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authorTrond Myklebust <Trond.Myklebust@netapp.com>2006-10-21 10:24:20 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-10-21 13:35:06 -0700
commit9eaef27b36a6b716384948da94b8fc5bfba7b712 (patch)
treeab69cf9c3863bb7ca564574c914e5b6bf8ad3162 /fs
parent[PATCH] cciss: Fix warnings (and bug on 1TB discs) (diff)
downloadlinux-dev-9eaef27b36a6b716384948da94b8fc5bfba7b712.tar.xz
linux-dev-9eaef27b36a6b716384948da94b8fc5bfba7b712.zip
[PATCH] VFS: Make d_materialise_unique() enforce directory uniqueness
If the caller tries to instantiate a directory using an inode that already has a dentry alias, then we attempt to rename the existing dentry instead of instantiating a new one. Fail with an ELOOP error if the rename would affect one of our parent directories. This behaviour is needed in order to avoid issues such as http://bugzilla.kernel.org/show_bug.cgi?id=7178 Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com> Cc: Miklos Szeredi <miklos@szeredi.hu> Cc: Maneesh Soni <maneesh@in.ibm.com> Cc: Dipankar Sarma <dipankar@in.ibm.com> Cc: Neil Brown <neilb@cse.unsw.edu.au> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@lst.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/dcache.c137
-rw-r--r--fs/nfs/dir.c7
2 files changed, 106 insertions, 38 deletions
diff --git a/fs/dcache.c b/fs/dcache.c
index 2bac4ba1d1d3..a1ff91eef108 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1469,23 +1469,21 @@ static void switch_names(struct dentry *dentry, struct dentry *target)
* deleted it.
*/
-/**
- * d_move - move a dentry
+/*
+ * d_move_locked - move a dentry
* @dentry: entry to move
* @target: new dentry
*
* Update the dcache to reflect the move of a file name. Negative
* dcache entries should not be moved in this way.
*/
-
-void d_move(struct dentry * dentry, struct dentry * target)
+static void d_move_locked(struct dentry * dentry, struct dentry * target)
{
struct hlist_head *list;
if (!dentry->d_inode)
printk(KERN_WARNING "VFS: moving negative dcache entry\n");
- spin_lock(&dcache_lock);
write_seqlock(&rename_lock);
/*
* XXXX: do we really need to take target->d_lock?
@@ -1536,10 +1534,84 @@ already_unhashed:
fsnotify_d_move(dentry);
spin_unlock(&dentry->d_lock);
write_sequnlock(&rename_lock);
+}
+
+/**
+ * d_move - move a dentry
+ * @dentry: entry to move
+ * @target: new dentry
+ *
+ * Update the dcache to reflect the move of a file name. Negative
+ * dcache entries should not be moved in this way.
+ */
+
+void d_move(struct dentry * dentry, struct dentry * target)
+{
+ spin_lock(&dcache_lock);
+ d_move_locked(dentry, target);
spin_unlock(&dcache_lock);
}
/*
+ * Helper that returns 1 if p1 is a parent of p2, else 0
+ */
+static int d_isparent(struct dentry *p1, struct dentry *p2)
+{
+ struct dentry *p;
+
+ for (p = p2; p->d_parent != p; p = p->d_parent) {
+ if (p->d_parent == p1)
+ return 1;
+ }
+ return 0;
+}
+
+/*
+ * This helper attempts to cope with remotely renamed directories
+ *
+ * It assumes that the caller is already holding
+ * dentry->d_parent->d_inode->i_mutex and the dcache_lock
+ *
+ * Note: If ever the locking in lock_rename() changes, then please
+ * remember to update this too...
+ *
+ * On return, dcache_lock will have been unlocked.
+ */
+static struct dentry *__d_unalias(struct dentry *dentry, struct dentry *alias)
+{
+ struct mutex *m1 = NULL, *m2 = NULL;
+ struct dentry *ret;
+
+ /* If alias and dentry share a parent, then no extra locks required */
+ if (alias->d_parent == dentry->d_parent)
+ goto out_unalias;
+
+ /* Check for loops */
+ ret = ERR_PTR(-ELOOP);
+ if (d_isparent(alias, dentry))
+ goto out_err;
+
+ /* See lock_rename() */
+ ret = ERR_PTR(-EBUSY);
+ if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
+ goto out_err;
+ m1 = &dentry->d_sb->s_vfs_rename_mutex;
+ if (!mutex_trylock(&alias->d_parent->d_inode->i_mutex))
+ goto out_err;
+ m2 = &alias->d_parent->d_inode->i_mutex;
+out_unalias:
+ d_move_locked(alias, dentry);
+ ret = alias;
+out_err:
+ spin_unlock(&dcache_lock);
+ if (m2)
+ mutex_unlock(m2);
+ if (m1)
+ mutex_unlock(m1);
+ return ret;
+}
+
+/*
* Prepare an anonymous dentry for life in the superblock's dentry tree as a
* named dentry in place of the dentry to be replaced.
*/
@@ -1581,7 +1653,7 @@ static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
*/
struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
{
- struct dentry *alias, *actual;
+ struct dentry *actual;
BUG_ON(!d_unhashed(dentry));
@@ -1593,26 +1665,27 @@ struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
goto found_lock;
}
- /* See if a disconnected directory already exists as an anonymous root
- * that we should splice into the tree instead */
- if (S_ISDIR(inode->i_mode) && (alias = __d_find_alias(inode, 1))) {
- spin_lock(&alias->d_lock);
-
- /* Is this a mountpoint that we could splice into our tree? */
- if (IS_ROOT(alias))
- goto connect_mountpoint;
-
- if (alias->d_name.len == dentry->d_name.len &&
- alias->d_parent == dentry->d_parent &&
- memcmp(alias->d_name.name,
- dentry->d_name.name,
- dentry->d_name.len) == 0)
- goto replace_with_alias;
-
- spin_unlock(&alias->d_lock);
-
- /* Doh! Seem to be aliasing directories for some reason... */
- dput(alias);
+ if (S_ISDIR(inode->i_mode)) {
+ struct dentry *alias;
+
+ /* Does an aliased dentry already exist? */
+ alias = __d_find_alias(inode, 0);
+ if (alias) {
+ actual = alias;
+ /* Is this an anonymous mountpoint that we could splice
+ * into our tree? */
+ if (IS_ROOT(alias)) {
+ spin_lock(&alias->d_lock);
+ __d_materialise_dentry(dentry, alias);
+ __d_drop(alias);
+ goto found;
+ }
+ /* Nope, but we must(!) avoid directory aliasing */
+ actual = __d_unalias(dentry, alias);
+ if (IS_ERR(actual))
+ dput(alias);
+ goto out_nolock;
+ }
}
/* Add a unique reference */
@@ -1628,7 +1701,7 @@ found:
_d_rehash(actual);
spin_unlock(&actual->d_lock);
spin_unlock(&dcache_lock);
-
+out_nolock:
if (actual == dentry) {
security_d_instantiate(dentry, inode);
return NULL;
@@ -1637,16 +1710,6 @@ found:
iput(inode);
return actual;
- /* Convert the anonymous/root alias into an ordinary dentry */
-connect_mountpoint:
- __d_materialise_dentry(dentry, alias);
-
- /* Replace the candidate dentry with the alias in the tree */
-replace_with_alias:
- __d_drop(alias);
- actual = alias;
- goto found;
-
shouldnt_be_hashed:
spin_unlock(&dcache_lock);
BUG();
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 4133ef5264e5..27b5a1051b1c 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -935,8 +935,11 @@ static struct dentry *nfs_lookup(struct inode *dir, struct dentry * dentry, stru
no_entry:
res = d_materialise_unique(dentry, inode);
- if (res != NULL)
+ if (res != NULL) {
+ if (IS_ERR(res))
+ goto out_unlock;
dentry = res;
+ }
nfs_renew_times(dentry);
nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
out_unlock:
@@ -1132,6 +1135,8 @@ static struct dentry *nfs_readdir_lookup(nfs_readdir_descriptor_t *desc)
alias = d_materialise_unique(dentry, inode);
if (alias != NULL) {
dput(dentry);
+ if (IS_ERR(alias))
+ return NULL;
dentry = alias;
}