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kernfs: Use a per-fs rwsem to protect per-fs list of kernfs_super_info.
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> Link: https://lore.kernel.org/r/20230309110932.2889010-3-imran.f.khan@oracle.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
parent
9caf696142
commit
c9f2dfb7b5
4 changed files with 8 additions and 6 deletions
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@ -944,6 +944,7 @@ struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
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idr_init(&root->ino_idr);
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idr_init(&root->ino_idr);
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init_rwsem(&root->kernfs_rwsem);
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init_rwsem(&root->kernfs_rwsem);
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init_rwsem(&root->kernfs_iattr_rwsem);
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init_rwsem(&root->kernfs_iattr_rwsem);
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init_rwsem(&root->kernfs_supers_rwsem);
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INIT_LIST_HEAD(&root->supers);
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INIT_LIST_HEAD(&root->supers);
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/*
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/*
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@ -922,8 +922,8 @@ repeat:
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root = kernfs_root(kn);
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root = kernfs_root(kn);
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/* kick fsnotify */
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/* kick fsnotify */
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down_write(&root->kernfs_rwsem);
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down_read(&root->kernfs_supers_rwsem);
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list_for_each_entry(info, &kernfs_root(kn)->supers, node) {
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list_for_each_entry(info, &kernfs_root(kn)->supers, node) {
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struct kernfs_node *parent;
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struct kernfs_node *parent;
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struct inode *p_inode = NULL;
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struct inode *p_inode = NULL;
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@ -960,7 +960,7 @@ repeat:
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iput(inode);
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iput(inode);
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}
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}
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up_write(&root->kernfs_rwsem);
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up_read(&root->kernfs_supers_rwsem);
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kernfs_put(kn);
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kernfs_put(kn);
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goto repeat;
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goto repeat;
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}
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}
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@ -48,6 +48,7 @@ struct kernfs_root {
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wait_queue_head_t deactivate_waitq;
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wait_queue_head_t deactivate_waitq;
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struct rw_semaphore kernfs_rwsem;
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struct rw_semaphore kernfs_rwsem;
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struct rw_semaphore kernfs_iattr_rwsem;
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struct rw_semaphore kernfs_iattr_rwsem;
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struct rw_semaphore kernfs_supers_rwsem;
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};
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};
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/* +1 to avoid triggering overflow warning when negating it */
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/* +1 to avoid triggering overflow warning when negating it */
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@ -351,9 +351,9 @@ int kernfs_get_tree(struct fs_context *fc)
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}
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}
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sb->s_flags |= SB_ACTIVE;
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sb->s_flags |= SB_ACTIVE;
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down_write(&root->kernfs_rwsem);
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down_write(&root->kernfs_supers_rwsem);
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list_add(&info->node, &info->root->supers);
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list_add(&info->node, &info->root->supers);
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up_write(&root->kernfs_rwsem);
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up_write(&root->kernfs_supers_rwsem);
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}
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}
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fc->root = dget(sb->s_root);
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fc->root = dget(sb->s_root);
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@ -380,9 +380,9 @@ void kernfs_kill_sb(struct super_block *sb)
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struct kernfs_super_info *info = kernfs_info(sb);
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struct kernfs_super_info *info = kernfs_info(sb);
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struct kernfs_root *root = info->root;
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struct kernfs_root *root = info->root;
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down_write(&root->kernfs_rwsem);
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down_write(&root->kernfs_supers_rwsem);
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list_del(&info->node);
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list_del(&info->node);
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up_write(&root->kernfs_rwsem);
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up_write(&root->kernfs_supers_rwsem);
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/*
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/*
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* Remove the superblock from fs_supers/s_instances
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* Remove the superblock from fs_supers/s_instances
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