Merge master.kernel.org:/pub/scm/linux/kernel/git/davej/agpgart

[linux-2.6] / fs / sysfs / dir.c

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 17a819151b91cde7fcc75b92f2de2522e7c57f04..c4342a0199727b19fe832c4eaff371c0c8e1b9ee 100644 (file)
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -13,14 +13,26 @@
 #include "sysfs.h"
 
 DECLARE_RWSEM(sysfs_rename_sem);
+spinlock_t sysfs_lock = SPIN_LOCK_UNLOCKED;
 
 static void sysfs_d_iput(struct dentry * dentry, struct inode * inode)
 {
        struct sysfs_dirent * sd = dentry->d_fsdata;
 
        if (sd) {
-               BUG_ON(sd->s_dentry != dentry);
-               sd->s_dentry = NULL;
+               /* sd->s_dentry is protected with sysfs_lock.  This
+                * allows sysfs_drop_dentry() to dereference it.
+                */
+               spin_lock(&sysfs_lock);
+
+               /* The dentry might have been deleted or another
+                * lookup could have happened updating sd->s_dentry to
+                * point the new dentry.  Ignore if it isn't pointing
+                * to this dentry.
+                */
+               if (sd->s_dentry == dentry)
+                       sd->s_dentry = NULL;
+               spin_unlock(&sysfs_lock);
                sysfs_put(sd);
        }
        iput(inode);
@@ -247,7 +259,10 @@ static int sysfs_attach_attr(struct sysfs_dirent * sd, struct dentry * dentry)
         }
 
        dentry->d_fsdata = sysfs_get(sd);
+       /* protect sd->s_dentry against sysfs_d_iput */
+       spin_lock(&sysfs_lock);
        sd->s_dentry = dentry;
+       spin_unlock(&sysfs_lock);
        error = sysfs_create(dentry, (attr->mode & S_IALLUGO) | S_IFREG, init);
        if (error) {
                sysfs_put(sd);
@@ -269,7 +284,10 @@ static int sysfs_attach_link(struct sysfs_dirent * sd, struct dentry * dentry)
        int err = 0;
 
        dentry->d_fsdata = sysfs_get(sd);
+       /* protect sd->s_dentry against sysfs_d_iput */
+       spin_lock(&sysfs_lock);
        sd->s_dentry = dentry;
+       spin_unlock(&sysfs_lock);
        err = sysfs_create(dentry, S_IFLNK|S_IRWXUGO, init_symlink);
        if (!err) {
                dentry->d_op = &sysfs_dentry_ops;