/* * Implement the manual drop-all-pagecache function */ #include <linux/kernel.h> #include <linux/mm.h> #include <linux/fs.h> #include <linux/writeback.h> #include <linux/sysctl.h> #include <linux/gfp.h> /* A global variable is a bit ugly, but it keeps the code simple */ int sysctl_drop_caches; static void drop_pagecache_sb(struct super_block *sb) { struct inode *inode, *toput_inode = NULL; spin_lock(&inode_lock); list_for_each_entry(inode, &sb->s_inodes, i_sb_list) { if (inode->i_state & (I_FREEING|I_CLEAR|I_WILL_FREE|I_NEW)) continue; if (inode->i_mapping->nrpages == 0) continue; __iget(inode); spin_unlock(&inode_lock); invalidate_mapping_pages(inode->i_mapping, 0, -1); iput(toput_inode); toput_inode = inode; spin_lock(&inode_lock); } spin_unlock(&inode_lock); iput(toput_inode); } static void drop_pagecache(void) { struct super_block *sb; spin_lock(&sb_lock); restart: list_for_each_entry(sb, &super_blocks, s_list) { sb->s_count++; spin_unlock(&sb_lock); down_read(&sb->s_umount); if (sb->s_root) drop_pagecache_sb(sb); up_read(&sb->s_umount); spin_lock(&sb_lock); if (__put_super_and_need_restart(sb)) goto restart; } spin_unlock(&sb_lock); } static void drop_slab(void) { int nr_objects; do { nr_objects = shrink_slab(1000, GFP_KERNEL, 1000); } while (nr_objects > 10); } int drop_caches_sysctl_handler(ctl_table *table, int write, struct file *file, void __user *buffer, size_t *length, loff_t *ppos) { proc_dointvec_minmax(table, write, file, buffer, length, ppos); if (write) { if (sysctl_drop_caches & 1) drop_pagecache(); if (sysctl_drop_caches & 2) drop_slab(); } return 0; }