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Message-ID: <1302ac46-f24c-bb49-9fac-6a3db748e57c@virtuozzo.com>
Date: Thu, 24 Sep 2020 10:40:16 +0300
From: Pavel Tikhomirov <ptikhomirov@...tuozzo.com>
To: Amir Goldstein <amir73il@...il.com>
Cc: Miklos Szeredi <miklos@...redi.hu>,
Vivek Goyal <vgoyal@...hat.com>,
overlayfs <linux-unionfs@...r.kernel.org>,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] ovl: introduce new "index=nouuid" option for inodes
index feature
On 9/23/20 7:36 PM, Amir Goldstein wrote:
>>> @@ -414,7 +415,7 @@ static int ovl_check_origin(struct ovl_fs *ofs, struct dentry *upperdentry,
>>> * Return 0 on match, -ESTALE on mismatch, < 0 on error.
>>> */
>>> static int ovl_verify_fh(struct dentry *dentry, const char *name,
>>> - const struct ovl_fh *fh)
>>> + const struct ovl_fh *fh, bool nouuid)
>>> {
>>> struct ovl_fh *ofh = ovl_get_fh(dentry, name);
>>> int err = 0;
>>> @@ -425,8 +426,14 @@ static int ovl_verify_fh(struct dentry *dentry, const char *name,
>>> if (IS_ERR(ofh))
>>> return PTR_ERR(ofh);
>>>
>>> - if (fh->fb.len != ofh->fb.len || memcmp(&fh->fb, &ofh->fb, fh->fb.len))
>>> + if (fh->fb.len != ofh->fb.len) {
>>> err = -ESTALE;
>>> + } else {
>>> + if (nouuid && !uuid_equal(&fh->fb.uuid, &ofh->fb.uuid))
>>> + ofh->fb.uuid = fh->fb.uuid;
>>> + if (memcmp(&fh->fb, &ofh->fb, fh->fb.len))
>>> + err = -ESTALE;
>>> + }
>>>
>
> On second thought I am wondering if we should do that differently.
> If users want to work with index=nouuid, they need to work with it from day 1.
> index=nouuid should export null uuid in NFS handles and write null uuid
> in trusted.overlay.origin xattr.
>
> So in ovl_encode_real_fh() you set null uuid and
> instead of relaxing uuid_equal() in ovl_decode_real_fh()
> you change it to uuid_is_null().
>
> Do you have a problem with that for Virtuozzo use case?
Actually we've enabled index=on by default in kernel config in Virtuozzo
only in the new update which is not yet released. So probably we can
switch to index=nouuid with null uuid in fh.
>
> Thanks,
> Amir.
>
--
Best regards, Tikhomirov Pavel
Software Developer, Virtuozzo.
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