blob: 4b37f7cea4dd28edac895ebbe9017d80e7031c16 [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;
Wu Fengguangd3ddec72009-09-23 20:33:40 +080045 int for_kupdate:1;
46 int range_cyclic:1;
47 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 {
66 WS_USED_B = 0,
67 WS_ONSTACK_B,
68};
69
70#define WS_USED (1 << WS_USED_B)
71#define WS_ONSTACK (1 << WS_ONSTACK_B)
72
73static inline bool bdi_work_on_stack(struct bdi_work *work)
Adrian Bunkf11b00f2008-04-29 00:58:56 -070074{
Jens Axboe03ba3782009-09-09 09:08:54 +020075 return test_bit(WS_ONSTACK_B, &work->state);
76}
77
78static inline void bdi_work_init(struct bdi_work *work,
Jens Axboeb6e51312009-09-16 15:13:54 +020079 struct wb_writeback_args *args)
Jens Axboe03ba3782009-09-09 09:08:54 +020080{
81 INIT_RCU_HEAD(&work->rcu_head);
Jens Axboeb6e51312009-09-16 15:13:54 +020082 work->args = *args;
Jens Axboe03ba3782009-09-09 09:08:54 +020083 work->state = WS_USED;
84}
85
Adrian Bunkf11b00f2008-04-29 00:58:56 -070086/**
87 * writeback_in_progress - determine whether there is writeback in progress
88 * @bdi: the device's backing_dev_info structure.
89 *
Jens Axboe03ba3782009-09-09 09:08:54 +020090 * Determine whether there is writeback waiting to be handled against a
91 * backing device.
Adrian Bunkf11b00f2008-04-29 00:58:56 -070092 */
93int writeback_in_progress(struct backing_dev_info *bdi)
94{
Jens Axboe03ba3782009-09-09 09:08:54 +020095 return !list_empty(&bdi->work_list);
Adrian Bunkf11b00f2008-04-29 00:58:56 -070096}
97
Jens Axboe03ba3782009-09-09 09:08:54 +020098static void bdi_work_clear(struct bdi_work *work)
Adrian Bunkf11b00f2008-04-29 00:58:56 -070099{
Jens Axboe03ba3782009-09-09 09:08:54 +0200100 clear_bit(WS_USED_B, &work->state);
101 smp_mb__after_clear_bit();
Nick Piggin1ef7d9a2009-09-15 21:37:55 +0200102 /*
103 * work can have disappeared at this point. bit waitq functions
104 * should be able to tolerate this, provided bdi_sched_wait does
105 * not dereference it's pointer argument.
106 */
Jens Axboe03ba3782009-09-09 09:08:54 +0200107 wake_up_bit(&work->state, WS_USED_B);
Adrian Bunkf11b00f2008-04-29 00:58:56 -0700108}
109
Jens Axboe03ba3782009-09-09 09:08:54 +0200110static void bdi_work_free(struct rcu_head *head)
Nick Piggin4195f732009-05-28 09:01:15 +0200111{
Jens Axboe03ba3782009-09-09 09:08:54 +0200112 struct bdi_work *work = container_of(head, struct bdi_work, rcu_head);
Nick Piggin4195f732009-05-28 09:01:15 +0200113
Jens Axboe03ba3782009-09-09 09:08:54 +0200114 if (!bdi_work_on_stack(work))
115 kfree(work);
116 else
117 bdi_work_clear(work);
118}
119
120static void wb_work_complete(struct bdi_work *work)
121{
Jens Axboec4a77a62009-09-16 15:18:25 +0200122 const enum writeback_sync_modes sync_mode = work->args.sync_mode;
Nick Piggin77b9d052009-09-15 21:34:51 +0200123 int onstack = bdi_work_on_stack(work);
Jens Axboe03ba3782009-09-09 09:08:54 +0200124
125 /*
126 * For allocated work, we can clear the done/seen bit right here.
127 * For on-stack work, we need to postpone both the clear and free
128 * to after the RCU grace period, since the stack could be invalidated
129 * as soon as bdi_work_clear() has done the wakeup.
130 */
Nick Piggin77b9d052009-09-15 21:34:51 +0200131 if (!onstack)
Jens Axboe03ba3782009-09-09 09:08:54 +0200132 bdi_work_clear(work);
Nick Piggin77b9d052009-09-15 21:34:51 +0200133 if (sync_mode == WB_SYNC_NONE || onstack)
Jens Axboe03ba3782009-09-09 09:08:54 +0200134 call_rcu(&work->rcu_head, bdi_work_free);
135}
136
137static void wb_clear_pending(struct bdi_writeback *wb, struct bdi_work *work)
138{
139 /*
140 * The caller has retrieved the work arguments from this work,
141 * drop our reference. If this is the last ref, delete and free it
142 */
143 if (atomic_dec_and_test(&work->pending)) {
144 struct backing_dev_info *bdi = wb->bdi;
145
146 spin_lock(&bdi->wb_lock);
147 list_del_rcu(&work->list);
148 spin_unlock(&bdi->wb_lock);
149
150 wb_work_complete(work);
Nick Piggin4195f732009-05-28 09:01:15 +0200151 }
152}
153
Jens Axboe03ba3782009-09-09 09:08:54 +0200154static void bdi_queue_work(struct backing_dev_info *bdi, struct bdi_work *work)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700155{
Jens Axboebcddc3f2009-09-13 20:07:36 +0200156 work->seen = bdi->wb_mask;
157 BUG_ON(!work->seen);
158 atomic_set(&work->pending, bdi->wb_cnt);
159 BUG_ON(!bdi->wb_cnt);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700160
Jens Axboebcddc3f2009-09-13 20:07:36 +0200161 /*
Nick Piggindeed62e2009-09-15 21:32:58 +0200162 * list_add_tail_rcu() contains the necessary barriers to
163 * make sure the above stores are seen before the item is
164 * noticed on the list
Jens Axboebcddc3f2009-09-13 20:07:36 +0200165 */
Jens Axboebcddc3f2009-09-13 20:07:36 +0200166 spin_lock(&bdi->wb_lock);
167 list_add_tail_rcu(&work->list, &bdi->work_list);
168 spin_unlock(&bdi->wb_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700169
170 /*
Jens Axboe03ba3782009-09-09 09:08:54 +0200171 * If the default thread isn't there, make sure we add it. When
172 * it gets created and wakes up, we'll run this work.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700173 */
Jens Axboe03ba3782009-09-09 09:08:54 +0200174 if (unlikely(list_empty_careful(&bdi->wb_list)))
175 wake_up_process(default_backing_dev_info.wb.task);
176 else {
177 struct bdi_writeback *wb = &bdi->wb;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700178
Nick Piggin1ef7d9a2009-09-15 21:37:55 +0200179 if (wb->task)
Jens Axboe03ba3782009-09-09 09:08:54 +0200180 wake_up_process(wb->task);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700181 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700182}
183
Jens Axboe03ba3782009-09-09 09:08:54 +0200184/*
185 * Used for on-stack allocated work items. The caller needs to wait until
186 * the wb threads have acked the work before it's safe to continue.
187 */
188static void bdi_wait_on_work_clear(struct bdi_work *work)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700189{
Jens Axboe03ba3782009-09-09 09:08:54 +0200190 wait_on_bit(&work->state, WS_USED_B, bdi_sched_wait,
191 TASK_UNINTERRUPTIBLE);
192}
193
Jens Axboef11fcae2009-09-15 09:53:35 +0200194static void bdi_alloc_queue_work(struct backing_dev_info *bdi,
Jens Axboeb6e51312009-09-16 15:13:54 +0200195 struct wb_writeback_args *args)
Jens Axboe03ba3782009-09-09 09:08:54 +0200196{
197 struct bdi_work *work;
198
Jens Axboebcddc3f2009-09-13 20:07:36 +0200199 /*
200 * This is WB_SYNC_NONE writeback, so if allocation fails just
201 * wakeup the thread for old dirty data writeback
202 */
Jens Axboe03ba3782009-09-09 09:08:54 +0200203 work = kmalloc(sizeof(*work), GFP_ATOMIC);
Jens Axboebcddc3f2009-09-13 20:07:36 +0200204 if (work) {
Jens Axboeb6e51312009-09-16 15:13:54 +0200205 bdi_work_init(work, args);
Jens Axboebcddc3f2009-09-13 20:07:36 +0200206 bdi_queue_work(bdi, work);
207 } else {
208 struct bdi_writeback *wb = &bdi->wb;
Jens Axboe03ba3782009-09-09 09:08:54 +0200209
Jens Axboebcddc3f2009-09-13 20:07:36 +0200210 if (wb->task)
211 wake_up_process(wb->task);
212 }
Jens Axboe03ba3782009-09-09 09:08:54 +0200213}
214
Jens Axboeb6e51312009-09-16 15:13:54 +0200215/**
216 * bdi_sync_writeback - start and wait for writeback
217 * @bdi: the backing device to write from
218 * @sb: write inodes from this super_block
219 *
220 * Description:
221 * This does WB_SYNC_ALL data integrity writeback and waits for the
222 * IO to complete. Callers must hold the sb s_umount semaphore for
223 * reading, to avoid having the super disappear before we are done.
224 */
225static void bdi_sync_writeback(struct backing_dev_info *bdi,
226 struct super_block *sb)
Jens Axboe03ba3782009-09-09 09:08:54 +0200227{
Jens Axboeb6e51312009-09-16 15:13:54 +0200228 struct wb_writeback_args args = {
229 .sb = sb,
230 .sync_mode = WB_SYNC_ALL,
231 .nr_pages = LONG_MAX,
232 .range_cyclic = 0,
233 };
234 struct bdi_work work;
Christoph Hellwigf0fad8a2009-09-11 09:47:56 +0200235
Jens Axboeb6e51312009-09-16 15:13:54 +0200236 bdi_work_init(&work, &args);
237 work.state |= WS_ONSTACK;
Christoph Hellwigf0fad8a2009-09-11 09:47:56 +0200238
Jens Axboeb6e51312009-09-16 15:13:54 +0200239 bdi_queue_work(bdi, &work);
240 bdi_wait_on_work_clear(&work);
241}
242
243/**
244 * bdi_start_writeback - start writeback
245 * @bdi: the backing device to write from
Jaswinder Singh Rajput4b6764f2010-01-01 20:35:23 -0800246 * @sb: write inodes from this super_block
Jens Axboeb6e51312009-09-16 15:13:54 +0200247 * @nr_pages: the number of pages to write
248 *
249 * Description:
250 * This does WB_SYNC_NONE opportunistic writeback. The IO is only
251 * started when this function returns, we make no guarentees on
252 * completion. Caller need not hold sb s_umount semaphore.
253 *
254 */
Jens Axboea72bfd42009-09-26 00:07:46 +0200255void bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
256 long nr_pages)
Jens Axboeb6e51312009-09-16 15:13:54 +0200257{
258 struct wb_writeback_args args = {
Jens Axboea72bfd42009-09-26 00:07:46 +0200259 .sb = sb,
Jens Axboeb6e51312009-09-16 15:13:54 +0200260 .sync_mode = WB_SYNC_NONE,
261 .nr_pages = nr_pages,
262 .range_cyclic = 1,
263 };
264
Wu Fengguangd3ddec72009-09-23 20:33:40 +0800265 /*
266 * We treat @nr_pages=0 as the special case to do background writeback,
267 * ie. to sync pages until the background dirty threshold is reached.
268 */
269 if (!nr_pages) {
270 args.nr_pages = LONG_MAX;
271 args.for_background = 1;
272 }
273
Jens Axboeb6e51312009-09-16 15:13:54 +0200274 bdi_alloc_queue_work(bdi, &args);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700275}
276
277/*
Andrew Morton6610a0b2007-10-16 23:30:32 -0700278 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
279 * furthest end of its superblock's dirty-inode list.
280 *
281 * Before stamping the inode's ->dirtied_when, we check to see whether it is
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200282 * already the most-recently-dirtied inode on the b_dirty list. If that is
Andrew Morton6610a0b2007-10-16 23:30:32 -0700283 * the case then the inode must have been redirtied while it was being written
284 * out and we don't reset its dirtied_when.
285 */
286static void redirty_tail(struct inode *inode)
287{
Jens Axboe03ba3782009-09-09 09:08:54 +0200288 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
Andrew Morton6610a0b2007-10-16 23:30:32 -0700289
Jens Axboe03ba3782009-09-09 09:08:54 +0200290 if (!list_empty(&wb->b_dirty)) {
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200291 struct inode *tail;
Andrew Morton6610a0b2007-10-16 23:30:32 -0700292
Jens Axboe03ba3782009-09-09 09:08:54 +0200293 tail = list_entry(wb->b_dirty.next, struct inode, i_list);
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200294 if (time_before(inode->dirtied_when, tail->dirtied_when))
Andrew Morton6610a0b2007-10-16 23:30:32 -0700295 inode->dirtied_when = jiffies;
296 }
Jens Axboe03ba3782009-09-09 09:08:54 +0200297 list_move(&inode->i_list, &wb->b_dirty);
Andrew Morton6610a0b2007-10-16 23:30:32 -0700298}
299
300/*
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200301 * requeue inode for re-scanning after bdi->b_io list is exhausted.
Andrew Mortonc986d1e2007-10-16 23:30:34 -0700302 */
Ken Chen0e0f4fc2007-10-16 23:30:38 -0700303static void requeue_io(struct inode *inode)
Andrew Mortonc986d1e2007-10-16 23:30:34 -0700304{
Jens Axboe03ba3782009-09-09 09:08:54 +0200305 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
306
307 list_move(&inode->i_list, &wb->b_more_io);
Andrew Mortonc986d1e2007-10-16 23:30:34 -0700308}
309
Joern Engel1c0eeaf2007-10-16 23:30:44 -0700310static void inode_sync_complete(struct inode *inode)
311{
312 /*
313 * Prevent speculative execution through spin_unlock(&inode_lock);
314 */
315 smp_mb();
316 wake_up_bit(&inode->i_state, __I_SYNC);
317}
318
Jeff Laytond2caa3c52009-04-02 16:56:37 -0700319static bool inode_dirtied_after(struct inode *inode, unsigned long t)
320{
321 bool ret = time_after(inode->dirtied_when, t);
322#ifndef CONFIG_64BIT
323 /*
324 * For inodes being constantly redirtied, dirtied_when can get stuck.
325 * It _appears_ to be in the future, but is actually in distant past.
326 * This test is necessary to prevent such wrapped-around relative times
Jens Axboe5b0830c2009-09-23 19:37:09 +0200327 * from permanently stopping the whole bdi writeback.
Jeff Laytond2caa3c52009-04-02 16:56:37 -0700328 */
329 ret = ret && time_before_eq(inode->dirtied_when, jiffies);
330#endif
331 return ret;
332}
333
Andrew Mortonc986d1e2007-10-16 23:30:34 -0700334/*
Fengguang Wu2c136572007-10-16 23:30:39 -0700335 * Move expired dirty inodes from @delaying_queue to @dispatch_queue.
336 */
337static void move_expired_inodes(struct list_head *delaying_queue,
338 struct list_head *dispatch_queue,
339 unsigned long *older_than_this)
340{
Shaohua Li5c034492009-09-24 14:42:33 +0200341 LIST_HEAD(tmp);
342 struct list_head *pos, *node;
Jens Axboecf137302009-09-24 15:12:57 +0200343 struct super_block *sb = NULL;
Shaohua Li5c034492009-09-24 14:42:33 +0200344 struct inode *inode;
Jens Axboecf137302009-09-24 15:12:57 +0200345 int do_sb_sort = 0;
Shaohua Li5c034492009-09-24 14:42:33 +0200346
Fengguang Wu2c136572007-10-16 23:30:39 -0700347 while (!list_empty(delaying_queue)) {
Shaohua Li5c034492009-09-24 14:42:33 +0200348 inode = list_entry(delaying_queue->prev, struct inode, i_list);
Fengguang Wu2c136572007-10-16 23:30:39 -0700349 if (older_than_this &&
Jeff Laytond2caa3c52009-04-02 16:56:37 -0700350 inode_dirtied_after(inode, *older_than_this))
Fengguang Wu2c136572007-10-16 23:30:39 -0700351 break;
Jens Axboecf137302009-09-24 15:12:57 +0200352 if (sb && sb != inode->i_sb)
353 do_sb_sort = 1;
354 sb = inode->i_sb;
Shaohua Li5c034492009-09-24 14:42:33 +0200355 list_move(&inode->i_list, &tmp);
356 }
357
Jens Axboecf137302009-09-24 15:12:57 +0200358 /* just one sb in list, splice to dispatch_queue and we're done */
359 if (!do_sb_sort) {
360 list_splice(&tmp, dispatch_queue);
361 return;
362 }
363
Shaohua Li5c034492009-09-24 14:42:33 +0200364 /* Move inodes from one superblock together */
365 while (!list_empty(&tmp)) {
366 inode = list_entry(tmp.prev, struct inode, i_list);
367 sb = inode->i_sb;
368 list_for_each_prev_safe(pos, node, &tmp) {
369 inode = list_entry(pos, struct inode, i_list);
370 if (inode->i_sb == sb)
371 list_move(&inode->i_list, dispatch_queue);
372 }
Fengguang Wu2c136572007-10-16 23:30:39 -0700373 }
374}
375
376/*
377 * Queue all expired dirty inodes for io, eldest first.
378 */
Jens Axboe03ba3782009-09-09 09:08:54 +0200379static void queue_io(struct bdi_writeback *wb, unsigned long *older_than_this)
Fengguang Wu2c136572007-10-16 23:30:39 -0700380{
Jens Axboe03ba3782009-09-09 09:08:54 +0200381 list_splice_init(&wb->b_more_io, wb->b_io.prev);
382 move_expired_inodes(&wb->b_dirty, &wb->b_io, older_than_this);
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200383}
384
Christoph Hellwiga9185b42010-03-05 09:21:37 +0100385static int write_inode(struct inode *inode, struct writeback_control *wbc)
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200386{
Jens Axboe03ba3782009-09-09 09:08:54 +0200387 if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode))
Christoph Hellwiga9185b42010-03-05 09:21:37 +0100388 return inode->i_sb->s_op->write_inode(inode, wbc);
Jens Axboe03ba3782009-09-09 09:08:54 +0200389 return 0;
Fengguang Wu2c136572007-10-16 23:30:39 -0700390}
391
392/*
Christoph Hellwig01c03192009-06-08 13:35:40 +0200393 * Wait for writeback on an inode to complete.
394 */
395static void inode_wait_for_writeback(struct inode *inode)
396{
397 DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
398 wait_queue_head_t *wqh;
399
400 wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
401 do {
402 spin_unlock(&inode_lock);
403 __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
404 spin_lock(&inode_lock);
405 } while (inode->i_state & I_SYNC);
406}
407
408/*
409 * Write out an inode's dirty pages. Called under inode_lock. Either the
410 * caller has ref on the inode (either via __iget or via syscall against an fd)
411 * or the inode has I_WILL_FREE set (via generic_forget_inode)
412 *
Linus Torvalds1da177e2005-04-16 15:20:36 -0700413 * If `wait' is set, wait on the writeout.
414 *
415 * The whole writeout design is quite complex and fragile. We want to avoid
416 * starvation of particular inodes when others are being redirtied, prevent
417 * livelocks, etc.
418 *
419 * Called under inode_lock.
420 */
421static int
Christoph Hellwig01c03192009-06-08 13:35:40 +0200422writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700423{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700424 struct address_space *mapping = inode->i_mapping;
Christoph Hellwig01c03192009-06-08 13:35:40 +0200425 unsigned dirty;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700426 int ret;
427
Christoph Hellwig01c03192009-06-08 13:35:40 +0200428 if (!atomic_read(&inode->i_count))
429 WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
430 else
431 WARN_ON(inode->i_state & I_WILL_FREE);
432
433 if (inode->i_state & I_SYNC) {
434 /*
435 * If this inode is locked for writeback and we are not doing
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200436 * writeback-for-data-integrity, move it to b_more_io so that
Christoph Hellwig01c03192009-06-08 13:35:40 +0200437 * writeback can proceed with the other inodes on s_io.
438 *
439 * We'll have another go at writing back this inode when we
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200440 * completed a full scan of b_io.
Christoph Hellwig01c03192009-06-08 13:35:40 +0200441 */
Christoph Hellwiga9185b42010-03-05 09:21:37 +0100442 if (wbc->sync_mode != WB_SYNC_ALL) {
Christoph Hellwig01c03192009-06-08 13:35:40 +0200443 requeue_io(inode);
444 return 0;
445 }
446
447 /*
448 * It's a data-integrity sync. We must wait.
449 */
450 inode_wait_for_writeback(inode);
451 }
452
Joern Engel1c0eeaf2007-10-16 23:30:44 -0700453 BUG_ON(inode->i_state & I_SYNC);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700454
Joern Engel1c0eeaf2007-10-16 23:30:44 -0700455 /* Set I_SYNC, reset I_DIRTY */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700456 dirty = inode->i_state & I_DIRTY;
Joern Engel1c0eeaf2007-10-16 23:30:44 -0700457 inode->i_state |= I_SYNC;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700458 inode->i_state &= ~I_DIRTY;
459
460 spin_unlock(&inode_lock);
461
462 ret = do_writepages(mapping, wbc);
463
Christoph Hellwig26821ed2010-03-05 09:21:21 +0100464 /*
465 * Make sure to wait on the data before writing out the metadata.
466 * This is important for filesystems that modify metadata on data
467 * I/O completion.
468 */
Christoph Hellwiga9185b42010-03-05 09:21:37 +0100469 if (wbc->sync_mode == WB_SYNC_ALL) {
Christoph Hellwig26821ed2010-03-05 09:21:21 +0100470 int err = filemap_fdatawait(mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700471 if (ret == 0)
472 ret = err;
473 }
474
Christoph Hellwig26821ed2010-03-05 09:21:21 +0100475 /* Don't write the inode if only I_DIRTY_PAGES was set */
476 if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
Christoph Hellwiga9185b42010-03-05 09:21:37 +0100477 int err = write_inode(inode, wbc);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700478 if (ret == 0)
479 ret = err;
480 }
481
482 spin_lock(&inode_lock);
Joern Engel1c0eeaf2007-10-16 23:30:44 -0700483 inode->i_state &= ~I_SYNC;
Wu Fengguang84a89242009-06-16 15:33:17 -0700484 if (!(inode->i_state & (I_FREEING | I_CLEAR))) {
Wu Fengguangb3af9462009-09-25 06:04:10 +0200485 if ((inode->i_state & I_DIRTY_PAGES) && wbc->for_kupdate) {
Wu Fengguangae1b7f72009-09-23 20:33:42 +0800486 /*
Wu Fengguangb3af9462009-09-25 06:04:10 +0200487 * More pages get dirtied by a fast dirtier.
488 */
489 goto select_queue;
490 } else if (inode->i_state & I_DIRTY) {
491 /*
492 * At least XFS will redirty the inode during the
493 * writeback (delalloc) and on io completion (isize).
Wu Fengguangae1b7f72009-09-23 20:33:42 +0800494 */
495 redirty_tail(inode);
496 } else if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700497 /*
498 * We didn't write back all the pages. nfs_writepages()
499 * sometimes bales out without doing anything. Redirty
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200500 * the inode; Move it from b_io onto b_more_io/b_dirty.
Andrew Morton1b43ef92007-10-16 23:30:35 -0700501 */
502 /*
503 * akpm: if the caller was the kupdate function we put
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200504 * this inode at the head of b_dirty so it gets first
Andrew Morton1b43ef92007-10-16 23:30:35 -0700505 * consideration. Otherwise, move it to the tail, for
506 * the reasons described there. I'm not really sure
507 * how much sense this makes. Presumably I had a good
508 * reasons for doing it this way, and I'd rather not
509 * muck with it at present.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700510 */
511 if (wbc->for_kupdate) {
512 /*
Fengguang Wu2c136572007-10-16 23:30:39 -0700513 * For the kupdate function we move the inode
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200514 * to b_more_io so it will get more writeout as
Fengguang Wu2c136572007-10-16 23:30:39 -0700515 * soon as the queue becomes uncongested.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700516 */
517 inode->i_state |= I_DIRTY_PAGES;
Wu Fengguangb3af9462009-09-25 06:04:10 +0200518select_queue:
Fengguang Wu8bc3be22008-02-04 22:29:36 -0800519 if (wbc->nr_to_write <= 0) {
520 /*
521 * slice used up: queue for next turn
522 */
523 requeue_io(inode);
524 } else {
525 /*
526 * somehow blocked: retry later
527 */
528 redirty_tail(inode);
529 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700530 } else {
531 /*
532 * Otherwise fully redirty the inode so that
533 * other inodes on this superblock will get some
534 * writeout. Otherwise heavy writing to one
535 * file would indefinitely suspend writeout of
536 * all the other files.
537 */
538 inode->i_state |= I_DIRTY_PAGES;
Andrew Morton1b43ef92007-10-16 23:30:35 -0700539 redirty_tail(inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700540 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700541 } else if (atomic_read(&inode->i_count)) {
542 /*
543 * The inode is clean, inuse
544 */
545 list_move(&inode->i_list, &inode_in_use);
546 } else {
547 /*
548 * The inode is clean, unused
549 */
550 list_move(&inode->i_list, &inode_unused);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700551 }
552 }
Joern Engel1c0eeaf2007-10-16 23:30:44 -0700553 inode_sync_complete(inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700554 return ret;
555}
556
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800557static void unpin_sb_for_writeback(struct super_block *sb)
Jens Axboe9ecc2732009-09-24 15:25:11 +0200558{
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800559 up_read(&sb->s_umount);
560 put_super(sb);
Jens Axboe9ecc2732009-09-24 15:25:11 +0200561}
562
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800563enum sb_pin_state {
564 SB_PINNED,
565 SB_NOT_PINNED,
566 SB_PIN_FAILED
567};
568
Jens Axboe03ba3782009-09-09 09:08:54 +0200569/*
570 * For WB_SYNC_NONE writeback, the caller does not have the sb pinned
571 * before calling writeback. So make sure that we do pin it, so it doesn't
572 * go away while we are writing inodes from it.
Jens Axboe03ba3782009-09-09 09:08:54 +0200573 */
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800574static enum sb_pin_state pin_sb_for_writeback(struct writeback_control *wbc,
575 struct super_block *sb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700576{
Jens Axboe9ecc2732009-09-24 15:25:11 +0200577 /*
Jens Axboe03ba3782009-09-09 09:08:54 +0200578 * Caller must already hold the ref for this
579 */
580 if (wbc->sync_mode == WB_SYNC_ALL) {
581 WARN_ON(!rwsem_is_locked(&sb->s_umount));
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800582 return SB_NOT_PINNED;
Jens Axboe03ba3782009-09-09 09:08:54 +0200583 }
Jens Axboe03ba3782009-09-09 09:08:54 +0200584 spin_lock(&sb_lock);
585 sb->s_count++;
586 if (down_read_trylock(&sb->s_umount)) {
587 if (sb->s_root) {
588 spin_unlock(&sb_lock);
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800589 return SB_PINNED;
Jens Axboe03ba3782009-09-09 09:08:54 +0200590 }
591 /*
592 * umounted, drop rwsem again and fall through to failure
593 */
594 up_read(&sb->s_umount);
595 }
Jens Axboe03ba3782009-09-09 09:08:54 +0200596 sb->s_count--;
597 spin_unlock(&sb_lock);
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800598 return SB_PIN_FAILED;
Jens Axboe03ba3782009-09-09 09:08:54 +0200599}
600
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800601/*
602 * Write a portion of b_io inodes which belong to @sb.
603 * If @wbc->sb != NULL, then find and write all such
604 * inodes. Otherwise write only ones which go sequentially
605 * in reverse order.
606 * Return 1, if the caller writeback routine should be
607 * interrupted. Otherwise return 0.
608 */
609static int writeback_sb_inodes(struct super_block *sb,
610 struct bdi_writeback *wb,
611 struct writeback_control *wbc)
Jens Axboe03ba3782009-09-09 09:08:54 +0200612{
Jens Axboe03ba3782009-09-09 09:08:54 +0200613 while (!list_empty(&wb->b_io)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700614 long pages_skipped;
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800615 struct inode *inode = list_entry(wb->b_io.prev,
616 struct inode, i_list);
617 if (wbc->sb && sb != inode->i_sb) {
618 /* super block given and doesn't
619 match, skip this inode */
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200620 redirty_tail(inode);
621 continue;
622 }
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800623 if (sb != inode->i_sb)
624 /* finish with this superblock */
625 return 0;
Wu Fengguang84a89242009-06-16 15:33:17 -0700626 if (inode->i_state & (I_NEW | I_WILL_FREE)) {
Nick Piggin7ef0d732009-03-12 14:31:38 -0700627 requeue_io(inode);
628 continue;
629 }
Jeff Laytond2caa3c52009-04-02 16:56:37 -0700630 /*
631 * Was this inode dirtied after sync_sb_inodes was called?
632 * This keeps sync from extra jobs and livelock.
633 */
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800634 if (inode_dirtied_after(inode, wbc->wb_start))
635 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700636
Wu Fengguang84a89242009-06-16 15:33:17 -0700637 BUG_ON(inode->i_state & (I_FREEING | I_CLEAR));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700638 __iget(inode);
639 pages_skipped = wbc->pages_skipped;
Christoph Hellwig01c03192009-06-08 13:35:40 +0200640 writeback_single_inode(inode, wbc);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700641 if (wbc->pages_skipped != pages_skipped) {
642 /*
643 * writeback is not making progress due to locked
644 * buffers. Skip this inode for now.
645 */
Andrew Mortonf57b9b72007-10-16 23:30:34 -0700646 redirty_tail(inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700647 }
648 spin_unlock(&inode_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700649 iput(inode);
OGAWA Hirofumi4ffc8442006-03-25 03:07:44 -0800650 cond_resched();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700651 spin_lock(&inode_lock);
Fengguang Wu8bc3be22008-02-04 22:29:36 -0800652 if (wbc->nr_to_write <= 0) {
653 wbc->more_io = 1;
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800654 return 1;
Fengguang Wu8bc3be22008-02-04 22:29:36 -0800655 }
Jens Axboe03ba3782009-09-09 09:08:54 +0200656 if (!list_empty(&wb->b_more_io))
Fengguang Wu8bc3be22008-02-04 22:29:36 -0800657 wbc->more_io = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700658 }
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800659 /* b_io is empty */
660 return 1;
661}
Nick Piggin38f21972009-01-06 14:40:25 -0800662
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800663static void writeback_inodes_wb(struct bdi_writeback *wb,
664 struct writeback_control *wbc)
665{
666 int ret = 0;
Jens Axboe9ecc2732009-09-24 15:25:11 +0200667
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800668 wbc->wb_start = jiffies; /* livelock avoidance */
669 spin_lock(&inode_lock);
670 if (!wbc->for_kupdate || list_empty(&wb->b_io))
671 queue_io(wb, wbc->older_than_this);
672
673 while (!list_empty(&wb->b_io)) {
674 struct inode *inode = list_entry(wb->b_io.prev,
675 struct inode, i_list);
676 struct super_block *sb = inode->i_sb;
677 enum sb_pin_state state;
678
679 if (wbc->sb && sb != wbc->sb) {
680 /* super block given and doesn't
681 match, skip this inode */
682 redirty_tail(inode);
683 continue;
684 }
685 state = pin_sb_for_writeback(wbc, sb);
686
687 if (state == SB_PIN_FAILED) {
688 requeue_io(inode);
689 continue;
690 }
691 ret = writeback_sb_inodes(sb, wb, wbc);
692
693 if (state == SB_PINNED)
694 unpin_sb_for_writeback(sb);
695 if (ret)
696 break;
697 }
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200698 spin_unlock(&inode_lock);
699 /* Leave any unwritten inodes on b_io */
700}
701
Jens Axboe03ba3782009-09-09 09:08:54 +0200702void writeback_inodes_wbc(struct writeback_control *wbc)
703{
704 struct backing_dev_info *bdi = wbc->bdi;
705
706 writeback_inodes_wb(&bdi->wb, wbc);
707}
708
709/*
710 * The maximum number of pages to writeout in a single bdi flush/kupdate
711 * operation. We do this so we don't hold I_SYNC against an inode for
712 * enormous amounts of time, which would block a userspace task which has
713 * been forced to throttle against that inode. Also, the code reevaluates
714 * the dirty each time it has written this many pages.
715 */
716#define MAX_WRITEBACK_PAGES 1024
717
718static inline bool over_bground_thresh(void)
719{
720 unsigned long background_thresh, dirty_thresh;
721
722 get_dirty_limits(&background_thresh, &dirty_thresh, NULL, NULL);
723
724 return (global_page_state(NR_FILE_DIRTY) +
725 global_page_state(NR_UNSTABLE_NFS) >= background_thresh);
726}
727
728/*
729 * Explicit flushing or periodic writeback of "old" data.
730 *
731 * Define "old": the first time one of an inode's pages is dirtied, we mark the
732 * dirtying-time in the inode's address_space. So this periodic writeback code
733 * just walks the superblock inode list, writing back any inodes which are
734 * older than a specific point in time.
735 *
736 * Try to run once per dirty_writeback_interval. But if a writeback event
737 * takes longer than a dirty_writeback_interval interval, then leave a
738 * one-second gap.
739 *
740 * older_than_this takes precedence over nr_to_write. So we'll only write back
741 * all dirty pages if they are all attached to "old" mappings.
742 */
Jens Axboec4a77a62009-09-16 15:18:25 +0200743static long wb_writeback(struct bdi_writeback *wb,
744 struct wb_writeback_args *args)
Jens Axboe03ba3782009-09-09 09:08:54 +0200745{
746 struct writeback_control wbc = {
747 .bdi = wb->bdi,
Jens Axboec4a77a62009-09-16 15:18:25 +0200748 .sb = args->sb,
749 .sync_mode = args->sync_mode,
Jens Axboe03ba3782009-09-09 09:08:54 +0200750 .older_than_this = NULL,
Jens Axboec4a77a62009-09-16 15:18:25 +0200751 .for_kupdate = args->for_kupdate,
Wu Fengguangb17621f2009-12-03 13:54:25 +0100752 .for_background = args->for_background,
Jens Axboec4a77a62009-09-16 15:18:25 +0200753 .range_cyclic = args->range_cyclic,
Jens Axboe03ba3782009-09-09 09:08:54 +0200754 };
755 unsigned long oldest_jif;
756 long wrote = 0;
Jan Karaa5989bd2009-09-16 19:22:48 +0200757 struct inode *inode;
Jens Axboe03ba3782009-09-09 09:08:54 +0200758
759 if (wbc.for_kupdate) {
760 wbc.older_than_this = &oldest_jif;
761 oldest_jif = jiffies -
762 msecs_to_jiffies(dirty_expire_interval * 10);
763 }
Jens Axboec4a77a62009-09-16 15:18:25 +0200764 if (!wbc.range_cyclic) {
765 wbc.range_start = 0;
766 wbc.range_end = LLONG_MAX;
767 }
Jens Axboe03ba3782009-09-09 09:08:54 +0200768
769 for (;;) {
770 /*
Wu Fengguangd3ddec72009-09-23 20:33:40 +0800771 * Stop writeback when nr_pages has been consumed
Jens Axboe03ba3782009-09-09 09:08:54 +0200772 */
Wu Fengguangd3ddec72009-09-23 20:33:40 +0800773 if (args->nr_pages <= 0)
Jens Axboe03ba3782009-09-09 09:08:54 +0200774 break;
775
776 /*
Wu Fengguangd3ddec72009-09-23 20:33:40 +0800777 * For background writeout, stop when we are below the
778 * background dirty threshold
Jens Axboe03ba3782009-09-09 09:08:54 +0200779 */
Wu Fengguangd3ddec72009-09-23 20:33:40 +0800780 if (args->for_background && !over_bground_thresh())
Jens Axboe03ba3782009-09-09 09:08:54 +0200781 break;
782
783 wbc.more_io = 0;
Jens Axboe03ba3782009-09-09 09:08:54 +0200784 wbc.nr_to_write = MAX_WRITEBACK_PAGES;
785 wbc.pages_skipped = 0;
786 writeback_inodes_wb(wb, &wbc);
Jens Axboec4a77a62009-09-16 15:18:25 +0200787 args->nr_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
Jens Axboe03ba3782009-09-09 09:08:54 +0200788 wrote += MAX_WRITEBACK_PAGES - wbc.nr_to_write;
789
790 /*
Jens Axboe71fd05a2009-09-23 19:32:26 +0200791 * If we consumed everything, see if we have more
Jens Axboe03ba3782009-09-09 09:08:54 +0200792 */
Jens Axboe71fd05a2009-09-23 19:32:26 +0200793 if (wbc.nr_to_write <= 0)
794 continue;
795 /*
796 * Didn't write everything and we don't have more IO, bail
797 */
798 if (!wbc.more_io)
Jens Axboe03ba3782009-09-09 09:08:54 +0200799 break;
Jens Axboe71fd05a2009-09-23 19:32:26 +0200800 /*
801 * Did we write something? Try for more
802 */
803 if (wbc.nr_to_write < MAX_WRITEBACK_PAGES)
804 continue;
805 /*
806 * Nothing written. Wait for some inode to
807 * become available for writeback. Otherwise
808 * we'll just busyloop.
809 */
810 spin_lock(&inode_lock);
811 if (!list_empty(&wb->b_more_io)) {
812 inode = list_entry(wb->b_more_io.prev,
813 struct inode, i_list);
814 inode_wait_for_writeback(inode);
Jens Axboe03ba3782009-09-09 09:08:54 +0200815 }
Jens Axboe71fd05a2009-09-23 19:32:26 +0200816 spin_unlock(&inode_lock);
Jens Axboe03ba3782009-09-09 09:08:54 +0200817 }
818
819 return wrote;
820}
821
822/*
823 * Return the next bdi_work struct that hasn't been processed by this
Jens Axboe8010c3b2009-09-15 20:04:57 +0200824 * wb thread yet. ->seen is initially set for each thread that exists
825 * for this device, when a thread first notices a piece of work it
826 * clears its bit. Depending on writeback type, the thread will notify
827 * completion on either receiving the work (WB_SYNC_NONE) or after
828 * it is done (WB_SYNC_ALL).
Jens Axboe03ba3782009-09-09 09:08:54 +0200829 */
830static struct bdi_work *get_next_work_item(struct backing_dev_info *bdi,
831 struct bdi_writeback *wb)
832{
833 struct bdi_work *work, *ret = NULL;
834
835 rcu_read_lock();
836
837 list_for_each_entry_rcu(work, &bdi->work_list, list) {
Nick Piggin77fad5e2009-09-15 21:34:12 +0200838 if (!test_bit(wb->nr, &work->seen))
Jens Axboe03ba3782009-09-09 09:08:54 +0200839 continue;
Nick Piggin77fad5e2009-09-15 21:34:12 +0200840 clear_bit(wb->nr, &work->seen);
Jens Axboe03ba3782009-09-09 09:08:54 +0200841
842 ret = work;
843 break;
844 }
845
846 rcu_read_unlock();
847 return ret;
848}
849
850static long wb_check_old_data_flush(struct bdi_writeback *wb)
851{
852 unsigned long expired;
853 long nr_pages;
854
855 expired = wb->last_old_flush +
856 msecs_to_jiffies(dirty_writeback_interval * 10);
857 if (time_before(jiffies, expired))
858 return 0;
859
860 wb->last_old_flush = jiffies;
861 nr_pages = global_page_state(NR_FILE_DIRTY) +
862 global_page_state(NR_UNSTABLE_NFS) +
863 (inodes_stat.nr_inodes - inodes_stat.nr_unused);
864
Jens Axboec4a77a62009-09-16 15:18:25 +0200865 if (nr_pages) {
866 struct wb_writeback_args args = {
867 .nr_pages = nr_pages,
868 .sync_mode = WB_SYNC_NONE,
869 .for_kupdate = 1,
870 .range_cyclic = 1,
871 };
872
873 return wb_writeback(wb, &args);
874 }
Jens Axboe03ba3782009-09-09 09:08:54 +0200875
876 return 0;
877}
878
879/*
880 * Retrieve work items and do the writeback they describe
881 */
882long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
883{
884 struct backing_dev_info *bdi = wb->bdi;
885 struct bdi_work *work;
Jens Axboec4a77a62009-09-16 15:18:25 +0200886 long wrote = 0;
Jens Axboe03ba3782009-09-09 09:08:54 +0200887
888 while ((work = get_next_work_item(bdi, wb)) != NULL) {
Jens Axboec4a77a62009-09-16 15:18:25 +0200889 struct wb_writeback_args args = work->args;
Jens Axboe03ba3782009-09-09 09:08:54 +0200890
891 /*
892 * Override sync mode, in case we must wait for completion
893 */
894 if (force_wait)
Jens Axboec4a77a62009-09-16 15:18:25 +0200895 work->args.sync_mode = args.sync_mode = WB_SYNC_ALL;
Jens Axboe03ba3782009-09-09 09:08:54 +0200896
897 /*
898 * If this isn't a data integrity operation, just notify
899 * that we have seen this work and we are now starting it.
900 */
Jens Axboec4a77a62009-09-16 15:18:25 +0200901 if (args.sync_mode == WB_SYNC_NONE)
Jens Axboe03ba3782009-09-09 09:08:54 +0200902 wb_clear_pending(wb, work);
903
Jens Axboec4a77a62009-09-16 15:18:25 +0200904 wrote += wb_writeback(wb, &args);
Jens Axboe03ba3782009-09-09 09:08:54 +0200905
906 /*
907 * This is a data integrity writeback, so only do the
908 * notification when we have completed the work.
909 */
Jens Axboec4a77a62009-09-16 15:18:25 +0200910 if (args.sync_mode == WB_SYNC_ALL)
Jens Axboe03ba3782009-09-09 09:08:54 +0200911 wb_clear_pending(wb, work);
912 }
913
914 /*
915 * Check for periodic writeback, kupdated() style
916 */
917 wrote += wb_check_old_data_flush(wb);
918
919 return wrote;
920}
921
922/*
923 * Handle writeback of dirty data for the device backed by this bdi. Also
924 * wakes up periodically and does kupdated style flushing.
925 */
926int bdi_writeback_task(struct bdi_writeback *wb)
927{
928 unsigned long last_active = jiffies;
929 unsigned long wait_jiffies = -1UL;
930 long pages_written;
931
932 while (!kthread_should_stop()) {
933 pages_written = wb_do_writeback(wb, 0);
934
935 if (pages_written)
936 last_active = jiffies;
937 else if (wait_jiffies != -1UL) {
938 unsigned long max_idle;
939
940 /*
941 * Longest period of inactivity that we tolerate. If we
942 * see dirty data again later, the task will get
943 * recreated automatically.
944 */
945 max_idle = max(5UL * 60 * HZ, wait_jiffies);
946 if (time_after(jiffies, max_idle + last_active))
947 break;
948 }
949
950 wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10);
Jens Axboe49db0412009-09-15 21:27:40 +0200951 schedule_timeout_interruptible(wait_jiffies);
Jens Axboe03ba3782009-09-09 09:08:54 +0200952 try_to_freeze();
953 }
954
955 return 0;
956}
957
958/*
Jens Axboeb6e51312009-09-16 15:13:54 +0200959 * Schedule writeback for all backing devices. This does WB_SYNC_NONE
960 * writeback, for integrity writeback see bdi_sync_writeback().
Jens Axboe03ba3782009-09-09 09:08:54 +0200961 */
Jens Axboeb6e51312009-09-16 15:13:54 +0200962static void bdi_writeback_all(struct super_block *sb, long nr_pages)
Jens Axboe03ba3782009-09-09 09:08:54 +0200963{
Jens Axboeb6e51312009-09-16 15:13:54 +0200964 struct wb_writeback_args args = {
965 .sb = sb,
966 .nr_pages = nr_pages,
967 .sync_mode = WB_SYNC_NONE,
968 };
Jens Axboe03ba3782009-09-09 09:08:54 +0200969 struct backing_dev_info *bdi;
Jens Axboe03ba3782009-09-09 09:08:54 +0200970
Jens Axboecfc4ba52009-09-14 13:12:40 +0200971 rcu_read_lock();
Jens Axboe03ba3782009-09-09 09:08:54 +0200972
Jens Axboecfc4ba52009-09-14 13:12:40 +0200973 list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
Jens Axboe03ba3782009-09-09 09:08:54 +0200974 if (!bdi_has_dirty_io(bdi))
975 continue;
976
Jens Axboeb6e51312009-09-16 15:13:54 +0200977 bdi_alloc_queue_work(bdi, &args);
Jens Axboe03ba3782009-09-09 09:08:54 +0200978 }
979
Jens Axboecfc4ba52009-09-14 13:12:40 +0200980 rcu_read_unlock();
Jens Axboe03ba3782009-09-09 09:08:54 +0200981}
982
983/*
984 * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
985 * the whole world.
986 */
987void wakeup_flusher_threads(long nr_pages)
988{
Jens Axboe03ba3782009-09-09 09:08:54 +0200989 if (nr_pages == 0)
990 nr_pages = global_page_state(NR_FILE_DIRTY) +
991 global_page_state(NR_UNSTABLE_NFS);
Jens Axboeb6e51312009-09-16 15:13:54 +0200992 bdi_writeback_all(NULL, nr_pages);
Jens Axboe03ba3782009-09-09 09:08:54 +0200993}
994
995static noinline void block_dump___mark_inode_dirty(struct inode *inode)
996{
997 if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
998 struct dentry *dentry;
999 const char *name = "?";
1000
1001 dentry = d_find_alias(inode);
1002 if (dentry) {
1003 spin_lock(&dentry->d_lock);
1004 name = (const char *) dentry->d_name.name;
1005 }
1006 printk(KERN_DEBUG
1007 "%s(%d): dirtied inode %lu (%s) on %s\n",
1008 current->comm, task_pid_nr(current), inode->i_ino,
1009 name, inode->i_sb->s_id);
1010 if (dentry) {
1011 spin_unlock(&dentry->d_lock);
1012 dput(dentry);
1013 }
1014 }
1015}
1016
1017/**
1018 * __mark_inode_dirty - internal function
1019 * @inode: inode to mark
1020 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
1021 * Mark an inode as dirty. Callers should use mark_inode_dirty or
1022 * mark_inode_dirty_sync.
1023 *
1024 * Put the inode on the super block's dirty list.
1025 *
1026 * CAREFUL! We mark it dirty unconditionally, but move it onto the
1027 * dirty list only if it is hashed or if it refers to a blockdev.
1028 * If it was not hashed, it will never be added to the dirty list
1029 * even if it is later hashed, as it will have been marked dirty already.
1030 *
1031 * In short, make sure you hash any inodes _before_ you start marking
1032 * them dirty.
1033 *
1034 * This function *must* be atomic for the I_DIRTY_PAGES case -
1035 * set_page_dirty() is called under spinlock in several places.
1036 *
1037 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
1038 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
1039 * the kernel-internal blockdev inode represents the dirtying time of the
1040 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
1041 * page->mapping->host, so the page-dirtying time is recorded in the internal
1042 * blockdev inode.
1043 */
1044void __mark_inode_dirty(struct inode *inode, int flags)
1045{
1046 struct super_block *sb = inode->i_sb;
1047
1048 /*
1049 * Don't do this for I_DIRTY_PAGES - that doesn't actually
1050 * dirty the inode itself
1051 */
1052 if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
1053 if (sb->s_op->dirty_inode)
1054 sb->s_op->dirty_inode(inode);
1055 }
1056
1057 /*
1058 * make sure that changes are seen by all cpus before we test i_state
1059 * -- mikulas
1060 */
1061 smp_mb();
1062
1063 /* avoid the locking if we can */
1064 if ((inode->i_state & flags) == flags)
1065 return;
1066
1067 if (unlikely(block_dump))
1068 block_dump___mark_inode_dirty(inode);
1069
1070 spin_lock(&inode_lock);
1071 if ((inode->i_state & flags) != flags) {
1072 const int was_dirty = inode->i_state & I_DIRTY;
1073
1074 inode->i_state |= flags;
1075
1076 /*
1077 * If the inode is being synced, just update its dirty state.
1078 * The unlocker will place the inode on the appropriate
1079 * superblock list, based upon its state.
1080 */
1081 if (inode->i_state & I_SYNC)
1082 goto out;
1083
1084 /*
1085 * Only add valid (hashed) inodes to the superblock's
1086 * dirty list. Add blockdev inodes as well.
1087 */
1088 if (!S_ISBLK(inode->i_mode)) {
1089 if (hlist_unhashed(&inode->i_hash))
1090 goto out;
1091 }
1092 if (inode->i_state & (I_FREEING|I_CLEAR))
1093 goto out;
1094
1095 /*
1096 * If the inode was already on b_dirty/b_io/b_more_io, don't
1097 * reposition it (that would break b_dirty time-ordering).
1098 */
1099 if (!was_dirty) {
1100 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
Jens Axboe500b0672009-09-09 09:10:25 +02001101 struct backing_dev_info *bdi = wb->bdi;
1102
1103 if (bdi_cap_writeback_dirty(bdi) &&
1104 !test_bit(BDI_registered, &bdi->state)) {
1105 WARN_ON(1);
1106 printk(KERN_ERR "bdi-%s not registered\n",
1107 bdi->name);
1108 }
Jens Axboe03ba3782009-09-09 09:08:54 +02001109
1110 inode->dirtied_when = jiffies;
1111 list_move(&inode->i_list, &wb->b_dirty);
1112 }
1113 }
1114out:
1115 spin_unlock(&inode_lock);
1116}
1117EXPORT_SYMBOL(__mark_inode_dirty);
1118
Jens Axboe66f3b8e2009-09-02 09:19:46 +02001119/*
1120 * Write out a superblock's list of dirty inodes. A wait will be performed
1121 * upon no inodes, all inodes or the final one, depending upon sync_mode.
1122 *
1123 * If older_than_this is non-NULL, then only write out inodes which
1124 * had their first dirtying at a time earlier than *older_than_this.
1125 *
Jens Axboe66f3b8e2009-09-02 09:19:46 +02001126 * If `bdi' is non-zero then we're being asked to writeback a specific queue.
1127 * This function assumes that the blockdev superblock's inodes are backed by
1128 * a variety of queues, so all inodes are searched. For other superblocks,
1129 * assume that all inodes are backed by the same queue.
1130 *
Jens Axboe66f3b8e2009-09-02 09:19:46 +02001131 * The inodes to be written are parked on bdi->b_io. They are moved back onto
1132 * bdi->b_dirty as they are selected for writing. This way, none can be missed
1133 * on the writer throttling path, and we get decent balancing between many
1134 * throttled threads: we don't want them all piling up on inode_sync_wait.
1135 */
Jens Axboeb6e51312009-09-16 15:13:54 +02001136static void wait_sb_inodes(struct super_block *sb)
Jens Axboe66f3b8e2009-09-02 09:19:46 +02001137{
Jens Axboe03ba3782009-09-09 09:08:54 +02001138 struct inode *inode, *old_inode = NULL;
Jens Axboe66f3b8e2009-09-02 09:19:46 +02001139
Jens Axboe03ba3782009-09-09 09:08:54 +02001140 /*
1141 * We need to be protected against the filesystem going from
1142 * r/o to r/w or vice versa.
1143 */
Jens Axboeb6e51312009-09-16 15:13:54 +02001144 WARN_ON(!rwsem_is_locked(&sb->s_umount));
Jens Axboe66f3b8e2009-09-02 09:19:46 +02001145
Jens Axboe03ba3782009-09-09 09:08:54 +02001146 spin_lock(&inode_lock);
1147
1148 /*
1149 * Data integrity sync. Must wait for all pages under writeback,
1150 * because there may have been pages dirtied before our sync
1151 * call, but which had writeout started before we write it out.
1152 * In which case, the inode may not be on the dirty list, but
1153 * we still have to wait for that writeout.
1154 */
Jens Axboeb6e51312009-09-16 15:13:54 +02001155 list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
Jens Axboe03ba3782009-09-09 09:08:54 +02001156 struct address_space *mapping;
1157
1158 if (inode->i_state & (I_FREEING|I_CLEAR|I_WILL_FREE|I_NEW))
1159 continue;
1160 mapping = inode->i_mapping;
1161 if (mapping->nrpages == 0)
1162 continue;
1163 __iget(inode);
1164 spin_unlock(&inode_lock);
1165 /*
1166 * We hold a reference to 'inode' so it couldn't have
1167 * been removed from s_inodes list while we dropped the
1168 * inode_lock. We cannot iput the inode now as we can
1169 * be holding the last reference and we cannot iput it
1170 * under inode_lock. So we keep the reference and iput
1171 * it later.
1172 */
1173 iput(old_inode);
1174 old_inode = inode;
1175
1176 filemap_fdatawait(mapping);
1177
1178 cond_resched();
Nick Piggin38f21972009-01-06 14:40:25 -08001179
Jens Axboe66f3b8e2009-09-02 09:19:46 +02001180 spin_lock(&inode_lock);
Jens Axboe66f3b8e2009-09-02 09:19:46 +02001181 }
Jens Axboe03ba3782009-09-09 09:08:54 +02001182 spin_unlock(&inode_lock);
1183 iput(old_inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001184}
1185
Jens Axboed8a85592009-09-02 12:34:32 +02001186/**
1187 * writeback_inodes_sb - writeback dirty inodes from given super_block
1188 * @sb: the superblock
Linus Torvalds1da177e2005-04-16 15:20:36 -07001189 *
Jens Axboed8a85592009-09-02 12:34:32 +02001190 * Start writeback on some inodes on this super_block. No guarantees are made
1191 * on how many (if any) will be written, and this function does not wait
1192 * for IO completion of submitted IO. The number of pages submitted is
1193 * returned.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001194 */
Jens Axboeb6e51312009-09-16 15:13:54 +02001195void writeback_inodes_sb(struct super_block *sb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001196{
Jens Axboed8a85592009-09-02 12:34:32 +02001197 unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY);
1198 unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS);
1199 long nr_to_write;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001200
Jens Axboed8a85592009-09-02 12:34:32 +02001201 nr_to_write = nr_dirty + nr_unstable +
Nick Piggin38f21972009-01-06 14:40:25 -08001202 (inodes_stat.nr_inodes - inodes_stat.nr_unused);
Nick Piggin38f21972009-01-06 14:40:25 -08001203
Jens Axboea72bfd42009-09-26 00:07:46 +02001204 bdi_start_writeback(sb->s_bdi, sb, nr_to_write);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001205}
Jens Axboed8a85592009-09-02 12:34:32 +02001206EXPORT_SYMBOL(writeback_inodes_sb);
1207
1208/**
Eric Sandeen17bd55d2009-12-23 07:57:07 -05001209 * writeback_inodes_sb_if_idle - start writeback if none underway
1210 * @sb: the superblock
1211 *
1212 * Invoke writeback_inodes_sb if no writeback is currently underway.
1213 * Returns 1 if writeback was started, 0 if not.
1214 */
1215int writeback_inodes_sb_if_idle(struct super_block *sb)
1216{
1217 if (!writeback_in_progress(sb->s_bdi)) {
1218 writeback_inodes_sb(sb);
1219 return 1;
1220 } else
1221 return 0;
1222}
1223EXPORT_SYMBOL(writeback_inodes_sb_if_idle);
1224
1225/**
Jens Axboed8a85592009-09-02 12:34:32 +02001226 * sync_inodes_sb - sync sb inode pages
1227 * @sb: the superblock
1228 *
1229 * This function writes and waits on any dirty inode belonging to this
1230 * super_block. The number of pages synced is returned.
1231 */
Jens Axboeb6e51312009-09-16 15:13:54 +02001232void sync_inodes_sb(struct super_block *sb)
Jens Axboed8a85592009-09-02 12:34:32 +02001233{
Jens Axboeb6e51312009-09-16 15:13:54 +02001234 bdi_sync_writeback(sb->s_bdi, sb);
1235 wait_sb_inodes(sb);
Jens Axboed8a85592009-09-02 12:34:32 +02001236}
1237EXPORT_SYMBOL(sync_inodes_sb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001238
Linus Torvalds1da177e2005-04-16 15:20:36 -07001239/**
Andrea Arcangeli7f04c262005-10-30 15:03:05 -08001240 * write_inode_now - write an inode to disk
1241 * @inode: inode to write to disk
1242 * @sync: whether the write should be synchronous or not
Linus Torvalds1da177e2005-04-16 15:20:36 -07001243 *
Andrea Arcangeli7f04c262005-10-30 15:03:05 -08001244 * This function commits an inode to disk immediately if it is dirty. This is
1245 * primarily needed by knfsd.
1246 *
1247 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001248 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001249int write_inode_now(struct inode *inode, int sync)
1250{
1251 int ret;
1252 struct writeback_control wbc = {
1253 .nr_to_write = LONG_MAX,
Mike Galbraith18914b12008-02-08 04:20:23 -08001254 .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
OGAWA Hirofumi111ebb62006-06-23 02:03:26 -07001255 .range_start = 0,
1256 .range_end = LLONG_MAX,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001257 };
1258
1259 if (!mapping_cap_writeback_dirty(inode->i_mapping))
Andrew Morton49364ce2005-11-07 00:59:15 -08001260 wbc.nr_to_write = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001261
1262 might_sleep();
1263 spin_lock(&inode_lock);
Christoph Hellwig01c03192009-06-08 13:35:40 +02001264 ret = writeback_single_inode(inode, &wbc);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001265 spin_unlock(&inode_lock);
1266 if (sync)
Joern Engel1c0eeaf2007-10-16 23:30:44 -07001267 inode_sync_wait(inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001268 return ret;
1269}
1270EXPORT_SYMBOL(write_inode_now);
1271
1272/**
1273 * sync_inode - write an inode and its pages to disk.
1274 * @inode: the inode to sync
1275 * @wbc: controls the writeback mode
1276 *
1277 * sync_inode() will write an inode and its pages to disk. It will also
1278 * correctly update the inode on its superblock's dirty inode lists and will
1279 * update inode->i_state.
1280 *
1281 * The caller must have a ref on the inode.
1282 */
1283int sync_inode(struct inode *inode, struct writeback_control *wbc)
1284{
1285 int ret;
1286
1287 spin_lock(&inode_lock);
Christoph Hellwig01c03192009-06-08 13:35:40 +02001288 ret = writeback_single_inode(inode, wbc);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001289 spin_unlock(&inode_lock);
1290 return ret;
1291}
1292EXPORT_SYMBOL(sync_inode);