Btrfs: unset DCACHE_DISCONNECTED when mounting default subvol
A user was running into errors from an NFS export of a subvolume that had a default subvol set. When we mount a default subvol we will use d_obtain_alias() to find an existing dentry for the subvolume in the case that the root subvol has already been mounted, or a dummy one is allocated in the case that the root subvol has not already been mounted. This allows us to connect the dentry later on if we wander into the path. However if we don't ever wander into the path we will keep DCACHE_DISCONNECTED set for a long time, which angers NFS. It doesn't appear to cause any problems but it is annoying nonetheless, so simply unset DCACHE_DISCONNECTED in the get_default_root case and switch btrfs_lookup() to use d_materialise_unique() instead which will make everything play nicely together and reconnect stuff if we wander into the defaul subvol path from a different way. With this patch I'm no longer getting the NFS errors when exporting a volume that has been mounted with a default subvol set. Thanks, cc: bfields@fieldses.org cc: ebiederm@xmission.com Signed-off-by: Josef Bacik <jbacik@fb.com> Acked-by: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Chris Mason <clm@fb.com>
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@ -5150,7 +5150,7 @@ static struct dentry *btrfs_lookup(struct inode *dir, struct dentry *dentry,
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return ERR_CAST(inode);
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}
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return d_splice_alias(inode, dentry);
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return d_materialise_unique(dentry, inode);
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}
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unsigned char btrfs_filetype_table[] = {
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@ -855,6 +855,7 @@ static struct dentry *get_default_root(struct super_block *sb,
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struct btrfs_path *path;
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struct btrfs_key location;
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struct inode *inode;
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struct dentry *dentry;
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u64 dir_id;
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int new = 0;
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@ -925,7 +926,13 @@ setup_root:
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return dget(sb->s_root);
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}
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return d_obtain_alias(inode);
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dentry = d_obtain_alias(inode);
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if (!IS_ERR(dentry)) {
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spin_lock(&dentry->d_lock);
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dentry->d_flags &= ~DCACHE_DISCONNECTED;
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spin_unlock(&dentry->d_lock);
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}
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return dentry;
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}
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static int btrfs_fill_super(struct super_block *sb,
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