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For example next patch modifies this interface to use hashed mutexes in place of a single global kernfs_open_file_mutex. Signed-off-by: Imran Khan Acked-by: Tejun Heo --- fs/kernfs/file.c | 60 ++++++++++++++++++++++++++++++++---------------- 1 file changed, 40 insertions(+), 20 deletions(-) diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c index 0cc288dcf51d9..205b5c71f30cb 100644 --- a/fs/kernfs/file.c +++ b/fs/kernfs/file.c @@ -49,6 +49,22 @@ struct kernfs_open_node { static LLIST_HEAD(kernfs_notify_list); +static inline struct mutex *kernfs_open_file_mutex_ptr(struct kernfs_node *kn) +{ + return &kernfs_open_file_mutex; +} + +static inline struct mutex *kernfs_open_file_mutex_lock(struct kernfs_node *kn) +{ + struct mutex *lock; + + lock = kernfs_open_file_mutex_ptr(kn); + + mutex_lock(lock); + + return lock; +} + /** * kernfs_deref_open_node - Get kernfs_open_node corresponding to @kn. * @@ -56,7 +72,7 @@ static LLIST_HEAD(kernfs_notify_list); * @kn: target kernfs_node. * * Fetch and return ->attr.open of @kn if @of->list is not empty or if - * kernfs_open_file_mutex is held. + * kernfs_open_file_mutex_ptr(kn) is held. * * We can rely on either of the following 2 conditions to ensure that * dereferencing ->attr.open outside RCU read-side critical section is safe. @@ -68,13 +84,13 @@ static LLIST_HEAD(kernfs_notify_list); * * or * - * 2. Update of ->attr.open happens under kernfs_open_file_mutex. So as long as - * the current updater (caller) is holding this mutex, other updaters will not - * be able to change ->attr.open and this means that we can safely deref - * ->attr.open outside RCU read-side critical section. + * 2. Update of ->attr.open happens under kernfs_open_file_mutex_ptr(kn). So as + * long as the current updater (caller) holds this mutex, other updaters can't + * change ->attr.open and this means that we can safely deref ->attr.open + * outside RCU read-side critical section. * * The caller needs to make sure that either @of->list is not empty or - * kernfs_open_file_mutex is held. + * kernfs_open_file_mutex_ptr(kn) is held. */ static struct kernfs_open_node * kernfs_deref_open_node(struct kernfs_open_file *of, struct kernfs_node *kn) @@ -83,7 +99,7 @@ kernfs_deref_open_node(struct kernfs_open_file *of, struct kernfs_node *kn) bool deref_ok; deref_ok = (of ? !list_empty(&of->list) : false) || - lockdep_is_held(&kernfs_open_file_mutex); + lockdep_is_held(kernfs_open_file_mutex_ptr(kn)); on = rcu_dereference_check(kn->attr.open, deref_ok); @@ -570,19 +586,20 @@ static int kernfs_get_open_node(struct kernfs_node *kn, struct kernfs_open_file *of) { struct kernfs_open_node *on, *new_on = NULL; + struct mutex *mutex = NULL; - mutex_lock(&kernfs_open_file_mutex); + mutex = kernfs_open_file_mutex_lock(kn); on = kernfs_deref_open_node(NULL, kn); if (on) { list_add_tail(&of->list, &on->files); - mutex_unlock(&kernfs_open_file_mutex); + mutex_unlock(mutex); return 0; } else { /* not there, initialize a new one */ new_on = kmalloc(sizeof(*new_on), GFP_KERNEL); if (!new_on) { - mutex_unlock(&kernfs_open_file_mutex); + mutex_unlock(mutex); return -ENOMEM; } atomic_set(&new_on->event, 1); @@ -591,7 +608,7 @@ static int kernfs_get_open_node(struct kernfs_node *kn, list_add_tail(&of->list, &new_on->files); rcu_assign_pointer(kn->attr.open, new_on); } - mutex_unlock(&kernfs_open_file_mutex); + mutex_unlock(mutex); return 0; } @@ -613,12 +630,13 @@ static void kernfs_unlink_open_file(struct kernfs_node *kn, struct kernfs_open_file *of) { struct kernfs_open_node *on; + struct mutex *mutex = NULL; - mutex_lock(&kernfs_open_file_mutex); + mutex = kernfs_open_file_mutex_lock(kn); on = kernfs_deref_open_node(NULL, kn); if (!on) { - mutex_unlock(&kernfs_open_file_mutex); + mutex_unlock(mutex); return; } @@ -630,7 +648,7 @@ static void kernfs_unlink_open_file(struct kernfs_node *kn, kfree_rcu(on, rcu_head); } - mutex_unlock(&kernfs_open_file_mutex); + mutex_unlock(mutex); } static int kernfs_fop_open(struct inode *inode, struct file *file) @@ -772,7 +790,7 @@ static void kernfs_release_file(struct kernfs_node *kn, * here because drain path may be called from places which can * cause circular dependency. */ - lockdep_assert_held(&kernfs_open_file_mutex); + lockdep_assert_held(kernfs_open_file_mutex_ptr(kn)); if (!of->released) { /* @@ -789,11 +807,12 @@ static int kernfs_fop_release(struct inode *inode, struct file *filp) { struct kernfs_node *kn = inode->i_private; struct kernfs_open_file *of = kernfs_of(filp); + struct mutex *mutex = NULL; if (kn->flags & KERNFS_HAS_RELEASE) { - mutex_lock(&kernfs_open_file_mutex); + mutex = kernfs_open_file_mutex_lock(kn); kernfs_release_file(kn, of); - mutex_unlock(&kernfs_open_file_mutex); + mutex_unlock(mutex); } kernfs_unlink_open_file(kn, of); @@ -808,6 +827,7 @@ void kernfs_drain_open_files(struct kernfs_node *kn) { struct kernfs_open_node *on; struct kernfs_open_file *of; + struct mutex *mutex = NULL; if (!(kn->flags & (KERNFS_HAS_MMAP | KERNFS_HAS_RELEASE))) return; @@ -823,10 +843,10 @@ void kernfs_drain_open_files(struct kernfs_node *kn) if (!rcu_access_pointer(kn->attr.open)) return; - mutex_lock(&kernfs_open_file_mutex); + mutex = kernfs_open_file_mutex_lock(kn); on = kernfs_deref_open_node(NULL, kn); if (!on) { - mutex_unlock(&kernfs_open_file_mutex); + mutex_unlock(mutex); return; } @@ -840,7 +860,7 @@ void kernfs_drain_open_files(struct kernfs_node *kn) kernfs_release_file(kn, of); } - mutex_unlock(&kernfs_open_file_mutex); + mutex_unlock(mutex); } /* -- 2.30.2