From: David Howells <dhowells@redhat.com>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: dhowells@redhat.com, Christian Brauner <christian@brauner.io>,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-api@vger.kernel.org, jannh@google.com, fweimer@redhat.com,
oleg@redhat.com, tglx@linutronix.de,
torvalds@linux-foundation.org, arnd@arndb.de, shuah@kernel.org,
tkjos@android.com, ldv@altlinux.org, miklos@szeredi.hu,
linux-alpha@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org,
linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org,
linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
linux-s390@vger.kernel.org, linux-sh@vger.kernel.org,
sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org,
linux-arch@vger.kernel.org, linux-kselftest@vger.kernel.org,
x86@kernel.org
Subject: Re: [PATCH 1/2] open: add close_range()
Date: Tue, 21 May 2019 17:30:27 +0100 [thread overview]
Message-ID: <28114.1558456227@warthog.procyon.org.uk> (raw)
In-Reply-To: <20190521150006.GJ17978@ZenIV.linux.org.uk>
Al Viro <viro@zeniv.linux.org.uk> wrote:
> Umm... That's going to be very painful if you dup2() something to MAX_INT and
> then run that; roughly 2G iterations of bouncing ->file_lock up and down,
> without anything that would yield CPU in process.
>
> If anything, I would suggest something like
>
> fd = *start_fd;
> grab the lock
> fdt = files_fdtable(files);
> more:
> look for the next eviction candidate in ->open_fds, starting at fd
> if there's none up to max_fd
> drop the lock
> return NULL
> *start_fd = fd + 1;
> if the fscker is really opened and not just reserved
> rcu_assign_pointer(fdt->fd[fd], NULL);
> __put_unused_fd(files, fd);
> drop the lock
> return the file we'd got
> if (unlikely(need_resched()))
> drop lock
> cond_resched();
> grab lock
> fdt = files_fdtable(files);
> goto more;
>
> with the main loop being basically
> while ((file = pick_next(files, &start_fd, max_fd)) != NULL)
> filp_close(file, files);
If we can live with close_from(int first) rather than close_range(), then this
can perhaps be done a lot more efficiently by:
new = alloc_fdtable(first);
spin_lock(&files->file_lock);
old = files_fdtable(files);
copy_fds(new, old, 0, first - 1);
rcu_assign_pointer(files->fdt, new);
spin_unlock(&files->file_lock);
clear_fds(old, 0, first - 1);
close_fdt_from(old, first);
kfree_rcu(old);
David
next prev parent reply other threads:[~2019-05-21 16:30 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-21 11:34 [PATCH 1/2] open: add close_range() Christian Brauner
2019-05-21 11:34 ` [PATCH 2/2] tests: add close_range() tests Christian Brauner
2019-05-21 12:09 ` [PATCH 1/2] open: add close_range() Florian Weimer
2019-05-21 13:04 ` Christian Brauner
2019-05-21 13:10 ` Florian Weimer
2019-05-21 13:18 ` Christian Brauner
2019-05-21 13:23 ` Christian Brauner
2019-05-21 15:00 ` Al Viro
2019-05-21 16:53 ` Christian Brauner
2019-05-21 16:30 ` David Howells [this message]
2019-05-21 16:41 ` Christian Brauner
2019-05-21 20:23 ` Linus Torvalds
2019-05-22 8:12 ` Christian Brauner
2019-05-21 19:20 ` Al Viro
2019-05-21 19:59 ` Matthew Wilcox
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=28114.1558456227@warthog.procyon.org.uk \
--to=dhowells@redhat.com \
--cc=arnd@arndb.de \
--cc=christian@brauner.io \
--cc=fweimer@redhat.com \
--cc=jannh@google.com \
--cc=ldv@altlinux.org \
--cc=linux-alpha@vger.kernel.org \
--cc=linux-api@vger.kernel.org \
--cc=linux-arch@vger.kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-ia64@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-kselftest@vger.kernel.org \
--cc=linux-m68k@lists.linux-m68k.org \
--cc=linux-mips@vger.kernel.org \
--cc=linux-parisc@vger.kernel.org \
--cc=linux-s390@vger.kernel.org \
--cc=linux-sh@vger.kernel.org \
--cc=linux-xtensa@linux-xtensa.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=miklos@szeredi.hu \
--cc=oleg@redhat.com \
--cc=shuah@kernel.org \
--cc=sparclinux@vger.kernel.org \
--cc=tglx@linutronix.de \
--cc=tkjos@android.com \
--cc=torvalds@linux-foundation.org \
--cc=viro@zeniv.linux.org.uk \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).