thr3ads.net - Btrfs devel - [PATCH] btrfs: allow mounting btrfs subvolumes with different ro/rw options [Jun 2013]

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harald@redhat.com

2013-Jun-18 15:29 UTC

[PATCH] btrfs: allow mounting btrfs subvolumes with different ro/rw options

From: Harald Hoyer <harald@redhat.com>

Given the following /etc/fstab entries:

/dev/sda3 /mnt/foo btrfs subvol=foo,ro 0
/dev/sda3 /mnt/bar btrfs subvol=bar,rw 0

you can''t issue:

$ mount /mnt/foo
$ mount /mnt/bar

You would have to do:

$ mount /mnt/foo
$ mount -o remount,rw /mnt/foo
$ mount --bind -o remount,ro /mnt/foo
$ mount /bar

or

$ mount /mnt/bar
$ mount --rw /mnt/foo
$ mount --bind -o remount,ro /mnt/foo

With this patch you can do

$ mount /mnt/foo
$ mount /mnt/bar

$ cat /proc/self/mountinfo
49 33 0:41 /foo /mnt/foo ro,relatime shared:36 - btrfs /dev/sda3
rw,ssd,space_cache
87 33 0:41 /bar /mnt/bar rw,relatime shared:74 - btrfs /dev/sda3
rw,ssd,space_cache
---
 fs/btrfs/super.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index f0857e0..80ed3e2 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -64,6 +64,8 @@
 static const struct super_operations btrfs_super_ops;
 static struct file_system_type btrfs_fs_type;
 
+static int btrfs_remount(struct super_block *sb, int *flags, char *data);
+
 static const char *btrfs_decode_error(int errno)
 {
 	char *errstr = "unknown";
@@ -1036,6 +1038,26 @@ static struct dentry *mount_subvol(const char
*subvol_name, int flags,
 	mnt = vfs_kern_mount(&btrfs_fs_type, flags, device_name,
 			     newargs);
 	kfree(newargs);
+
+	if (PTR_RET(mnt) == -EBUSY) {
+		if (flags & MS_RDONLY) {
+			mnt = vfs_kern_mount(&btrfs_fs_type, flags & ~MS_RDONLY,
device_name,
+					     newargs);
+		} else {
+			int r;
+			mnt = vfs_kern_mount(&btrfs_fs_type, flags | MS_RDONLY, device_name,
+					     newargs);
+			if (IS_ERR(mnt))
+				return ERR_CAST(mnt);
+
+			r = btrfs_remount(mnt->mnt_sb, &flags, NULL);
+			if (r < 0) {
+				/* FIXME: release vfsmount mnt ??*/
+				return ERR_PTR(r);
+			}
+		}
+	}
+
 	if (IS_ERR(mnt))
 		return ERR_CAST(mnt);
 
-- 
1.8.2.1

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Harald Hoyer

2013-Sep-02 10:55 UTC

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Re: [PATCH] btrfs: allow mounting btrfs subvolumes with different ro/rw options

On 06/18/2013 05:29 PM, harald@redhat.com wrote:> From: Harald Hoyer <harald@redhat.com>
> 
> Given the following /etc/fstab entries:
> 
> /dev/sda3 /mnt/foo btrfs subvol=foo,ro 0
> /dev/sda3 /mnt/bar btrfs subvol=bar,rw 0
> 
> you can''t issue:
> 
> $ mount /mnt/foo
> $ mount /mnt/bar
> 
> You would have to do:
> 
> $ mount /mnt/foo
> $ mount -o remount,rw /mnt/foo
> $ mount --bind -o remount,ro /mnt/foo
> $ mount /bar
> 
> or
> 
> $ mount /mnt/bar
> $ mount --rw /mnt/foo
> $ mount --bind -o remount,ro /mnt/foo
> 
> With this patch you can do
> 
> $ mount /mnt/foo
> $ mount /mnt/bar
> 
> $ cat /proc/self/mountinfo
> 49 33 0:41 /foo /mnt/foo ro,relatime shared:36 - btrfs /dev/sda3
rw,ssd,space_cache
> 87 33 0:41 /bar /mnt/bar rw,relatime shared:74 - btrfs /dev/sda3
rw,ssd,space_cache
> ---
>  fs/btrfs/super.c | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index f0857e0..80ed3e2 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -64,6 +64,8 @@
>  static const struct super_operations btrfs_super_ops;
>  static struct file_system_type btrfs_fs_type;
>  
> +static int btrfs_remount(struct super_block *sb, int *flags, char *data);
> +
>  static const char *btrfs_decode_error(int errno)
>  {
>  	char *errstr = "unknown";
> @@ -1036,6 +1038,26 @@ static struct dentry *mount_subvol(const char
*subvol_name, int flags,
>  	mnt = vfs_kern_mount(&btrfs_fs_type, flags, device_name,
>  			     newargs);
>  	kfree(newargs);
> +
> +	if (PTR_RET(mnt) == -EBUSY) {
> +		if (flags & MS_RDONLY) {
> +			mnt = vfs_kern_mount(&btrfs_fs_type, flags & ~MS_RDONLY,
device_name,
> +					     newargs);
> +		} else {
> +			int r;
> +			mnt = vfs_kern_mount(&btrfs_fs_type, flags | MS_RDONLY,
device_name,
> +					     newargs);
> +			if (IS_ERR(mnt))
> +				return ERR_CAST(mnt);
> +
> +			r = btrfs_remount(mnt->mnt_sb, &flags, NULL);
> +			if (r < 0) {
> +				/* FIXME: release vfsmount mnt ??*/
> +				return ERR_PTR(r);
> +			}
> +		}
> +	}
> +
>  	if (IS_ERR(mnt))
>  		return ERR_CAST(mnt);
>  
> 
Any comments?
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Harald Hoyer

2013-Sep-14 11:26 UTC

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Re: [PATCH] btrfs: allow mounting btrfs subvolumes with different ro/rw options

On 09/02/2013 12:55 PM, Harald Hoyer wrote:> On 06/18/2013 05:29 PM, harald@redhat.com wrote:
>> From: Harald Hoyer <harald@redhat.com>
>>
>> Given the following /etc/fstab entries:
>>
>> /dev/sda3 /mnt/foo btrfs subvol=foo,ro 0
>> /dev/sda3 /mnt/bar btrfs subvol=bar,rw 0
>>
>> you can''t issue:
>>
>> $ mount /mnt/foo
>> $ mount /mnt/bar
>>
>> You would have to do:
>>
>> $ mount /mnt/foo
>> $ mount -o remount,rw /mnt/foo
>> $ mount --bind -o remount,ro /mnt/foo
>> $ mount /bar
>>
>> or
>>
>> $ mount /mnt/bar
>> $ mount --rw /mnt/foo
>> $ mount --bind -o remount,ro /mnt/foo
>>
>> With this patch you can do
>>
>> $ mount /mnt/foo
>> $ mount /mnt/bar
>>
>> $ cat /proc/self/mountinfo
>> 49 33 0:41 /foo /mnt/foo ro,relatime shared:36 - btrfs /dev/sda3
rw,ssd,space_cache
>> 87 33 0:41 /bar /mnt/bar rw,relatime shared:74 - btrfs /dev/sda3
rw,ssd,space_cache
>> ---
>>  fs/btrfs/super.c | 22 ++++++++++++++++++++++
>>  1 file changed, 22 insertions(+)
>>
>> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
>> index f0857e0..80ed3e2 100644
>> --- a/fs/btrfs/super.c
>> +++ b/fs/btrfs/super.c
>> @@ -64,6 +64,8 @@
>>  static const struct super_operations btrfs_super_ops;
>>  static struct file_system_type btrfs_fs_type;
>>  
>> +static int btrfs_remount(struct super_block *sb, int *flags, char
*data);
>> +
>>  static const char *btrfs_decode_error(int errno)
>>  {
>>  	char *errstr = "unknown";
>> @@ -1036,6 +1038,26 @@ static struct dentry *mount_subvol(const char
*subvol_name, int flags,
>>  	mnt = vfs_kern_mount(&btrfs_fs_type, flags, device_name,
>>  			     newargs);
>>  	kfree(newargs);
>> +
>> +	if (PTR_RET(mnt) == -EBUSY) {
>> +		if (flags & MS_RDONLY) {
>> +			mnt = vfs_kern_mount(&btrfs_fs_type, flags & ~MS_RDONLY,
device_name,
>> +					     newargs);
>> +		} else {
>> +			int r;
>> +			mnt = vfs_kern_mount(&btrfs_fs_type, flags | MS_RDONLY,
device_name,
>> +					     newargs);
>> +			if (IS_ERR(mnt))
>> +				return ERR_CAST(mnt);
>> +
>> +			r = btrfs_remount(mnt->mnt_sb, &flags, NULL);
>> +			if (r < 0) {
>> +				/* FIXME: release vfsmount mnt ??*/
>> +				return ERR_PTR(r);
>> +			}
>> +		}
>> +	}
>> +
>>  	if (IS_ERR(mnt))
>>  		return ERR_CAST(mnt);
>>  
>>
> 
> Any comments?
> 
Not even a "no, we don''t want that" ?
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David Sterba

2013-Nov-18 10:53 UTC

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Re: [PATCH] btrfs: allow mounting btrfs subvolumes with different ro/rw options

On Sat, Sep 14, 2013 at 01:26:22PM +0200, Harald Hoyer
wrote:> > Any comments?
> Not even a "no, we don''t want that" ?
Please resend.

david
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Harald Hoyer

2013-Nov-19 10:36 UTC

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Re: [PATCH] btrfs: allow mounting btrfs subvolumes with different ro/rw options

On 11/18/2013 11:53 AM, David Sterba wrote:> On Sat, Sep 14, 2013 at 01:26:22PM +0200, Harald Hoyer wrote:
>>> Any comments?
>> Not even a "no, we don''t want that" ?
> 
> Please resend.
> 
> david
> 
done
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Btrfs devel - Jun 2013 - [PATCH] btrfs: allow mounting btrfs subvolumes with different ro/rw options

[PATCH] btrfs: allow mounting btrfs subvolumes with different ro/rw options

Re: [PATCH] btrfs: allow mounting btrfs subvolumes with different ro/rw options

Re: [PATCH] btrfs: allow mounting btrfs subvolumes with different ro/rw options

Re: [PATCH] btrfs: allow mounting btrfs subvolumes with different ro/rw options

Re: [PATCH] btrfs: allow mounting btrfs subvolumes with different ro/rw options