diff options
| -rw-r--r-- | fs/kernfs/file.c | 17 | ||||
| -rw-r--r-- | fs/kernfs/kernfs-internal.h | 4 | ||||
| -rw-r--r-- | fs/kernfs/mount.c | 19 | ||||
| -rw-r--r-- | include/linux/kernfs.h | 57 |
4 files changed, 83 insertions, 14 deletions
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c index 3b354caad6b5..bb933221b4ba 100644 --- a/fs/kernfs/file.c +++ b/fs/kernfs/file.c @@ -18,19 +18,6 @@ #include "kernfs-internal.h" -/* - * 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. - * - * kernfs_node->attr.open points to kernfs_open_node. attr.open is - * RCU protected. - * - * 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_open_file_mutex. - */ -static DEFINE_MUTEX(kernfs_open_file_mutex); - struct kernfs_open_node { struct rcu_head rcu_head; atomic_t event; @@ -51,7 +38,9 @@ static LLIST_HEAD(kernfs_notify_list); static inline struct mutex *kernfs_open_file_mutex_ptr(struct kernfs_node *kn) { - return &kernfs_open_file_mutex; + int idx = hash_ptr(kn, NR_KERNFS_LOCK_BITS); + + return &kernfs_locks->open_file_mutex[idx]; } static inline struct mutex *kernfs_open_file_mutex_lock(struct kernfs_node *kn) diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h index eeaa779b929c..3ae214d02d44 100644 --- a/fs/kernfs/kernfs-internal.h +++ b/fs/kernfs/kernfs-internal.h @@ -164,4 +164,8 @@ void kernfs_drain_open_files(struct kernfs_node *kn); */ extern const struct inode_operations kernfs_symlink_iops; +/* + * kernfs locks + */ +extern struct kernfs_global_locks *kernfs_locks; #endif /* __KERNFS_INTERNAL_H */ diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c index cfa79715fc1a..d0859f72d2d6 100644 --- a/fs/kernfs/mount.c +++ b/fs/kernfs/mount.c @@ -20,6 +20,7 @@ #include "kernfs-internal.h" struct kmem_cache *kernfs_node_cache, *kernfs_iattrs_cache; +struct kernfs_global_locks *kernfs_locks; static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry) { @@ -387,6 +388,22 @@ void kernfs_kill_sb(struct super_block *sb) kfree(info); } +static void __init kernfs_mutex_init(void) +{ + int count; + + for (count = 0; count < NR_KERNFS_LOCKS; count++) + mutex_init(&kernfs_locks->open_file_mutex[count]); +} + +static void __init kernfs_lock_init(void) +{ + kernfs_locks = kmalloc(sizeof(struct kernfs_global_locks), GFP_KERNEL); + WARN_ON(!kernfs_locks); + + kernfs_mutex_init(); +} + void __init kernfs_init(void) { kernfs_node_cache = kmem_cache_create("kernfs_node_cache", @@ -397,4 +414,6 @@ void __init kernfs_init(void) kernfs_iattrs_cache = kmem_cache_create("kernfs_iattrs_cache", sizeof(struct kernfs_iattrs), 0, SLAB_PANIC, NULL); + + kernfs_lock_init(); } diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h index 2dd9c8df0f4f..13e703f615f7 100644 --- a/include/linux/kernfs.h +++ b/include/linux/kernfs.h @@ -18,6 +18,7 @@ #include <linux/uidgid.h> #include <linux/wait.h> #include <linux/rwsem.h> +#include <linux/cache.h> struct file; struct dentry; @@ -34,6 +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, |