From 6f61076406251626be39651d114fac412b1e0c39 Mon Sep 17 00:00:00 2001 From: Louis Rilling Date: Mon, 16 Jun 2008 19:00:58 +0200 Subject: configfs: Introduce configfs_dirent_lock This patch introduces configfs_dirent_lock spinlock to protect configfs_dirent traversals against linkage mutations (add/del/move). This will allow configfs_detach_prep() to avoid locking i_mutexes. Locking rules for configfs_dirent linkage mutations are the same plus the requirement of taking configfs_dirent_lock. For configfs_dirent walking, one can either take appropriate i_mutex as before, or take configfs_dirent_lock. The spinlock could actually be a mutex, but the critical sections are either O(1) or should not be too long (default groups walking in last patch). ChangeLog: - Clarify the comment on configfs_dirent_lock usage - Move sd->s_element init before linking the new dirent - In lseek(), do not release configfs_dirent_lock before the dirent is relinked. Signed-off-by: Louis Rilling Signed-off-by: Joel Becker --- fs/configfs/symlink.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'fs/configfs/symlink.c') diff --git a/fs/configfs/symlink.c b/fs/configfs/symlink.c index 2a731ef5f305..676c84c416da 100644 --- a/fs/configfs/symlink.c +++ b/fs/configfs/symlink.c @@ -169,7 +169,9 @@ int configfs_unlink(struct inode *dir, struct dentry *dentry) parent_item = configfs_get_config_item(dentry->d_parent); type = parent_item->ci_type; + spin_lock(&configfs_dirent_lock); list_del_init(&sd->s_sibling); + spin_unlock(&configfs_dirent_lock); configfs_drop_dentry(sd, dentry->d_parent); dput(dentry); configfs_put(sd); -- cgit v1.2.2 From 5301a77da2da1e4c22573e0e8d394a653b8ad9f9 Mon Sep 17 00:00:00 2001 From: Louis Rilling Date: Mon, 16 Jun 2008 19:00:59 +0200 Subject: configfs: Protect configfs_dirent s_links list mutations Symlinks to a config_item are listed under its configfs_dirent s_links, but the list mutations are not protected by any common lock. This patch uses the configfs_dirent_lock spinlock to add the necessary protection. Note: we should also protect the list_empty() test in configfs_detach_prep() but 1/ the lock should not be released immediately because nothing would prevent the list from being filled after a successful list_empty() test, making the problem tricky, 2/ this will be solved by the rmdir() vs rename() deadlock bugfix. Signed-off-by: Louis Rilling Signed-off-by: Joel Becker --- fs/configfs/symlink.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'fs/configfs/symlink.c') diff --git a/fs/configfs/symlink.c b/fs/configfs/symlink.c index 676c84c416da..faeb4417a10d 100644 --- a/fs/configfs/symlink.c +++ b/fs/configfs/symlink.c @@ -77,12 +77,15 @@ static int create_link(struct config_item *parent_item, sl = kmalloc(sizeof(struct configfs_symlink), GFP_KERNEL); if (sl) { sl->sl_target = config_item_get(item); - /* FIXME: needs a lock, I'd bet */ + spin_lock(&configfs_dirent_lock); list_add(&sl->sl_list, &target_sd->s_links); + spin_unlock(&configfs_dirent_lock); ret = configfs_create_link(sl, parent_item->ci_dentry, dentry); if (ret) { + spin_lock(&configfs_dirent_lock); list_del_init(&sl->sl_list); + spin_unlock(&configfs_dirent_lock); config_item_put(item); kfree(sl); } @@ -186,8 +189,9 @@ int configfs_unlink(struct inode *dir, struct dentry *dentry) type->ct_item_ops->drop_link(parent_item, sl->sl_target); - /* FIXME: Needs lock */ + spin_lock(&configfs_dirent_lock); list_del_init(&sl->sl_list); + spin_unlock(&configfs_dirent_lock); /* Put reference from create_link() */ config_item_put(sl->sl_target); -- cgit v1.2.2 From e75206517504461778c283b942440ef312e437d5 Mon Sep 17 00:00:00 2001 From: Louis Rilling Date: Thu, 12 Jun 2008 17:26:47 +0200 Subject: configfs: call drop_link() to cleanup after create_link() failure When allow_link() succeeds but create_link() fails, the subsystem is not informed of the failure. This patch fixes this by calling drop_link() on create_link() failures. Signed-off-by: Louis Rilling Signed-off-by: Joel Becker --- fs/configfs/symlink.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'fs/configfs/symlink.c') diff --git a/fs/configfs/symlink.c b/fs/configfs/symlink.c index faeb4417a10d..0004d18c40ac 100644 --- a/fs/configfs/symlink.c +++ b/fs/configfs/symlink.c @@ -140,8 +140,12 @@ int configfs_symlink(struct inode *dir, struct dentry *dentry, const char *symna goto out_put; ret = type->ct_item_ops->allow_link(parent_item, target_item); - if (!ret) + if (!ret) { ret = create_link(parent_item, target_item, dentry); + if (ret && type->ct_item_ops->drop_link) + type->ct_item_ops->drop_link(parent_item, + target_item); + } config_item_put(target_item); path_put(&nd.path); -- cgit v1.2.2