An attempt to freeze a filesystem that does not support such operation is
reported as EOPNOTSUPP to user. Running unfreeze to the same filesystem
returns EINVAL. Later is a little misleading, users can mix that message
with return value from unfreezing when filesystem is not frozen.
Signed-off-by: Sami Kerola <[email protected]>
---
fs/ioctl.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/fs/ioctl.c b/fs/ioctl.c
index cb9b02940805..1d6372ef4008 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -566,6 +566,10 @@ static int ioctl_fsthaw(struct file *filp)
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
+ /* If filesystem doesn't support thaw feature, return. */
+ if (!sb->s_op->unfreeze_fs)
+ return -EOPNOTSUPP;
+
/* Thaw */
if (sb->s_op->thaw_super)
return sb->s_op->thaw_super(sb);
--
2.11.0
On Sun, Dec 18, 2016 at 06:57:27PM +0000, Sami Kerola wrote:
> An attempt to freeze a filesystem that does not support such operation is
> reported as EOPNOTSUPP to user. Running unfreeze to the same filesystem
> returns EINVAL. Later is a little misleading, users can mix that message
> with return value from unfreezing when filesystem is not frozen.
This is going to break gfs2 with it's odd ->that_super method.
On 19 December 2016 at 10:24, Christoph Hellwig <[email protected]> wrote:
> On Sun, Dec 18, 2016 at 06:57:27PM +0000, Sami Kerola wrote:
>> An attempt to freeze a filesystem that does not support such operation is
>> reported as EOPNOTSUPP to user. Running unfreeze to the same filesystem
>> returns EINVAL. Later is a little misleading, users can mix that message
>> with return value from unfreezing when filesystem is not frozen.
>
> This is going to break gfs2 with it's odd ->that_super method.
Thank you for feedback, there's just one small problem with it. I don't
quite understand the breakage.
Proposed change uses similar logic as ioctl_fsfreeze()[1] and it works fine.
If I am not entirely mistaking freeze and thaw hooks where added[2] to avoid
issues with gfs2. And looking gfs2 super_operations init[3] does not make
me any wiser what might be wrong.
Maybe feedback had typo s/that_super/thaw_super/[4]. But even then it is
unclear to me how a null could cause breakage.
[1] https://github.com/torvalds/linux/blob/master/fs/ioctl.c#L553
[2] https://github.com/torvalds/linux/commit/48b6bca6b7b8309697fc8a101793befe92d249d9
[3] https://github.com/torvalds/linux/blob/master/fs/gfs2/super.c#L1683
[4] https://github.com/torvalds/linux/blob/master/fs/super.c#L1446
--
Sami Kerola
http://www.iki.fi/kerolasa/