From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ameer Hamza <ahamza@ixsystems.com>
Subject: Re: [PATCH v2] Add new open(2) flag - O_EMPTY_PATH
Date: Mon, 2 Jan 2023 19:35:38 +0500
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To: David Laight <David.Laight@ACULAB.COM>
Cc: "viro@zeniv.linux.org.uk" <viro@zeniv.linux.org.uk>, "jlayton@kernel.org" <jlayton@kernel.org>, "chuck.lever@oracle.com" <chuck.lever@oracle.com>, "arnd@arndb.de" <arnd@arndb.de>, "guoren@kernel.org" <guoren@kernel.org>, "palmer@rivosinc.com" <palmer@rivosinc.com>, "f.fainelli@gmail.com" <f.fainelli@gmail.com>, "slark_xiao@163.com" <slark_xiao@163.com>, "richard.henderson@linaro.org" <richard.henderson@linaro.org>, "ink@jurassic.park.msu.ru" <ink@jurassic.park.msu.ru>, "mattst88@gmail.com" <mattst88@gmail.com>, "James.Bottomley@HansenPartnership.com" <James.Bottomley@HansenPartnership.com>, "deller@gmx.de" <deller@gmx.de>, "davem@davemloft.net" <davem@davemloft.net>, "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>, linux-kernel@vger.kernel.

On Mon, Jan 02, 2023 at 02:01:38PM +0000, David Laight wrote:
> From: Ameer Hamza
> > Sent: 31 December 2022 23:56
> > 
> > This patch adds a new flag O_EMPTY_PATH that allows openat and open
> > system calls to open a file referenced by fd if the path is empty,
> > and it is very similar to the FreeBSD O_EMPTY_PATH flag. This can be
> > beneficial in some cases since it would avoid having to grant /proc
> > access to things like samba containers for reopening files to change
> > flags in a race-free way.
> > 
> 
> But what does it do?
> (Apart from add code to a common kernel code path.)
> 
> 	David
It can convert an O_PATH descriptor to one suitable for r/w work.
If we already have a file descriptor: {opath_fd = open(&lt;path&gt;, O_PATH);}, we can call {openat(opath_fd, "", O_EMPTY_PATH | O_RDWR)} instead of going through procfs {open(/proc/self/fd/&lt;opath_fd&gt;, O_RDWR)}.
> 
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