[PATCH 1/3][BUGFIX] configfs: Introduce configfs_dirent_lock
From: Louis Rilling
Date: Thu Jun 12 2008 - 09:44:28 EST
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).
Signed-off-by: Louis Rilling <Louis.Rilling@xxxxxxxxxxx>
---
fs/configfs/configfs_internal.h | 3 +++
fs/configfs/dir.c | 25 +++++++++++++++++++++++++
fs/configfs/inode.c | 2 ++
fs/configfs/symlink.c | 2 ++
4 files changed, 32 insertions(+)
Index: b/fs/configfs/configfs_internal.h
===================================================================
--- a/fs/configfs/configfs_internal.h 2008-06-12 13:44:27.000000000 +0200
+++ b/fs/configfs/configfs_internal.h 2008-06-12 13:44:34.000000000 +0200
@@ -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;
Index: b/fs/configfs/dir.c
===================================================================
--- a/fs/configfs/dir.c 2008-06-12 13:44:27.000000000 +0200
+++ b/fs/configfs/dir.c 2008-06-12 15:20:26.000000000 +0200
@@ -35,6 +35,11 @@
#include "configfs_internal.h"
DECLARE_RWSEM(configfs_rename_sem);
+/*
+ * Protects configfs_dirent traversals against linkage mutations
+ * Can be used as an alternative to taking the concerned i_mutex
+ */
+DEFINE_SPINLOCK(configfs_dirent_lock);
static void configfs_d_iput(struct dentry * dentry,
struct inode * inode)
@@ -79,7 +84,9 @@ static struct configfs_dirent *configfs_
atomic_set(&sd->s_count, 1);
INIT_LIST_HEAD(&sd->s_links);
INIT_LIST_HEAD(&sd->s_children);
+ spin_lock(&configfs_dirent_lock);
list_add(&sd->s_sibling, &parent_sd->s_children);
+ spin_unlock(&configfs_dirent_lock);
sd->s_element = element;
return sd;
@@ -173,7 +180,9 @@ static int create_dir(struct config_item
} 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 +233,9 @@ int configfs_create_link(struct configfs
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 +249,9 @@ 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 +423,9 @@ static void detach_attrs(struct config_i
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 +1283,9 @@ static int configfs_dir_close(struct ino
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 +1325,9 @@ static int configfs_readdir(struct file
/* 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 +1350,9 @@ static int configfs_readdir(struct file
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++;
}
@@ -1362,7 +1383,9 @@ static loff_t configfs_dir_lseek(struct
struct list_head *p;
loff_t n = file->f_pos - 2;
+ spin_lock(&configfs_dirent_lock);
list_del(&cursor->s_sibling);
+ spin_unlock(&configfs_dirent_lock);
p = sd->s_children.next;
while (n && p != &sd->s_children) {
struct configfs_dirent *next;
@@ -1372,7 +1395,9 @@ static loff_t configfs_dir_lseek(struct
n--;
p = p->next;
}
+ spin_lock(&configfs_dirent_lock);
list_add_tail(&cursor->s_sibling, p);
+ spin_unlock(&configfs_dirent_lock);
}
}
mutex_unlock(&dentry->d_inode->i_mutex);
Index: b/fs/configfs/inode.c
===================================================================
--- a/fs/configfs/inode.c 2008-06-12 13:44:27.000000000 +0200
+++ b/fs/configfs/inode.c 2008-06-12 13:44:34.000000000 +0200
@@ -247,7 +247,9 @@ void configfs_hash_and_remove(struct den
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;
Index: b/fs/configfs/symlink.c
===================================================================
--- a/fs/configfs/symlink.c 2008-06-12 13:44:27.000000000 +0200
+++ b/fs/configfs/symlink.c 2008-06-12 13:44:34.000000000 +0200
@@ -169,7 +169,9 @@ int configfs_unlink(struct inode *dir, s
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);
--
Dr Louis Rilling Kerlabs
Skype: louis.rilling Batiment Germanium
Phone: (+33|0) 6 80 89 08 23 80 avenue des Buttes de Coesmes
http://www.kerlabs.com/ 35700 Rennes
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