Right now per-fs kernfs_rwsem protects list of kernfs_super_info instances
for a kernfs_root. Since kernfs_rwsem is used to synchronize several other
operations across kernfs and since most of these operations don't impact
kernfs_super_info, we can use a separate per-fs rwsem to synchronize access
to list of kernfs_super_info.
This helps in reducing contention around kernfs_rwsem and also allows
operations that change/access list of kernfs_super_info to proceed without
contending for kernfs_rwsem.
Signed-off-by: Imran Khan <imran.f.khan@xxxxxxxxxx>
---
fs/kernfs/dir.c | 1 +
fs/kernfs/file.c | 2 ++
fs/kernfs/kernfs-internal.h | 1 +
fs/kernfs/mount.c | 8 ++++----
4 files changed, 8 insertions(+), 4 deletions(-)
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 953b2717c60e6..2cdb8516e5287 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -944,6 +944,7 @@ struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
idr_init(&root->ino_idr);
init_rwsem(&root->kernfs_rwsem);
init_rwsem(&root->kernfs_iattr_rwsem);
+ init_rwsem(&root->kernfs_supers_rwsem);
INIT_LIST_HEAD(&root->supers);
/*
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index e4a50e4ff0d23..b84cf0cd4bd44 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -924,6 +924,7 @@ static void kernfs_notify_workfn(struct work_struct *work)
/* kick fsnotify */
down_write(&root->kernfs_rwsem);
+ down_write(&root->kernfs_supers_rwsem);
list_for_each_entry(info, &kernfs_root(kn)->supers, node) {
struct kernfs_node *parent;
struct inode *p_inode = NULL;
@@ -960,6 +961,7 @@ static void kernfs_notify_workfn(struct work_struct *work)
iput(inode);
}
+ up_write(&root->kernfs_supers_rwsem);
up_write(&root->kernfs_rwsem);
kernfs_put(kn);
goto repeat;
diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h
index 3297093c920de..a9b854cdfdb5f 100644
--- a/fs/kernfs/kernfs-internal.h
+++ b/fs/kernfs/kernfs-internal.h
@@ -48,6 +48,7 @@ struct kernfs_root {
wait_queue_head_t deactivate_waitq;
struct rw_semaphore kernfs_rwsem;
struct rw_semaphore kernfs_iattr_rwsem;
+ struct rw_semaphore kernfs_supers_rwsem;
};
/* +1 to avoid triggering overflow warning when negating it */
diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
index e08e8d9998070..d49606accb07b 100644
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -351,9 +351,9 @@ int kernfs_get_tree(struct fs_context *fc)
}
sb->s_flags |= SB_ACTIVE;
- down_write(&root->kernfs_rwsem);
+ down_write(&root->kernfs_supers_rwsem);
list_add(&info->node, &info->root->supers);
- up_write(&root->kernfs_rwsem);
+ up_write(&root->kernfs_supers_rwsem);
}
fc->root = dget(sb->s_root);
@@ -380,9 +380,9 @@ void kernfs_kill_sb(struct super_block *sb)
struct kernfs_super_info *info = kernfs_info(sb);
struct kernfs_root *root = info->root;
- down_write(&root->kernfs_rwsem);
+ down_write(&root->kernfs_supers_rwsem);
list_del(&info->node);
- up_write(&root->kernfs_rwsem);
+ up_write(&root->kernfs_supers_rwsem);
/*
* Remove the superblock from fs_supers/s_instances
--
2.34.1
