From 6f61076406251626be39651d114fac412b1e0c39 Mon Sep 17 00:00:00 2001
From: Louis Rilling <Louis.Rilling@kerlabs.com>
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 <Louis.Rilling@kerlabs.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
---
 fs/configfs/configfs_internal.h |  3 +++
 fs/configfs/dir.c               | 28 +++++++++++++++++++++++++++-
 fs/configfs/inode.c             |  2 ++
 fs/configfs/symlink.c           |  2 ++
 4 files changed, 34 insertions(+), 1 deletion(-)

(limited to 'fs/configfs')

diff --git a/fs/configfs/configfs_internal.h b/fs/configfs/configfs_internal.h
index cca98609aa7f..5a33b58e66da 100644
--- a/fs/configfs/configfs_internal.h
+++ b/fs/configfs/configfs_internal.h
@@ -26,6 +26,7 @@
 
 #include <linux/slab.h>
 #include <linux/list.h>
+#include <linux/spinlock.h>
 
 struct configfs_dirent {
 	atomic_t		s_count;
@@ -49,6 +50,8 @@ struct configfs_dirent {
 #define CONFIGFS_USET_DROPPING	0x0100
 #define CONFIGFS_NOT_PINNED	(CONFIGFS_ITEM_ATTR)
 
+extern spinlock_t configfs_dirent_lock;
+
 extern struct vfsmount * configfs_mount;
 extern struct kmem_cache *configfs_dir_cachep;
 
diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index a48dc7dd8765..2619f485bc3d 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -35,6 +35,14 @@
 #include "configfs_internal.h"
 
 DECLARE_RWSEM(configfs_rename_sem);
+/*
+ * Protects mutations of configfs_dirent linkage together with proper i_mutex
+ * Mutators of configfs_dirent linkage must *both* have the proper inode locked
+ * and configfs_dirent_lock locked, in that order.
+ * This allows one to safely traverse configfs_dirent trees without having to
+ * lock inodes.
+ */
+DEFINE_SPINLOCK(configfs_dirent_lock);
 
 static void configfs_d_iput(struct dentry * dentry,
 			    struct inode * inode)
@@ -79,8 +87,10 @@ static struct configfs_dirent *configfs_new_dirent(struct configfs_dirent * pare
 	atomic_set(&sd->s_count, 1);
 	INIT_LIST_HEAD(&sd->s_links);
 	INIT_LIST_HEAD(&sd->s_children);
-	list_add(&sd->s_sibling, &parent_sd->s_children);
 	sd->s_element = element;
+	spin_lock(&configfs_dirent_lock);
+	list_add(&sd->s_sibling, &parent_sd->s_children);
+	spin_unlock(&configfs_dirent_lock);
 
 	return sd;
 }
@@ -173,7 +183,9 @@ static int create_dir(struct config_item * k, struct dentry * p,
 		} else {
 			struct configfs_dirent *sd = d->d_fsdata;
 			if (sd) {
+				spin_lock(&configfs_dirent_lock);
 				list_del_init(&sd->s_sibling);
+				spin_unlock(&configfs_dirent_lock);
 				configfs_put(sd);
 			}
 		}
@@ -224,7 +236,9 @@ int configfs_create_link(struct configfs_symlink *sl,
 		else {
 			struct configfs_dirent *sd = dentry->d_fsdata;
 			if (sd) {
+				spin_lock(&configfs_dirent_lock);
 				list_del_init(&sd->s_sibling);
+				spin_unlock(&configfs_dirent_lock);
 				configfs_put(sd);
 			}
 		}
@@ -238,7 +252,9 @@ static void remove_dir(struct dentry * d)
 	struct configfs_dirent * sd;
 
 	sd = d->d_fsdata;
+	spin_lock(&configfs_dirent_lock);
 	list_del_init(&sd->s_sibling);
+	spin_unlock(&configfs_dirent_lock);
 	configfs_put(sd);
 	if (d->d_inode)
 		simple_rmdir(parent->d_inode,d);
@@ -410,7 +426,9 @@ static void detach_attrs(struct config_item * item)
 	list_for_each_entry_safe(sd, tmp, &parent_sd->s_children, s_sibling) {
 		if (!sd->s_element || !(sd->s_type & CONFIGFS_NOT_PINNED))
 			continue;
+		spin_lock(&configfs_dirent_lock);
 		list_del_init(&sd->s_sibling);
+		spin_unlock(&configfs_dirent_lock);
 		configfs_drop_dentry(sd, dentry);
 		configfs_put(sd);
 	}
@@ -1268,7 +1286,9 @@ static int configfs_dir_close(struct inode *inode, struct file *file)
 	struct configfs_dirent * cursor = file->private_data;
 
 	mutex_lock(&dentry->d_inode->i_mutex);
+	spin_lock(&configfs_dirent_lock);
 	list_del_init(&cursor->s_sibling);
+	spin_unlock(&configfs_dirent_lock);
 	mutex_unlock(&dentry->d_inode->i_mutex);
 
 	release_configfs_dirent(cursor);
@@ -1308,7 +1328,9 @@ static int configfs_readdir(struct file * filp, void * dirent, filldir_t filldir
 			/* fallthrough */
 		default:
 			if (filp->f_pos == 2) {
+				spin_lock(&configfs_dirent_lock);
 				list_move(q, &parent_sd->s_children);
+				spin_unlock(&configfs_dirent_lock);
 			}
 			for (p=q->next; p!= &parent_sd->s_children; p=p->next) {
 				struct configfs_dirent *next;
@@ -1331,7 +1353,9 @@ static int configfs_readdir(struct file * filp, void * dirent, filldir_t filldir
 						 dt_type(next)) < 0)
 					return 0;
 
+				spin_lock(&configfs_dirent_lock);
 				list_move(q, p);
+				spin_unlock(&configfs_dirent_lock);
 				p = q;
 				filp->f_pos++;
 			}
@@ -1362,6 +1386,7 @@ static loff_t configfs_dir_lseek(struct file * file, loff_t offset, int origin)
 			struct list_head *p;
 			loff_t n = file->f_pos - 2;
 
+			spin_lock(&configfs_dirent_lock);
 			list_del(&cursor->s_sibling);
 			p = sd->s_children.next;
 			while (n && p != &sd->s_children) {
@@ -1373,6 +1398,7 @@ static loff_t configfs_dir_lseek(struct file * file, loff_t offset, int origin)
 				p = p->next;
 			}
 			list_add_tail(&cursor->s_sibling, p);
+			spin_unlock(&configfs_dirent_lock);
 		}
 	}
 	mutex_unlock(&dentry->d_inode->i_mutex);
diff --git a/fs/configfs/inode.c b/fs/configfs/inode.c
index b9a1d810346d..4803ccc94480 100644
--- a/fs/configfs/inode.c
+++ b/fs/configfs/inode.c
@@ -247,7 +247,9 @@ void configfs_hash_and_remove(struct dentry * dir, const char * name)
 		if (!sd->s_element)
 			continue;
 		if (!strcmp(configfs_get_name(sd), name)) {
+			spin_lock(&configfs_dirent_lock);
 			list_del_init(&sd->s_sibling);
+			spin_unlock(&configfs_dirent_lock);
 			configfs_drop_dentry(sd, dir);
 			configfs_put(sd);
 			break;
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 v1.2.3


From 5301a77da2da1e4c22573e0e8d394a653b8ad9f9 Mon Sep 17 00:00:00 2001
From: Louis Rilling <Louis.Rilling@kerlabs.com>
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 <Louis.Rilling@kerlabs.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
---
 fs/configfs/dir.c     | 5 +++--
 fs/configfs/symlink.c | 8 ++++++--
 2 files changed, 9 insertions(+), 4 deletions(-)

(limited to 'fs/configfs')

diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index 2619f485bc3d..a08e5c2f25e8 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -37,10 +37,11 @@
 DECLARE_RWSEM(configfs_rename_sem);
 /*
  * Protects mutations of configfs_dirent linkage together with proper i_mutex
+ * Also protects mutations of symlinks linkage to target configfs_dirent
  * Mutators of configfs_dirent linkage must *both* have the proper inode locked
  * and configfs_dirent_lock locked, in that order.
- * This allows one to safely traverse configfs_dirent trees without having to
- * lock inodes.
+ * This allows one to safely traverse configfs_dirent trees and symlinks without
+ * having to lock inodes.
  */
 DEFINE_SPINLOCK(configfs_dirent_lock);
 
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 v1.2.3


From 107ed40bd070df5e4a0a012042c45c40963dc574 Mon Sep 17 00:00:00 2001
From: Louis Rilling <Louis.Rilling@kerlabs.com>
Date: Mon, 16 Jun 2008 19:01:00 +0200
Subject: configfs: Make configfs_new_dirent() return error code instead of
 NULL

This patch makes configfs_new_dirent return negative error code instead of NULL,
which will be useful in the next patch to differentiate ENOMEM from ENOENT.

Signed-off-by: Louis Rilling <Louis.Rilling@kerlabs.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
---
 fs/configfs/dir.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

(limited to 'fs/configfs')

diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index a08e5c2f25e8..918a332babfe 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -30,6 +30,7 @@
 #include <linux/mount.h>
 #include <linux/module.h>
 #include <linux/slab.h>
+#include <linux/err.h>
 
 #include <linux/configfs.h>
 #include "configfs_internal.h"
@@ -83,7 +84,7 @@ static struct configfs_dirent *configfs_new_dirent(struct configfs_dirent * pare
 
 	sd = kmem_cache_zalloc(configfs_dir_cachep, GFP_KERNEL);
 	if (!sd)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	atomic_set(&sd->s_count, 1);
 	INIT_LIST_HEAD(&sd->s_links);
@@ -129,8 +130,8 @@ int configfs_make_dirent(struct configfs_dirent * parent_sd,
 	struct configfs_dirent * sd;
 
 	sd = configfs_new_dirent(parent_sd, element);
-	if (!sd)
-		return -ENOMEM;
+	if (IS_ERR(sd))
+		return PTR_ERR(sd);
 
 	sd->s_mode = mode;
 	sd->s_type = type;
@@ -1277,7 +1278,7 @@ static int configfs_dir_open(struct inode *inode, struct file *file)
 	file->private_data = configfs_new_dirent(parent_sd, NULL);
 	mutex_unlock(&dentry->d_inode->i_mutex);
 
-	return file->private_data ? 0 : -ENOMEM;
+	return IS_ERR(file->private_data) ? PTR_ERR(file->private_data) : 0;
 
 }
 
-- 
cgit v1.2.3


From b3e76af87441fc36eef3516d73ab2314e7b2d911 Mon Sep 17 00:00:00 2001
From: Louis Rilling <Louis.Rilling@kerlabs.com>
Date: Mon, 16 Jun 2008 19:01:01 +0200
Subject: configfs: Fix deadlock with racing rmdir() and rename()

This patch fixes the deadlock between racing sys_rename() and configfs_rmdir().

The idea is to avoid locking i_mutexes of default groups in
configfs_detach_prep(), and rely instead on the new configfs_dirent_lock to
protect against configfs_dirent's linkage mutations. To ensure that an mkdir()
racing with rmdir() will not create new items in a to-be-removed default group,
we make configfs_new_dirent() check for the CONFIGFS_USET_DROPPING flag right
before linking the new dirent, and return error if the flag is set. This makes
racing mkdir()/symlink()/dir_open() fail in places where errors could already
happen, resp. in (attach_item()|attach_group())/create_link()/new_dirent().

configfs_depend() remains safe since it locks all the path from configfs root,
and is thus mutually exclusive with rmdir().

An advantage of this is that now detach_groups() unconditionnaly takes the
default groups i_mutex, which makes it more consistent with populate_groups().

Signed-off-by: Louis Rilling <Louis.Rilling@kerlabs.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
---
 fs/configfs/dir.c | 45 +++++++++++++++++++++++++--------------------
 1 file changed, 25 insertions(+), 20 deletions(-)

(limited to 'fs/configfs')

diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index 918a332babfe..d5b5985716ba 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -43,6 +43,10 @@ DECLARE_RWSEM(configfs_rename_sem);
  * and configfs_dirent_lock locked, in that order.
  * This allows one to safely traverse configfs_dirent trees and symlinks without
  * having to lock inodes.
+ *
+ * Protects setting of CONFIGFS_USET_DROPPING: checking the flag
+ * unlocked is not reliable unless in detach_groups() called from
+ * rmdir()/unregister() and from configfs_attach_group()
  */
 DEFINE_SPINLOCK(configfs_dirent_lock);
 
@@ -91,6 +95,11 @@ static struct configfs_dirent *configfs_new_dirent(struct configfs_dirent * pare
 	INIT_LIST_HEAD(&sd->s_children);
 	sd->s_element = element;
 	spin_lock(&configfs_dirent_lock);
+	if (parent_sd->s_type & CONFIGFS_USET_DROPPING) {
+		spin_unlock(&configfs_dirent_lock);
+		kmem_cache_free(configfs_dir_cachep, sd);
+		return ERR_PTR(-ENOENT);
+	}
 	list_add(&sd->s_sibling, &parent_sd->s_children);
 	spin_unlock(&configfs_dirent_lock);
 
@@ -349,11 +358,11 @@ static struct dentry * configfs_lookup(struct inode *dir,
 
 /*
  * Only subdirectories count here.  Files (CONFIGFS_NOT_PINNED) are
- * attributes and are removed by rmdir().  We recurse, taking i_mutex
- * on all children that are candidates for default detach.  If the
- * result is clean, then configfs_detach_group() will handle dropping
- * i_mutex.  If there is an error, the caller will clean up the i_mutex
- * holders via configfs_detach_rollback().
+ * attributes and are removed by rmdir().  We recurse, setting
+ * CONFIGFS_USET_DROPPING on all children that are candidates for
+ * default detach.
+ * If there is an error, the caller will reset the flags via
+ * configfs_detach_rollback().
  */
 static int configfs_detach_prep(struct dentry *dentry)
 {
@@ -370,8 +379,7 @@ static int configfs_detach_prep(struct dentry *dentry)
 		if (sd->s_type & CONFIGFS_NOT_PINNED)
 			continue;
 		if (sd->s_type & CONFIGFS_USET_DEFAULT) {
-			mutex_lock(&sd->s_dentry->d_inode->i_mutex);
-			/* Mark that we've taken i_mutex */
+			/* Mark that we're trying to drop the group */
 			sd->s_type |= CONFIGFS_USET_DROPPING;
 
 			/*
@@ -392,7 +400,7 @@ out:
 }
 
 /*
- * Walk the tree, dropping i_mutex wherever CONFIGFS_USET_DROPPING is
+ * Walk the tree, resetting CONFIGFS_USET_DROPPING wherever it was
  * set.
  */
 static void configfs_detach_rollback(struct dentry *dentry)
@@ -403,11 +411,7 @@ static void configfs_detach_rollback(struct dentry *dentry)
 	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
 		if (sd->s_type & CONFIGFS_USET_DEFAULT) {
 			configfs_detach_rollback(sd->s_dentry);
-
-			if (sd->s_type & CONFIGFS_USET_DROPPING) {
-				sd->s_type &= ~CONFIGFS_USET_DROPPING;
-				mutex_unlock(&sd->s_dentry->d_inode->i_mutex);
-			}
+			sd->s_type &= ~CONFIGFS_USET_DROPPING;
 		}
 	}
 }
@@ -486,16 +490,12 @@ static void detach_groups(struct config_group *group)
 
 		child = sd->s_dentry;
 
+		mutex_lock(&child->d_inode->i_mutex);
+
 		configfs_detach_group(sd->s_element);
 		child->d_inode->i_flags |= S_DEAD;
 
-		/*
-		 * From rmdir/unregister, a configfs_detach_prep() pass
-		 * has taken our i_mutex for us.  Drop it.
-		 * From mkdir/register cleanup, there is no sem held.
-		 */
-		if (sd->s_type & CONFIGFS_USET_DROPPING)
-			mutex_unlock(&child->d_inode->i_mutex);
+		mutex_unlock(&child->d_inode->i_mutex);
 
 		d_delete(child);
 		dput(child);
@@ -1181,12 +1181,15 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
 		return -EINVAL;
 	}
 
+	spin_lock(&configfs_dirent_lock);
 	ret = configfs_detach_prep(dentry);
 	if (ret) {
 		configfs_detach_rollback(dentry);
+		spin_unlock(&configfs_dirent_lock);
 		config_item_put(parent_item);
 		return ret;
 	}
+	spin_unlock(&configfs_dirent_lock);
 
 	/* Get a working ref for the duration of this function */
 	item = configfs_get_config_item(dentry);
@@ -1476,9 +1479,11 @@ void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
 	mutex_lock_nested(&configfs_sb->s_root->d_inode->i_mutex,
 			  I_MUTEX_PARENT);
 	mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
+	spin_lock(&configfs_dirent_lock);
 	if (configfs_detach_prep(dentry)) {
 		printk(KERN_ERR "configfs: Tried to unregister non-empty subsystem!\n");
 	}
+	spin_unlock(&configfs_dirent_lock);
 	configfs_detach_group(&group->cg_item);
 	dentry->d_inode->i_flags |= S_DEAD;
 	mutex_unlock(&dentry->d_inode->i_mutex);
-- 
cgit v1.2.3


From 6d8344baee99402de58b5fa5dfea197242955c15 Mon Sep 17 00:00:00 2001
From: Louis Rilling <Louis.Rilling@kerlabs.com>
Date: Mon, 16 Jun 2008 19:01:02 +0200
Subject: configfs: Fix failing mkdir() making racing rmdir() fail

When fixing the rename() vs rmdir() deadlock, we stopped locking default groups'
inodes in configfs_detach_prep(), letting racing mkdir() in default groups
proceed concurrently. This enables races like below happen, which leads to a
failing mkdir() making rmdir() fail, despite the group to remove having no
user-created directory under it in the end.

	process A: 			process B:
	/* PWD=A/B */
	mkdir("C")
	  make_item("C")
	  attach_group("C")
					rmdir("A")
					  detach_prep("A")
					    detach_prep("B")
					      error because of "C"
					  return -ENOTEMPTY
	    attach_group("C/D")
	      error (eg -ENOMEM)
	  return -ENOMEM

This patch prevents such scenarii by making rmdir() wait as long as
detach_prep() fails because a racing mkdir() is in the middle of attach_group().
To achieve this, mkdir() sets a flag CONFIGFS_USET_IN_MKDIR in parent's
configfs_dirent before calling attach_group(), and clears the flag once
attach_group() is done. detach_prep() fails with -EAGAIN whenever the flag is
hit and returns the guilty inode's mutex so that rmdir() can wait on it.

Signed-off-by: Louis Rilling <Louis.Rilling@kerlabs.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
---
 fs/configfs/configfs_internal.h |  1 +
 fs/configfs/dir.c               | 53 +++++++++++++++++++++++++++++++++--------
 2 files changed, 44 insertions(+), 10 deletions(-)

(limited to 'fs/configfs')

diff --git a/fs/configfs/configfs_internal.h b/fs/configfs/configfs_internal.h
index 5a33b58e66da..da015c12e3ea 100644
--- a/fs/configfs/configfs_internal.h
+++ b/fs/configfs/configfs_internal.h
@@ -48,6 +48,7 @@ struct configfs_dirent {
 #define CONFIGFS_USET_DIR	0x0040
 #define CONFIGFS_USET_DEFAULT	0x0080
 #define CONFIGFS_USET_DROPPING	0x0100
+#define CONFIGFS_USET_IN_MKDIR	0x0200
 #define CONFIGFS_NOT_PINNED	(CONFIGFS_ITEM_ATTR)
 
 extern spinlock_t configfs_dirent_lock;
diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index d5b5985716ba..614e382a6049 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -364,7 +364,7 @@ static struct dentry * configfs_lookup(struct inode *dir,
  * If there is an error, the caller will reset the flags via
  * configfs_detach_rollback().
  */
-static int configfs_detach_prep(struct dentry *dentry)
+static int configfs_detach_prep(struct dentry *dentry, struct mutex **wait_mutex)
 {
 	struct configfs_dirent *parent_sd = dentry->d_fsdata;
 	struct configfs_dirent *sd;
@@ -379,6 +379,12 @@ static int configfs_detach_prep(struct dentry *dentry)
 		if (sd->s_type & CONFIGFS_NOT_PINNED)
 			continue;
 		if (sd->s_type & CONFIGFS_USET_DEFAULT) {
+			/* Abort if racing with mkdir() */
+			if (sd->s_type & CONFIGFS_USET_IN_MKDIR) {
+				if (wait_mutex)
+					*wait_mutex = &sd->s_dentry->d_inode->i_mutex;
+				return -EAGAIN;
+			}
 			/* Mark that we're trying to drop the group */
 			sd->s_type |= CONFIGFS_USET_DROPPING;
 
@@ -386,7 +392,7 @@ static int configfs_detach_prep(struct dentry *dentry)
 			 * Yup, recursive.  If there's a problem, blame
 			 * deep nesting of default_groups
 			 */
-			ret = configfs_detach_prep(sd->s_dentry);
+			ret = configfs_detach_prep(sd->s_dentry, wait_mutex);
 			if (!ret)
 				continue;
 		} else
@@ -1113,11 +1119,26 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
 	 */
 	module_got = 1;
 
+	/*
+	 * Make racing rmdir() fail if it did not tag parent with
+	 * CONFIGFS_USET_DROPPING
+	 * Note: if CONFIGFS_USET_DROPPING is already set, attach_group() will
+	 * fail and let rmdir() terminate correctly
+	 */
+	spin_lock(&configfs_dirent_lock);
+	/* This will make configfs_detach_prep() fail */
+	sd->s_type |= CONFIGFS_USET_IN_MKDIR;
+	spin_unlock(&configfs_dirent_lock);
+
 	if (group)
 		ret = configfs_attach_group(parent_item, item, dentry);
 	else
 		ret = configfs_attach_item(parent_item, item, dentry);
 
+	spin_lock(&configfs_dirent_lock);
+	sd->s_type &= ~CONFIGFS_USET_IN_MKDIR;
+	spin_unlock(&configfs_dirent_lock);
+
 out_unlink:
 	if (ret) {
 		/* Tear down everything we built up */
@@ -1182,13 +1203,25 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
 	}
 
 	spin_lock(&configfs_dirent_lock);
-	ret = configfs_detach_prep(dentry);
-	if (ret) {
-		configfs_detach_rollback(dentry);
-		spin_unlock(&configfs_dirent_lock);
-		config_item_put(parent_item);
-		return ret;
-	}
+	do {
+		struct mutex *wait_mutex;
+
+		ret = configfs_detach_prep(dentry, &wait_mutex);
+		if (ret) {
+			configfs_detach_rollback(dentry);
+			spin_unlock(&configfs_dirent_lock);
+			if (ret != -EAGAIN) {
+				config_item_put(parent_item);
+				return ret;
+			}
+
+			/* Wait until the racing operation terminates */
+			mutex_lock(wait_mutex);
+			mutex_unlock(wait_mutex);
+
+			spin_lock(&configfs_dirent_lock);
+		}
+	} while (ret == -EAGAIN);
 	spin_unlock(&configfs_dirent_lock);
 
 	/* Get a working ref for the duration of this function */
@@ -1480,7 +1513,7 @@ void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
 			  I_MUTEX_PARENT);
 	mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
 	spin_lock(&configfs_dirent_lock);
-	if (configfs_detach_prep(dentry)) {
+	if (configfs_detach_prep(dentry, NULL)) {
 		printk(KERN_ERR "configfs: Tried to unregister non-empty subsystem!\n");
 	}
 	spin_unlock(&configfs_dirent_lock);
-- 
cgit v1.2.3


From 11c3b79218390a139f2d474ee1e983a672d5839a Mon Sep 17 00:00:00 2001
From: Joel Becker <joel.becker@oracle.com>
Date: Thu, 12 Jun 2008 14:00:18 -0700
Subject: configfs: Allow ->make_item() and ->make_group() to return detailed
 errors.

The configfs operations ->make_item() and ->make_group() currently
return a new item/group.  A return of NULL signifies an error.  Because
of this, -ENOMEM is the only return code bubbled up the stack.

Multiple folks have requested the ability to return specific error codes
when these operations fail.  This patch adds that ability by changing the
->make_item/group() ops to return an int.

Also updated are the in-kernel users of configfs.

Signed-off-by: Joel Becker <joel.becker@oracle.com>
---
 Documentation/filesystems/configfs/configfs.txt    | 10 +++--
 .../filesystems/configfs/configfs_example.c        | 14 ++++---
 drivers/net/netconsole.c                           | 10 +++--
 fs/configfs/dir.c                                  | 13 +++----
 fs/dlm/config.c                                    | 45 ++++++++++++++--------
 fs/ocfs2/cluster/heartbeat.c                       | 17 ++++----
 fs/ocfs2/cluster/nodemanager.c                     | 45 ++++++++++++++--------
 include/linux/configfs.h                           |  4 +-
 8 files changed, 94 insertions(+), 64 deletions(-)

(limited to 'fs/configfs')

diff --git a/Documentation/filesystems/configfs/configfs.txt b/Documentation/filesystems/configfs/configfs.txt
index 44c97e6accb2..15838d706ea2 100644
--- a/Documentation/filesystems/configfs/configfs.txt
+++ b/Documentation/filesystems/configfs/configfs.txt
@@ -233,10 +233,12 @@ accomplished via the group operations specified on the group's
 config_item_type.
 
 	struct configfs_group_operations {
-		struct config_item *(*make_item)(struct config_group *group,
-						 const char *name);
-		struct config_group *(*make_group)(struct config_group *group,
-						   const char *name);
+		int (*make_item)(struct config_group *group,
+				 const char *name,
+				 struct config_item **new_item);
+		int (*make_group)(struct config_group *group,
+				  const char *name,
+				  struct config_group **new_group);
 		int (*commit_item)(struct config_item *item);
 		void (*disconnect_notify)(struct config_group *group,
 					  struct config_item *item);
diff --git a/Documentation/filesystems/configfs/configfs_example.c b/Documentation/filesystems/configfs/configfs_example.c
index 25151fd5c2c6..0b422acd470c 100644
--- a/Documentation/filesystems/configfs/configfs_example.c
+++ b/Documentation/filesystems/configfs/configfs_example.c
@@ -273,13 +273,13 @@ static inline struct simple_children *to_simple_children(struct config_item *ite
 	return item ? container_of(to_config_group(item), struct simple_children, group) : NULL;
 }
 
-static struct config_item *simple_children_make_item(struct config_group *group, const char *name)
+static int simple_children_make_item(struct config_group *group, const char *name, struct config_item **new_item)
 {
 	struct simple_child *simple_child;
 
 	simple_child = kzalloc(sizeof(struct simple_child), GFP_KERNEL);
 	if (!simple_child)
-		return NULL;
+		return -ENOMEM;
 
 
 	config_item_init_type_name(&simple_child->item, name,
@@ -287,7 +287,8 @@ static struct config_item *simple_children_make_item(struct config_group *group,
 
 	simple_child->storeme = 0;
 
-	return &simple_child->item;
+	*new_item = &simple_child->item;
+	return 0;
 }
 
 static struct configfs_attribute simple_children_attr_description = {
@@ -359,20 +360,21 @@ static struct configfs_subsystem simple_children_subsys = {
  * children of its own.
  */
 
-static struct config_group *group_children_make_group(struct config_group *group, const char *name)
+static int group_children_make_group(struct config_group *group, const char *name, struct config_group **new_group)
 {
 	struct simple_children *simple_children;
 
 	simple_children = kzalloc(sizeof(struct simple_children),
 				  GFP_KERNEL);
 	if (!simple_children)
-		return NULL;
+		return -ENOMEM;
 
 
 	config_group_init_type_name(&simple_children->group, name,
 				    &simple_children_type);
 
-	return &simple_children->group;
+	*new_group = &simple_children->group;
+	return 0;
 }
 
 static struct configfs_attribute group_children_attr_description = {
diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 665341e43055..387a13395015 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -585,8 +585,9 @@ static struct config_item_type netconsole_target_type = {
  * Group operations and type for netconsole_subsys.
  */
 
-static struct config_item *make_netconsole_target(struct config_group *group,
-						  const char *name)
+static int make_netconsole_target(struct config_group *group,
+				  const char *name,
+				  struct config_item **new_item)
 {
 	unsigned long flags;
 	struct netconsole_target *nt;
@@ -598,7 +599,7 @@ static struct config_item *make_netconsole_target(struct config_group *group,
 	nt = kzalloc(sizeof(*nt), GFP_KERNEL);
 	if (!nt) {
 		printk(KERN_ERR "netconsole: failed to allocate memory\n");
-		return NULL;
+		return -ENOMEM;
 	}
 
 	nt->np.name = "netconsole";
@@ -615,7 +616,8 @@ static struct config_item *make_netconsole_target(struct config_group *group,
 	list_add(&nt->list, &target_list);
 	spin_unlock_irqrestore(&target_list_lock, flags);
 
-	return &nt->item;
+	*new_item = &nt->item;
+	return 0;
 }
 
 static void drop_netconsole_target(struct config_group *group,
diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index 614e382a6049..0e64312a084c 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -1073,25 +1073,24 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
 	group = NULL;
 	item = NULL;
 	if (type->ct_group_ops->make_group) {
-		group = type->ct_group_ops->make_group(to_config_group(parent_item), name);
-		if (group) {
+		ret = type->ct_group_ops->make_group(to_config_group(parent_item), name, &group);
+		if (!ret) {
 			link_group(to_config_group(parent_item), group);
 			item = &group->cg_item;
 		}
 	} else {
-		item = type->ct_group_ops->make_item(to_config_group(parent_item), name);
-		if (item)
+		ret = type->ct_group_ops->make_item(to_config_group(parent_item), name, &item);
+		if (!ret)
 			link_obj(parent_item, item);
 	}
 	mutex_unlock(&subsys->su_mutex);
 
 	kfree(name);
-	if (!item) {
+	if (ret) {
 		/*
-		 * If item == NULL, then link_obj() was never called.
+		 * If ret != 0, then link_obj() was never called.
 		 * There are no extra references to clean up.
 		 */
-		ret = -ENOMEM;
 		goto out_put;
 	}
 
diff --git a/fs/dlm/config.c b/fs/dlm/config.c
index eac23bd288b2..492d8caaaf25 100644
--- a/fs/dlm/config.c
+++ b/fs/dlm/config.c
@@ -41,16 +41,20 @@ struct comm;
 struct nodes;
 struct node;
 
-static struct config_group *make_cluster(struct config_group *, const char *);
+static int make_cluster(struct config_group *, const char *,
+			struct config_group **);
 static void drop_cluster(struct config_group *, struct config_item *);
 static void release_cluster(struct config_item *);
-static struct config_group *make_space(struct config_group *, const char *);
+static int make_space(struct config_group *, const char *,
+		      struct config_group **);
 static void drop_space(struct config_group *, struct config_item *);
 static void release_space(struct config_item *);
-static struct config_item *make_comm(struct config_group *, const char *);
+static int make_comm(struct config_group *, const char *,
+		     struct config_item **);
 static void drop_comm(struct config_group *, struct config_item *);
 static void release_comm(struct config_item *);
-static struct config_item *make_node(struct config_group *, const char *);
+static int make_node(struct config_group *, const char *,
+		     struct config_item **);
 static void drop_node(struct config_group *, struct config_item *);
 static void release_node(struct config_item *);
 
@@ -392,8 +396,8 @@ static struct node *to_node(struct config_item *i)
 	return i ? container_of(i, struct node, item) : NULL;
 }
 
-static struct config_group *make_cluster(struct config_group *g,
-					 const char *name)
+static int make_cluster(struct config_group *g, const char *name,
+			struct config_group **new_g)
 {
 	struct cluster *cl = NULL;
 	struct spaces *sps = NULL;
@@ -431,14 +435,15 @@ static struct config_group *make_cluster(struct config_group *g,
 
 	space_list = &sps->ss_group;
 	comm_list = &cms->cs_group;
-	return &cl->group;
+	*new_g = &cl->group;
+	return 0;
 
  fail:
 	kfree(cl);
 	kfree(gps);
 	kfree(sps);
 	kfree(cms);
-	return NULL;
+	return -ENOMEM;
 }
 
 static void drop_cluster(struct config_group *g, struct config_item *i)
@@ -466,7 +471,8 @@ static void release_cluster(struct config_item *i)
 	kfree(cl);
 }
 
-static struct config_group *make_space(struct config_group *g, const char *name)
+static int make_space(struct config_group *g, const char *name,
+		      struct config_group **new_g)
 {
 	struct space *sp = NULL;
 	struct nodes *nds = NULL;
@@ -489,13 +495,14 @@ static struct config_group *make_space(struct config_group *g, const char *name)
 	INIT_LIST_HEAD(&sp->members);
 	mutex_init(&sp->members_lock);
 	sp->members_count = 0;
-	return &sp->group;
+	*new_g = &sp->group;
+	return 0;
 
  fail:
 	kfree(sp);
 	kfree(gps);
 	kfree(nds);
-	return NULL;
+	return -ENOMEM;
 }
 
 static void drop_space(struct config_group *g, struct config_item *i)
@@ -522,19 +529,21 @@ static void release_space(struct config_item *i)
 	kfree(sp);
 }
 
-static struct config_item *make_comm(struct config_group *g, const char *name)
+static int make_comm(struct config_group *g, const char *name,
+		     struct config_item **new_i)
 {
 	struct comm *cm;
 
 	cm = kzalloc(sizeof(struct comm), GFP_KERNEL);
 	if (!cm)
-		return NULL;
+		return -ENOMEM;
 
 	config_item_init_type_name(&cm->item, name, &comm_type);
 	cm->nodeid = -1;
 	cm->local = 0;
 	cm->addr_count = 0;
-	return &cm->item;
+	*new_i = &cm->item;
+	return 0;
 }
 
 static void drop_comm(struct config_group *g, struct config_item *i)
@@ -554,14 +563,15 @@ static void release_comm(struct config_item *i)
 	kfree(cm);
 }
 
-static struct config_item *make_node(struct config_group *g, const char *name)
+static int make_node(struct config_group *g, const char *name,
+		     struct config_item **new_i)
 {
 	struct space *sp = to_space(g->cg_item.ci_parent);
 	struct node *nd;
 
 	nd = kzalloc(sizeof(struct node), GFP_KERNEL);
 	if (!nd)
-		return NULL;
+		return -ENOMEM;
 
 	config_item_init_type_name(&nd->item, name, &node_type);
 	nd->nodeid = -1;
@@ -573,7 +583,8 @@ static struct config_item *make_node(struct config_group *g, const char *name)
 	sp->members_count++;
 	mutex_unlock(&sp->members_lock);
 
-	return &nd->item;
+	*new_i = &nd->item;
+	return 0;
 }
 
 static void drop_node(struct config_group *g, struct config_item *i)
diff --git a/fs/ocfs2/cluster/heartbeat.c b/fs/ocfs2/cluster/heartbeat.c
index f02ccb34604d..443d108211ab 100644
--- a/fs/ocfs2/cluster/heartbeat.c
+++ b/fs/ocfs2/cluster/heartbeat.c
@@ -1489,25 +1489,28 @@ static struct o2hb_heartbeat_group *to_o2hb_heartbeat_group(struct config_group
 		: NULL;
 }
 
-static struct config_item *o2hb_heartbeat_group_make_item(struct config_group *group,
-							  const char *name)
+static int o2hb_heartbeat_group_make_item(struct config_group *group,
+					  const char *name,
+					  struct config_item **new_item)
 {
 	struct o2hb_region *reg = NULL;
-	struct config_item *ret = NULL;
+	int ret = 0;
 
 	reg = kzalloc(sizeof(struct o2hb_region), GFP_KERNEL);
-	if (reg == NULL)
-		goto out; /* ENOMEM */
+	if (reg == NULL) {
+		ret = -ENOMEM;
+		goto out;
+	}
 
 	config_item_init_type_name(&reg->hr_item, name, &o2hb_region_type);
 
-	ret = &reg->hr_item;
+	*new_item = &reg->hr_item;
 
 	spin_lock(&o2hb_live_lock);
 	list_add_tail(&reg->hr_all_item, &o2hb_all_regions);
 	spin_unlock(&o2hb_live_lock);
 out:
-	if (ret == NULL)
+	if (ret)
 		kfree(reg);
 
 	return ret;
diff --git a/fs/ocfs2/cluster/nodemanager.c b/fs/ocfs2/cluster/nodemanager.c
index cfdb08b484ed..b364b7052e46 100644
--- a/fs/ocfs2/cluster/nodemanager.c
+++ b/fs/ocfs2/cluster/nodemanager.c
@@ -644,27 +644,32 @@ out:
 	return ret;
 }
 
-static struct config_item *o2nm_node_group_make_item(struct config_group *group,
-						     const char *name)
+static int o2nm_node_group_make_item(struct config_group *group,
+				     const char *name,
+				     struct config_item **new_item)
 {
 	struct o2nm_node *node = NULL;
-	struct config_item *ret = NULL;
+	int ret = 0;
 
-	if (strlen(name) > O2NM_MAX_NAME_LEN)
-		goto out; /* ENAMETOOLONG */
+	if (strlen(name) > O2NM_MAX_NAME_LEN) {
+		ret = -ENAMETOOLONG;
+		goto out;
+	}
 
 	node = kzalloc(sizeof(struct o2nm_node), GFP_KERNEL);
-	if (node == NULL)
-		goto out; /* ENOMEM */
+	if (node == NULL) {
+		ret = -ENOMEM;
+		goto out;
+	}
 
 	strcpy(node->nd_name, name); /* use item.ci_namebuf instead? */
 	config_item_init_type_name(&node->nd_item, name, &o2nm_node_type);
 	spin_lock_init(&node->nd_lock);
 
-	ret = &node->nd_item;
+	*new_item = &node->nd_item;
 
 out:
-	if (ret == NULL)
+	if (ret)
 		kfree(node);
 
 	return ret;
@@ -751,25 +756,31 @@ static struct o2nm_cluster_group *to_o2nm_cluster_group(struct config_group *gro
 }
 #endif
 
-static struct config_group *o2nm_cluster_group_make_group(struct config_group *group,
-							  const char *name)
+static int o2nm_cluster_group_make_group(struct config_group *group,
+					 const char *name,
+					 struct config_group **new_group)
 {
 	struct o2nm_cluster *cluster = NULL;
 	struct o2nm_node_group *ns = NULL;
-	struct config_group *o2hb_group = NULL, *ret = NULL;
+	struct config_group *o2hb_group = NULL;
 	void *defs = NULL;
+	int ret = 0;
 
 	/* this runs under the parent dir's i_mutex; there can be only
 	 * one caller in here at a time */
-	if (o2nm_single_cluster)
-		goto out; /* ENOSPC */
+	if (o2nm_single_cluster) {
+		ret = -ENOSPC;
+		goto out;
+	}
 
 	cluster = kzalloc(sizeof(struct o2nm_cluster), GFP_KERNEL);
 	ns = kzalloc(sizeof(struct o2nm_node_group), GFP_KERNEL);
 	defs = kcalloc(3, sizeof(struct config_group *), GFP_KERNEL);
 	o2hb_group = o2hb_alloc_hb_set();
-	if (cluster == NULL || ns == NULL || o2hb_group == NULL || defs == NULL)
+	if (cluster == NULL || ns == NULL || o2hb_group == NULL || defs == NULL) {
+		ret = -ENOMEM;
 		goto out;
+	}
 
 	config_group_init_type_name(&cluster->cl_group, name,
 				    &o2nm_cluster_type);
@@ -786,11 +797,11 @@ static struct config_group *o2nm_cluster_group_make_group(struct config_group *g
 	cluster->cl_idle_timeout_ms    = O2NET_IDLE_TIMEOUT_MS_DEFAULT;
 	cluster->cl_keepalive_delay_ms = O2NET_KEEPALIVE_DELAY_MS_DEFAULT;
 
-	ret = &cluster->cl_group;
+	*new_group = &cluster->cl_group;
 	o2nm_single_cluster = cluster;
 
 out:
-	if (ret == NULL) {
+	if (ret) {
 		kfree(cluster);
 		kfree(ns);
 		o2hb_free_hb_set(o2hb_group);
diff --git a/include/linux/configfs.h b/include/linux/configfs.h
index 3ae65b1bf90f..0488f937634a 100644
--- a/include/linux/configfs.h
+++ b/include/linux/configfs.h
@@ -165,8 +165,8 @@ struct configfs_item_operations {
 };
 
 struct configfs_group_operations {
-	struct config_item *(*make_item)(struct config_group *group, const char *name);
-	struct config_group *(*make_group)(struct config_group *group, const char *name);
+	int (*make_item)(struct config_group *group, const char *name, struct config_item **new_item);
+	int (*make_group)(struct config_group *group, const char *name, struct config_group **new_group);
 	int (*commit_item)(struct config_item *item);
 	void (*disconnect_notify)(struct config_group *group, struct config_item *item);
 	void (*drop_item)(struct config_group *group, struct config_item *item);
-- 
cgit v1.2.3


From e75206517504461778c283b942440ef312e437d5 Mon Sep 17 00:00:00 2001
From: Louis Rilling <Louis.Rilling@kerlabs.com>
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 <Louis.Rilling@kerlabs.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
---
 fs/configfs/symlink.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

(limited to 'fs/configfs')

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 v1.2.3