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[PATCH] configfs: Lock new directory inodes before removing on cleanup after failure 

Once a new configfs directory is created by configfs_attach_item() or
configfs_attach_group(), a failure in the remaining initialization steps leads
to removing a directory which inode the VFS may have already accessed.

This commit adds the necessary inode locking to safely remove configfs
directories while cleaning up after a failure. As an advantage, the locking
rules of populate_groups() and detach_groups() become the same: the caller must
have the group's inode mutex locked.

Signed-off-by: Louis Rilling <louis.rilling@kerlabs.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>
This commit is contained in:
Louis Rilling 2008-07-04 16:56:06 +02:00 committed by Mark Fasheh
parent 2a109f2a41
commit 2e2ce171c3
1 changed files with 29 additions and 19 deletions
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48
fs/configfs/dir.c
View File

@ -324,6 +324,8 @@ static void remove_dir(struct dentry * d)
* The only thing special about this is that we remove any files in
* the directory before we remove the directory, and we've inlined
* what used to be configfs_rmdir() below, instead of calling separately.
*
* Caller holds the mutex of the item's inode
*/
static void configfs_remove_dir(struct config_item * item)
@ -612,36 +614,21 @@ static int create_default_group(struct config_group *parent_group,
static int populate_groups(struct config_group *group)
{
struct config_group *new_group;
struct dentry *dentry = group->cg_item.ci_dentry;
int ret = 0;
int i;
if (group->default_groups) {
/*
* FYI, we're faking mkdir here
* I'm not sure we need this semaphore, as we're called
* from our parent's mkdir. That holds our parent's
* i_mutex, so afaik lookup cannot continue through our
* parent to find us, let alone mess with our tree.
* That said, taking our i_mutex is closer to mkdir
* emulation, and shouldn't hurt.
*/
mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
for (i = 0; group->default_groups[i]; i++) {
new_group = group->default_groups[i];
ret = create_default_group(group, new_group);
if (ret)
if (ret) {
detach_groups(group);
break;
}
}
mutex_unlock(&dentry->d_inode->i_mutex);
}
if (ret)
detach_groups(group);
return ret;
}
@ -756,7 +743,15 @@ static int configfs_attach_item(struct config_item *parent_item,
if (!ret) {
ret = populate_attrs(item);
if (ret) {
/*
* We are going to remove an inode and its dentry but
* the VFS may already have hit and used them. Thus,
* we must lock them as rmdir() would.
*/
mutex_lock(&dentry->d_inode->i_mutex);
configfs_remove_dir(item);
dentry->d_inode->i_flags |= S_DEAD;
mutex_unlock(&dentry->d_inode->i_mutex);
d_delete(dentry);
}
}
@ -764,6 +759,7 @@ static int configfs_attach_item(struct config_item *parent_item,
return ret;
}
/* Caller holds the mutex of the item's inode */
static void configfs_detach_item(struct config_item *item)
{
detach_attrs(item);
@ -782,16 +778,30 @@ static int configfs_attach_group(struct config_item *parent_item,
sd = dentry->d_fsdata;
sd->s_type |= CONFIGFS_USET_DIR;
/*
* FYI, we're faking mkdir in populate_groups()
* We must lock the group's inode to avoid races with the VFS
* which can already hit the inode and try to add/remove entries
* under it.
*
* We must also lock the inode to remove it safely in case of
* error, as rmdir() would.
*/
mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
ret = populate_groups(to_config_group(item));
if (ret) {
configfs_detach_item(item);
d_delete(dentry);
dentry->d_inode->i_flags |= S_DEAD;
}
mutex_unlock(&dentry->d_inode->i_mutex);
if (ret)
d_delete(dentry);
}
return ret;
}
/* Caller holds the mutex of the group's inode */
static void configfs_detach_group(struct config_item *item)
{
detach_groups(to_config_group(item));