sysfs: Gut sysfs_addrm_start and sysfs_addrm_finish

With lazy inode updates and dentry operations bringing everything
into sync on demand there is no longer any need to immediately
update the vfs or grab i_mutex to protect those updates as we
make changes to sysfs.

Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 4 insertions, 89 deletions

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index e319379d36db..f3af45e47eaa 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -386,12 +386,6 @@ struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode, int type)
         return NULL;
 }
 
-static int sysfs_ilookup_test(struct inode *inode, void *arg)
-{
-        struct sysfs_dirent *sd = arg;
-        return inode->i_ino == sd->s_ino;
-}
-
 /**
  *      sysfs_addrm_start - prepare for sysfs_dirent add/remove
  *      @acxt: pointer to sysfs_addrm_cxt to be used
@@ -399,47 +393,20 @@ static int sysfs_ilookup_test(struct inode *inode, void *arg)
  *
  *      This function is called when the caller is about to add or
  *      remove sysfs_dirent under @parent_sd.  This function acquires
- *      sysfs_mutex, grabs inode for @parent_sd if available and lock
- *      i_mutex of it.  @acxt is used to keep and pass context to
+ *      sysfs_mutex.  @acxt is used to keep and pass context to
  *      other addrm functions.
  *
  *      LOCKING:
  *      Kernel thread context (may sleep).  sysfs_mutex is locked on
- *      return.  i_mutex of parent inode is locked on return if
- *      available.
+ *      return.
  */
 void sysfs_addrm_start(struct sysfs_addrm_cxt *acxt,
                        struct sysfs_dirent *parent_sd)
 {
-        struct inode *inode;
-
         memset(acxt, 0, sizeof(*acxt));
         acxt->parent_sd = parent_sd;
 
-        /* Lookup parent inode.  inode initialization is protected by
-         * sysfs_mutex, so inode existence can be determined by
-         * looking up inode while holding sysfs_mutex.
-         */
         mutex_lock(&sysfs_mutex);
-
-        inode = ilookup5(sysfs_sb, parent_sd->s_ino, sysfs_ilookup_test,
-                         parent_sd);
-        if (inode) {
-                WARN_ON(inode->i_state & I_NEW);
-
-                /* parent inode available */
-                acxt->parent_inode = inode;
-
-                /* sysfs_mutex is below i_mutex in lock hierarchy.
-                 * First, trylock i_mutex.  If fails, unlock
-                 * sysfs_mutex and lock them in order.
-                 */
-                if (!mutex_trylock(&inode->i_mutex)) {
-                        mutex_unlock(&sysfs_mutex);
-                        mutex_lock(&inode->i_mutex);
-                        mutex_lock(&sysfs_mutex);
-                }
-        }
 }
 
 /**
@@ -471,11 +438,6 @@ int __sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
 
         sd->s_parent = sysfs_get(acxt->parent_sd);
 
-        if (sysfs_type(sd) == SYSFS_DIR && acxt->parent_inode)
-                inc_nlink(acxt->parent_inode);
-
-        acxt->cnt++;
-
         sysfs_link_sibling(sd);
 
         /* Update timestamps on the parent */
@@ -579,40 +541,6 @@ void sysfs_remove_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
         sd->s_flags |= SYSFS_FLAG_REMOVED;
         sd->s_sibling = acxt->removed;
         acxt->removed = sd;
-
-        if (sysfs_type(sd) == SYSFS_DIR && acxt->parent_inode)
-                drop_nlink(acxt->parent_inode);
-
-        acxt->cnt++;
-}
-
-/**
- *      sysfs_dec_nlink - Decrement link count for the specified sysfs_dirent
- *      @sd: target sysfs_dirent
- *
- *      Decrement nlink for @sd.  @sd must have been unlinked from its
- *      parent on entry to this function such that it can't be looked
- *      up anymore.
- */
-static void sysfs_dec_nlink(struct sysfs_dirent *sd)
-{
-        struct inode *inode;
-
-        inode = ilookup(sysfs_sb, sd->s_ino);
-        if (!inode)
-                return;
-
-        /* adjust nlink and update timestamp */
-        mutex_lock(&inode->i_mutex);
-
-        inode->i_ctime = CURRENT_TIME;
-        drop_nlink(inode);
-        if (sysfs_type(sd) == SYSFS_DIR)
-                drop_nlink(inode);
-
-        mutex_unlock(&inode->i_mutex);
-
-        iput(inode);
 }
 
 /**
@@ -621,25 +549,15 @@ static void sysfs_dec_nlink(struct sysfs_dirent *sd)
  *
  *      Finish up sysfs_dirent add/remove.  Resources acquired by
  *      sysfs_addrm_start() are released and removed sysfs_dirents are
- *      cleaned up.  Timestamps on the parent inode are updated.
+ *      cleaned up.
  *
  *      LOCKING:
- *      All mutexes acquired by sysfs_addrm_start() are released.
+ *      sysfs_mutex is released.
  */
 void sysfs_addrm_finish(struct sysfs_addrm_cxt *acxt)
 {
         /* release resources acquired by sysfs_addrm_start() */
         mutex_unlock(&sysfs_mutex);
-        if (acxt->parent_inode) {
-                struct inode *inode = acxt->parent_inode;
-
-                /* if added/removed, update timestamps on the parent */
-                if (acxt->cnt)
-                        inode->i_ctime = inode->i_mtime = CURRENT_TIME;
-
-                mutex_unlock(&inode->i_mutex);
-                iput(inode);
-        }
 
         /* kill removed sysfs_dirents */
         while (acxt->removed) {
@@ -648,7 +566,6 @@ void sysfs_addrm_finish(struct sysfs_addrm_cxt *acxt)
                 acxt->removed = sd->s_sibling;
                 sd->s_sibling = NULL;
 
-                sysfs_dec_nlink(sd);
                 sysfs_deactivate(sd);
                 unmap_bin_file(sd);
                 sysfs_put(sd);
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index 12ccc07459d8..90b35012abb2 100644
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -89,9 +89,7 @@ static inline unsigned int sysfs_type(struct sysfs_dirent *sd)
  */
 struct sysfs_addrm_cxt {
         struct sysfs_dirent     *parent_sd;
-        struct inode            *parent_inode;
         struct sysfs_dirent     *removed;
-        int                     cnt;
 };
 
 /*