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From: Amir Goldstein <amir73il@gmail.com>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: overlayfs <linux-unionfs@vger.kernel.org>,
	Miklos Szeredi <miklos@szeredi.hu>,
	"Eric W. Biederman" <ebiederm@xmission.com>
Subject: Re: [PATCH 7/9] ovl: Introduce read/write barriers around metacopy flag update
Date: Mon, 16 Oct 2017 16:31:20 +0300	[thread overview]
Message-ID: <CAOQ4uxjV_1WHh5P=Hv6BY+JhEkXFfPFLSNd0ZpbNf1s0hbdH2Q@mail.gmail.com> (raw)
In-Reply-To: <20171016132453.GB31318@redhat.com>

On Mon, Oct 16, 2017 at 4:24 PM, Vivek Goyal <vgoyal@redhat.com> wrote:
> On Sat, Oct 14, 2017 at 09:05:17AM +0300, Amir Goldstein wrote:
>
> [..]
>> > When I read memory-barrier.txt, it seems to suggest that RELEASE can let
>> > instructions outside critical region sneak into critical region. If that's
>> > the case, actually clearing of metaflag can happen before xattr actually
>> > got removed. Though I can't think what will go wrong in that case.
>>
>> clear_bit takes a spinlock so I *think* clearing of flag cannot sneak
>> before removing xattr.
>
> Which spinlock does clear_bit take? Are you referring to ovl_inode->lock mutex?
>
See set_bit() and clear_bit() in
include/asm-generic/bitops/atomic.h

  reply	other threads:[~2017-10-16 13:31 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-10-10 15:32 [RFC PATCH 0/9][V3] overlayfs: Delayed copy up of data Vivek Goyal
2017-10-10 15:32 ` [PATCH 1/9] ovl: ovl_check_setxattr() get rid of redundant -EOPNOTSUPP check Vivek Goyal
2017-10-10 15:32 ` [PATCH 2/9] ovl: During copy up, first copy up metadata and then data Vivek Goyal
2017-10-10 15:32 ` [PATCH 3/9] ovl: Provide a mount option metacopy=on/off for metadata copyup Vivek Goyal
2017-10-11  1:36   ` Amir Goldstein
2017-10-11 13:57     ` Vivek Goyal
2017-10-11 16:29       ` Amir Goldstein
2017-10-11 16:53         ` Vivek Goyal
2017-10-11 17:36           ` Amir Goldstein
2017-10-11 18:34             ` Vivek Goyal
2017-10-11 20:29               ` Amir Goldstein
2017-10-12 13:23                 ` Vivek Goyal
2017-10-12 13:39                   ` Amir Goldstein
2017-10-10 15:32 ` [PATCH 4/9] ovl: Copy up only metadata during copy up where it makes sense Vivek Goyal
2017-10-10 15:32 ` [PATCH 5/9] ovl: Set xattr OVL_XATTR_METACOPY on upper file Vivek Goyal
2017-10-10 17:03   ` Amir Goldstein
2017-10-11 20:16     ` Vivek Goyal
2017-10-11 20:44       ` Amir Goldstein
2017-10-10 15:32 ` [PATCH 6/9] ovl: Fix ovl_getattr() to get number of blocks from lower Vivek Goyal
2017-10-10 15:32 ` [PATCH 7/9] ovl: Introduce read/write barriers around metacopy flag update Vivek Goyal
2017-10-10 17:12   ` Amir Goldstein
2017-10-11 20:27     ` Vivek Goyal
2017-10-11 21:08       ` Amir Goldstein
2017-10-13 18:27         ` Vivek Goyal
2017-10-14  6:05           ` Amir Goldstein
2017-10-14  7:00             ` Amir Goldstein
2017-10-16 13:24               ` Vivek Goyal
2017-10-16 13:24             ` Vivek Goyal
2017-10-16 13:31               ` Amir Goldstein [this message]
2017-10-10 15:32 ` [PATCH 8/9] ovl: Set OVL_METACOPY flag during ovl_lookup() Vivek Goyal
2017-10-10 15:32 ` [PATCH 9/9] ovl: Return lower dentry if only metadata copy up took place Vivek Goyal

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