[PATCH 11/13] sysfs: Gut sysfs_addrm_start and sysfs_addrm_finish

Eric W. Biederman
2009-11-03T11:58:36Z

From: Eric W. Biederman <ebiederm@aristanetworks.com>

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.

Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>
---
fs/sysfs/dir.c | 91 ++---------------------------------------------------
fs/sysfs/sysfs.h | 2 -
2 files changed, 4 insertions(+), 89 deletions(-)

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 25d052a..a05b027 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 12ccc07..90b3501 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;
};

/*
--
1.6.5.2.143.g8cc62