diff options
| author | Nick Piggin <npiggin@kernel.dk> | 2011-01-07 17:49:20 +1100 |
|---|---|---|
| committer | Nick Piggin <npiggin@kernel.dk> | 2011-01-07 17:50:17 +1100 |
| commit | 5adcee1d8d32d7f305f6f5aaefdbf8f35adca177 (patch) | |
| tree | 9292ebc9bb6a21b364a97a44d1b6857a565159c5 /kernel/cgroup.c | |
| parent | 3e880fb5e4bb6a012035e3edd0586ee2817c2e24 (diff) | |
| download | lwn-5adcee1d8d32d7f305f6f5aaefdbf8f35adca177.tar.gz lwn-5adcee1d8d32d7f305f6f5aaefdbf8f35adca177.zip | |
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>
Diffstat (limited to 'kernel/cgroup.c')
| -rw-r--r-- | kernel/cgroup.c | 27 |
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; |