fs: scale files_lock
[linux-2.6.git] / fs / file_table.c
index 6f0e62e..a04bdd8 100644 (file)
@@ -20,7 +20,9 @@
 #include <linux/cdev.h>
 #include <linux/fsnotify.h>
 #include <linux/sysctl.h>
+#include <linux/lglock.h>
 #include <linux/percpu_counter.h>
+#include <linux/percpu.h>
 #include <linux/ima.h>
 
 #include <asm/atomic.h>
@@ -32,7 +34,8 @@ struct files_stat_struct files_stat = {
        .max_files = NR_FILE
 };
 
-static __cacheline_aligned_in_smp DEFINE_SPINLOCK(files_lock);
+DECLARE_LGLOCK(files_lglock);
+DEFINE_LGLOCK(files_lglock);
 
 /* SLAB cache for file structures */
 static struct kmem_cache *filp_cachep __read_mostly;
@@ -336,30 +339,98 @@ void put_filp(struct file *file)
        }
 }
 
+static inline int file_list_cpu(struct file *file)
+{
+#ifdef CONFIG_SMP
+       return file->f_sb_list_cpu;
+#else
+       return smp_processor_id();
+#endif
+}
+
+/* helper for file_sb_list_add to reduce ifdefs */
+static inline void __file_sb_list_add(struct file *file, struct super_block *sb)
+{
+       struct list_head *list;
+#ifdef CONFIG_SMP
+       int cpu;
+       cpu = smp_processor_id();
+       file->f_sb_list_cpu = cpu;
+       list = per_cpu_ptr(sb->s_files, cpu);
+#else
+       list = &sb->s_files;
+#endif
+       list_add(&file->f_u.fu_list, list);
+}
+
+/**
+ * file_sb_list_add - add a file to the sb's file list
+ * @file: file to add
+ * @sb: sb to add it to
+ *
+ * Use this function to associate a file with the superblock of the inode it
+ * refers to.
+ */
 void file_sb_list_add(struct file *file, struct super_block *sb)
 {
-       spin_lock(&files_lock);
-       BUG_ON(!list_empty(&file->f_u.fu_list));
-       list_add(&file->f_u.fu_list, &sb->s_files);
-       spin_unlock(&files_lock);
+       lg_local_lock(files_lglock);
+       __file_sb_list_add(file, sb);
+       lg_local_unlock(files_lglock);
 }
 
+/**
+ * file_sb_list_del - remove a file from the sb's file list
+ * @file: file to remove
+ * @sb: sb to remove it from
+ *
+ * Use this function to remove a file from its superblock.
+ */
 void file_sb_list_del(struct file *file)
 {
        if (!list_empty(&file->f_u.fu_list)) {
-               spin_lock(&files_lock);
+               lg_local_lock_cpu(files_lglock, file_list_cpu(file));
                list_del_init(&file->f_u.fu_list);
-               spin_unlock(&files_lock);
+               lg_local_unlock_cpu(files_lglock, file_list_cpu(file));
        }
 }
 
+#ifdef CONFIG_SMP
+
+/*
+ * These macros iterate all files on all CPUs for a given superblock.
+ * files_lglock must be held globally.
+ */
+#define do_file_list_for_each_entry(__sb, __file)              \
+{                                                              \
+       int i;                                                  \
+       for_each_possible_cpu(i) {                              \
+               struct list_head *list;                         \
+               list = per_cpu_ptr((__sb)->s_files, i);         \
+               list_for_each_entry((__file), list, f_u.fu_list)
+
+#define while_file_list_for_each_entry                         \
+       }                                                       \
+}
+
+#else
+
+#define do_file_list_for_each_entry(__sb, __file)              \
+{                                                              \
+       struct list_head *list;                                 \
+       list = &(sb)->s_files;                                  \
+       list_for_each_entry((__file), list, f_u.fu_list)
+
+#define while_file_list_for_each_entry                         \
+}
+
+#endif
+
 int fs_may_remount_ro(struct super_block *sb)
 {
        struct file *file;
-
        /* Check that no files are currently opened for writing. */
-       spin_lock(&files_lock);
-       list_for_each_entry(file, &sb->s_files, f_u.fu_list) {
+       lg_global_lock(files_lglock);
+       do_file_list_for_each_entry(sb, file) {
                struct inode *inode = file->f_path.dentry->d_inode;
 
                /* File with pending delete? */
@@ -369,11 +440,11 @@ int fs_may_remount_ro(struct super_block *sb)
                /* Writeable file? */
                if (S_ISREG(inode->i_mode) && (file->f_mode & FMODE_WRITE))
                        goto too_bad;
-       }
-       spin_unlock(&files_lock);
+       } while_file_list_for_each_entry;
+       lg_global_unlock(files_lglock);
        return 1; /* Tis' cool bro. */
 too_bad:
-       spin_unlock(&files_lock);
+       lg_global_unlock(files_lglock);
        return 0;
 }
 
@@ -389,8 +460,8 @@ void mark_files_ro(struct super_block *sb)
        struct file *f;
 
 retry:
-       spin_lock(&files_lock);
-       list_for_each_entry(f, &sb->s_files, f_u.fu_list) {
+       lg_global_lock(files_lglock);
+       do_file_list_for_each_entry(sb, f) {
                struct vfsmount *mnt;
                if (!S_ISREG(f->f_path.dentry->d_inode->i_mode))
                       continue;
@@ -406,12 +477,12 @@ retry:
                file_release_write(f);
                mnt = mntget(f->f_path.mnt);
                /* This can sleep, so we can't hold the spinlock. */
-               spin_unlock(&files_lock);
+               lg_global_unlock(files_lglock);
                mnt_drop_write(mnt);
                mntput(mnt);
                goto retry;
-       }
-       spin_unlock(&files_lock);
+       } while_file_list_for_each_entry;
+       lg_global_unlock(files_lglock);
 }
 
 void __init files_init(unsigned long mempages)
@@ -431,5 +502,6 @@ void __init files_init(unsigned long mempages)
        if (files_stat.max_files < NR_FILE)
                files_stat.max_files = NR_FILE;
        files_defer_init();
+       lg_lock_init(files_lglock);
        percpu_counter_init(&nr_files, 0);
 }