From: Al Viro <viro@ZenIV.linux.org.uk>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Linux-Fsdevel <linux-fsdevel@vger.kernel.org>,
Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-unionfs@vger.kernel.org
Subject: Re: [GIT PULL] overlay filesystem v25
Date: Sat, 25 Oct 2014 18:06:09 +0100 [thread overview]
Message-ID: <20141025170609.GK7996@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CAJfpegvM8d-cizf=3KmTSFVgAYPBDp_0fQAh+G2Q87u=taXm3A@mail.gmail.com>
On Sat, Oct 25, 2014 at 11:53:52AM +0200, Miklos Szeredi wrote:
> Yes, but it's not about race with copy-up (which the ovl_path_upper()
> protects against), but race of two fsync calls with each other. If
> there's no synchronization between them, then that od->upperfile does
> indeed count as lockless access, no matter that the assignment was
> done under lock.
p = global;
if (!p) { // outside of lock
p = alloc();
grab lock
if (!global) {
global = p;
} else {
destroy(p);
p = global;
}
drop lock
}
is a very common pattern, especially if you look for cases when lock is
a spinlock and allocation is blocking (in those cases you'll often see
destroy() part done after dropping the lock; that's where what I fucked up in
what I'd originally pushed. And it wasn't even needed - fput() under
->i_mutex is OK...)
next prev parent reply other threads:[~2014-10-25 19:51 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-23 23:25 [GIT PULL] overlay filesystem v25 Miklos Szeredi
2014-10-24 2:20 ` Al Viro
2014-10-24 3:24 ` Al Viro
2014-10-24 7:24 ` Miklos Szeredi
2014-10-25 8:18 ` Al Viro
2014-10-25 9:53 ` Miklos Szeredi
2014-10-25 17:06 ` Al Viro [this message]
2014-10-27 8:06 ` Miklos Szeredi
2014-10-27 15:59 ` Paul E. McKenney
2014-10-27 17:28 ` Al Viro
2014-10-27 17:36 ` Paul E. McKenney
2014-10-28 1:12 ` Al Viro
2014-10-28 4:11 ` Paul E. McKenney
2014-10-28 22:55 ` Al Viro
2014-10-28 23:25 ` Paul E. McKenney
2014-10-24 7:28 ` Geert Uytterhoeven
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