diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/cgroup.c | 43 |
1 files changed, 32 insertions, 11 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index c4bc8dac3b1d..583f8f66a7e1 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -2277,6 +2277,17 @@ static int cgroup_sane_behavior_show(struct cgroup *cgrp, struct cftype *cft, return 0; } +/* return the css for the given cgroup file */ +static struct cgroup_subsys_state *cgroup_file_css(struct cfent *cfe) +{ + struct cftype *cft = cfe->type; + struct cgroup *cgrp = __d_cgrp(cfe->dentry->d_parent); + + if (cft->ss) + return cgrp->subsys[cft->ss->subsys_id]; + return NULL; +} + /* A buffer size big enough for numbers or short strings */ #define CGROUP_LOCAL_BUFFER_SIZE 64 @@ -2354,8 +2365,6 @@ static ssize_t cgroup_file_write(struct file *file, const char __user *buf, struct cftype *cft = __d_cft(file->f_dentry); struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent); - if (cgroup_is_dead(cgrp)) - return -ENODEV; if (cft->write) return cft->write(cgrp, cft, file, buf, nbytes, ppos); if (cft->write_u64 || cft->write_s64) @@ -2399,9 +2408,6 @@ static ssize_t cgroup_file_read(struct file *file, char __user *buf, struct cftype *cft = __d_cft(file->f_dentry); struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent); - if (cgroup_is_dead(cgrp)) - return -ENODEV; - if (cft->read) return cft->read(cgrp, cft, file, buf, nbytes, ppos); if (cft->read_u64) @@ -2447,15 +2453,22 @@ static const struct file_operations cgroup_seqfile_operations = { static int cgroup_file_open(struct inode *inode, struct file *file) { + struct cfent *cfe = __d_cfe(file->f_dentry); + struct cftype *cft = __d_cft(file->f_dentry); + struct cgroup_subsys_state *css = cgroup_file_css(cfe); int err; - struct cfent *cfe; - struct cftype *cft; err = generic_file_open(inode, file); if (err) return err; - cfe = __d_cfe(file->f_dentry); - cft = cfe->type; + + /* + * If the file belongs to a subsystem, pin the css. Will be + * unpinned either on open failure or release. This ensures that + * @css stays alive for all file operations. + */ + if (css && !css_tryget(css)) + return -ENODEV; if (cft->read_map || cft->read_seq_string) { file->f_op = &cgroup_seqfile_operations; @@ -2464,15 +2477,23 @@ static int cgroup_file_open(struct inode *inode, struct file *file) err = cft->open(inode, file); } + if (css && err) + css_put(css); return err; } static int cgroup_file_release(struct inode *inode, struct file *file) { + struct cfent *cfe = __d_cfe(file->f_dentry); struct cftype *cft = __d_cft(file->f_dentry); + struct cgroup_subsys_state *css = cgroup_file_css(cfe); + int ret = 0; + if (cft->release) - return cft->release(inode, file); - return 0; + ret = cft->release(inode, file); + if (css) + css_put(css); + return ret; } /* |