Messages in this thread Patch in this message | | | From | Imran Khan <> | Subject | [RESEND PATCH v7 5/8] kernfs: Use a per-fs rwsem to protect per-fs list of kernfs_super_info. | Date | Thu, 17 Mar 2022 18:26:09 +1100 |
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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@oracle.com> --- fs/kernfs/dir.c | 1 + fs/kernfs/file.c | 2 ++ fs/kernfs/kernfs-internal.h | 1 + fs/kernfs/mount.c | 8 ++++---- include/linux/kernfs.h | 1 + 5 files changed, 9 insertions(+), 4 deletions(-)
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c index 61a8edc4ba8b..17b438498c0b 100644 --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -917,6 +917,7 @@ struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops, idr_init(&root->ino_idr); init_rwsem(&root->kernfs_rwsem); INIT_LIST_HEAD(&root->supers); + init_rwsem(&root->supers_rwsem); /* * On 64bit ino setups, id is ino. On 32bit, low 32bits are ino. diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c index 95426df9f030..07003d47343d 100644 --- a/fs/kernfs/file.c +++ b/fs/kernfs/file.c @@ -854,6 +854,7 @@ static void kernfs_notify_workfn(struct work_struct *work) /* kick fsnotify */ down_write(&root->kernfs_rwsem); + down_write(&root->supers_rwsem); list_for_each_entry(info, &kernfs_root(kn)->supers, node) { struct kernfs_node *parent; struct inode *p_inode = NULL; @@ -889,6 +890,7 @@ static void kernfs_notify_workfn(struct work_struct *work) iput(inode); } + up_write(&root->supers_rwsem); up_write(&root->kernfs_rwsem); kernfs_put(kn); diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h index 25c3329bd60e..6e6398a72578 100644 --- a/fs/kernfs/kernfs-internal.h +++ b/fs/kernfs/kernfs-internal.h @@ -47,6 +47,7 @@ struct kernfs_root { wait_queue_head_t deactivate_waitq; struct rw_semaphore kernfs_rwsem; + struct rw_semaphore supers_rwsem; }; /* +1 to avoid triggering overflow warning when negating it */ diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c index 809b738739b1..d35142226c34 100644 --- a/fs/kernfs/mount.c +++ b/fs/kernfs/mount.c @@ -347,9 +347,9 @@ int kernfs_get_tree(struct fs_context *fc) } sb->s_flags |= SB_ACTIVE; - down_write(&root->kernfs_rwsem); + down_write(&root->supers_rwsem); list_add(&info->node, &info->root->supers); - up_write(&root->kernfs_rwsem); + up_write(&root->supers_rwsem); } fc->root = dget(sb->s_root); @@ -376,9 +376,9 @@ 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->supers_rwsem); list_del(&info->node); - up_write(&root->kernfs_rwsem); + up_write(&root->supers_rwsem); /* * Remove the superblock from fs_supers/s_instances diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h index e82e57c007e9..9f0926f553fc 100644 --- a/include/linux/kernfs.h +++ b/include/linux/kernfs.h @@ -267,6 +267,7 @@ struct kernfs_root { wait_queue_head_t deactivate_waitq; struct rw_semaphore kernfs_rwsem; + struct rw_semaphore supers_rwsem; }; #endif -- 2.30.2
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