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Message-Id: <1242662968-11684-30-git-send-email-jblunck@suse.de>
Date: Mon, 18 May 2009 18:09:25 +0200
From: Jan Blunck <jblunck@...e.de>
To: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Cc: viro@...iv.linux.org.uk, bharata@...ibm.com, dwmw2@...radead.org,
mszeredi@...e.cz, vaurora@...hat.com
Subject: [PATCH 29/32] union mount: Support for fallthru entries in union mount lookup
From: Valerie Aurora (Henson) <vaurora@...hat.com>
A fallthru directory entry overrides the opaque flag for its parent
directory (for this directory entry only). Before, we stopped
building the union stack when we encountered an opaque directory; now
we include directories below opaque directories in the union stack and
check for opacity during lookup.
Signed-off-by: Jan Blunck <jblunck@...e.de>
Signed-off-by: Valerie Aurora (Henson) <vaurora@...hat.com>
---
fs/dcache.c | 7 +++----
fs/namei.c | 59 +++++++++++++++++++++++++++++++++++++++++++++--------------
2 files changed, 48 insertions(+), 18 deletions(-)
diff --git a/fs/dcache.c b/fs/dcache.c
index b6fb688..844a76a 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1086,7 +1086,7 @@ struct dentry *d_alloc_name(struct dentry *parent, const char *name)
static void __d_instantiate(struct dentry *dentry, struct inode *inode)
{
if (inode) {
- dentry->d_flags &= ~DCACHE_WHITEOUT;
+ dentry->d_flags &= ~(DCACHE_WHITEOUT|DCACHE_FALLTHRU);
list_add(&dentry->d_alias, &inode->i_dentry);
}
dentry->d_inode = inode;
@@ -1650,9 +1650,8 @@ void d_delete(struct dentry * dentry)
static void __d_rehash(struct dentry * entry, struct hlist_head *list)
{
-
- entry->d_flags &= ~DCACHE_UNHASHED;
- hlist_add_head_rcu(&entry->d_hash, list);
+ entry->d_flags &= ~DCACHE_UNHASHED;
+ hlist_add_head_rcu(&entry->d_hash, list);
}
static void _d_rehash(struct dentry * entry)
diff --git a/fs/namei.c b/fs/namei.c
index 684619c..1f96a66 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -414,6 +414,28 @@ static struct dentry *cache_lookup(struct dentry *parent, struct qstr *name,
return dentry;
}
+/*
+ * Theory of operation for opaque, whiteout, and fallthru:
+ *
+ * whiteout: Unconditionally stop lookup here - ENOENT
+ *
+ * opaque: Don't lookup in directories lower in the union stack
+ *
+ * fallthru: While looking up an entry, ignore the opaque flag for the
+ * current directory only.
+ *
+ * A union stack is a linked list of directory dentries which appear
+ * in the same place in the namespace. When constructing the union
+ * stack, we include directories below opaque directories so that we
+ * can properly handle fallthrus. All non-fallthru lookups have to
+ * check for the opaque flag on the parent directory and obey it.
+ *
+ * In general, the code pattern is to lookup the the topmost entry
+ * first (either the first visible non-negative dentry or a negative
+ * dentry in the topmost layer of the union), then build the union
+ * stack for the newly looked-up entry (if it is a directory).
+ */
+
/**
* __cache_lookup_topmost - lookup the topmost (non-)negative dentry
*
@@ -443,6 +465,10 @@ static int __cache_lookup_topmost(struct nameidata *nd, struct qstr *name,
if (!dentry || (dentry->d_inode || d_is_whiteout(dentry)))
return !dentry;
+ /* Keep going through opaque directories if we found a fallthru */
+ if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(dentry))
+ return !dentry;
+
/* look for the first non-negative or whiteout dentry */
while (follow_union_down(&nd->path.mnt, &nd->path.dentry)) {
@@ -468,6 +494,10 @@ static int __cache_lookup_topmost(struct nameidata *nd, struct qstr *name,
if (dentry->d_inode || d_is_whiteout(dentry))
goto out_dput;
+ /* Stop the lookup on opaque parent and non-fallthru child */
+ if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(dentry))
+ goto out_dput;
+
dput(dentry);
}
@@ -526,9 +556,6 @@ static int __cache_lookup_build_union(struct nameidata *nd, struct qstr *name,
path_put(&last);
last.dentry = dentry;
last.mnt = mntget(nd->path.mnt);
-
- if (IS_OPAQUE(last.dentry->d_inode))
- break;
}
if (last.dentry != path->dentry)
@@ -568,8 +595,7 @@ static int cache_lookup_union(struct nameidata *nd, struct qstr *name,
/* only directories can be part of a union stack */
if (!path->dentry->d_inode ||
- !S_ISDIR(path->dentry->d_inode->i_mode) ||
- IS_OPAQUE(path->dentry->d_inode))
+ !S_ISDIR(path->dentry->d_inode->i_mode))
goto out;
/* Build the union stack for this part */
@@ -736,6 +762,9 @@ static int __real_lookup_topmost(struct nameidata *nd, struct qstr *name,
if (path->dentry->d_inode || d_is_whiteout(path->dentry))
return 0;
+ if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(path->dentry))
+ return 0;
+
while (follow_union_down(&nd->path.mnt, &nd->path.dentry)) {
name->hash = full_name_hash(name->name, name->len);
if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) {
@@ -756,6 +785,9 @@ static int __real_lookup_topmost(struct nameidata *nd, struct qstr *name,
goto out;
}
+ if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(next.dentry))
+ goto out;
+
dput(next.dentry);
}
out:
@@ -815,9 +847,6 @@ static int __real_lookup_build_union(struct nameidata *nd, struct qstr *name,
path_put(&last);
last.dentry = next.dentry;
last.mnt = mntget(next.mnt);
-
- if (IS_OPAQUE(last.dentry->d_inode))
- break;
}
if (last.dentry != path->dentry)
@@ -839,8 +868,7 @@ static int real_lookup_union(struct nameidata *nd, struct qstr *name,
/* only directories can be part of a union stack */
if (!path->dentry->d_inode ||
- !S_ISDIR(path->dentry->d_inode->i_mode) ||
- IS_OPAQUE(path->dentry->d_inode))
+ !S_ISDIR(path->dentry->d_inode->i_mode))
goto out;
/* Build the union stack for this part */
@@ -1125,7 +1153,7 @@ static int do_lookup(struct nameidata *nd, struct qstr *name,
{
int err;
- if (IS_MNT_UNION(nd->path.mnt) && !IS_OPAQUE(nd->path.dentry->d_inode))
+ if (IS_MNT_UNION(nd->path.mnt))
goto need_union_lookup;
path->dentry = __d_lookup(nd->path.dentry, name);
@@ -1622,6 +1650,9 @@ static int __hash_lookup_topmost(struct nameidata *nd, struct qstr *name,
if (path->dentry->d_inode || d_is_whiteout(path->dentry))
return 0;
+ if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(path->dentry))
+ return 0;
+
while (follow_union_down(&nd->path.mnt, &nd->path.dentry)) {
name->hash = full_name_hash(name->name, name->len);
if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) {
@@ -1644,6 +1675,9 @@ static int __hash_lookup_topmost(struct nameidata *nd, struct qstr *name,
goto out;
}
+ if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(next.dentry))
+ goto out;
+
dput(next.dentry);
}
out:
@@ -1698,9 +1732,6 @@ static int __hash_lookup_build_union(struct nameidata *nd, struct qstr *name,
path_put(&last);
last.dentry = next.dentry;
last.mnt = mntget(next.mnt);
-
- if (IS_OPAQUE(last.dentry->d_inode))
- break;
}
if (last.dentry != path->dentry)
--
1.6.1.3
--
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