Date: 21 Sep 2009 20:51:34 -0400
Message-ID: <20090922005134.20722.qmail@science.horizon.com>
From: "George Spelvin" <linux@horizon.com>
To: Joel.Becker@oracle.com
Subject: Re: [GIT PULL] ocfs2 changes for 2.6.32
Cc: linux@horizon.com, linux-kernel@vger.kernel.org,
       torvalds@linux-foundation.org
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1062
Lines: 28

> Perhaps ->copyfile takes the following flags:
>
> #define ALLOW_COW_SHARED	0x0001
> #define REQUIRE_COW_SHARED	0x0002
> #define REQUIRE_BASIC_ATTRS	0x0004
> #define REQUIRE_FULL_ATTRS	0x0008
> #define REQUIRE_ATOMIC		0x0010
> #define SNAPSHOT		(REQUIRE_COW_SHARED |
>				 REQUIRE_BASIC_ATTRS |
>				 REQUIRE_ATOMIC)
> #define SNAPSHOT_PRESERVE	(SNAPSHOT | REQUIRE_FULL_ATTRS)

Um, could I strongly suggest that flags == 0 be the "succeed if at all
possible case", and various options limit it.

In particular, invert ALLOW_COW_SHARED to REQUIRE_ALLOCATE.

Another possibly useful flag would be REQUIRE_OPTIMIZED.
I.e. if it's not appreciably faster than a read/write loop, perhaps
the application would prefer to do it itself.

We also have to define the error code to return in case of a flag
violation.  ENOTSUP?
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