On Fri, Feb 14, 2014 at 05:19:29PM -0500, J. Bruce Fields wrote:
> On Fri, Feb 14, 2014 at 09:02:30AM -0800, Eric W. Biederman wrote:
> > "J. Bruce Fields" <bfields@xxxxxxxxxxxx> writes:
> >
> > > On Fri, Feb 14, 2014 at 07:49:35AM -0800, Eric W. Biederman wrote:
> > >>
> > >> I believe we want both groups of dentries on the s_anon list so that if
> > >> they remain disconnected when the filesystem is unmounted we can
> > >> find them and deal with them.
> > >
> > > Note it's IS_ROOT(), not DCACHE_DISCONNECTED, that determines whether a
> > > hashed dentry is on s_anon or not. (See
> > > 7632e465feb182cadc3c9aa1282a057201818a8c for more detailed
> > > discussion.)
> >
> > Interesting. It remains the case that d_obtain_alias that sets
> > DCACHE_DISCONNECTED is the only way to get on the s_anon list.
>
> You're right, I forgot that.
>
> > >From the rest of the conversation below I think what is needed is
> > d_obtain_alias_root. A function like d_obtain_alias but that does not
> > set DCACHE_DISCONNECTED, that places IS_ROOT dentries on the s_anon list
> > and that is usually expected to not find an alias.
>
> Sounds good.
So, something like this.
(Untested, and will also screw up nilfs2 until we fix d_splice_alias not
to require DCACHE_DISCONNECTED dentries.)
--b.
commit c2bc8557e935b24caa2174403b093bc00dc62112
Author: J. Bruce Fields <bfields@xxxxxxxxxx>
Date: Fri Feb 14 17:35:37 2014 -0500
dcache: d_obtain_alias callers don't all want DISCONNECTED
There are a few d_obtain_alias callers that are using it to get the
root of a filesystem which may already have an alias somewhere else.
This is not the same as the filehandle-lookup case, and none of them
actually need DCACHE_DISCONNECTED set.
In the btrfs case this was causing a spurious printk from
nfsd/nfsfh.c:fh_verify when it found an unexpected DCACHE_DISCONNECTED
dentry.
Which isn't really a serious problem, but it would really be clearer if
we reserved DCACHE_DISCONNECTED for those cases where it's actually
needed.
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 97cc241..07ce96b 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -925,7 +925,7 @@ setup_root:
return dget(sb->s_root);
}
- return d_obtain_alias(inode);
+ return d_obtain_alias_root(inode);
}
static int btrfs_fill_super(struct super_block *sb,
diff --git a/fs/ceph/super.c b/fs/ceph/super.c
index 2df963f..9666950 100644
--- a/fs/ceph/super.c
+++ b/fs/ceph/super.c
@@ -732,7 +732,7 @@ static struct dentry *open_root_dentry(struct ceph_fs_client *fsc,
goto out;
}
} else {
- root = d_obtain_alias(inode);
+ root = d_obtain_alias_root(inode);
}
ceph_init_dentry(root);
dout("open_root_inode success, root dentry is %p\n", root);
diff --git a/fs/dcache.c b/fs/dcache.c
index b4572fa..f30f783 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1832,25 +1832,7 @@ struct dentry *d_find_any_alias(struct inode *inode)
}
EXPORT_SYMBOL(d_find_any_alias);
-/**
- * d_obtain_alias - find or allocate a dentry for a given inode
- * @inode: inode to allocate the dentry for
- *
- * Obtain a dentry for an inode resulting from NFS filehandle conversion or
- * similar open by handle operations. The returned dentry may be anonymous,
- * or may have a full name (if the inode was already in the cache).
- *
- * When called on a directory inode, we must ensure that the inode only ever
- * has one dentry. If a dentry is found, that is returned instead of
- * allocating a new one.
- *
- * On successful return, the reference to the inode has been transferred
- * to the dentry. In case of an error the reference on the inode is released.
- * To make it easier to use in export operations a %NULL or IS_ERR inode may
- * be passed in and will be the error will be propagate to the return value,
- * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
- */
-struct dentry *d_obtain_alias(struct inode *inode)
+struct dentry *__d_obtain_alias(struct inode *inode, int disconnected)
{
static const struct qstr anonstring = QSTR_INIT("/", 1);
struct dentry *tmp;
@@ -1881,7 +1863,10 @@ struct dentry *d_obtain_alias(struct inode *inode)
}
/* attach a disconnected dentry */
- add_flags = d_flags_for_inode(inode) | DCACHE_DISCONNECTED;
+ add_flags = d_flags_for_inode(inode);
+
+ if (disconnected)
+ add_flags |= DCACHE_DISCONNECTED;
spin_lock(&tmp->d_lock);
tmp->d_inode = inode;
@@ -1902,9 +1887,53 @@ struct dentry *d_obtain_alias(struct inode *inode)
iput(inode);
return res;
}
+
+/**
+ * d_obtain_alias - find or allocate a DISCONNECTED dentry for a given inode
+ * @inode: inode to allocate the dentry for
+ *
+ * Obtain a dentry for an inode resulting from NFS filehandle conversion or
+ * similar open by handle operations. The returned dentry may be anonymous,
+ * or may have a full name (if the inode was already in the cache).
+ *
+ * When called on a directory inode, we must ensure that the inode only ever
+ * has one dentry. If a dentry is found, that is returned instead of
+ * allocating a new one.
+ *
+ * On successful return, the reference to the inode has been transferred
+ * to the dentry. In case of an error the reference on the inode is released.
+ * To make it easier to use in export operations a %NULL or IS_ERR inode may
+ * be passed in and the error will be propagated to the return value,
+ * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
+ */
+struct dentry *d_obtain_alias(struct inode *inode)
+{
+ return __d_obtain_alias(inode, 1);
+}
EXPORT_SYMBOL(d_obtain_alias);
/**
+ * d_obtain_alias_root - find or allocate a dentry for a given inode
+ * @inode: inode to allocate the dentry for
+ *
+ * Obtain an IS_ROOT dentry for the root of a filesystem.
+ *
+ * We must ensure that directory inodes only ever have one dentry. If a
+ * dentry is found, that is returned instead of allocating a new one.
+ *
+ * On successful return, the reference to the inode has been transferred
+ * to the dentry. In case of an error the reference on the inode is
+ * released. A %NULL or IS_ERR inode may be passed in and will be the
+ * error will be propagate to the return value, with a %NULL @inode
+ * replaced by ERR_PTR(-ESTALE).
+ */
+struct dentry *d_obtain_alias_root(struct inode *inode)
+{
+ return __d_obtain_alias(inode, 0);
+}
+EXPORT_SYMBOL(d_obtain_alias_root);
+
+/**
* d_add_ci - lookup or allocate new dentry with case-exact name
* @inode: the inode case-insensitive lookup has found
* @dentry: the negative dentry that was passed to the parent's lookup func
diff --git a/fs/nfs/getroot.c b/fs/nfs/getroot.c
index 66984a9..7b32522 100644
--- a/fs/nfs/getroot.c
+++ b/fs/nfs/getroot.c
@@ -112,7 +112,7 @@ struct dentry *nfs_get_root(struct super_block *sb, struct nfs_fh *mntfh,
* if the dentry tree reaches them; however if the dentry already
* exists, we'll pick it up at this point and use it as the root
*/
- ret = d_obtain_alias(inode);
+ ret = d_obtain_alias_root(inode);
if (IS_ERR(ret)) {
dprintk("nfs_get_root: get root dentry failed\n");
goto out;
diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
index 7ac2a12..a518a73 100644
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -942,7 +942,7 @@ static int nilfs_get_root_dentry(struct super_block *sb,
iput(inode);
}
} else {
- dentry = d_obtain_alias(inode);
+ dentry = d_obtain_alias_root(inode);
if (IS_ERR(dentry)) {
ret = PTR_ERR(dentry);
goto failed_dentry;
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index bf72e9a..2973aab 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -247,6 +247,7 @@ extern struct dentry * d_splice_alias(struct inode *, struct dentry *);
extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
extern struct dentry *d_find_any_alias(struct inode *inode);
extern struct dentry * d_obtain_alias(struct inode *);
+extern struct dentry * d_obtain_alias_root(struct inode *);
extern void shrink_dcache_sb(struct super_block *);
extern void shrink_dcache_parent(struct dentry *);
extern void shrink_dcache_for_umount(struct super_block *);
--
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