date: Wed, 15 May 2024 13:10:49 +0200 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] pidfd: add pidfdfs To: Christian Brauner , linux-fsdevel@vger.kernel.org Cc: Linus Torvalds , Alexander Viro , Seth Forshee , Tycho Andersen References: <20240213-vfs-pidfd_fs-v1-0-f863f58cfce1@kernel.org> <20240213-vfs-pidfd_fs-v1-2-f863f58cfce1@kernel.org> Content-Language: en-US From: Jiri Slaby Autocrypt: addr=jirislaby@kernel.org; keydata= xsFNBE6S54YBEACzzjLwDUbU5elY4GTg/NdotjA0jyyJtYI86wdKraekbNE0bC4zV+ryvH4j rrcDwGs6tFVrAHvdHeIdI07s1iIx5R/ndcHwt4fvI8CL5PzPmn5J+h0WERR5rFprRh6axhOk rSD5CwQl19fm4AJCS6A9GJtOoiLpWn2/IbogPc71jQVrupZYYx51rAaHZ0D2KYK/uhfc6neJ i0WqPlbtIlIrpvWxckucNu6ZwXjFY0f3qIRg3Vqh5QxPkojGsq9tXVFVLEkSVz6FoqCHrUTx wr+aw6qqQVgvT/McQtsI0S66uIkQjzPUrgAEtWUv76rM4ekqL9stHyvTGw0Fjsualwb0Gwdx ReTZzMgheAyoy/umIOKrSEpWouVoBt5FFSZUyjuDdlPPYyPav+hpI6ggmCTld3u2hyiHji2H cDpcLM2LMhlHBipu80s9anNeZhCANDhbC5E+NZmuwgzHBcan8WC7xsPXPaiZSIm7TKaVoOcL 9tE5aN3jQmIlrT7ZUX52Ff/hSdx/JKDP3YMNtt4B0cH6ejIjtqTd+Ge8sSttsnNM0CQUkXps w98jwz+Lxw/bKMr3NSnnFpUZaxwji3BC9vYyxKMAwNelBCHEgS/OAa3EJoTfuYOK6wT6nadm YqYjwYbZE5V/SwzMbpWu7Jwlvuwyfo5mh7w5iMfnZE+vHFwp/wARAQABzSFKaXJpIFNsYWJ5 IDxqaXJpc2xhYnlAa2VybmVsLm9yZz7CwXcEEwEIACEFAlW3RUwCGwMFCwkIBwIGFQgJCgsC BBYCAwECHgECF4AACgkQvSWxBAa0cEnVTg//TQpdIAr8Tn0VAeUjdVIH9XCFw+cPSU+zMSCH eCZoA/N6gitEcnvHoFVVM7b3hK2HgoFUNbmYC0RdcSc80pOF5gCnACSP9XWHGWzeKCARRcQR 4s5YD8I4VV5hqXcKo2DFAtIOVbHDW+0okOzcecdasCakUTr7s2fXz97uuoc2gIBB7bmHUGAH XQXHvdnCLjDjR+eJN+zrtbqZKYSfj89s/ZHn5Slug6w8qOPT1sVNGG+eWPlc5s7XYhT9z66E l5C0rG35JE4PhC+tl7BaE5IwjJlBMHf/cMJxNHAYoQ1hWQCKOfMDQ6bsEr++kGUCbHkrEFwD UVA72iLnnnlZCMevwE4hc0zVhseWhPc/KMYObU1sDGqaCesRLkE3tiE7X2cikmj/qH0CoMWe gjnwnQ2qVJcaPSzJ4QITvchEQ+tbuVAyvn9H+9MkdT7b7b2OaqYsUP8rn/2k1Td5zknUz7iF oJ0Z9wPTl6tDfF8phaMIPISYrhceVOIoL+rWfaikhBulZTIT5ihieY9nQOw6vhOfWkYvv0Dl o4GRnb2ybPQpfEs7WtetOsUgiUbfljTgILFw3CsPW8JESOGQc0Pv8ieznIighqPPFz9g+zSu Ss/rpcsqag5n9rQp/H3WW5zKUpeYcKGaPDp/vSUovMcjp8USIhzBBrmI7UWAtuedG9prjqfO wU0ETpLnhgEQAM+cDWLL+Wvc9cLhA2OXZ/gMmu7NbYKjfth1UyOuBd5emIO+d4RfFM02XFTI t4MxwhAryhsKQQcA4iQNldkbyeviYrPKWjLTjRXT5cD2lpWzr+Jx7mX7InV5JOz1Qq+P+nJW YIBjUKhI03ux89p58CYil24Zpyn2F5cX7U+inY8lJIBwLPBnc9Z0An/DVnUOD+0wIcYVnZAK DiIXODkGqTg3fhZwbbi+KAhtHPFM2fGw2VTUf62IHzV+eBSnamzPOBc1XsJYKRo3FHNeLuS8 f4wUe7bWb9O66PPFK/RkeqNX6akkFBf9VfrZ1rTEKAyJ2uqf1EI1olYnENk4+00IBa+BavGQ 8UW9dGW3nbPrfuOV5UUvbnsSQwj67pSdrBQqilr5N/5H9z7VCDQ0dhuJNtvDSlTf2iUFBqgk 3smln31PUYiVPrMP0V4ja0i9qtO/TB01rTfTyXTRtqz53qO5dGsYiliJO5aUmh8swVpotgK4 /57h3zGsaXO9PGgnnAdqeKVITaFTLY1ISg+Ptb4KoliiOjrBMmQUSJVtkUXMrCMCeuPDGHo7 39Xc75lcHlGuM3yEB//htKjyprbLeLf1y4xPyTeeF5zg/0ztRZNKZicgEmxyUNBHHnBKHQxz 1j+mzH0HjZZtXjGu2KLJ18G07q0fpz2ZPk2D53Ww39VNI/J9ABEBAAHCwV8EGAECAAkFAk6S 54YCGwwACgkQvSWxBAa0cEk3tRAAgO+DFpbyIa4RlnfpcW17AfnpZi9VR5+zr496n2jH/1ld wRO/S+QNSA8qdABqMb9WI4BNaoANgcg0AS429Mq0taaWKkAjkkGAT7mD1Q5PiLr06Y/+Kzdr 90eUVneqM2TUQQbK+Kh7JwmGVrRGNqQrDk+gRNvKnGwFNeTkTKtJ0P8jYd7P1gZb9Fwj9YLx jhn/sVIhNmEBLBoI7PL+9fbILqJPHgAwW35rpnq4f/EYTykbk1sa13Tav6btJ+4QOgbcezWI wZ5w/JVfEJW9JXp3BFAVzRQ5nVrrLDAJZ8Y5ioWcm99JtSIIxXxt9FJaGc1Bgsi5K/+dyTKL wLMJgiBzbVx8G+fCJJ9YtlNOPWhbKPlrQ8+AY52Aagi9WNhe6XfJdh5g6ptiOILm330mkR4g W6nEgZVyIyTq3ekOuruftWL99qpP5zi+eNrMmLRQx9iecDNgFr342R9bTDlb1TLuRb+/tJ98 f/bIWIr0cqQmqQ33FgRhrG1+Xml6UXyJ2jExmlO8JljuOGeXYh6ZkIEyzqzffzBLXZCujlYQ DFXpyMNVJ2ZwPmX2mWEoYuaBU0JN7wM+/zWgOf2zRwhEuD3A2cO2PxoiIfyUEfB9SSmffaK/ S4xXoB6wvGENZ85Hg37C7WDNdaAt6Xh2uQIly5grkgvWppkNy4ZHxE+jeNsU7tg= In-Reply-To: <20240213-vfs-pidfd_fs-v1-2-f863f58cfce1@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 13. 02. 24, 17:45, Christian Brauner wrote: > This moves pidfds from the anonymous inode infrastructure to a tiny > pseudo filesystem. This has been on my todo for quite a while as it will > unblock further work that we weren't able to do simply because of the > very justified limitations of anonymous inodes. Moving pidfds to a tiny > pseudo filesystem allows: > > * statx() on pidfds becomes useful for the first time. > * pidfds can be compared simply via statx() and then comparing inode > numbers. > * pidfds have unique inode numbers for the system lifetime. > * struct pid is now stashed in inode->i_private instead of > file->private_data. This means it is now possible to introduce > concepts that operate on a process once all file descriptors have been > closed. A concrete example is kill-on-last-close. > * file->private_data is freed up for per-file options for pidfds. > * Each struct pid will refer to a different inode but the same struct > pid will refer to the same inode if it's opened multiple times. In > contrast to now where each struct pid refers to the same inode. Even > if we were to move to anon_inode_create_getfile() which creates new > inodes we'd still be associating the same struct pid with multiple > different inodes. > * Pidfds now go through the regular dentry_open() path which means that > all security hooks are called unblocking proper LSM management for > pidfds. In addition fsnotify hooks are called and allow for listening > to open events on pidfds. > > The tiny pseudo filesystem is not visible anywhere in userspace exactly > like e.g., pipefs and sockfs. There's no lookup, there's no complex > inode operations, nothing. Dentries and inodes are always deleted when > the last pidfd is closed. This breaks lsof and util-linux. Without the commit, lsof shows: systemd ... 59 [pidfd:899] With the commit: systemd ... 1187 pidfd And that user-visible change breaks a lot of stuff, incl. lsof tests. For util-linux, its test fail with: > [ 125s] --- tests/expected/lsfd/column-name-pidfd 2024-05-06 07:20:54.655845940 +0000 > [ 125s] +++ tests/output/lsfd/column-name-pidfd 2024-05-15 01:04:15.406666666 +0000 > [ 125s] @@ -1,2 +1,2 @@ > [ 125s] -3 anon_inode:[pidfd] pid=1 comm= nspid=1 > [ 125s] +3 pidfd:[INODENUM] pidfd:[INODENUM] > [ 125s] pidfd:ASSOC,KNAME,NAME: 0 > [ 125s] lsfd: NAME and KNAME column: [02] pidfd ... FAILED (lsfd/column-name-pidfd) And: > [ 125s] --- tests/expected/lsfd/column-type-pidfd 2024-05-06 07:20:54.655845940 +0000 > [ 125s] +++ tests/output/lsfd/column-type-pidfd 2024-05-15 01:04:15.573333333 +0000 > [ 125s] @@ -1,2 +1,2 @@ > [ 125s] -3 UNKN pidfd > [ 125s] +3 REG REG > [ 125s] pidfd:ASSOC,STTYPE,TYPE: 0 > [ 125s] lsfd: TYPE and STTYPE column: [02] pidfd ... FAILED (lsfd/column-type-pidfd) Any ideas? thanks, -- js suse labs