sysfs: use iget_locked() instead of new_inode()

After dentry is reclaimed, sysfs always used to allocate new dentry
and inode if the file is accessed again.  This causes problem with
operations which only pin the inode.  For example, if inotify watch is
added to a sysfs file and the dentry for the file is reclaimed, the
next update event creates new dentry and new inode making the inotify
watch miss all the events from there on.

This patch fixes it by using iget_locked() instead of new_inode().
sysfs_new_inode() is renamed to sysfs_get_inode() and inode is
initialized iff the inode is newly allocated.  sysfs_instantiate() is
responsible for unlocking new inodes.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index bbf3525fd222e43e32f988decbcfd1f3eeede35b..06dff2c30c9b48ad1a9f55ebaa5b9bd627b8bc95 100644 (file)
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -219,14 +219,16 @@ static int create_dir(struct kobject *kobj, struct dentry *parent,
                goto out_drop;
        sd->s_elem.dir.kobj = kobj;
 
-       inode = sysfs_new_inode(sd);
+       inode = sysfs_get_inode(sd);
        if (!inode)
                goto out_sput;
 
-       inode->i_op = &sysfs_dir_inode_operations;
-       inode->i_fop = &sysfs_dir_operations;
-       /* directory inodes start off with i_nlink == 2 (for "." entry) */
-       inc_nlink(inode);
+       if (inode->i_state & I_NEW) {
+               inode->i_op = &sysfs_dir_inode_operations;
+               inode->i_fop = &sysfs_dir_operations;
+               /* directory inodes start off with i_nlink == 2 (for ".") */
+               inc_nlink(inode);
+       }
 
        /* link in */
        error = -EEXIST;
@@ -310,20 +312,23 @@ static struct dentry * sysfs_lookup(struct inode *dir, struct dentry *dentry,
                return NULL;
 
        /* attach dentry and inode */
-       inode = sysfs_new_inode(sd);
+       inode = sysfs_get_inode(sd);
        if (!inode)
                return ERR_PTR(-ENOMEM);
 
-       /* initialize inode according to type */
-       if (sd->s_type & SYSFS_KOBJ_ATTR) {
-               inode->i_size = PAGE_SIZE;
-               inode->i_fop = &sysfs_file_operations;
-       } else if (sd->s_type & SYSFS_KOBJ_BIN_ATTR) {
-               struct bin_attribute *bin_attr = sd->s_elem.bin_attr.bin_attr;
-               inode->i_size = bin_attr->size;
-               inode->i_fop = &bin_fops;
-       } else if (sd->s_type & SYSFS_KOBJ_LINK)
-               inode->i_op = &sysfs_symlink_inode_operations;
+       if (inode->i_state & I_NEW) {
+               /* initialize inode according to type */
+               if (sd->s_type & SYSFS_KOBJ_ATTR) {
+                       inode->i_size = PAGE_SIZE;
+                       inode->i_fop = &sysfs_file_operations;
+               } else if (sd->s_type & SYSFS_KOBJ_BIN_ATTR) {
+                       struct bin_attribute *bin_attr =
+                               sd->s_elem.bin_attr.bin_attr;
+                       inode->i_size = bin_attr->size;
+                       inode->i_fop = &bin_fops;
+               } else if (sd->s_type & SYSFS_KOBJ_LINK)
+                       inode->i_op = &sysfs_symlink_inode_operations;
+       }
 
        sysfs_instantiate(dentry, inode);
        sysfs_attach_dentry(sd, dentry);

diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
index 26d8503c8997afbe84ccc3598c71c73b11776cf1..3eab9c46a71b6f30a27b51d2f5c0521a9f3275c2 100644 (file)
--- a/fs/sysfs/inode.c
+++ b/fs/sysfs/inode.c
@@ -153,10 +153,12 @@ void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode)
 }
 
 /**
- *     sysfs_new_inode - allocate new inode for sysfs_dirent
+ *     sysfs_get_inode - get inode for sysfs_dirent
  *     @sd: sysfs_dirent to allocate inode for
  *
- *     Allocate inode for @sd and initialize basics.
+ *     Get inode for @sd.  If such inode doesn't exist, a new inode
+ *     is allocated and basics are initialized.  New inode is
+ *     returned locked.
  *
  *     LOCKING:
  *     Kernel thread context (may sleep).
@@ -164,12 +166,12 @@ void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode)
  *     RETURNS:
  *     Pointer to allocated inode on success, NULL on failure.
  */
-struct inode * sysfs_new_inode(struct sysfs_dirent *sd)
+struct inode * sysfs_get_inode(struct sysfs_dirent *sd)
 {
        struct inode *inode;
 
-       inode = new_inode(sysfs_sb);
-       if (inode)
+       inode = iget_locked(sysfs_sb, sd->s_ino);
+       if (inode && (inode->i_state & I_NEW))
                sysfs_init_inode(sd, inode);
 
        return inode;
@@ -180,7 +182,7 @@ struct inode * sysfs_new_inode(struct sysfs_dirent *sd)
  *     @dentry: dentry to be instantiated
  *     @inode: inode associated with @sd
  *
- *     Instantiate @dentry with @inode.
+ *     Unlock @inode if locked and instantiate @dentry with @inode.
  *
  *     LOCKING:
  *     None.
@@ -189,9 +191,13 @@ void sysfs_instantiate(struct dentry *dentry, struct inode *inode)
 {
        BUG_ON(!dentry || dentry->d_inode);
 
-       if (dentry->d_parent && dentry->d_parent->d_inode) {
-               struct inode *p_inode = dentry->d_parent->d_inode;
-               p_inode->i_mtime = p_inode->i_ctime = CURRENT_TIME;
+       if (inode->i_state & I_NEW) {
+               unlock_new_inode(inode);
+
+               if (dentry->d_parent && dentry->d_parent->d_inode) {
+                       struct inode *p_inode = dentry->d_parent->d_inode;
+                       p_inode->i_mtime = p_inode->i_ctime = CURRENT_TIME;
+               }
        }
 
        d_instantiate(dentry, inode);

diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index 143fdbe56c142b5ed8cca7acdf6e63ba8e442786..627bf3940dfad703d714497b15d6955fffd3fb16 100644 (file)
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -58,7 +58,7 @@ extern struct kmem_cache *sysfs_dir_cachep;
 
 extern void sysfs_delete_inode(struct inode *inode);
 extern void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode);
-extern struct inode * sysfs_new_inode(struct sysfs_dirent *sd);
+extern struct inode * sysfs_get_inode(struct sysfs_dirent *sd);
 extern void sysfs_instantiate(struct dentry *dentry, struct inode *inode);
 
 extern void release_sysfs_dirent(struct sysfs_dirent * sd);