linux-kernel - Re: [PATCH] xfs: allow ro mounts if rtdev or logdev are read-only

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Message-ID: <68fe75c0-852b-4e81-ab39-1c10a3af506b@wdc.com>
Date: Mon, 28 Apr 2025 12:27:37 +0000
From: Hans Holmberg <Hans.Holmberg@....com>
To: "Darrick J. Wong" <djwong@...nel.org>
CC: Carlos Maiolino <cem@...nel.org>, Dave Chinner <david@...morbit.com>, hch
	<hch@....de>, "linux-xfs@...r.kernel.org" <linux-xfs@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] xfs: allow ro mounts if rtdev or logdev are read-only

On 25/04/2025 16:54, Darrick J. Wong wrote:
> On Fri, Apr 25, 2025 at 08:52:53AM +0000, Hans Holmberg wrote:
>> Allow read-only mounts on rtdevs and logdevs that are marked as
>> read-only and make sure those mounts can't be remounted read-write.
> 
> If the log device is readonly, does that mean the filesystem gets
> mounted norecovery too?  Your test might want to check that a dirty log
> is not recovered even if the filesystem mounts.
> 

Read only-mounts do not mean that norecovery is set, but xfs will fail
to mount if recovery is needed and the logdev/rtdev/.. is read-only.
To mount in this state, the user needs to pass in norecovery.



> --D
> 
>> Signed-off-by: Hans Holmberg <hans.holmberg@....com>
>> ---
>>
>> I will post a couple of xfstests to add coverage for these cases.
>>
>>  fs/xfs/xfs_super.c | 24 +++++++++++++++++++++---
>>  1 file changed, 21 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
>> index b2dd0c0bf509..d7ac1654bc80 100644
>> --- a/fs/xfs/xfs_super.c
>> +++ b/fs/xfs/xfs_super.c
>> @@ -380,10 +380,14 @@ xfs_blkdev_get(
>>  	struct file		**bdev_filep)
>>  {
>>  	int			error = 0;
>> +	blk_mode_t		mode;
>>  
>> -	*bdev_filep = bdev_file_open_by_path(name,
>> -		BLK_OPEN_READ | BLK_OPEN_WRITE | BLK_OPEN_RESTRICT_WRITES,
>> -		mp->m_super, &fs_holder_ops);
>> +	mode = BLK_OPEN_READ | BLK_OPEN_RESTRICT_WRITES;
>> +	if (!xfs_is_readonly(mp))
>> +		mode |= BLK_OPEN_WRITE;
>> +
>> +	*bdev_filep = bdev_file_open_by_path(name, mode,
>> +			mp->m_super, &fs_holder_ops);
>>  	if (IS_ERR(*bdev_filep)) {
>>  		error = PTR_ERR(*bdev_filep);
>>  		*bdev_filep = NULL;
>> @@ -1969,6 +1973,20 @@ xfs_remount_rw(
>>  	struct xfs_sb		*sbp = &mp->m_sb;
>>  	int error;
>>  
>> +	if (mp->m_logdev_targp && mp->m_logdev_targp != mp->m_ddev_targp &&
>> +	    bdev_read_only(mp->m_logdev_targp->bt_bdev)) {
>> +		xfs_warn(mp,
>> +			"ro->rw transition prohibited by read-only logdev");
>> +		return -EACCES;
>> +	}
>> +
>> +	if (mp->m_rtdev_targp &&
>> +	    bdev_read_only(mp->m_rtdev_targp->bt_bdev)) {
>> +		xfs_warn(mp,
>> +			"ro->rw transition prohibited by read-only rtdev");
>> +		return -EACCES;
>> +	}
>> +
>>  	if (xfs_has_norecovery(mp)) {
>>  		xfs_warn(mp,
>>  			"ro->rw transition prohibited on norecovery mount");
>> -- 
>> 2.34.1
>>
> 
>