blob: 68ece4b1891620e99b9f6e18c982deabcc23b5e5 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * fs/fs-writeback.c
3 *
4 * Copyright (C) 2002, Linus Torvalds.
5 *
6 * Contains all the functions related to writing back and waiting
7 * upon dirty inodes against superblocks, and writing back dirty
8 * pages against inodes. ie: data writeback. Writeout of the
9 * inode itself is not handled here.
10 *
Francois Camie1f8e872008-10-15 22:01:59 -070011 * 10Apr2002 Andrew Morton
Linus Torvalds1da177e2005-04-16 15:20:36 -070012 * Split out of fs/inode.c
13 * Additions for address_space-based writeback
14 */
15
16#include <linux/kernel.h>
Jens Axboef5ff8422007-09-21 09:19:54 +020017#include <linux/module.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070018#include <linux/spinlock.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090019#include <linux/slab.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070020#include <linux/sched.h>
21#include <linux/fs.h>
22#include <linux/mm.h>
Jens Axboe03ba3782009-09-09 09:08:54 +020023#include <linux/kthread.h>
24#include <linux/freezer.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070025#include <linux/writeback.h>
26#include <linux/blkdev.h>
27#include <linux/backing-dev.h>
28#include <linux/buffer_head.h>
David Howells07f3f052006-09-30 20:52:18 +020029#include "internal.h"
Linus Torvalds1da177e2005-04-16 15:20:36 -070030
Jens Axboe66f3b8e2009-09-02 09:19:46 +020031#define inode_to_bdi(inode) ((inode)->i_mapping->backing_dev_info)
Adrian Bunkf11b00f2008-04-29 00:58:56 -070032
Jens Axboe03ba3782009-09-09 09:08:54 +020033/*
Jens Axboed0bceac2009-05-18 08:20:32 +020034 * We don't actually have pdflush, but this one is exported though /proc...
35 */
36int nr_pdflush_threads;
37
38/*
Jens Axboec4a77a62009-09-16 15:18:25 +020039 * Passed into wb_writeback(), essentially a subset of writeback_control
40 */
41struct wb_writeback_args {
42 long nr_pages;
43 struct super_block *sb;
44 enum writeback_sync_modes sync_mode;
H Hartley Sweeten52957fe2010-04-01 20:36:30 -050045 unsigned int for_kupdate:1;
46 unsigned int range_cyclic:1;
47 unsigned int for_background:1;
Jens Axboec4a77a62009-09-16 15:18:25 +020048};
49
50/*
Jens Axboe03ba3782009-09-09 09:08:54 +020051 * Work items for the bdi_writeback threads
Adrian Bunkf11b00f2008-04-29 00:58:56 -070052 */
Jens Axboe03ba3782009-09-09 09:08:54 +020053struct bdi_work {
Jens Axboe8010c3b2009-09-15 20:04:57 +020054 struct list_head list; /* pending work list */
55 struct rcu_head rcu_head; /* for RCU free/clear of work */
Jens Axboe03ba3782009-09-09 09:08:54 +020056
Jens Axboe8010c3b2009-09-15 20:04:57 +020057 unsigned long seen; /* threads that have seen this work */
58 atomic_t pending; /* number of threads still to do work */
Jens Axboe03ba3782009-09-09 09:08:54 +020059
Jens Axboe8010c3b2009-09-15 20:04:57 +020060 struct wb_writeback_args args; /* writeback arguments */
Jens Axboe03ba3782009-09-09 09:08:54 +020061
Jens Axboe8010c3b2009-09-15 20:04:57 +020062 unsigned long state; /* flag bits, see WS_* */
Jens Axboe03ba3782009-09-09 09:08:54 +020063};
64
65enum {
Christoph Hellwig7f0e7be2010-06-08 18:14:34 +020066 WS_INPROGRESS = 0,
67 WS_ONSTACK,
Jens Axboe03ba3782009-09-09 09:08:54 +020068};
69
Jens Axboe03ba3782009-09-09 09:08:54 +020070static inline void bdi_work_init(struct bdi_work *work,
Jens Axboeb6e51312009-09-16 15:13:54 +020071 struct wb_writeback_args *args)
Jens Axboe03ba3782009-09-09 09:08:54 +020072{
73 INIT_RCU_HEAD(&work->rcu_head);
Jens Axboeb6e51312009-09-16 15:13:54 +020074 work->args = *args;
Christoph Hellwig7f0e7be2010-06-08 18:14:34 +020075 __set_bit(WS_INPROGRESS, &work->state);
Jens Axboe03ba3782009-09-09 09:08:54 +020076}
77
Adrian Bunkf11b00f2008-04-29 00:58:56 -070078/**
79 * writeback_in_progress - determine whether there is writeback in progress
80 * @bdi: the device's backing_dev_info structure.
81 *
Jens Axboe03ba3782009-09-09 09:08:54 +020082 * Determine whether there is writeback waiting to be handled against a
83 * backing device.
Adrian Bunkf11b00f2008-04-29 00:58:56 -070084 */
85int writeback_in_progress(struct backing_dev_info *bdi)
86{
Jens Axboe03ba3782009-09-09 09:08:54 +020087 return !list_empty(&bdi->work_list);
Adrian Bunkf11b00f2008-04-29 00:58:56 -070088}
89
Jens Axboe03ba3782009-09-09 09:08:54 +020090static void bdi_work_free(struct rcu_head *head)
Nick Piggin4195f732009-05-28 09:01:15 +020091{
Jens Axboe03ba3782009-09-09 09:08:54 +020092 struct bdi_work *work = container_of(head, struct bdi_work, rcu_head);
Nick Piggin4195f732009-05-28 09:01:15 +020093
Christoph Hellwig7f0e7be2010-06-08 18:14:34 +020094 clear_bit(WS_INPROGRESS, &work->state);
95 smp_mb__after_clear_bit();
96 wake_up_bit(&work->state, WS_INPROGRESS);
97
98 if (!test_bit(WS_ONSTACK, &work->state))
Jens Axboe03ba3782009-09-09 09:08:54 +020099 kfree(work);
Jens Axboe03ba3782009-09-09 09:08:54 +0200100}
101
102static void wb_clear_pending(struct bdi_writeback *wb, struct bdi_work *work)
103{
104 /*
105 * The caller has retrieved the work arguments from this work,
106 * drop our reference. If this is the last ref, delete and free it
107 */
108 if (atomic_dec_and_test(&work->pending)) {
109 struct backing_dev_info *bdi = wb->bdi;
110
111 spin_lock(&bdi->wb_lock);
112 list_del_rcu(&work->list);
113 spin_unlock(&bdi->wb_lock);
114
Christoph Hellwig7f0e7be2010-06-08 18:14:34 +0200115 call_rcu(&work->rcu_head, bdi_work_free);
Nick Piggin4195f732009-05-28 09:01:15 +0200116 }
117}
118
Jens Axboe03ba3782009-09-09 09:08:54 +0200119static void bdi_queue_work(struct backing_dev_info *bdi, struct bdi_work *work)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700120{
Jens Axboebcddc3f2009-09-13 20:07:36 +0200121 work->seen = bdi->wb_mask;
122 BUG_ON(!work->seen);
123 atomic_set(&work->pending, bdi->wb_cnt);
124 BUG_ON(!bdi->wb_cnt);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700125
Jens Axboebcddc3f2009-09-13 20:07:36 +0200126 /*
Nick Piggindeed62e2009-09-15 21:32:58 +0200127 * list_add_tail_rcu() contains the necessary barriers to
128 * make sure the above stores are seen before the item is
129 * noticed on the list
Jens Axboebcddc3f2009-09-13 20:07:36 +0200130 */
Jens Axboebcddc3f2009-09-13 20:07:36 +0200131 spin_lock(&bdi->wb_lock);
132 list_add_tail_rcu(&work->list, &bdi->work_list);
133 spin_unlock(&bdi->wb_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700134
135 /*
Jens Axboe03ba3782009-09-09 09:08:54 +0200136 * If the default thread isn't there, make sure we add it. When
137 * it gets created and wakes up, we'll run this work.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700138 */
Jens Axboe03ba3782009-09-09 09:08:54 +0200139 if (unlikely(list_empty_careful(&bdi->wb_list)))
140 wake_up_process(default_backing_dev_info.wb.task);
141 else {
142 struct bdi_writeback *wb = &bdi->wb;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700143
Nick Piggin1ef7d9a2009-09-15 21:37:55 +0200144 if (wb->task)
Jens Axboe03ba3782009-09-09 09:08:54 +0200145 wake_up_process(wb->task);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700146 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700147}
148
Jens Axboe03ba3782009-09-09 09:08:54 +0200149/*
150 * Used for on-stack allocated work items. The caller needs to wait until
151 * the wb threads have acked the work before it's safe to continue.
152 */
Christoph Hellwig7f0e7be2010-06-08 18:14:34 +0200153static void bdi_wait_on_work_done(struct bdi_work *work)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700154{
Christoph Hellwig7f0e7be2010-06-08 18:14:34 +0200155 wait_on_bit(&work->state, WS_INPROGRESS, bdi_sched_wait,
Jens Axboe03ba3782009-09-09 09:08:54 +0200156 TASK_UNINTERRUPTIBLE);
157}
158
Jens Axboef11fcae2009-09-15 09:53:35 +0200159static void bdi_alloc_queue_work(struct backing_dev_info *bdi,
Jens Axboef17625b2010-06-01 11:05:22 +0200160 struct wb_writeback_args *args)
Jens Axboe03ba3782009-09-09 09:08:54 +0200161{
162 struct bdi_work *work;
163
Jens Axboebcddc3f2009-09-13 20:07:36 +0200164 /*
165 * This is WB_SYNC_NONE writeback, so if allocation fails just
166 * wakeup the thread for old dirty data writeback
167 */
Jens Axboe03ba3782009-09-09 09:08:54 +0200168 work = kmalloc(sizeof(*work), GFP_ATOMIC);
Jens Axboebcddc3f2009-09-13 20:07:36 +0200169 if (work) {
Jens Axboeb6e51312009-09-16 15:13:54 +0200170 bdi_work_init(work, args);
Jens Axboebcddc3f2009-09-13 20:07:36 +0200171 bdi_queue_work(bdi, work);
172 } else {
173 struct bdi_writeback *wb = &bdi->wb;
Jens Axboe03ba3782009-09-09 09:08:54 +0200174
Jens Axboebcddc3f2009-09-13 20:07:36 +0200175 if (wb->task)
176 wake_up_process(wb->task);
177 }
Jens Axboe03ba3782009-09-09 09:08:54 +0200178}
179
Jens Axboeb6e51312009-09-16 15:13:54 +0200180/**
Christoph Hellwig3c4d7162010-06-08 18:14:43 +0200181 * bdi_queue_work_onstack - start and wait for writeback
Jens Axboeb6e51312009-09-16 15:13:54 +0200182 * @sb: write inodes from this super_block
183 *
184 * Description:
Christoph Hellwig3c4d7162010-06-08 18:14:43 +0200185 * This function initiates writeback and waits for the operation to
186 * complete. Callers must hold the sb s_umount semaphore for
Jens Axboeb6e51312009-09-16 15:13:54 +0200187 * reading, to avoid having the super disappear before we are done.
188 */
Christoph Hellwig3c4d7162010-06-08 18:14:43 +0200189static void bdi_queue_work_onstack(struct wb_writeback_args *args)
Jens Axboe03ba3782009-09-09 09:08:54 +0200190{
Jens Axboeb6e51312009-09-16 15:13:54 +0200191 struct bdi_work work;
Christoph Hellwigf0fad8a2009-09-11 09:47:56 +0200192
Christoph Hellwig3c4d7162010-06-08 18:14:43 +0200193 bdi_work_init(&work, args);
Christoph Hellwig7f0e7be2010-06-08 18:14:34 +0200194 __set_bit(WS_ONSTACK, &work.state);
Christoph Hellwigf0fad8a2009-09-11 09:47:56 +0200195
Christoph Hellwig3c4d7162010-06-08 18:14:43 +0200196 bdi_queue_work(args->sb->s_bdi, &work);
Christoph Hellwig7f0e7be2010-06-08 18:14:34 +0200197 bdi_wait_on_work_done(&work);
Jens Axboeb6e51312009-09-16 15:13:54 +0200198}
199
200/**
201 * bdi_start_writeback - start writeback
202 * @bdi: the backing device to write from
Jaswinder Singh Rajput4b6764f2010-01-01 20:35:23 -0800203 * @sb: write inodes from this super_block
Jens Axboeb6e51312009-09-16 15:13:54 +0200204 * @nr_pages: the number of pages to write
205 *
206 * Description:
207 * This does WB_SYNC_NONE opportunistic writeback. The IO is only
208 * started when this function returns, we make no guarentees on
Jens Axboe0e3c9a22010-06-01 11:08:43 +0200209 * completion. Caller need not hold sb s_umount semaphore.
Jens Axboeb6e51312009-09-16 15:13:54 +0200210 *
211 */
Jens Axboea72bfd42009-09-26 00:07:46 +0200212void bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
Jens Axboe0e3c9a22010-06-01 11:08:43 +0200213 long nr_pages)
Jens Axboeb6e51312009-09-16 15:13:54 +0200214{
215 struct wb_writeback_args args = {
Jens Axboea72bfd42009-09-26 00:07:46 +0200216 .sb = sb,
Jens Axboeb6e51312009-09-16 15:13:54 +0200217 .sync_mode = WB_SYNC_NONE,
218 .nr_pages = nr_pages,
219 .range_cyclic = 1,
220 };
221
Wu Fengguangd3ddec72009-09-23 20:33:40 +0800222 /*
223 * We treat @nr_pages=0 as the special case to do background writeback,
224 * ie. to sync pages until the background dirty threshold is reached.
225 */
226 if (!nr_pages) {
227 args.nr_pages = LONG_MAX;
228 args.for_background = 1;
229 }
230
Jens Axboef17625b2010-06-01 11:05:22 +0200231 bdi_alloc_queue_work(bdi, &args);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700232}
233
234/*
Andrew Morton6610a0b2007-10-16 23:30:32 -0700235 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
236 * furthest end of its superblock's dirty-inode list.
237 *
238 * Before stamping the inode's ->dirtied_when, we check to see whether it is
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200239 * already the most-recently-dirtied inode on the b_dirty list. If that is
Andrew Morton6610a0b2007-10-16 23:30:32 -0700240 * the case then the inode must have been redirtied while it was being written
241 * out and we don't reset its dirtied_when.
242 */
243static void redirty_tail(struct inode *inode)
244{
Jens Axboe03ba3782009-09-09 09:08:54 +0200245 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
Andrew Morton6610a0b2007-10-16 23:30:32 -0700246
Jens Axboe03ba3782009-09-09 09:08:54 +0200247 if (!list_empty(&wb->b_dirty)) {
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200248 struct inode *tail;
Andrew Morton6610a0b2007-10-16 23:30:32 -0700249
Jens Axboe03ba3782009-09-09 09:08:54 +0200250 tail = list_entry(wb->b_dirty.next, struct inode, i_list);
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200251 if (time_before(inode->dirtied_when, tail->dirtied_when))
Andrew Morton6610a0b2007-10-16 23:30:32 -0700252 inode->dirtied_when = jiffies;
253 }
Jens Axboe03ba3782009-09-09 09:08:54 +0200254 list_move(&inode->i_list, &wb->b_dirty);
Andrew Morton6610a0b2007-10-16 23:30:32 -0700255}
256
257/*
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200258 * requeue inode for re-scanning after bdi->b_io list is exhausted.
Andrew Mortonc986d1e2007-10-16 23:30:34 -0700259 */
Ken Chen0e0f4fc2007-10-16 23:30:38 -0700260static void requeue_io(struct inode *inode)
Andrew Mortonc986d1e2007-10-16 23:30:34 -0700261{
Jens Axboe03ba3782009-09-09 09:08:54 +0200262 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
263
264 list_move(&inode->i_list, &wb->b_more_io);
Andrew Mortonc986d1e2007-10-16 23:30:34 -0700265}
266
Joern Engel1c0eeaf2007-10-16 23:30:44 -0700267static void inode_sync_complete(struct inode *inode)
268{
269 /*
270 * Prevent speculative execution through spin_unlock(&inode_lock);
271 */
272 smp_mb();
273 wake_up_bit(&inode->i_state, __I_SYNC);
274}
275
Jeff Laytond2caa3c52009-04-02 16:56:37 -0700276static bool inode_dirtied_after(struct inode *inode, unsigned long t)
277{
278 bool ret = time_after(inode->dirtied_when, t);
279#ifndef CONFIG_64BIT
280 /*
281 * For inodes being constantly redirtied, dirtied_when can get stuck.
282 * It _appears_ to be in the future, but is actually in distant past.
283 * This test is necessary to prevent such wrapped-around relative times
Jens Axboe5b0830c2009-09-23 19:37:09 +0200284 * from permanently stopping the whole bdi writeback.
Jeff Laytond2caa3c52009-04-02 16:56:37 -0700285 */
286 ret = ret && time_before_eq(inode->dirtied_when, jiffies);
287#endif
288 return ret;
289}
290
Andrew Mortonc986d1e2007-10-16 23:30:34 -0700291/*
Fengguang Wu2c136572007-10-16 23:30:39 -0700292 * Move expired dirty inodes from @delaying_queue to @dispatch_queue.
293 */
294static void move_expired_inodes(struct list_head *delaying_queue,
295 struct list_head *dispatch_queue,
296 unsigned long *older_than_this)
297{
Shaohua Li5c034492009-09-24 14:42:33 +0200298 LIST_HEAD(tmp);
299 struct list_head *pos, *node;
Jens Axboecf137302009-09-24 15:12:57 +0200300 struct super_block *sb = NULL;
Shaohua Li5c034492009-09-24 14:42:33 +0200301 struct inode *inode;
Jens Axboecf137302009-09-24 15:12:57 +0200302 int do_sb_sort = 0;
Shaohua Li5c034492009-09-24 14:42:33 +0200303
Fengguang Wu2c136572007-10-16 23:30:39 -0700304 while (!list_empty(delaying_queue)) {
Shaohua Li5c034492009-09-24 14:42:33 +0200305 inode = list_entry(delaying_queue->prev, struct inode, i_list);
Fengguang Wu2c136572007-10-16 23:30:39 -0700306 if (older_than_this &&
Jeff Laytond2caa3c52009-04-02 16:56:37 -0700307 inode_dirtied_after(inode, *older_than_this))
Fengguang Wu2c136572007-10-16 23:30:39 -0700308 break;
Jens Axboecf137302009-09-24 15:12:57 +0200309 if (sb && sb != inode->i_sb)
310 do_sb_sort = 1;
311 sb = inode->i_sb;
Shaohua Li5c034492009-09-24 14:42:33 +0200312 list_move(&inode->i_list, &tmp);
313 }
314
Jens Axboecf137302009-09-24 15:12:57 +0200315 /* just one sb in list, splice to dispatch_queue and we're done */
316 if (!do_sb_sort) {
317 list_splice(&tmp, dispatch_queue);
318 return;
319 }
320
Shaohua Li5c034492009-09-24 14:42:33 +0200321 /* Move inodes from one superblock together */
322 while (!list_empty(&tmp)) {
323 inode = list_entry(tmp.prev, struct inode, i_list);
324 sb = inode->i_sb;
325 list_for_each_prev_safe(pos, node, &tmp) {
326 inode = list_entry(pos, struct inode, i_list);
327 if (inode->i_sb == sb)
328 list_move(&inode->i_list, dispatch_queue);
329 }
Fengguang Wu2c136572007-10-16 23:30:39 -0700330 }
331}
332
333/*
334 * Queue all expired dirty inodes for io, eldest first.
335 */
Jens Axboe03ba3782009-09-09 09:08:54 +0200336static void queue_io(struct bdi_writeback *wb, unsigned long *older_than_this)
Fengguang Wu2c136572007-10-16 23:30:39 -0700337{
Jens Axboe03ba3782009-09-09 09:08:54 +0200338 list_splice_init(&wb->b_more_io, wb->b_io.prev);
339 move_expired_inodes(&wb->b_dirty, &wb->b_io, older_than_this);
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200340}
341
Christoph Hellwiga9185b42010-03-05 09:21:37 +0100342static int write_inode(struct inode *inode, struct writeback_control *wbc)
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200343{
Jens Axboe03ba3782009-09-09 09:08:54 +0200344 if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode))
Christoph Hellwiga9185b42010-03-05 09:21:37 +0100345 return inode->i_sb->s_op->write_inode(inode, wbc);
Jens Axboe03ba3782009-09-09 09:08:54 +0200346 return 0;
Fengguang Wu2c136572007-10-16 23:30:39 -0700347}
348
349/*
Christoph Hellwig01c03192009-06-08 13:35:40 +0200350 * Wait for writeback on an inode to complete.
351 */
352static void inode_wait_for_writeback(struct inode *inode)
353{
354 DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
355 wait_queue_head_t *wqh;
356
357 wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
Richard Kennedy58a9d3d82010-05-24 14:32:38 -0700358 while (inode->i_state & I_SYNC) {
Christoph Hellwig01c03192009-06-08 13:35:40 +0200359 spin_unlock(&inode_lock);
360 __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
361 spin_lock(&inode_lock);
Richard Kennedy58a9d3d82010-05-24 14:32:38 -0700362 }
Christoph Hellwig01c03192009-06-08 13:35:40 +0200363}
364
365/*
366 * Write out an inode's dirty pages. Called under inode_lock. Either the
367 * caller has ref on the inode (either via __iget or via syscall against an fd)
368 * or the inode has I_WILL_FREE set (via generic_forget_inode)
369 *
Linus Torvalds1da177e2005-04-16 15:20:36 -0700370 * If `wait' is set, wait on the writeout.
371 *
372 * The whole writeout design is quite complex and fragile. We want to avoid
373 * starvation of particular inodes when others are being redirtied, prevent
374 * livelocks, etc.
375 *
376 * Called under inode_lock.
377 */
378static int
Christoph Hellwig01c03192009-06-08 13:35:40 +0200379writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700380{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700381 struct address_space *mapping = inode->i_mapping;
Christoph Hellwig01c03192009-06-08 13:35:40 +0200382 unsigned dirty;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700383 int ret;
384
Christoph Hellwig01c03192009-06-08 13:35:40 +0200385 if (!atomic_read(&inode->i_count))
386 WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
387 else
388 WARN_ON(inode->i_state & I_WILL_FREE);
389
390 if (inode->i_state & I_SYNC) {
391 /*
392 * If this inode is locked for writeback and we are not doing
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200393 * writeback-for-data-integrity, move it to b_more_io so that
Christoph Hellwig01c03192009-06-08 13:35:40 +0200394 * writeback can proceed with the other inodes on s_io.
395 *
396 * We'll have another go at writing back this inode when we
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200397 * completed a full scan of b_io.
Christoph Hellwig01c03192009-06-08 13:35:40 +0200398 */
Christoph Hellwiga9185b42010-03-05 09:21:37 +0100399 if (wbc->sync_mode != WB_SYNC_ALL) {
Christoph Hellwig01c03192009-06-08 13:35:40 +0200400 requeue_io(inode);
401 return 0;
402 }
403
404 /*
405 * It's a data-integrity sync. We must wait.
406 */
407 inode_wait_for_writeback(inode);
408 }
409
Joern Engel1c0eeaf2007-10-16 23:30:44 -0700410 BUG_ON(inode->i_state & I_SYNC);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700411
Dmitry Monakhov5547e8a2010-05-07 13:35:44 +0400412 /* Set I_SYNC, reset I_DIRTY_PAGES */
Joern Engel1c0eeaf2007-10-16 23:30:44 -0700413 inode->i_state |= I_SYNC;
Dmitry Monakhov5547e8a2010-05-07 13:35:44 +0400414 inode->i_state &= ~I_DIRTY_PAGES;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700415 spin_unlock(&inode_lock);
416
417 ret = do_writepages(mapping, wbc);
418
Christoph Hellwig26821ed2010-03-05 09:21:21 +0100419 /*
420 * Make sure to wait on the data before writing out the metadata.
421 * This is important for filesystems that modify metadata on data
422 * I/O completion.
423 */
Christoph Hellwiga9185b42010-03-05 09:21:37 +0100424 if (wbc->sync_mode == WB_SYNC_ALL) {
Christoph Hellwig26821ed2010-03-05 09:21:21 +0100425 int err = filemap_fdatawait(mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700426 if (ret == 0)
427 ret = err;
428 }
429
Dmitry Monakhov5547e8a2010-05-07 13:35:44 +0400430 /*
431 * Some filesystems may redirty the inode during the writeback
432 * due to delalloc, clear dirty metadata flags right before
433 * write_inode()
434 */
435 spin_lock(&inode_lock);
436 dirty = inode->i_state & I_DIRTY;
437 inode->i_state &= ~(I_DIRTY_SYNC | I_DIRTY_DATASYNC);
438 spin_unlock(&inode_lock);
Christoph Hellwig26821ed2010-03-05 09:21:21 +0100439 /* Don't write the inode if only I_DIRTY_PAGES was set */
440 if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
Christoph Hellwiga9185b42010-03-05 09:21:37 +0100441 int err = write_inode(inode, wbc);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700442 if (ret == 0)
443 ret = err;
444 }
445
446 spin_lock(&inode_lock);
Joern Engel1c0eeaf2007-10-16 23:30:44 -0700447 inode->i_state &= ~I_SYNC;
Wu Fengguang84a89242009-06-16 15:33:17 -0700448 if (!(inode->i_state & (I_FREEING | I_CLEAR))) {
Wu Fengguangb3af9462009-09-25 06:04:10 +0200449 if ((inode->i_state & I_DIRTY_PAGES) && wbc->for_kupdate) {
Wu Fengguangae1b7f72009-09-23 20:33:42 +0800450 /*
Wu Fengguangb3af9462009-09-25 06:04:10 +0200451 * More pages get dirtied by a fast dirtier.
452 */
453 goto select_queue;
454 } else if (inode->i_state & I_DIRTY) {
455 /*
456 * At least XFS will redirty the inode during the
457 * writeback (delalloc) and on io completion (isize).
Wu Fengguangae1b7f72009-09-23 20:33:42 +0800458 */
459 redirty_tail(inode);
460 } else if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700461 /*
462 * We didn't write back all the pages. nfs_writepages()
463 * sometimes bales out without doing anything. Redirty
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200464 * the inode; Move it from b_io onto b_more_io/b_dirty.
Andrew Morton1b43ef92007-10-16 23:30:35 -0700465 */
466 /*
467 * akpm: if the caller was the kupdate function we put
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200468 * this inode at the head of b_dirty so it gets first
Andrew Morton1b43ef92007-10-16 23:30:35 -0700469 * consideration. Otherwise, move it to the tail, for
470 * the reasons described there. I'm not really sure
471 * how much sense this makes. Presumably I had a good
472 * reasons for doing it this way, and I'd rather not
473 * muck with it at present.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700474 */
475 if (wbc->for_kupdate) {
476 /*
Fengguang Wu2c136572007-10-16 23:30:39 -0700477 * For the kupdate function we move the inode
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200478 * to b_more_io so it will get more writeout as
Fengguang Wu2c136572007-10-16 23:30:39 -0700479 * soon as the queue becomes uncongested.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700480 */
481 inode->i_state |= I_DIRTY_PAGES;
Wu Fengguangb3af9462009-09-25 06:04:10 +0200482select_queue:
Fengguang Wu8bc3be22008-02-04 22:29:36 -0800483 if (wbc->nr_to_write <= 0) {
484 /*
485 * slice used up: queue for next turn
486 */
487 requeue_io(inode);
488 } else {
489 /*
490 * somehow blocked: retry later
491 */
492 redirty_tail(inode);
493 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700494 } else {
495 /*
496 * Otherwise fully redirty the inode so that
497 * other inodes on this superblock will get some
498 * writeout. Otherwise heavy writing to one
499 * file would indefinitely suspend writeout of
500 * all the other files.
501 */
502 inode->i_state |= I_DIRTY_PAGES;
Andrew Morton1b43ef92007-10-16 23:30:35 -0700503 redirty_tail(inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700504 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700505 } else if (atomic_read(&inode->i_count)) {
506 /*
507 * The inode is clean, inuse
508 */
509 list_move(&inode->i_list, &inode_in_use);
510 } else {
511 /*
512 * The inode is clean, unused
513 */
514 list_move(&inode->i_list, &inode_unused);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700515 }
516 }
Joern Engel1c0eeaf2007-10-16 23:30:44 -0700517 inode_sync_complete(inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700518 return ret;
519}
520
Jens Axboe03ba3782009-09-09 09:08:54 +0200521/*
Christoph Hellwigd19de7e2010-06-08 18:14:58 +0200522 * For background writeback the caller does not have the sb pinned
Jens Axboe03ba3782009-09-09 09:08:54 +0200523 * before calling writeback. So make sure that we do pin it, so it doesn't
524 * go away while we are writing inodes from it.
Jens Axboe03ba3782009-09-09 09:08:54 +0200525 */
Christoph Hellwigd19de7e2010-06-08 18:14:58 +0200526static bool pin_sb_for_writeback(struct super_block *sb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700527{
Jens Axboe03ba3782009-09-09 09:08:54 +0200528 spin_lock(&sb_lock);
529 sb->s_count++;
530 if (down_read_trylock(&sb->s_umount)) {
531 if (sb->s_root) {
532 spin_unlock(&sb_lock);
Christoph Hellwigd19de7e2010-06-08 18:14:58 +0200533 return true;
Jens Axboe03ba3782009-09-09 09:08:54 +0200534 }
535 /*
536 * umounted, drop rwsem again and fall through to failure
537 */
538 up_read(&sb->s_umount);
539 }
Jens Axboe03ba3782009-09-09 09:08:54 +0200540 sb->s_count--;
541 spin_unlock(&sb_lock);
Christoph Hellwigd19de7e2010-06-08 18:14:58 +0200542 return false;
Jens Axboe03ba3782009-09-09 09:08:54 +0200543}
544
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800545/*
546 * Write a portion of b_io inodes which belong to @sb.
547 * If @wbc->sb != NULL, then find and write all such
548 * inodes. Otherwise write only ones which go sequentially
549 * in reverse order.
550 * Return 1, if the caller writeback routine should be
551 * interrupted. Otherwise return 0.
552 */
553static int writeback_sb_inodes(struct super_block *sb,
554 struct bdi_writeback *wb,
555 struct writeback_control *wbc)
Jens Axboe03ba3782009-09-09 09:08:54 +0200556{
Jens Axboe03ba3782009-09-09 09:08:54 +0200557 while (!list_empty(&wb->b_io)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700558 long pages_skipped;
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800559 struct inode *inode = list_entry(wb->b_io.prev,
560 struct inode, i_list);
561 if (wbc->sb && sb != inode->i_sb) {
562 /* super block given and doesn't
563 match, skip this inode */
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200564 redirty_tail(inode);
565 continue;
566 }
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800567 if (sb != inode->i_sb)
568 /* finish with this superblock */
569 return 0;
Wu Fengguang84a89242009-06-16 15:33:17 -0700570 if (inode->i_state & (I_NEW | I_WILL_FREE)) {
Nick Piggin7ef0d732009-03-12 14:31:38 -0700571 requeue_io(inode);
572 continue;
573 }
Jeff Laytond2caa3c52009-04-02 16:56:37 -0700574 /*
575 * Was this inode dirtied after sync_sb_inodes was called?
576 * This keeps sync from extra jobs and livelock.
577 */
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800578 if (inode_dirtied_after(inode, wbc->wb_start))
579 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700580
Wu Fengguang84a89242009-06-16 15:33:17 -0700581 BUG_ON(inode->i_state & (I_FREEING | I_CLEAR));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700582 __iget(inode);
583 pages_skipped = wbc->pages_skipped;
Christoph Hellwig01c03192009-06-08 13:35:40 +0200584 writeback_single_inode(inode, wbc);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700585 if (wbc->pages_skipped != pages_skipped) {
586 /*
587 * writeback is not making progress due to locked
588 * buffers. Skip this inode for now.
589 */
Andrew Mortonf57b9b72007-10-16 23:30:34 -0700590 redirty_tail(inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700591 }
592 spin_unlock(&inode_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700593 iput(inode);
OGAWA Hirofumi4ffc8442006-03-25 03:07:44 -0800594 cond_resched();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700595 spin_lock(&inode_lock);
Fengguang Wu8bc3be22008-02-04 22:29:36 -0800596 if (wbc->nr_to_write <= 0) {
597 wbc->more_io = 1;
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800598 return 1;
Fengguang Wu8bc3be22008-02-04 22:29:36 -0800599 }
Jens Axboe03ba3782009-09-09 09:08:54 +0200600 if (!list_empty(&wb->b_more_io))
Fengguang Wu8bc3be22008-02-04 22:29:36 -0800601 wbc->more_io = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700602 }
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800603 /* b_io is empty */
604 return 1;
605}
Nick Piggin38f21972009-01-06 14:40:25 -0800606
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800607static void writeback_inodes_wb(struct bdi_writeback *wb,
608 struct writeback_control *wbc)
609{
610 int ret = 0;
Jens Axboe9ecc2732009-09-24 15:25:11 +0200611
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800612 wbc->wb_start = jiffies; /* livelock avoidance */
613 spin_lock(&inode_lock);
614 if (!wbc->for_kupdate || list_empty(&wb->b_io))
615 queue_io(wb, wbc->older_than_this);
616
617 while (!list_empty(&wb->b_io)) {
618 struct inode *inode = list_entry(wb->b_io.prev,
619 struct inode, i_list);
620 struct super_block *sb = inode->i_sb;
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800621
Christoph Hellwigd19de7e2010-06-08 18:14:58 +0200622 if (wbc->sb) {
623 /*
624 * We are requested to write out inodes for a specific
625 * superblock. This means we already have s_umount
626 * taken by the caller which also waits for us to
627 * complete the writeout.
628 */
629 if (sb != wbc->sb) {
630 redirty_tail(inode);
631 continue;
632 }
633
634 WARN_ON(!rwsem_is_locked(&sb->s_umount));
635
636 ret = writeback_sb_inodes(sb, wb, wbc);
637 } else {
638 if (!pin_sb_for_writeback(sb))
639 continue;
640 ret = writeback_sb_inodes(sb, wb, wbc);
641 drop_super(sb);
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800642 }
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800643
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800644 if (ret)
645 break;
646 }
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200647 spin_unlock(&inode_lock);
648 /* Leave any unwritten inodes on b_io */
649}
650
Jens Axboe03ba3782009-09-09 09:08:54 +0200651void writeback_inodes_wbc(struct writeback_control *wbc)
652{
653 struct backing_dev_info *bdi = wbc->bdi;
654
655 writeback_inodes_wb(&bdi->wb, wbc);
656}
657
658/*
659 * The maximum number of pages to writeout in a single bdi flush/kupdate
660 * operation. We do this so we don't hold I_SYNC against an inode for
661 * enormous amounts of time, which would block a userspace task which has
662 * been forced to throttle against that inode. Also, the code reevaluates
663 * the dirty each time it has written this many pages.
664 */
665#define MAX_WRITEBACK_PAGES 1024
666
667static inline bool over_bground_thresh(void)
668{
669 unsigned long background_thresh, dirty_thresh;
670
671 get_dirty_limits(&background_thresh, &dirty_thresh, NULL, NULL);
672
673 return (global_page_state(NR_FILE_DIRTY) +
674 global_page_state(NR_UNSTABLE_NFS) >= background_thresh);
675}
676
677/*
678 * Explicit flushing or periodic writeback of "old" data.
679 *
680 * Define "old": the first time one of an inode's pages is dirtied, we mark the
681 * dirtying-time in the inode's address_space. So this periodic writeback code
682 * just walks the superblock inode list, writing back any inodes which are
683 * older than a specific point in time.
684 *
685 * Try to run once per dirty_writeback_interval. But if a writeback event
686 * takes longer than a dirty_writeback_interval interval, then leave a
687 * one-second gap.
688 *
689 * older_than_this takes precedence over nr_to_write. So we'll only write back
690 * all dirty pages if they are all attached to "old" mappings.
691 */
Jens Axboec4a77a62009-09-16 15:18:25 +0200692static long wb_writeback(struct bdi_writeback *wb,
693 struct wb_writeback_args *args)
Jens Axboe03ba3782009-09-09 09:08:54 +0200694{
695 struct writeback_control wbc = {
696 .bdi = wb->bdi,
Jens Axboec4a77a62009-09-16 15:18:25 +0200697 .sb = args->sb,
698 .sync_mode = args->sync_mode,
Jens Axboe03ba3782009-09-09 09:08:54 +0200699 .older_than_this = NULL,
Jens Axboec4a77a62009-09-16 15:18:25 +0200700 .for_kupdate = args->for_kupdate,
Wu Fengguangb17621f2009-12-03 13:54:25 +0100701 .for_background = args->for_background,
Jens Axboec4a77a62009-09-16 15:18:25 +0200702 .range_cyclic = args->range_cyclic,
Jens Axboe03ba3782009-09-09 09:08:54 +0200703 };
704 unsigned long oldest_jif;
705 long wrote = 0;
Jan Karaa5989bd2009-09-16 19:22:48 +0200706 struct inode *inode;
Jens Axboe03ba3782009-09-09 09:08:54 +0200707
708 if (wbc.for_kupdate) {
709 wbc.older_than_this = &oldest_jif;
710 oldest_jif = jiffies -
711 msecs_to_jiffies(dirty_expire_interval * 10);
712 }
Jens Axboec4a77a62009-09-16 15:18:25 +0200713 if (!wbc.range_cyclic) {
714 wbc.range_start = 0;
715 wbc.range_end = LLONG_MAX;
716 }
Jens Axboe03ba3782009-09-09 09:08:54 +0200717
718 for (;;) {
719 /*
Wu Fengguangd3ddec72009-09-23 20:33:40 +0800720 * Stop writeback when nr_pages has been consumed
Jens Axboe03ba3782009-09-09 09:08:54 +0200721 */
Wu Fengguangd3ddec72009-09-23 20:33:40 +0800722 if (args->nr_pages <= 0)
Jens Axboe03ba3782009-09-09 09:08:54 +0200723 break;
724
725 /*
Wu Fengguangd3ddec72009-09-23 20:33:40 +0800726 * For background writeout, stop when we are below the
727 * background dirty threshold
Jens Axboe03ba3782009-09-09 09:08:54 +0200728 */
Wu Fengguangd3ddec72009-09-23 20:33:40 +0800729 if (args->for_background && !over_bground_thresh())
Jens Axboe03ba3782009-09-09 09:08:54 +0200730 break;
731
732 wbc.more_io = 0;
Jens Axboe03ba3782009-09-09 09:08:54 +0200733 wbc.nr_to_write = MAX_WRITEBACK_PAGES;
734 wbc.pages_skipped = 0;
735 writeback_inodes_wb(wb, &wbc);
Jens Axboec4a77a62009-09-16 15:18:25 +0200736 args->nr_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
Jens Axboe03ba3782009-09-09 09:08:54 +0200737 wrote += MAX_WRITEBACK_PAGES - wbc.nr_to_write;
738
739 /*
Jens Axboe71fd05a2009-09-23 19:32:26 +0200740 * If we consumed everything, see if we have more
Jens Axboe03ba3782009-09-09 09:08:54 +0200741 */
Jens Axboe71fd05a2009-09-23 19:32:26 +0200742 if (wbc.nr_to_write <= 0)
743 continue;
744 /*
745 * Didn't write everything and we don't have more IO, bail
746 */
747 if (!wbc.more_io)
Jens Axboe03ba3782009-09-09 09:08:54 +0200748 break;
Jens Axboe71fd05a2009-09-23 19:32:26 +0200749 /*
750 * Did we write something? Try for more
751 */
752 if (wbc.nr_to_write < MAX_WRITEBACK_PAGES)
753 continue;
754 /*
755 * Nothing written. Wait for some inode to
756 * become available for writeback. Otherwise
757 * we'll just busyloop.
758 */
759 spin_lock(&inode_lock);
760 if (!list_empty(&wb->b_more_io)) {
761 inode = list_entry(wb->b_more_io.prev,
762 struct inode, i_list);
763 inode_wait_for_writeback(inode);
Jens Axboe03ba3782009-09-09 09:08:54 +0200764 }
Jens Axboe71fd05a2009-09-23 19:32:26 +0200765 spin_unlock(&inode_lock);
Jens Axboe03ba3782009-09-09 09:08:54 +0200766 }
767
768 return wrote;
769}
770
771/*
772 * Return the next bdi_work struct that hasn't been processed by this
Jens Axboe8010c3b2009-09-15 20:04:57 +0200773 * wb thread yet. ->seen is initially set for each thread that exists
774 * for this device, when a thread first notices a piece of work it
775 * clears its bit. Depending on writeback type, the thread will notify
776 * completion on either receiving the work (WB_SYNC_NONE) or after
777 * it is done (WB_SYNC_ALL).
Jens Axboe03ba3782009-09-09 09:08:54 +0200778 */
779static struct bdi_work *get_next_work_item(struct backing_dev_info *bdi,
780 struct bdi_writeback *wb)
781{
782 struct bdi_work *work, *ret = NULL;
783
784 rcu_read_lock();
785
786 list_for_each_entry_rcu(work, &bdi->work_list, list) {
Nick Piggin77fad5e2009-09-15 21:34:12 +0200787 if (!test_bit(wb->nr, &work->seen))
Jens Axboe03ba3782009-09-09 09:08:54 +0200788 continue;
Nick Piggin77fad5e2009-09-15 21:34:12 +0200789 clear_bit(wb->nr, &work->seen);
Jens Axboe03ba3782009-09-09 09:08:54 +0200790
791 ret = work;
792 break;
793 }
794
795 rcu_read_unlock();
796 return ret;
797}
798
799static long wb_check_old_data_flush(struct bdi_writeback *wb)
800{
801 unsigned long expired;
802 long nr_pages;
803
Jens Axboe69b62d02010-05-17 12:51:03 +0200804 /*
805 * When set to zero, disable periodic writeback
806 */
807 if (!dirty_writeback_interval)
808 return 0;
809
Jens Axboe03ba3782009-09-09 09:08:54 +0200810 expired = wb->last_old_flush +
811 msecs_to_jiffies(dirty_writeback_interval * 10);
812 if (time_before(jiffies, expired))
813 return 0;
814
815 wb->last_old_flush = jiffies;
816 nr_pages = global_page_state(NR_FILE_DIRTY) +
817 global_page_state(NR_UNSTABLE_NFS) +
818 (inodes_stat.nr_inodes - inodes_stat.nr_unused);
819
Jens Axboec4a77a62009-09-16 15:18:25 +0200820 if (nr_pages) {
821 struct wb_writeback_args args = {
822 .nr_pages = nr_pages,
823 .sync_mode = WB_SYNC_NONE,
824 .for_kupdate = 1,
825 .range_cyclic = 1,
826 };
827
828 return wb_writeback(wb, &args);
829 }
Jens Axboe03ba3782009-09-09 09:08:54 +0200830
831 return 0;
832}
833
834/*
835 * Retrieve work items and do the writeback they describe
836 */
837long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
838{
839 struct backing_dev_info *bdi = wb->bdi;
840 struct bdi_work *work;
Jens Axboec4a77a62009-09-16 15:18:25 +0200841 long wrote = 0;
Jens Axboe03ba3782009-09-09 09:08:54 +0200842
843 while ((work = get_next_work_item(bdi, wb)) != NULL) {
Jens Axboec4a77a62009-09-16 15:18:25 +0200844 struct wb_writeback_args args = work->args;
Jens Axboe03ba3782009-09-09 09:08:54 +0200845
846 /*
847 * Override sync mode, in case we must wait for completion
848 */
849 if (force_wait)
Jens Axboec4a77a62009-09-16 15:18:25 +0200850 work->args.sync_mode = args.sync_mode = WB_SYNC_ALL;
Jens Axboe03ba3782009-09-09 09:08:54 +0200851
852 /*
853 * If this isn't a data integrity operation, just notify
854 * that we have seen this work and we are now starting it.
855 */
Christoph Hellwig7f0e7be2010-06-08 18:14:34 +0200856 if (!test_bit(WS_ONSTACK, &work->state))
Jens Axboe03ba3782009-09-09 09:08:54 +0200857 wb_clear_pending(wb, work);
858
Jens Axboec4a77a62009-09-16 15:18:25 +0200859 wrote += wb_writeback(wb, &args);
Jens Axboe03ba3782009-09-09 09:08:54 +0200860
861 /*
862 * This is a data integrity writeback, so only do the
863 * notification when we have completed the work.
864 */
Christoph Hellwig7f0e7be2010-06-08 18:14:34 +0200865 if (test_bit(WS_ONSTACK, &work->state))
Jens Axboe03ba3782009-09-09 09:08:54 +0200866 wb_clear_pending(wb, work);
867 }
868
869 /*
870 * Check for periodic writeback, kupdated() style
871 */
872 wrote += wb_check_old_data_flush(wb);
873
874 return wrote;
875}
876
877/*
878 * Handle writeback of dirty data for the device backed by this bdi. Also
879 * wakes up periodically and does kupdated style flushing.
880 */
881int bdi_writeback_task(struct bdi_writeback *wb)
882{
883 unsigned long last_active = jiffies;
884 unsigned long wait_jiffies = -1UL;
885 long pages_written;
886
887 while (!kthread_should_stop()) {
888 pages_written = wb_do_writeback(wb, 0);
889
890 if (pages_written)
891 last_active = jiffies;
892 else if (wait_jiffies != -1UL) {
893 unsigned long max_idle;
894
895 /*
896 * Longest period of inactivity that we tolerate. If we
897 * see dirty data again later, the task will get
898 * recreated automatically.
899 */
900 max_idle = max(5UL * 60 * HZ, wait_jiffies);
901 if (time_after(jiffies, max_idle + last_active))
902 break;
903 }
904
Jens Axboe69b62d02010-05-17 12:51:03 +0200905 if (dirty_writeback_interval) {
906 wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10);
907 schedule_timeout_interruptible(wait_jiffies);
Jens Axboef9eadbb2010-05-18 14:31:45 +0200908 } else {
909 set_current_state(TASK_INTERRUPTIBLE);
910 if (list_empty_careful(&wb->bdi->work_list) &&
911 !kthread_should_stop())
912 schedule();
913 __set_current_state(TASK_RUNNING);
914 }
Jens Axboe69b62d02010-05-17 12:51:03 +0200915
Jens Axboe03ba3782009-09-09 09:08:54 +0200916 try_to_freeze();
917 }
918
919 return 0;
920}
921
922/*
Jens Axboeb6e51312009-09-16 15:13:54 +0200923 * Schedule writeback for all backing devices. This does WB_SYNC_NONE
Christoph Hellwig3c4d7162010-06-08 18:14:43 +0200924 * writeback, for integrity writeback see bdi_queue_work_onstack().
Jens Axboe03ba3782009-09-09 09:08:54 +0200925 */
Jens Axboeb6e51312009-09-16 15:13:54 +0200926static void bdi_writeback_all(struct super_block *sb, long nr_pages)
Jens Axboe03ba3782009-09-09 09:08:54 +0200927{
Jens Axboeb6e51312009-09-16 15:13:54 +0200928 struct wb_writeback_args args = {
929 .sb = sb,
930 .nr_pages = nr_pages,
931 .sync_mode = WB_SYNC_NONE,
932 };
Jens Axboe03ba3782009-09-09 09:08:54 +0200933 struct backing_dev_info *bdi;
Jens Axboe03ba3782009-09-09 09:08:54 +0200934
Jens Axboecfc4ba52009-09-14 13:12:40 +0200935 rcu_read_lock();
Jens Axboe03ba3782009-09-09 09:08:54 +0200936
Jens Axboecfc4ba52009-09-14 13:12:40 +0200937 list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
Jens Axboe03ba3782009-09-09 09:08:54 +0200938 if (!bdi_has_dirty_io(bdi))
939 continue;
940
Jens Axboef17625b2010-06-01 11:05:22 +0200941 bdi_alloc_queue_work(bdi, &args);
Jens Axboe03ba3782009-09-09 09:08:54 +0200942 }
943
Jens Axboecfc4ba52009-09-14 13:12:40 +0200944 rcu_read_unlock();
Jens Axboe03ba3782009-09-09 09:08:54 +0200945}
946
947/*
948 * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
949 * the whole world.
950 */
951void wakeup_flusher_threads(long nr_pages)
952{
Jens Axboe03ba3782009-09-09 09:08:54 +0200953 if (nr_pages == 0)
954 nr_pages = global_page_state(NR_FILE_DIRTY) +
955 global_page_state(NR_UNSTABLE_NFS);
Jens Axboeb6e51312009-09-16 15:13:54 +0200956 bdi_writeback_all(NULL, nr_pages);
Jens Axboe03ba3782009-09-09 09:08:54 +0200957}
958
959static noinline void block_dump___mark_inode_dirty(struct inode *inode)
960{
961 if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
962 struct dentry *dentry;
963 const char *name = "?";
964
965 dentry = d_find_alias(inode);
966 if (dentry) {
967 spin_lock(&dentry->d_lock);
968 name = (const char *) dentry->d_name.name;
969 }
970 printk(KERN_DEBUG
971 "%s(%d): dirtied inode %lu (%s) on %s\n",
972 current->comm, task_pid_nr(current), inode->i_ino,
973 name, inode->i_sb->s_id);
974 if (dentry) {
975 spin_unlock(&dentry->d_lock);
976 dput(dentry);
977 }
978 }
979}
980
981/**
982 * __mark_inode_dirty - internal function
983 * @inode: inode to mark
984 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
985 * Mark an inode as dirty. Callers should use mark_inode_dirty or
986 * mark_inode_dirty_sync.
987 *
988 * Put the inode on the super block's dirty list.
989 *
990 * CAREFUL! We mark it dirty unconditionally, but move it onto the
991 * dirty list only if it is hashed or if it refers to a blockdev.
992 * If it was not hashed, it will never be added to the dirty list
993 * even if it is later hashed, as it will have been marked dirty already.
994 *
995 * In short, make sure you hash any inodes _before_ you start marking
996 * them dirty.
997 *
998 * This function *must* be atomic for the I_DIRTY_PAGES case -
999 * set_page_dirty() is called under spinlock in several places.
1000 *
1001 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
1002 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
1003 * the kernel-internal blockdev inode represents the dirtying time of the
1004 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
1005 * page->mapping->host, so the page-dirtying time is recorded in the internal
1006 * blockdev inode.
1007 */
1008void __mark_inode_dirty(struct inode *inode, int flags)
1009{
1010 struct super_block *sb = inode->i_sb;
1011
1012 /*
1013 * Don't do this for I_DIRTY_PAGES - that doesn't actually
1014 * dirty the inode itself
1015 */
1016 if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
1017 if (sb->s_op->dirty_inode)
1018 sb->s_op->dirty_inode(inode);
1019 }
1020
1021 /*
1022 * make sure that changes are seen by all cpus before we test i_state
1023 * -- mikulas
1024 */
1025 smp_mb();
1026
1027 /* avoid the locking if we can */
1028 if ((inode->i_state & flags) == flags)
1029 return;
1030
1031 if (unlikely(block_dump))
1032 block_dump___mark_inode_dirty(inode);
1033
1034 spin_lock(&inode_lock);
1035 if ((inode->i_state & flags) != flags) {
1036 const int was_dirty = inode->i_state & I_DIRTY;
1037
1038 inode->i_state |= flags;
1039
1040 /*
1041 * If the inode is being synced, just update its dirty state.
1042 * The unlocker will place the inode on the appropriate
1043 * superblock list, based upon its state.
1044 */
1045 if (inode->i_state & I_SYNC)
1046 goto out;
1047
1048 /*
1049 * Only add valid (hashed) inodes to the superblock's
1050 * dirty list. Add blockdev inodes as well.
1051 */
1052 if (!S_ISBLK(inode->i_mode)) {
1053 if (hlist_unhashed(&inode->i_hash))
1054 goto out;
1055 }
1056 if (inode->i_state & (I_FREEING|I_CLEAR))
1057 goto out;
1058
1059 /*
1060 * If the inode was already on b_dirty/b_io/b_more_io, don't
1061 * reposition it (that would break b_dirty time-ordering).
1062 */
1063 if (!was_dirty) {
1064 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
Jens Axboe500b0672009-09-09 09:10:25 +02001065 struct backing_dev_info *bdi = wb->bdi;
1066
1067 if (bdi_cap_writeback_dirty(bdi) &&
1068 !test_bit(BDI_registered, &bdi->state)) {
1069 WARN_ON(1);
1070 printk(KERN_ERR "bdi-%s not registered\n",
1071 bdi->name);
1072 }
Jens Axboe03ba3782009-09-09 09:08:54 +02001073
1074 inode->dirtied_when = jiffies;
1075 list_move(&inode->i_list, &wb->b_dirty);
1076 }
1077 }
1078out:
1079 spin_unlock(&inode_lock);
1080}
1081EXPORT_SYMBOL(__mark_inode_dirty);
1082
Jens Axboe66f3b8e2009-09-02 09:19:46 +02001083/*
1084 * Write out a superblock's list of dirty inodes. A wait will be performed
1085 * upon no inodes, all inodes or the final one, depending upon sync_mode.
1086 *
1087 * If older_than_this is non-NULL, then only write out inodes which
1088 * had their first dirtying at a time earlier than *older_than_this.
1089 *
Jens Axboe66f3b8e2009-09-02 09:19:46 +02001090 * If `bdi' is non-zero then we're being asked to writeback a specific queue.
1091 * This function assumes that the blockdev superblock's inodes are backed by
1092 * a variety of queues, so all inodes are searched. For other superblocks,
1093 * assume that all inodes are backed by the same queue.
1094 *
Jens Axboe66f3b8e2009-09-02 09:19:46 +02001095 * The inodes to be written are parked on bdi->b_io. They are moved back onto
1096 * bdi->b_dirty as they are selected for writing. This way, none can be missed
1097 * on the writer throttling path, and we get decent balancing between many
1098 * throttled threads: we don't want them all piling up on inode_sync_wait.
1099 */
Jens Axboeb6e51312009-09-16 15:13:54 +02001100static void wait_sb_inodes(struct super_block *sb)
Jens Axboe66f3b8e2009-09-02 09:19:46 +02001101{
Jens Axboe03ba3782009-09-09 09:08:54 +02001102 struct inode *inode, *old_inode = NULL;
Jens Axboe66f3b8e2009-09-02 09:19:46 +02001103
Jens Axboe03ba3782009-09-09 09:08:54 +02001104 /*
1105 * We need to be protected against the filesystem going from
1106 * r/o to r/w or vice versa.
1107 */
Jens Axboeb6e51312009-09-16 15:13:54 +02001108 WARN_ON(!rwsem_is_locked(&sb->s_umount));
Jens Axboe66f3b8e2009-09-02 09:19:46 +02001109
Jens Axboe03ba3782009-09-09 09:08:54 +02001110 spin_lock(&inode_lock);
1111
1112 /*
1113 * Data integrity sync. Must wait for all pages under writeback,
1114 * because there may have been pages dirtied before our sync
1115 * call, but which had writeout started before we write it out.
1116 * In which case, the inode may not be on the dirty list, but
1117 * we still have to wait for that writeout.
1118 */
Jens Axboeb6e51312009-09-16 15:13:54 +02001119 list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
Jens Axboe03ba3782009-09-09 09:08:54 +02001120 struct address_space *mapping;
1121
1122 if (inode->i_state & (I_FREEING|I_CLEAR|I_WILL_FREE|I_NEW))
1123 continue;
1124 mapping = inode->i_mapping;
1125 if (mapping->nrpages == 0)
1126 continue;
1127 __iget(inode);
1128 spin_unlock(&inode_lock);
1129 /*
1130 * We hold a reference to 'inode' so it couldn't have
1131 * been removed from s_inodes list while we dropped the
1132 * inode_lock. We cannot iput the inode now as we can
1133 * be holding the last reference and we cannot iput it
1134 * under inode_lock. So we keep the reference and iput
1135 * it later.
1136 */
1137 iput(old_inode);
1138 old_inode = inode;
1139
1140 filemap_fdatawait(mapping);
1141
1142 cond_resched();
Nick Piggin38f21972009-01-06 14:40:25 -08001143
Jens Axboe66f3b8e2009-09-02 09:19:46 +02001144 spin_lock(&inode_lock);
Jens Axboe66f3b8e2009-09-02 09:19:46 +02001145 }
Jens Axboe03ba3782009-09-09 09:08:54 +02001146 spin_unlock(&inode_lock);
1147 iput(old_inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001148}
1149
Jens Axboed8a85592009-09-02 12:34:32 +02001150/**
1151 * writeback_inodes_sb - writeback dirty inodes from given super_block
1152 * @sb: the superblock
Linus Torvalds1da177e2005-04-16 15:20:36 -07001153 *
Jens Axboed8a85592009-09-02 12:34:32 +02001154 * Start writeback on some inodes on this super_block. No guarantees are made
1155 * on how many (if any) will be written, and this function does not wait
1156 * for IO completion of submitted IO. The number of pages submitted is
1157 * returned.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001158 */
Jens Axboeb6e51312009-09-16 15:13:54 +02001159void writeback_inodes_sb(struct super_block *sb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001160{
Jens Axboe0e3c9a22010-06-01 11:08:43 +02001161 unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY);
1162 unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS);
Christoph Hellwig3c4d7162010-06-08 18:14:43 +02001163 struct wb_writeback_args args = {
1164 .sb = sb,
1165 .sync_mode = WB_SYNC_NONE,
1166 };
Jens Axboe0e3c9a22010-06-01 11:08:43 +02001167
Christoph Hellwigcf37e972010-06-08 18:14:51 +02001168 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1169
Christoph Hellwig3c4d7162010-06-08 18:14:43 +02001170 args.nr_pages = nr_dirty + nr_unstable +
Jens Axboe0e3c9a22010-06-01 11:08:43 +02001171 (inodes_stat.nr_inodes - inodes_stat.nr_unused);
1172
Christoph Hellwig3c4d7162010-06-08 18:14:43 +02001173 bdi_queue_work_onstack(&args);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001174}
Jens Axboed8a85592009-09-02 12:34:32 +02001175EXPORT_SYMBOL(writeback_inodes_sb);
1176
1177/**
Eric Sandeen17bd55d2009-12-23 07:57:07 -05001178 * writeback_inodes_sb_if_idle - start writeback if none underway
1179 * @sb: the superblock
1180 *
1181 * Invoke writeback_inodes_sb if no writeback is currently underway.
1182 * Returns 1 if writeback was started, 0 if not.
1183 */
1184int writeback_inodes_sb_if_idle(struct super_block *sb)
1185{
1186 if (!writeback_in_progress(sb->s_bdi)) {
Christoph Hellwigcf37e972010-06-08 18:14:51 +02001187 down_read(&sb->s_umount);
Eric Sandeen17bd55d2009-12-23 07:57:07 -05001188 writeback_inodes_sb(sb);
Christoph Hellwigcf37e972010-06-08 18:14:51 +02001189 up_read(&sb->s_umount);
Eric Sandeen17bd55d2009-12-23 07:57:07 -05001190 return 1;
1191 } else
1192 return 0;
1193}
1194EXPORT_SYMBOL(writeback_inodes_sb_if_idle);
1195
1196/**
Jens Axboed8a85592009-09-02 12:34:32 +02001197 * sync_inodes_sb - sync sb inode pages
1198 * @sb: the superblock
1199 *
1200 * This function writes and waits on any dirty inode belonging to this
1201 * super_block. The number of pages synced is returned.
1202 */
Jens Axboeb6e51312009-09-16 15:13:54 +02001203void sync_inodes_sb(struct super_block *sb)
Jens Axboed8a85592009-09-02 12:34:32 +02001204{
Christoph Hellwig3c4d7162010-06-08 18:14:43 +02001205 struct wb_writeback_args args = {
1206 .sb = sb,
1207 .sync_mode = WB_SYNC_ALL,
1208 .nr_pages = LONG_MAX,
1209 .range_cyclic = 0,
1210 };
1211
Christoph Hellwigcf37e972010-06-08 18:14:51 +02001212 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1213
Christoph Hellwig3c4d7162010-06-08 18:14:43 +02001214 bdi_queue_work_onstack(&args);
Jens Axboeb6e51312009-09-16 15:13:54 +02001215 wait_sb_inodes(sb);
Jens Axboed8a85592009-09-02 12:34:32 +02001216}
1217EXPORT_SYMBOL(sync_inodes_sb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001218
Linus Torvalds1da177e2005-04-16 15:20:36 -07001219/**
Andrea Arcangeli7f04c262005-10-30 15:03:05 -08001220 * write_inode_now - write an inode to disk
1221 * @inode: inode to write to disk
1222 * @sync: whether the write should be synchronous or not
Linus Torvalds1da177e2005-04-16 15:20:36 -07001223 *
Andrea Arcangeli7f04c262005-10-30 15:03:05 -08001224 * This function commits an inode to disk immediately if it is dirty. This is
1225 * primarily needed by knfsd.
1226 *
1227 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001228 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001229int write_inode_now(struct inode *inode, int sync)
1230{
1231 int ret;
1232 struct writeback_control wbc = {
1233 .nr_to_write = LONG_MAX,
Mike Galbraith18914b12008-02-08 04:20:23 -08001234 .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
OGAWA Hirofumi111ebb62006-06-23 02:03:26 -07001235 .range_start = 0,
1236 .range_end = LLONG_MAX,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001237 };
1238
1239 if (!mapping_cap_writeback_dirty(inode->i_mapping))
Andrew Morton49364ce2005-11-07 00:59:15 -08001240 wbc.nr_to_write = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001241
1242 might_sleep();
1243 spin_lock(&inode_lock);
Christoph Hellwig01c03192009-06-08 13:35:40 +02001244 ret = writeback_single_inode(inode, &wbc);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001245 spin_unlock(&inode_lock);
1246 if (sync)
Joern Engel1c0eeaf2007-10-16 23:30:44 -07001247 inode_sync_wait(inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001248 return ret;
1249}
1250EXPORT_SYMBOL(write_inode_now);
1251
1252/**
1253 * sync_inode - write an inode and its pages to disk.
1254 * @inode: the inode to sync
1255 * @wbc: controls the writeback mode
1256 *
1257 * sync_inode() will write an inode and its pages to disk. It will also
1258 * correctly update the inode on its superblock's dirty inode lists and will
1259 * update inode->i_state.
1260 *
1261 * The caller must have a ref on the inode.
1262 */
1263int sync_inode(struct inode *inode, struct writeback_control *wbc)
1264{
1265 int ret;
1266
1267 spin_lock(&inode_lock);
Christoph Hellwig01c03192009-06-08 13:35:40 +02001268 ret = writeback_single_inode(inode, wbc);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001269 spin_unlock(&inode_lock);
1270 return ret;
1271}
1272EXPORT_SYMBOL(sync_inode);