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From: Shakeel Butt To: Lorenzo Stoakes Cc: Christian Brauner , Shuah Khan , "Liam R . Howlett" , Suren Baghdasaryan , Vlastimil Babka , pedro.falcato@gmail.com, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, Oliver Sang , John Hubbard Subject: Re: [PATCH v4 1/4] pidfd: extend pidfd_get_pid() and de-duplicate pid lookup Message-ID: References: <94a3210afe96c9d1d6f9460d7d37a43e5bc5f550.1729198898.git.lorenzo.stoakes@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <94a3210afe96c9d1d6f9460d7d37a43e5bc5f550.1729198898.git.lorenzo.stoakes@oracle.com> X-Migadu-Flow: FLOW_OUT X-Stat-Signature: 4zejs8n4ne7xhd85y8f1ojcz5799z1c5 X-Rspamd-Queue-Id: AB3B2160014 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1729642804-986099 X-HE-Meta: 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 dVRWP0zN 6Mg2NS/YXOl7gQXbDcOPiSC3OgvhHvCGWxtmp4SQjgJZu9bYHLE+rVOAMFcN4V7XlbLTSs/QhTwwak0S6B/bAPmWCUfJ8SgV2TBdjirEhr7F6Vc0XmHl8Qjwhw9sapfeb/sckQNFEt2MYUcvtG/AkWz/YXEL2x1iQR4VLYKVft7/AbD4yZhjHlsle2N/piglzLhMf9OPzOZ7hpELgHLokgeXkTME+xJeTuhQWEEhK2u3zUh+Nhx+zaQSSoJcusX/73eKw3ief0O4J8tsg1YiVI0FZI8/PAitcRos3 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 Thu, Oct 17, 2024 at 10:05:49PM GMT, Lorenzo Stoakes wrote: > The means by which a pid is determined from a pidfd is duplicated, with > some callers holding a reference to the (pid)fd, and others explicitly > pinning the pid. > > Introduce __pidfd_get_pid() which narrows this to one approach of pinning > the pid, with an optional output parameters for file->f_flags to avoid the > need to hold onto a file to retrieve this. > > Additionally, allow the ability to open a pidfd by opening a /proc/ > directory, utilised by the pidfd_send_signal() system call, providing a > pidfd_get_pid_proc() helper function to do so. > > Doing this allows us to eliminate open-coded pidfd pid lookup and to > consistently handle this in one place. > > This lays the groundwork for a subsequent patch which adds a new sentinel > pidfd to explicitly reference the current process (i.e. thread group > leader) without the need for a pidfd. > > Signed-off-by: Lorenzo Stoakes Reviewed-by: Shakeel Butt