[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <20210104190832.GL3579531@ZenIV.linux.org.uk>
Date: Mon, 4 Jan 2021 19:08:32 +0000
From: Al Viro <viro@...iv.linux.org.uk>
To: Eric Biggers <ebiggers@...nel.org>
Cc: linux-fsdevel@...r.kernel.org, Daeho Jeong <daeho43@...il.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] vfs: don't unnecessarily clone write access for
writable fds
On Mon, Jan 04, 2021 at 10:55:15AM -0800, Eric Biggers wrote:
> On Tue, Sep 22, 2020 at 09:44:18AM -0700, Eric Biggers wrote:
> > From: Eric Biggers <ebiggers@...gle.com>
> >
> > There's no need for mnt_want_write_file() to increment mnt_writers when
> > the file is already open for writing, provided that
> > mnt_drop_write_file() is changed to conditionally decrement it.
> >
> > We seem to have ended up in the current situation because
> > mnt_want_write_file() used to be paired with mnt_drop_write(), due to
> > mnt_drop_write_file() not having been added yet. So originally
> > mnt_want_write_file() had to always increment mnt_writers.
> >
> > But later mnt_drop_write_file() was added, and all callers of
> > mnt_want_write_file() were paired with it. This makes the compatibility
> > between mnt_want_write_file() and mnt_drop_write() no longer necessary.
> >
> > Therefore, make __mnt_want_write_file() and __mnt_drop_write_file() skip
> > incrementing mnt_writers on files already open for writing. This
> > removes the only caller of mnt_clone_write(), so remove that too.
> >
> > Signed-off-by: Eric Biggers <ebiggers@...gle.com>
> > ---
> >
> > v3: added note to porting file.
> > v2: keep the check for emergency r/o remounts.
> >
> > Documentation/filesystems/porting.rst | 7 ++++
> > fs/namespace.c | 53 ++++++++++-----------------
> > include/linux/mount.h | 1 -
> > 3 files changed, 27 insertions(+), 34 deletions(-)
>
> Ping.
Applied.
Powered by blists - more mailing lists