linux-kernel - [PATCH] erofs: derive fsid from on-disk UUID for .statfs() if possible

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Date: Tue,  9 Apr 2024 16:11:35 +0800
From: Hongzhen Luo <hongzhen@...ux.alibaba.com>
To: xiang@...nel.org,
	chao@...nel.org,
	linux-erofs@...ts.ozlabs.org
Cc: huyue2@...lpad.com,
	jefflexu@...ux.alibaba.com,
	dhavale@...gle.com,
	linux-kernel@...r.kernel.org,
	Hongzhen Luo <hongzhen@...ux.alibaba.com>
Subject: [PATCH] erofs: derive fsid from on-disk UUID for .statfs() if possible

Use the superblock's UUID to generate the fsid when it's non-null.

Signed-off-by: Hongzhen Luo <hongzhen@...ux.alibaba.com>
---
 fs/erofs/super.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index c0eb139adb07..83bd8ee3b5ba 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -923,22 +923,20 @@ static int erofs_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
 	struct super_block *sb = dentry->d_sb;
 	struct erofs_sb_info *sbi = EROFS_SB(sb);
-	u64 id = 0;
-
-	if (!erofs_is_fscache_mode(sb))
-		id = huge_encode_dev(sb->s_bdev->bd_dev);
 
 	buf->f_type = sb->s_magic;
 	buf->f_bsize = sb->s_blocksize;
 	buf->f_blocks = sbi->total_blocks;
 	buf->f_bfree = buf->f_bavail = 0;
-
 	buf->f_files = ULLONG_MAX;
 	buf->f_ffree = ULLONG_MAX - sbi->inos;
-
 	buf->f_namelen = EROFS_NAME_LEN;
 
-	buf->f_fsid    = u64_to_fsid(id);
+	if (uuid_is_null(&sb->s_uuid))
+		buf->f_fsid = u64_to_fsid(erofs_is_fscache_mode(sb) ? 0 :
+				huge_encode_dev(sb->s_bdev->bd_dev));
+	else
+		buf->f_fsid = uuid_to_fsid((__u8 *)&sb->s_uuid);
 	return 0;
 }
 
-- 
2.37.1