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authorNick Piggin <npiggin@kernel.dk>2011-01-07 17:49:20 +1100
committerNick Piggin <npiggin@kernel.dk>2011-01-07 17:50:17 +1100
commit5adcee1d8d32d7f305f6f5aaefdbf8f35adca177 (patch)
tree9292ebc9bb6a21b364a97a44d1b6857a565159c5
parent3e880fb5e4bb6a012035e3edd0586ee2817c2e24 (diff)
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cgroup fs: avoid switching ->d_op on live dentry
Switching d_op on a live dentry is racy in general, so avoid it. In this case it is a negative dentry, which is safer, but there are still concurrent ops which may be called on d_op in that case (eg. d_revalidate). So in general a filesystem may not do this. Fix cgroupfs so as not to do this. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
-rw-r--r--kernel/cgroup.c27
1 files changed, 22 insertions, 5 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 66a416b42c18..163c890f436d 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -763,6 +763,8 @@ EXPORT_SYMBOL_GPL(cgroup_unlock);
* -> cgroup_mkdir.
*/
+static struct dentry *cgroup_lookup(struct inode *dir,
+ struct dentry *dentry, struct nameidata *nd);
static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode);
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
static int cgroup_populate_dir(struct cgroup *cgrp);
@@ -2180,7 +2182,7 @@ static const struct file_operations cgroup_file_operations = {
};
static const struct inode_operations cgroup_dir_inode_operations = {
- .lookup = simple_lookup,
+ .lookup = cgroup_lookup,
.mkdir = cgroup_mkdir,
.rmdir = cgroup_rmdir,
.rename = cgroup_rename,
@@ -2196,13 +2198,29 @@ static inline struct cftype *__file_cft(struct file *file)
return __d_cft(file->f_dentry);
}
-static int cgroup_create_file(struct dentry *dentry, mode_t mode,
- struct super_block *sb)
+static int cgroup_delete_dentry(struct dentry *dentry)
+{
+ return 1;
+}
+
+static struct dentry *cgroup_lookup(struct inode *dir,
+ struct dentry *dentry, struct nameidata *nd)
{
- static const struct dentry_operations cgroup_dops = {
+ static const struct dentry_operations cgroup_dentry_operations = {
+ .d_delete = cgroup_delete_dentry,
.d_iput = cgroup_diput,
};
+ if (dentry->d_name.len > NAME_MAX)
+ return ERR_PTR(-ENAMETOOLONG);
+ dentry->d_op = &cgroup_dentry_operations;
+ d_add(dentry, NULL);
+ return NULL;
+}
+
+static int cgroup_create_file(struct dentry *dentry, mode_t mode,
+ struct super_block *sb)
+{
struct inode *inode;
if (!dentry)
@@ -2228,7 +2246,6 @@ static int cgroup_create_file(struct dentry *dentry, mode_t mode,
inode->i_size = 0;
inode->i_fop = &cgroup_file_operations;
}
- dentry->d_op = &cgroup_dops;
d_instantiate(dentry, inode);
dget(dentry); /* Extra count - pin the dentry in core */
return 0;