1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Implement the manual drop-all-pagecache function 4 */ 5 6 #include <linux/pagemap.h> 7 #include <linux/kernel.h> 8 #include <linux/mm.h> 9 #include <linux/fs.h> 10 #include <linux/writeback.h> 11 #include <linux/sysctl.h> 12 #include <linux/gfp.h> 13 #include "internal.h" 14 15 /* A global variable is a bit ugly, but it keeps the code simple */ 16 int sysctl_drop_caches; 17 18 static void drop_pagecache_sb(struct super_block *sb, void *unused) 19 { 20 struct inode *inode, *toput_inode = NULL; 21 22 spin_lock(&sb->s_inode_list_lock); 23 list_for_each_entry(inode, &sb->s_inodes, i_sb_list) { 24 spin_lock(&inode->i_lock); 25 /* 26 * We must skip inodes in unusual state. We may also skip 27 * inodes without pages but we deliberately won't in case 28 * we need to reschedule to avoid softlockups. 29 */ 30 if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) || 31 (mapping_empty(inode->i_mapping) && !need_resched())) { 32 spin_unlock(&inode->i_lock); 33 continue; 34 } 35 __iget(inode); 36 spin_unlock(&inode->i_lock); 37 spin_unlock(&sb->s_inode_list_lock); 38 39 invalidate_mapping_pages(inode->i_mapping, 0, -1); 40 iput(toput_inode); 41 toput_inode = inode; 42 43 cond_resched(); 44 spin_lock(&sb->s_inode_list_lock); 45 } 46 spin_unlock(&sb->s_inode_list_lock); 47 iput(toput_inode); 48 } 49 50 int drop_caches_sysctl_handler(struct ctl_table *table, int write, 51 void *buffer, size_t *length, loff_t *ppos) 52 { 53 int ret; 54 55 ret = proc_dointvec_minmax(table, write, buffer, length, ppos); 56 if (ret) 57 return ret; 58 if (write) { 59 static int stfu; 60 61 if (sysctl_drop_caches & 1) { 62 iterate_supers(drop_pagecache_sb, NULL); 63 count_vm_event(DROP_PAGECACHE); 64 } 65 if (sysctl_drop_caches & 2) { 66 drop_slab(); 67 count_vm_event(DROP_SLAB); 68 } 69 if (!stfu) { 70 pr_info("%s (%d): drop_caches: %d\n", 71 current->comm, task_pid_nr(current), 72 sysctl_drop_caches); 73 } 74 stfu |= sysctl_drop_caches & 4; 75 } 76 return 0; 77 } 78