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Subject: Re: [PATCH] UBIFS: Add freeze support in ubifs
To: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>,
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From: Richard Weinberger <richard@nod.at>
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Date: Sun, 27 Sep 2015 10:06:31 +0200
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Yang,

Am 27.09.2015 um 04:39 schrieb Dongsheng Yang:
> We need to do nothing in ubifs, as all is already done in vfs.

Please more details. :-)
The current changelog reads like every filesystem should implement
it as nop. Which is obviously not the case.

fs/super.c checks whether ->freeze_fs() is implemented, so
a nop-implementation does not make sense here.

I bet you hit this in fs/ioctl.c:
        /* If filesystem doesn't support freeze feature, return. */
        if (sb->s_op->freeze_fs == NULL && sb->s_op->freeze_super == NULL)
                return -EOPNOTSUPP;

Correct?

And the most important detail is missing, why is UBIFS allowed
to have a nop-implementation?

Thanks,
//richard