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authorPaul Menage <menage@google.com>2008-02-07 00:13:45 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-02-07 08:42:18 -0800
commit8dc4f3e17dd5f7e59ce568155ccd8974af879315 (patch)
tree959b1197fea798c9daae4dd6c9596ab710d41fda /kernel/cgroup.c
parent622d42cac9ed42098aa50c53994f625abfa3d473 (diff)
cgroups: move cgroups destroy() callbacks to cgroup_diput()
Move the calls to the cgroup subsystem destroy() methods from cgroup_rmdir() to cgroup_diput(). This allows control file reads and writes to access their subsystem state without having to be concerned with locking against cgroup destruction - the control file dentry will keep the cgroup and its subsystem state objects alive until the file is closed. The documentation is updated to reflect the changed semantics of destroy(); additionally the locking comments for destroy() and some other methods were clarified and decrustified. Signed-off-by: Paul Menage <menage@google.com> Cc: Paul Jackson <pj@sgi.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/cgroup.c')
-rw-r--r--kernel/cgroup.c36
1 files changed, 24 insertions, 12 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 7d207414f2c7..b0fee0c61445 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -591,6 +591,7 @@ static void cgroup_diput(struct dentry *dentry, struct inode *inode)
/* is dentry a directory ? if so, kfree() associated cgroup */
if (S_ISDIR(inode->i_mode)) {
struct cgroup *cgrp = dentry->d_fsdata;
+ struct cgroup_subsys *ss;
BUG_ON(!(cgroup_is_removed(cgrp)));
/* It's possible for external users to be holding css
* reference counts on a cgroup; css_put() needs to
@@ -599,6 +600,23 @@ static void cgroup_diput(struct dentry *dentry, struct inode *inode)
* queue the cgroup to be handled by the release
* agent */
synchronize_rcu();
+
+ mutex_lock(&cgroup_mutex);
+ /*
+ * Release the subsystem state objects.
+ */
+ for_each_subsys(cgrp->root, ss) {
+ if (cgrp->subsys[ss->subsys_id])
+ ss->destroy(ss, cgrp);
+ }
+
+ cgrp->root->number_of_cgroups--;
+ mutex_unlock(&cgroup_mutex);
+
+ /* Drop the active superblock reference that we took when we
+ * created the cgroup */
+ deactivate_super(cgrp->root->sb);
+
kfree(cgrp);
}
iput(inode);
@@ -1330,6 +1348,10 @@ static ssize_t cgroup_common_file_write(struct cgroup *cgrp,
mutex_lock(&cgroup_mutex);
+ /*
+ * This was already checked for in cgroup_file_write(), but
+ * check again now we're holding cgroup_mutex.
+ */
if (cgroup_is_removed(cgrp)) {
retval = -ENODEV;
goto out2;
@@ -1370,7 +1392,7 @@ 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 (!cft)
+ if (!cft || cgroup_is_removed(cgrp))
return -ENODEV;
if (cft->write)
return cft->write(cgrp, cft, file, buf, nbytes, ppos);
@@ -1440,7 +1462,7 @@ 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 (!cft)
+ if (!cft || cgroup_is_removed(cgrp))
return -ENODEV;
if (cft->read)
@@ -2120,7 +2142,6 @@ static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
struct cgroup *cgrp = dentry->d_fsdata;
struct dentry *d;
struct cgroup *parent;
- struct cgroup_subsys *ss;
struct super_block *sb;
struct cgroupfs_root *root;
@@ -2145,11 +2166,6 @@ static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
return -EBUSY;
}
- for_each_subsys(root, ss) {
- if (cgrp->subsys[ss->subsys_id])
- ss->destroy(ss, cgrp);
- }
-
spin_lock(&release_list_lock);
set_bit(CGRP_REMOVED, &cgrp->flags);
if (!list_empty(&cgrp->release_list))
@@ -2164,15 +2180,11 @@ static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
cgroup_d_remove_dir(d);
dput(d);
- root->number_of_cgroups--;
set_bit(CGRP_RELEASABLE, &parent->flags);
check_for_release(parent);
mutex_unlock(&cgroup_mutex);
- /* Drop the active superblock reference that we took when we
- * created the cgroup */
- deactivate_super(sb);
return 0;
}

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