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