Re: [PATCH v9 9/9] btrfs: Use sb_want_write() to protect sysfs feature change.

[Qu Wenruo <quwenruo@xxxxxxxxxxxxxx>]

OK, it's 4.2 merge windows now...

But still no new comments?

Thanks,
Qu

Qu Wenruo wrote on 2015/05/15 14:47 +0800:
> Ping.
>
> Any comments?
> Other v7 patchset is reviewed by David.
>
> But I didn't find it in 4.1 merge windows.
> Is something wrong or we are waiting for the vfs patch merged first?
>
> Thanks,
> Qu
>
> -------- Original Message  --------
> Subject: [PATCH v9 9/9] btrfs: Use sb_want_write() to protect sysfs
> feature change.
> From: Qu Wenruo <quwenruo@xxxxxxxxxxxxxx>
> To: <linux-btrfs@xxxxxxxxxxxxxxx>
> Date: 2015年02月16日 09:02
>
> > Just like label change, use sb_want_write() to do a correct protection.
> >
> > Signed-off-by: Qu Wenruo <quwenruo@xxxxxxxxxxxxxx>
> > ---
> > v4:
> >    Newly introduced.
> > v5:
> >    Change to sb_want_write().
> > v6:
> >    Move sb_want_write() to the beginning of the function.
> > v7:
> >    None
> > v8:
> >    Move sb_want_write() after get fs_info.
> > v9:
> >    Fix a unpaired sb_drop_write() in error handler.
> > ---
> >   fs/btrfs/sysfs.c | 25 +++++++++++++++++--------
> >   1 file changed, 17 insertions(+), 8 deletions(-)
> >
> > diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
> > index 7e548f7..19876ba 100644
> > --- a/fs/btrfs/sysfs.c
> > +++ b/fs/btrfs/sysfs.c
> > @@ -121,10 +121,14 @@ static ssize_t btrfs_feature_attr_store(struct
> > kobject *kobj,
> >       if (!fs_info)
> >           return -EPERM;
> >
> > -    ret = kstrtoul(skip_spaces(buf), 0, &val);
> > +    ret = sb_want_write(fs_info->sb);
> >       if (ret)
> >           return ret;
> >
> > +    ret = kstrtoul(skip_spaces(buf), 0, &val);
> > +    if (ret)
> > +        goto out;
> > +
> >       if (fa->feature_set == FEAT_COMPAT) {
> >           set = BTRFS_FEATURE_COMPAT_SAFE_SET;
> >           clear = BTRFS_FEATURE_COMPAT_SAFE_CLEAR;
> > @@ -141,22 +145,25 @@ static ssize_t btrfs_feature_attr_store(struct
> > kobject *kobj,
> >       /* Nothing to do */
> >       if ((val && (features & fa->feature_bit)) ||
> >           (!val && !(features & fa->feature_bit)))
> > -        return count;
> > +        goto out;
> >
> >       if ((val && !(set & fa->feature_bit)) ||
> >           (!val && !(clear & fa->feature_bit))) {
> >           btrfs_info(fs_info,
> >               "%sabling feature %s on mounted fs is not supported.",
> >               val ? "En" : "Dis", fa->kobj_attr.attr.name);
> > -        return -EPERM;
> > +        ret = -EPERM;
> > +        goto out;
> >       }
> >
> >       btrfs_info(fs_info, "%s %s feature flag",
> >              val ? "Setting" : "Clearing", fa->kobj_attr.attr.name);
> >
> >       trans = btrfs_start_transaction(fs_info->fs_root, 0);
> > -    if (IS_ERR(trans))
> > -        return PTR_ERR(trans);
> > +    if (IS_ERR(trans)) {
> > +        ret = PTR_ERR(trans);
> > +        goto out;
> > +    }
> >
> >       spin_lock(&fs_info->super_lock);
> >       features = get_features(fs_info, fa->feature_set);
> > @@ -168,10 +175,12 @@ static ssize_t btrfs_feature_attr_store(struct
> > kobject *kobj,
> >       spin_unlock(&fs_info->super_lock);
> >
> >       ret = btrfs_commit_transaction(trans, fs_info->fs_root);
> > -    if (ret)
> > -        return ret;
> >
> > -    return count;
> > +out:
> > +    sb_drop_write(fs_info->sb);
> > +    if (!ret)
> > +        return count;
> > +    return ret;
> >   }
> >
> >   static umode_t btrfs_feature_visible(struct kobject *kobj,
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