diff options
Diffstat (limited to 'include/linux/kernfs.h')
| -rw-r--r-- | include/linux/kernfs.h | 84 |
1 files changed, 66 insertions, 18 deletions
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h index 3ccce6f24548..73f5c120def8 100644 --- a/include/linux/kernfs.h +++ b/include/linux/kernfs.h @@ -6,7 +6,6 @@ #ifndef __LINUX_KERNFS_H #define __LINUX_KERNFS_H -#include <linux/kernel.h> #include <linux/err.h> #include <linux/list.h> #include <linux/mutex.h> @@ -14,14 +13,19 @@ #include <linux/lockdep.h> #include <linux/rbtree.h> #include <linux/atomic.h> +#include <linux/bug.h> +#include <linux/types.h> #include <linux/uidgid.h> #include <linux/wait.h> +#include <linux/rwsem.h> +#include <linux/cache.h> struct file; struct dentry; struct iattr; struct seq_file; struct vm_area_struct; +struct vm_operations_struct; struct super_block; struct file_system_type; struct poll_table_struct; @@ -31,6 +35,62 @@ struct kernfs_fs_context; struct kernfs_open_node; struct kernfs_iattrs; +/* + * NR_KERNFS_LOCK_BITS determines size (NR_KERNFS_LOCKS) of hash + * table of locks. + * Having a small hash table would impact scalability, since + * more and more kernfs_node objects will end up using same lock + * and having a very large hash table would waste memory. + * + * At the moment size of hash table of locks is being set based on + * the number of CPUs as follows: + * + * NR_CPU NR_KERNFS_LOCK_BITS NR_KERNFS_LOCKS + * 1 1 2 + * 2-3 2 4 + * 4-7 4 16 + * 8-15 6 64 + * 16-31 8 256 + * 32 and more 10 1024 + * + * The above relation between NR_CPU and number of locks is based + * on some internal experimentation which involved booting qemu + * with different values of smp, performing some sysfs operations + * on all CPUs and observing how increase in number of locks impacts + * completion time of these sysfs operations on each CPU. + */ +#ifdef CONFIG_SMP +#define NR_KERNFS_LOCK_BITS (2 * (ilog2(NR_CPUS < 32 ? NR_CPUS : 32))) +#else +#define NR_KERNFS_LOCK_BITS 1 +#endif + +#define NR_KERNFS_LOCKS (1 << NR_KERNFS_LOCK_BITS) + +/* + * There's one kernfs_open_file for each open file and one kernfs_open_node + * for each kernfs_node with one or more open files. + * + * filp->private_data points to seq_file whose ->private points to + * kernfs_open_file. + * + * kernfs_open_files are chained at kernfs_open_node->files, which is + * protected by kernfs_global_locks.open_file_mutex[i]. + * + * To reduce possible contention in sysfs access, arising due to single + * locks, use an array of locks (e.g. open_file_mutex) and use kernfs_node + * object address as hash keys to get the index of these locks. + * + * Hashed mutexes are safe to use here because operations using these don't + * rely on global exclusion. + * + * In future we intend to replace other global locks with hashed ones as well. + * kernfs_global_locks acts as a holder for all such hash tables. + */ +struct kernfs_global_locks { + struct mutex open_file_mutex[NR_KERNFS_LOCKS]; +}; + enum kernfs_node_type { KERNFS_DIR = 0x0001, KERNFS_FILE = 0x0002, @@ -48,10 +108,12 @@ enum kernfs_node_flag { KERNFS_HAS_SEQ_SHOW = 0x0040, KERNFS_HAS_MMAP = 0x0080, KERNFS_LOCKDEP = 0x0100, + KERNFS_HIDDEN = 0x0200, KERNFS_SUICIDAL = 0x0400, KERNFS_SUICIDED = 0x0800, KERNFS_EMPTY_DIR = 0x1000, KERNFS_HAS_RELEASE = 0x2000, + KERNFS_REMOVING = 0x4000, }; /* @flags for kernfs_create_root() */ @@ -111,7 +173,7 @@ struct kernfs_elem_symlink { struct kernfs_elem_attr { const struct kernfs_ops *ops; - struct kernfs_open_node *open; + struct kernfs_open_node __rcu *open; loff_t size; struct kernfs_node *notify_next; /* for kernfs_notify() */ }; @@ -182,22 +244,7 @@ struct kernfs_syscall_ops { struct kernfs_root *root); }; -struct kernfs_root { - /* published fields */ - struct kernfs_node *kn; - unsigned int flags; /* KERNFS_ROOT_* flags */ - - /* private fields, do not use outside kernfs proper */ - struct idr ino_idr; - u32 last_id_lowbits; - u32 id_highbits; - struct kernfs_syscall_ops *syscall_ops; - - /* list of kernfs_super_info of this root, protected by kernfs_rwsem */ - struct list_head supers; - - wait_queue_head_t deactivate_waitq; -}; +struct kernfs_node *kernfs_root_to_node(struct kernfs_root *root); struct kernfs_open_file { /* published fields */ @@ -384,6 +431,7 @@ struct kernfs_node *kernfs_create_link(struct kernfs_node *parent, const char *name, struct kernfs_node *target); void kernfs_activate(struct kernfs_node *kn); +void kernfs_show(struct kernfs_node *kn, bool show); void kernfs_remove(struct kernfs_node *kn); void kernfs_break_active_protection(struct kernfs_node *kn); void kernfs_unbreak_active_protection(struct kernfs_node *kn); |