linux-kernel - Re: [PATCH] UBIFS: fill f

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Date:	Wed, 03 Sep 2008 12:44:33 +0300
From:	Artem Bityutskiy <dedekind@...radead.org>
To:	David Woodhouse <dwmw2@...radead.org>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	Adrian Hunter <ext-adrian.hunter@...ia.com>
Subject: Re: [PATCH] UBIFS: fill f_fsid

On Mon, 2008-09-01 at 10:43 +0100, David Woodhouse wrote:
> For btrfs I xor the first 64 bits with the second 64 bits, and put
> _that_ into f_fsid. You're just putting the first 64 bits in and
> ignoring the second 64 bits. Neither is really _better_ than the other;
> you just alter the circumstances in which you get collisions. But I
> suppose we might as well be consistent about how we do it?
Like this?

From: Artem Bityutskiy <Artem.Bityutskiy@...ia.com>
Date: Wed, 3 Sep 2008 14:16:42 +0300
Subject: [PATCH] UBIFS: amend f_fsid

David Woodhouse suggested to be consistent with other FSes
and xor the beginning and the end of the UUID.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@...ia.com>
---
 fs/ubifs/super.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index ab9b5cb..83fe0a5 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -370,6 +370,7 @@ static int ubifs_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
 	struct ubifs_info *c = dentry->d_sb->s_fs_info;
 	unsigned long long free;
+	__le32 *uuid = (__le32 *)c->uuid;
 
 	free = ubifs_get_free_space(c);
 	dbg_gen("free space %lld bytes (%lld blocks)",
@@ -386,8 +387,8 @@ static int ubifs_statfs(struct dentry *dentry, struct kstatfs *buf)
 	buf->f_files = 0;
 	buf->f_ffree = 0;
 	buf->f_namelen = UBIFS_MAX_NLEN;
-	memcpy(&buf->f_fsid, c->uuid, sizeof(__kernel_fsid_t));
-
+	buf->f_fsid.val[0] = le32_to_cpu(uuid[0]) ^ le32_to_cpu(uuid[2]);
+	buf->f_fsid.val[1] = le32_to_cpu(uuid[1]) ^ le32_to_cpu(uuid[3]);
 	return 0;
 }
 
-- 
1.5.4.1


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