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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 */
Christoph Hellwig83ba7b02010-07-06 08:59:53 +020041struct wb_writeback_work {
Jens Axboec4a77a62009-09-16 15:18:25 +020042 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
Jens Axboe8010c3b2009-09-15 20:04:57 +020049 struct list_head list; /* pending work list */
Christoph Hellwig83ba7b02010-07-06 08:59:53 +020050 struct completion *done; /* set if the caller waits */
Jens Axboe03ba3782009-09-09 09:08:54 +020051};
52
Adrian Bunkf11b00f2008-04-29 00:58:56 -070053/**
54 * writeback_in_progress - determine whether there is writeback in progress
55 * @bdi: the device's backing_dev_info structure.
56 *
Jens Axboe03ba3782009-09-09 09:08:54 +020057 * Determine whether there is writeback waiting to be handled against a
58 * backing device.
Adrian Bunkf11b00f2008-04-29 00:58:56 -070059 */
60int writeback_in_progress(struct backing_dev_info *bdi)
61{
Jens Axboe03ba3782009-09-09 09:08:54 +020062 return !list_empty(&bdi->work_list);
Adrian Bunkf11b00f2008-04-29 00:58:56 -070063}
64
Christoph Hellwig83ba7b02010-07-06 08:59:53 +020065static void bdi_queue_work(struct backing_dev_info *bdi,
66 struct wb_writeback_work *work)
Nick Piggin4195f732009-05-28 09:01:15 +020067{
Jens Axboebcddc3f2009-09-13 20:07:36 +020068 spin_lock(&bdi->wb_lock);
Christoph Hellwig83ba7b02010-07-06 08:59:53 +020069 list_add_tail(&work->list, &bdi->work_list);
Jens Axboebcddc3f2009-09-13 20:07:36 +020070 spin_unlock(&bdi->wb_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -070071
72 /*
Jens Axboe03ba3782009-09-09 09:08:54 +020073 * If the default thread isn't there, make sure we add it. When
74 * it gets created and wakes up, we'll run this work.
Linus Torvalds1da177e2005-04-16 15:20:36 -070075 */
Jens Axboe03ba3782009-09-09 09:08:54 +020076 if (unlikely(list_empty_careful(&bdi->wb_list)))
77 wake_up_process(default_backing_dev_info.wb.task);
78 else {
79 struct bdi_writeback *wb = &bdi->wb;
Linus Torvalds1da177e2005-04-16 15:20:36 -070080
Nick Piggin1ef7d9a2009-09-15 21:37:55 +020081 if (wb->task)
Jens Axboe03ba3782009-09-09 09:08:54 +020082 wake_up_process(wb->task);
Linus Torvalds1da177e2005-04-16 15:20:36 -070083 }
Linus Torvalds1da177e2005-04-16 15:20:36 -070084}
85
Christoph Hellwig83ba7b02010-07-06 08:59:53 +020086static void
87__bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
88 bool range_cyclic, bool for_background)
Linus Torvalds1da177e2005-04-16 15:20:36 -070089{
Christoph Hellwig83ba7b02010-07-06 08:59:53 +020090 struct wb_writeback_work *work;
Jens Axboe03ba3782009-09-09 09:08:54 +020091
Jens Axboebcddc3f2009-09-13 20:07:36 +020092 /*
93 * This is WB_SYNC_NONE writeback, so if allocation fails just
94 * wakeup the thread for old dirty data writeback
95 */
Christoph Hellwig83ba7b02010-07-06 08:59:53 +020096 work = kzalloc(sizeof(*work), GFP_ATOMIC);
97 if (!work) {
98 if (bdi->wb.task)
99 wake_up_process(bdi->wb.task);
100 return;
Jens Axboebcddc3f2009-09-13 20:07:36 +0200101 }
Jens Axboe03ba3782009-09-09 09:08:54 +0200102
Christoph Hellwig83ba7b02010-07-06 08:59:53 +0200103 work->sync_mode = WB_SYNC_NONE;
104 work->nr_pages = nr_pages;
105 work->range_cyclic = range_cyclic;
106 work->for_background = for_background;
Christoph Hellwigf0fad8a2009-09-11 09:47:56 +0200107
Christoph Hellwig83ba7b02010-07-06 08:59:53 +0200108 bdi_queue_work(bdi, work);
Jens Axboeb6e51312009-09-16 15:13:54 +0200109}
110
111/**
112 * bdi_start_writeback - start writeback
113 * @bdi: the backing device to write from
114 * @nr_pages: the number of pages to write
115 *
116 * Description:
117 * This does WB_SYNC_NONE opportunistic writeback. The IO is only
118 * started when this function returns, we make no guarentees on
Jens Axboe0e3c9a22010-06-01 11:08:43 +0200119 * completion. Caller need not hold sb s_umount semaphore.
Jens Axboeb6e51312009-09-16 15:13:54 +0200120 *
121 */
Christoph Hellwigc5444192010-06-08 18:15:15 +0200122void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages)
Jens Axboeb6e51312009-09-16 15:13:54 +0200123{
Christoph Hellwig83ba7b02010-07-06 08:59:53 +0200124 __bdi_start_writeback(bdi, nr_pages, true, false);
Christoph Hellwigc5444192010-06-08 18:15:15 +0200125}
Wu Fengguangd3ddec72009-09-23 20:33:40 +0800126
Christoph Hellwigc5444192010-06-08 18:15:15 +0200127/**
128 * bdi_start_background_writeback - start background writeback
129 * @bdi: the backing device to write from
130 *
131 * Description:
132 * This does WB_SYNC_NONE background writeback. The IO is only
133 * started when this function returns, we make no guarentees on
134 * completion. Caller need not hold sb s_umount semaphore.
135 */
136void bdi_start_background_writeback(struct backing_dev_info *bdi)
137{
Christoph Hellwig83ba7b02010-07-06 08:59:53 +0200138 __bdi_start_writeback(bdi, LONG_MAX, true, true);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700139}
140
141/*
Andrew Morton6610a0b2007-10-16 23:30:32 -0700142 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
143 * furthest end of its superblock's dirty-inode list.
144 *
145 * Before stamping the inode's ->dirtied_when, we check to see whether it is
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200146 * already the most-recently-dirtied inode on the b_dirty list. If that is
Andrew Morton6610a0b2007-10-16 23:30:32 -0700147 * the case then the inode must have been redirtied while it was being written
148 * out and we don't reset its dirtied_when.
149 */
150static void redirty_tail(struct inode *inode)
151{
Jens Axboe03ba3782009-09-09 09:08:54 +0200152 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
Andrew Morton6610a0b2007-10-16 23:30:32 -0700153
Jens Axboe03ba3782009-09-09 09:08:54 +0200154 if (!list_empty(&wb->b_dirty)) {
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200155 struct inode *tail;
Andrew Morton6610a0b2007-10-16 23:30:32 -0700156
Jens Axboe03ba3782009-09-09 09:08:54 +0200157 tail = list_entry(wb->b_dirty.next, struct inode, i_list);
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200158 if (time_before(inode->dirtied_when, tail->dirtied_when))
Andrew Morton6610a0b2007-10-16 23:30:32 -0700159 inode->dirtied_when = jiffies;
160 }
Jens Axboe03ba3782009-09-09 09:08:54 +0200161 list_move(&inode->i_list, &wb->b_dirty);
Andrew Morton6610a0b2007-10-16 23:30:32 -0700162}
163
164/*
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200165 * requeue inode for re-scanning after bdi->b_io list is exhausted.
Andrew Mortonc986d1e2007-10-16 23:30:34 -0700166 */
Ken Chen0e0f4fc2007-10-16 23:30:38 -0700167static void requeue_io(struct inode *inode)
Andrew Mortonc986d1e2007-10-16 23:30:34 -0700168{
Jens Axboe03ba3782009-09-09 09:08:54 +0200169 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
170
171 list_move(&inode->i_list, &wb->b_more_io);
Andrew Mortonc986d1e2007-10-16 23:30:34 -0700172}
173
Joern Engel1c0eeaf2007-10-16 23:30:44 -0700174static void inode_sync_complete(struct inode *inode)
175{
176 /*
177 * Prevent speculative execution through spin_unlock(&inode_lock);
178 */
179 smp_mb();
180 wake_up_bit(&inode->i_state, __I_SYNC);
181}
182
Jeff Laytond2caa3c52009-04-02 16:56:37 -0700183static bool inode_dirtied_after(struct inode *inode, unsigned long t)
184{
185 bool ret = time_after(inode->dirtied_when, t);
186#ifndef CONFIG_64BIT
187 /*
188 * For inodes being constantly redirtied, dirtied_when can get stuck.
189 * It _appears_ to be in the future, but is actually in distant past.
190 * This test is necessary to prevent such wrapped-around relative times
Jens Axboe5b0830c2009-09-23 19:37:09 +0200191 * from permanently stopping the whole bdi writeback.
Jeff Laytond2caa3c52009-04-02 16:56:37 -0700192 */
193 ret = ret && time_before_eq(inode->dirtied_when, jiffies);
194#endif
195 return ret;
196}
197
Andrew Mortonc986d1e2007-10-16 23:30:34 -0700198/*
Fengguang Wu2c136572007-10-16 23:30:39 -0700199 * Move expired dirty inodes from @delaying_queue to @dispatch_queue.
200 */
201static void move_expired_inodes(struct list_head *delaying_queue,
202 struct list_head *dispatch_queue,
203 unsigned long *older_than_this)
204{
Shaohua Li5c034492009-09-24 14:42:33 +0200205 LIST_HEAD(tmp);
206 struct list_head *pos, *node;
Jens Axboecf137302009-09-24 15:12:57 +0200207 struct super_block *sb = NULL;
Shaohua Li5c034492009-09-24 14:42:33 +0200208 struct inode *inode;
Jens Axboecf137302009-09-24 15:12:57 +0200209 int do_sb_sort = 0;
Shaohua Li5c034492009-09-24 14:42:33 +0200210
Fengguang Wu2c136572007-10-16 23:30:39 -0700211 while (!list_empty(delaying_queue)) {
Shaohua Li5c034492009-09-24 14:42:33 +0200212 inode = list_entry(delaying_queue->prev, struct inode, i_list);
Fengguang Wu2c136572007-10-16 23:30:39 -0700213 if (older_than_this &&
Jeff Laytond2caa3c52009-04-02 16:56:37 -0700214 inode_dirtied_after(inode, *older_than_this))
Fengguang Wu2c136572007-10-16 23:30:39 -0700215 break;
Jens Axboecf137302009-09-24 15:12:57 +0200216 if (sb && sb != inode->i_sb)
217 do_sb_sort = 1;
218 sb = inode->i_sb;
Shaohua Li5c034492009-09-24 14:42:33 +0200219 list_move(&inode->i_list, &tmp);
220 }
221
Jens Axboecf137302009-09-24 15:12:57 +0200222 /* just one sb in list, splice to dispatch_queue and we're done */
223 if (!do_sb_sort) {
224 list_splice(&tmp, dispatch_queue);
225 return;
226 }
227
Shaohua Li5c034492009-09-24 14:42:33 +0200228 /* Move inodes from one superblock together */
229 while (!list_empty(&tmp)) {
230 inode = list_entry(tmp.prev, struct inode, i_list);
231 sb = inode->i_sb;
232 list_for_each_prev_safe(pos, node, &tmp) {
233 inode = list_entry(pos, struct inode, i_list);
234 if (inode->i_sb == sb)
235 list_move(&inode->i_list, dispatch_queue);
236 }
Fengguang Wu2c136572007-10-16 23:30:39 -0700237 }
238}
239
240/*
241 * Queue all expired dirty inodes for io, eldest first.
242 */
Jens Axboe03ba3782009-09-09 09:08:54 +0200243static void queue_io(struct bdi_writeback *wb, unsigned long *older_than_this)
Fengguang Wu2c136572007-10-16 23:30:39 -0700244{
Jens Axboe03ba3782009-09-09 09:08:54 +0200245 list_splice_init(&wb->b_more_io, wb->b_io.prev);
246 move_expired_inodes(&wb->b_dirty, &wb->b_io, older_than_this);
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200247}
248
Christoph Hellwiga9185b42010-03-05 09:21:37 +0100249static int write_inode(struct inode *inode, struct writeback_control *wbc)
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200250{
Jens Axboe03ba3782009-09-09 09:08:54 +0200251 if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode))
Christoph Hellwiga9185b42010-03-05 09:21:37 +0100252 return inode->i_sb->s_op->write_inode(inode, wbc);
Jens Axboe03ba3782009-09-09 09:08:54 +0200253 return 0;
Fengguang Wu2c136572007-10-16 23:30:39 -0700254}
255
256/*
Christoph Hellwig01c03192009-06-08 13:35:40 +0200257 * Wait for writeback on an inode to complete.
258 */
259static void inode_wait_for_writeback(struct inode *inode)
260{
261 DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
262 wait_queue_head_t *wqh;
263
264 wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
Richard Kennedy58a9d3d82010-05-24 14:32:38 -0700265 while (inode->i_state & I_SYNC) {
Christoph Hellwig01c03192009-06-08 13:35:40 +0200266 spin_unlock(&inode_lock);
267 __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
268 spin_lock(&inode_lock);
Richard Kennedy58a9d3d82010-05-24 14:32:38 -0700269 }
Christoph Hellwig01c03192009-06-08 13:35:40 +0200270}
271
272/*
273 * Write out an inode's dirty pages. Called under inode_lock. Either the
274 * caller has ref on the inode (either via __iget or via syscall against an fd)
275 * or the inode has I_WILL_FREE set (via generic_forget_inode)
276 *
Linus Torvalds1da177e2005-04-16 15:20:36 -0700277 * If `wait' is set, wait on the writeout.
278 *
279 * The whole writeout design is quite complex and fragile. We want to avoid
280 * starvation of particular inodes when others are being redirtied, prevent
281 * livelocks, etc.
282 *
283 * Called under inode_lock.
284 */
285static int
Christoph Hellwig01c03192009-06-08 13:35:40 +0200286writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700287{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700288 struct address_space *mapping = inode->i_mapping;
Christoph Hellwig01c03192009-06-08 13:35:40 +0200289 unsigned dirty;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700290 int ret;
291
Christoph Hellwig01c03192009-06-08 13:35:40 +0200292 if (!atomic_read(&inode->i_count))
293 WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
294 else
295 WARN_ON(inode->i_state & I_WILL_FREE);
296
297 if (inode->i_state & I_SYNC) {
298 /*
299 * If this inode is locked for writeback and we are not doing
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200300 * writeback-for-data-integrity, move it to b_more_io so that
Christoph Hellwig01c03192009-06-08 13:35:40 +0200301 * writeback can proceed with the other inodes on s_io.
302 *
303 * We'll have another go at writing back this inode when we
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200304 * completed a full scan of b_io.
Christoph Hellwig01c03192009-06-08 13:35:40 +0200305 */
Christoph Hellwiga9185b42010-03-05 09:21:37 +0100306 if (wbc->sync_mode != WB_SYNC_ALL) {
Christoph Hellwig01c03192009-06-08 13:35:40 +0200307 requeue_io(inode);
308 return 0;
309 }
310
311 /*
312 * It's a data-integrity sync. We must wait.
313 */
314 inode_wait_for_writeback(inode);
315 }
316
Joern Engel1c0eeaf2007-10-16 23:30:44 -0700317 BUG_ON(inode->i_state & I_SYNC);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700318
Dmitry Monakhov5547e8a2010-05-07 13:35:44 +0400319 /* Set I_SYNC, reset I_DIRTY_PAGES */
Joern Engel1c0eeaf2007-10-16 23:30:44 -0700320 inode->i_state |= I_SYNC;
Dmitry Monakhov5547e8a2010-05-07 13:35:44 +0400321 inode->i_state &= ~I_DIRTY_PAGES;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700322 spin_unlock(&inode_lock);
323
324 ret = do_writepages(mapping, wbc);
325
Christoph Hellwig26821ed2010-03-05 09:21:21 +0100326 /*
327 * Make sure to wait on the data before writing out the metadata.
328 * This is important for filesystems that modify metadata on data
329 * I/O completion.
330 */
Christoph Hellwiga9185b42010-03-05 09:21:37 +0100331 if (wbc->sync_mode == WB_SYNC_ALL) {
Christoph Hellwig26821ed2010-03-05 09:21:21 +0100332 int err = filemap_fdatawait(mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700333 if (ret == 0)
334 ret = err;
335 }
336
Dmitry Monakhov5547e8a2010-05-07 13:35:44 +0400337 /*
338 * Some filesystems may redirty the inode during the writeback
339 * due to delalloc, clear dirty metadata flags right before
340 * write_inode()
341 */
342 spin_lock(&inode_lock);
343 dirty = inode->i_state & I_DIRTY;
344 inode->i_state &= ~(I_DIRTY_SYNC | I_DIRTY_DATASYNC);
345 spin_unlock(&inode_lock);
Christoph Hellwig26821ed2010-03-05 09:21:21 +0100346 /* Don't write the inode if only I_DIRTY_PAGES was set */
347 if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
Christoph Hellwiga9185b42010-03-05 09:21:37 +0100348 int err = write_inode(inode, wbc);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700349 if (ret == 0)
350 ret = err;
351 }
352
353 spin_lock(&inode_lock);
Joern Engel1c0eeaf2007-10-16 23:30:44 -0700354 inode->i_state &= ~I_SYNC;
Wu Fengguang84a89242009-06-16 15:33:17 -0700355 if (!(inode->i_state & (I_FREEING | I_CLEAR))) {
Wu Fengguangb3af9462009-09-25 06:04:10 +0200356 if ((inode->i_state & I_DIRTY_PAGES) && wbc->for_kupdate) {
Wu Fengguangae1b7f72009-09-23 20:33:42 +0800357 /*
Wu Fengguangb3af9462009-09-25 06:04:10 +0200358 * More pages get dirtied by a fast dirtier.
359 */
360 goto select_queue;
361 } else if (inode->i_state & I_DIRTY) {
362 /*
363 * At least XFS will redirty the inode during the
364 * writeback (delalloc) and on io completion (isize).
Wu Fengguangae1b7f72009-09-23 20:33:42 +0800365 */
366 redirty_tail(inode);
367 } else if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700368 /*
369 * We didn't write back all the pages. nfs_writepages()
370 * sometimes bales out without doing anything. Redirty
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200371 * the inode; Move it from b_io onto b_more_io/b_dirty.
Andrew Morton1b43ef92007-10-16 23:30:35 -0700372 */
373 /*
374 * akpm: if the caller was the kupdate function we put
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200375 * this inode at the head of b_dirty so it gets first
Andrew Morton1b43ef92007-10-16 23:30:35 -0700376 * consideration. Otherwise, move it to the tail, for
377 * the reasons described there. I'm not really sure
378 * how much sense this makes. Presumably I had a good
379 * reasons for doing it this way, and I'd rather not
380 * muck with it at present.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700381 */
382 if (wbc->for_kupdate) {
383 /*
Fengguang Wu2c136572007-10-16 23:30:39 -0700384 * For the kupdate function we move the inode
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200385 * to b_more_io so it will get more writeout as
Fengguang Wu2c136572007-10-16 23:30:39 -0700386 * soon as the queue becomes uncongested.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700387 */
388 inode->i_state |= I_DIRTY_PAGES;
Wu Fengguangb3af9462009-09-25 06:04:10 +0200389select_queue:
Fengguang Wu8bc3be22008-02-04 22:29:36 -0800390 if (wbc->nr_to_write <= 0) {
391 /*
392 * slice used up: queue for next turn
393 */
394 requeue_io(inode);
395 } else {
396 /*
397 * somehow blocked: retry later
398 */
399 redirty_tail(inode);
400 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700401 } else {
402 /*
403 * Otherwise fully redirty the inode so that
404 * other inodes on this superblock will get some
405 * writeout. Otherwise heavy writing to one
406 * file would indefinitely suspend writeout of
407 * all the other files.
408 */
409 inode->i_state |= I_DIRTY_PAGES;
Andrew Morton1b43ef92007-10-16 23:30:35 -0700410 redirty_tail(inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700411 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700412 } else if (atomic_read(&inode->i_count)) {
413 /*
414 * The inode is clean, inuse
415 */
416 list_move(&inode->i_list, &inode_in_use);
417 } else {
418 /*
419 * The inode is clean, unused
420 */
421 list_move(&inode->i_list, &inode_unused);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700422 }
423 }
Joern Engel1c0eeaf2007-10-16 23:30:44 -0700424 inode_sync_complete(inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700425 return ret;
426}
427
Jens Axboe03ba3782009-09-09 09:08:54 +0200428/*
Christoph Hellwigd19de7e2010-06-08 18:14:58 +0200429 * For background writeback the caller does not have the sb pinned
Jens Axboe03ba3782009-09-09 09:08:54 +0200430 * before calling writeback. So make sure that we do pin it, so it doesn't
431 * go away while we are writing inodes from it.
Jens Axboe03ba3782009-09-09 09:08:54 +0200432 */
Christoph Hellwigd19de7e2010-06-08 18:14:58 +0200433static bool pin_sb_for_writeback(struct super_block *sb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700434{
Jens Axboe03ba3782009-09-09 09:08:54 +0200435 spin_lock(&sb_lock);
Christoph Hellwig29cb48592010-06-09 15:31:01 +0200436 if (list_empty(&sb->s_instances)) {
437 spin_unlock(&sb_lock);
438 return false;
439 }
440
Jens Axboe03ba3782009-09-09 09:08:54 +0200441 sb->s_count++;
Christoph Hellwig29cb48592010-06-09 15:31:01 +0200442 spin_unlock(&sb_lock);
443
Jens Axboe03ba3782009-09-09 09:08:54 +0200444 if (down_read_trylock(&sb->s_umount)) {
Christoph Hellwig29cb48592010-06-09 15:31:01 +0200445 if (sb->s_root)
Christoph Hellwigd19de7e2010-06-08 18:14:58 +0200446 return true;
Jens Axboe03ba3782009-09-09 09:08:54 +0200447 up_read(&sb->s_umount);
448 }
Christoph Hellwig29cb48592010-06-09 15:31:01 +0200449
450 put_super(sb);
Christoph Hellwigd19de7e2010-06-08 18:14:58 +0200451 return false;
Jens Axboe03ba3782009-09-09 09:08:54 +0200452}
453
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800454/*
455 * Write a portion of b_io inodes which belong to @sb.
Christoph Hellwigedadfb12010-06-10 12:07:54 +0200456 *
457 * If @only_this_sb is true, then find and write all such
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800458 * inodes. Otherwise write only ones which go sequentially
459 * in reverse order.
Christoph Hellwigedadfb12010-06-10 12:07:54 +0200460 *
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800461 * Return 1, if the caller writeback routine should be
462 * interrupted. Otherwise return 0.
463 */
Christoph Hellwigedadfb12010-06-10 12:07:54 +0200464static int writeback_sb_inodes(struct super_block *sb, struct bdi_writeback *wb,
465 struct writeback_control *wbc, bool only_this_sb)
Jens Axboe03ba3782009-09-09 09:08:54 +0200466{
Jens Axboe03ba3782009-09-09 09:08:54 +0200467 while (!list_empty(&wb->b_io)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700468 long pages_skipped;
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800469 struct inode *inode = list_entry(wb->b_io.prev,
470 struct inode, i_list);
Christoph Hellwigedadfb12010-06-10 12:07:54 +0200471
472 if (inode->i_sb != sb) {
473 if (only_this_sb) {
474 /*
475 * We only want to write back data for this
476 * superblock, move all inodes not belonging
477 * to it back onto the dirty list.
478 */
479 redirty_tail(inode);
480 continue;
481 }
482
483 /*
484 * The inode belongs to a different superblock.
485 * Bounce back to the caller to unpin this and
486 * pin the next superblock.
487 */
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800488 return 0;
Christoph Hellwigedadfb12010-06-10 12:07:54 +0200489 }
490
Wu Fengguang84a89242009-06-16 15:33:17 -0700491 if (inode->i_state & (I_NEW | I_WILL_FREE)) {
Nick Piggin7ef0d732009-03-12 14:31:38 -0700492 requeue_io(inode);
493 continue;
494 }
Jeff Laytond2caa3c52009-04-02 16:56:37 -0700495 /*
496 * Was this inode dirtied after sync_sb_inodes was called?
497 * This keeps sync from extra jobs and livelock.
498 */
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800499 if (inode_dirtied_after(inode, wbc->wb_start))
500 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700501
Wu Fengguang84a89242009-06-16 15:33:17 -0700502 BUG_ON(inode->i_state & (I_FREEING | I_CLEAR));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700503 __iget(inode);
504 pages_skipped = wbc->pages_skipped;
Christoph Hellwig01c03192009-06-08 13:35:40 +0200505 writeback_single_inode(inode, wbc);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700506 if (wbc->pages_skipped != pages_skipped) {
507 /*
508 * writeback is not making progress due to locked
509 * buffers. Skip this inode for now.
510 */
Andrew Mortonf57b9b72007-10-16 23:30:34 -0700511 redirty_tail(inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700512 }
513 spin_unlock(&inode_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700514 iput(inode);
OGAWA Hirofumi4ffc8442006-03-25 03:07:44 -0800515 cond_resched();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700516 spin_lock(&inode_lock);
Fengguang Wu8bc3be22008-02-04 22:29:36 -0800517 if (wbc->nr_to_write <= 0) {
518 wbc->more_io = 1;
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800519 return 1;
Fengguang Wu8bc3be22008-02-04 22:29:36 -0800520 }
Jens Axboe03ba3782009-09-09 09:08:54 +0200521 if (!list_empty(&wb->b_more_io))
Fengguang Wu8bc3be22008-02-04 22:29:36 -0800522 wbc->more_io = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700523 }
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800524 /* b_io is empty */
525 return 1;
526}
Nick Piggin38f21972009-01-06 14:40:25 -0800527
Christoph Hellwig9c3a8ee2010-06-10 12:07:27 +0200528void writeback_inodes_wb(struct bdi_writeback *wb,
529 struct writeback_control *wbc)
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800530{
531 int ret = 0;
Jens Axboe9ecc2732009-09-24 15:25:11 +0200532
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800533 wbc->wb_start = jiffies; /* livelock avoidance */
534 spin_lock(&inode_lock);
535 if (!wbc->for_kupdate || list_empty(&wb->b_io))
536 queue_io(wb, wbc->older_than_this);
537
538 while (!list_empty(&wb->b_io)) {
539 struct inode *inode = list_entry(wb->b_io.prev,
540 struct inode, i_list);
541 struct super_block *sb = inode->i_sb;
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800542
Christoph Hellwigedadfb12010-06-10 12:07:54 +0200543 if (!pin_sb_for_writeback(sb)) {
544 requeue_io(inode);
545 continue;
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800546 }
Christoph Hellwigedadfb12010-06-10 12:07:54 +0200547 ret = writeback_sb_inodes(sb, wb, wbc, false);
548 drop_super(sb);
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800549
Edward Shishkinf11c9c52010-03-11 14:09:47 -0800550 if (ret)
551 break;
552 }
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200553 spin_unlock(&inode_lock);
554 /* Leave any unwritten inodes on b_io */
555}
556
Christoph Hellwigedadfb12010-06-10 12:07:54 +0200557static void __writeback_inodes_sb(struct super_block *sb,
558 struct bdi_writeback *wb, struct writeback_control *wbc)
559{
560 WARN_ON(!rwsem_is_locked(&sb->s_umount));
561
562 wbc->wb_start = jiffies; /* livelock avoidance */
563 spin_lock(&inode_lock);
564 if (!wbc->for_kupdate || list_empty(&wb->b_io))
565 queue_io(wb, wbc->older_than_this);
566 writeback_sb_inodes(sb, wb, wbc, true);
567 spin_unlock(&inode_lock);
568}
569
Jens Axboe03ba3782009-09-09 09:08:54 +0200570/*
571 * The maximum number of pages to writeout in a single bdi flush/kupdate
572 * operation. We do this so we don't hold I_SYNC against an inode for
573 * enormous amounts of time, which would block a userspace task which has
574 * been forced to throttle against that inode. Also, the code reevaluates
575 * the dirty each time it has written this many pages.
576 */
577#define MAX_WRITEBACK_PAGES 1024
578
579static inline bool over_bground_thresh(void)
580{
581 unsigned long background_thresh, dirty_thresh;
582
583 get_dirty_limits(&background_thresh, &dirty_thresh, NULL, NULL);
584
585 return (global_page_state(NR_FILE_DIRTY) +
586 global_page_state(NR_UNSTABLE_NFS) >= background_thresh);
587}
588
589/*
590 * Explicit flushing or periodic writeback of "old" data.
591 *
592 * Define "old": the first time one of an inode's pages is dirtied, we mark the
593 * dirtying-time in the inode's address_space. So this periodic writeback code
594 * just walks the superblock inode list, writing back any inodes which are
595 * older than a specific point in time.
596 *
597 * Try to run once per dirty_writeback_interval. But if a writeback event
598 * takes longer than a dirty_writeback_interval interval, then leave a
599 * one-second gap.
600 *
601 * older_than_this takes precedence over nr_to_write. So we'll only write back
602 * all dirty pages if they are all attached to "old" mappings.
603 */
Jens Axboec4a77a62009-09-16 15:18:25 +0200604static long wb_writeback(struct bdi_writeback *wb,
Christoph Hellwig83ba7b02010-07-06 08:59:53 +0200605 struct wb_writeback_work *work)
Jens Axboe03ba3782009-09-09 09:08:54 +0200606{
607 struct writeback_control wbc = {
Christoph Hellwig83ba7b02010-07-06 08:59:53 +0200608 .sync_mode = work->sync_mode,
Jens Axboe03ba3782009-09-09 09:08:54 +0200609 .older_than_this = NULL,
Christoph Hellwig83ba7b02010-07-06 08:59:53 +0200610 .for_kupdate = work->for_kupdate,
611 .for_background = work->for_background,
612 .range_cyclic = work->range_cyclic,
Jens Axboe03ba3782009-09-09 09:08:54 +0200613 };
614 unsigned long oldest_jif;
615 long wrote = 0;
Jan Karaa5989bd2009-09-16 19:22:48 +0200616 struct inode *inode;
Jens Axboe03ba3782009-09-09 09:08:54 +0200617
618 if (wbc.for_kupdate) {
619 wbc.older_than_this = &oldest_jif;
620 oldest_jif = jiffies -
621 msecs_to_jiffies(dirty_expire_interval * 10);
622 }
Jens Axboec4a77a62009-09-16 15:18:25 +0200623 if (!wbc.range_cyclic) {
624 wbc.range_start = 0;
625 wbc.range_end = LLONG_MAX;
626 }
Jens Axboe03ba3782009-09-09 09:08:54 +0200627
628 for (;;) {
629 /*
Wu Fengguangd3ddec72009-09-23 20:33:40 +0800630 * Stop writeback when nr_pages has been consumed
Jens Axboe03ba3782009-09-09 09:08:54 +0200631 */
Christoph Hellwig83ba7b02010-07-06 08:59:53 +0200632 if (work->nr_pages <= 0)
Jens Axboe03ba3782009-09-09 09:08:54 +0200633 break;
634
635 /*
Wu Fengguangd3ddec72009-09-23 20:33:40 +0800636 * For background writeout, stop when we are below the
637 * background dirty threshold
Jens Axboe03ba3782009-09-09 09:08:54 +0200638 */
Christoph Hellwig83ba7b02010-07-06 08:59:53 +0200639 if (work->for_background && !over_bground_thresh())
Jens Axboe03ba3782009-09-09 09:08:54 +0200640 break;
641
642 wbc.more_io = 0;
Jens Axboe03ba3782009-09-09 09:08:54 +0200643 wbc.nr_to_write = MAX_WRITEBACK_PAGES;
644 wbc.pages_skipped = 0;
Christoph Hellwig83ba7b02010-07-06 08:59:53 +0200645 if (work->sb)
646 __writeback_inodes_sb(work->sb, wb, &wbc);
Christoph Hellwigedadfb12010-06-10 12:07:54 +0200647 else
648 writeback_inodes_wb(wb, &wbc);
Christoph Hellwig83ba7b02010-07-06 08:59:53 +0200649 work->nr_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
Jens Axboe03ba3782009-09-09 09:08:54 +0200650 wrote += MAX_WRITEBACK_PAGES - wbc.nr_to_write;
651
652 /*
Jens Axboe71fd05a2009-09-23 19:32:26 +0200653 * If we consumed everything, see if we have more
Jens Axboe03ba3782009-09-09 09:08:54 +0200654 */
Jens Axboe71fd05a2009-09-23 19:32:26 +0200655 if (wbc.nr_to_write <= 0)
656 continue;
657 /*
658 * Didn't write everything and we don't have more IO, bail
659 */
660 if (!wbc.more_io)
Jens Axboe03ba3782009-09-09 09:08:54 +0200661 break;
Jens Axboe71fd05a2009-09-23 19:32:26 +0200662 /*
663 * Did we write something? Try for more
664 */
665 if (wbc.nr_to_write < MAX_WRITEBACK_PAGES)
666 continue;
667 /*
668 * Nothing written. Wait for some inode to
669 * become available for writeback. Otherwise
670 * we'll just busyloop.
671 */
672 spin_lock(&inode_lock);
673 if (!list_empty(&wb->b_more_io)) {
674 inode = list_entry(wb->b_more_io.prev,
675 struct inode, i_list);
676 inode_wait_for_writeback(inode);
Jens Axboe03ba3782009-09-09 09:08:54 +0200677 }
Jens Axboe71fd05a2009-09-23 19:32:26 +0200678 spin_unlock(&inode_lock);
Jens Axboe03ba3782009-09-09 09:08:54 +0200679 }
680
681 return wrote;
682}
683
684/*
Christoph Hellwig83ba7b02010-07-06 08:59:53 +0200685 * Return the next wb_writeback_work struct that hasn't been processed yet.
Jens Axboe03ba3782009-09-09 09:08:54 +0200686 */
Christoph Hellwig83ba7b02010-07-06 08:59:53 +0200687static struct wb_writeback_work *
688get_next_work_item(struct backing_dev_info *bdi, struct bdi_writeback *wb)
Jens Axboe03ba3782009-09-09 09:08:54 +0200689{
Christoph Hellwig83ba7b02010-07-06 08:59:53 +0200690 struct wb_writeback_work *work = NULL;
Jens Axboe03ba3782009-09-09 09:08:54 +0200691
Christoph Hellwig83ba7b02010-07-06 08:59:53 +0200692 spin_lock(&bdi->wb_lock);
693 if (!list_empty(&bdi->work_list)) {
694 work = list_entry(bdi->work_list.next,
695 struct wb_writeback_work, list);
696 list_del_init(&work->list);
Jens Axboe03ba3782009-09-09 09:08:54 +0200697 }
Christoph Hellwig83ba7b02010-07-06 08:59:53 +0200698 spin_unlock(&bdi->wb_lock);
699 return work;
Jens Axboe03ba3782009-09-09 09:08:54 +0200700}
701
702static long wb_check_old_data_flush(struct bdi_writeback *wb)
703{
704 unsigned long expired;
705 long nr_pages;
706
Jens Axboe69b62d02010-05-17 12:51:03 +0200707 /*
708 * When set to zero, disable periodic writeback
709 */
710 if (!dirty_writeback_interval)
711 return 0;
712
Jens Axboe03ba3782009-09-09 09:08:54 +0200713 expired = wb->last_old_flush +
714 msecs_to_jiffies(dirty_writeback_interval * 10);
715 if (time_before(jiffies, expired))
716 return 0;
717
718 wb->last_old_flush = jiffies;
719 nr_pages = global_page_state(NR_FILE_DIRTY) +
720 global_page_state(NR_UNSTABLE_NFS) +
721 (inodes_stat.nr_inodes - inodes_stat.nr_unused);
722
Jens Axboec4a77a62009-09-16 15:18:25 +0200723 if (nr_pages) {
Christoph Hellwig83ba7b02010-07-06 08:59:53 +0200724 struct wb_writeback_work work = {
Jens Axboec4a77a62009-09-16 15:18:25 +0200725 .nr_pages = nr_pages,
726 .sync_mode = WB_SYNC_NONE,
727 .for_kupdate = 1,
728 .range_cyclic = 1,
729 };
730
Christoph Hellwig83ba7b02010-07-06 08:59:53 +0200731 return wb_writeback(wb, &work);
Jens Axboec4a77a62009-09-16 15:18:25 +0200732 }
Jens Axboe03ba3782009-09-09 09:08:54 +0200733
734 return 0;
735}
736
737/*
738 * Retrieve work items and do the writeback they describe
739 */
740long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
741{
742 struct backing_dev_info *bdi = wb->bdi;
Christoph Hellwig83ba7b02010-07-06 08:59:53 +0200743 struct wb_writeback_work *work;
Jens Axboec4a77a62009-09-16 15:18:25 +0200744 long wrote = 0;
Jens Axboe03ba3782009-09-09 09:08:54 +0200745
746 while ((work = get_next_work_item(bdi, wb)) != NULL) {
Jens Axboe03ba3782009-09-09 09:08:54 +0200747 /*
748 * Override sync mode, in case we must wait for completion
Christoph Hellwig83ba7b02010-07-06 08:59:53 +0200749 * because this thread is exiting now.
Jens Axboe03ba3782009-09-09 09:08:54 +0200750 */
751 if (force_wait)
Christoph Hellwig83ba7b02010-07-06 08:59:53 +0200752 work->sync_mode = WB_SYNC_ALL;
753
754 wrote += wb_writeback(wb, work);
Jens Axboe03ba3782009-09-09 09:08:54 +0200755
756 /*
Christoph Hellwig83ba7b02010-07-06 08:59:53 +0200757 * Notify the caller of completion if this is a synchronous
758 * work item, otherwise just free it.
Jens Axboe03ba3782009-09-09 09:08:54 +0200759 */
Christoph Hellwig83ba7b02010-07-06 08:59:53 +0200760 if (work->done)
761 complete(work->done);
762 else
763 kfree(work);
Jens Axboe03ba3782009-09-09 09:08:54 +0200764 }
765
766 /*
767 * Check for periodic writeback, kupdated() style
768 */
769 wrote += wb_check_old_data_flush(wb);
770
771 return wrote;
772}
773
774/*
775 * Handle writeback of dirty data for the device backed by this bdi. Also
776 * wakes up periodically and does kupdated style flushing.
777 */
778int bdi_writeback_task(struct bdi_writeback *wb)
779{
780 unsigned long last_active = jiffies;
781 unsigned long wait_jiffies = -1UL;
782 long pages_written;
783
784 while (!kthread_should_stop()) {
785 pages_written = wb_do_writeback(wb, 0);
786
787 if (pages_written)
788 last_active = jiffies;
789 else if (wait_jiffies != -1UL) {
790 unsigned long max_idle;
791
792 /*
793 * Longest period of inactivity that we tolerate. If we
794 * see dirty data again later, the task will get
795 * recreated automatically.
796 */
797 max_idle = max(5UL * 60 * HZ, wait_jiffies);
798 if (time_after(jiffies, max_idle + last_active))
799 break;
800 }
801
Jens Axboe69b62d02010-05-17 12:51:03 +0200802 if (dirty_writeback_interval) {
803 wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10);
804 schedule_timeout_interruptible(wait_jiffies);
Jens Axboef9eadbb2010-05-18 14:31:45 +0200805 } else {
806 set_current_state(TASK_INTERRUPTIBLE);
807 if (list_empty_careful(&wb->bdi->work_list) &&
808 !kthread_should_stop())
809 schedule();
810 __set_current_state(TASK_RUNNING);
811 }
Jens Axboe69b62d02010-05-17 12:51:03 +0200812
Jens Axboe03ba3782009-09-09 09:08:54 +0200813 try_to_freeze();
814 }
815
816 return 0;
817}
818
819/*
Jens Axboe03ba3782009-09-09 09:08:54 +0200820 * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
821 * the whole world.
822 */
823void wakeup_flusher_threads(long nr_pages)
824{
Christoph Hellwigb8c2f342010-06-08 18:15:07 +0200825 struct backing_dev_info *bdi;
Christoph Hellwigb8c2f342010-06-08 18:15:07 +0200826
Christoph Hellwig83ba7b02010-07-06 08:59:53 +0200827 if (!nr_pages) {
828 nr_pages = global_page_state(NR_FILE_DIRTY) +
Jens Axboe03ba3782009-09-09 09:08:54 +0200829 global_page_state(NR_UNSTABLE_NFS);
Christoph Hellwigb8c2f342010-06-08 18:15:07 +0200830 }
831
832 rcu_read_lock();
833 list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
834 if (!bdi_has_dirty_io(bdi))
835 continue;
Christoph Hellwig83ba7b02010-07-06 08:59:53 +0200836 __bdi_start_writeback(bdi, nr_pages, false, false);
Christoph Hellwigb8c2f342010-06-08 18:15:07 +0200837 }
838 rcu_read_unlock();
Jens Axboe03ba3782009-09-09 09:08:54 +0200839}
840
841static noinline void block_dump___mark_inode_dirty(struct inode *inode)
842{
843 if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
844 struct dentry *dentry;
845 const char *name = "?";
846
847 dentry = d_find_alias(inode);
848 if (dentry) {
849 spin_lock(&dentry->d_lock);
850 name = (const char *) dentry->d_name.name;
851 }
852 printk(KERN_DEBUG
853 "%s(%d): dirtied inode %lu (%s) on %s\n",
854 current->comm, task_pid_nr(current), inode->i_ino,
855 name, inode->i_sb->s_id);
856 if (dentry) {
857 spin_unlock(&dentry->d_lock);
858 dput(dentry);
859 }
860 }
861}
862
863/**
864 * __mark_inode_dirty - internal function
865 * @inode: inode to mark
866 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
867 * Mark an inode as dirty. Callers should use mark_inode_dirty or
868 * mark_inode_dirty_sync.
869 *
870 * Put the inode on the super block's dirty list.
871 *
872 * CAREFUL! We mark it dirty unconditionally, but move it onto the
873 * dirty list only if it is hashed or if it refers to a blockdev.
874 * If it was not hashed, it will never be added to the dirty list
875 * even if it is later hashed, as it will have been marked dirty already.
876 *
877 * In short, make sure you hash any inodes _before_ you start marking
878 * them dirty.
879 *
880 * This function *must* be atomic for the I_DIRTY_PAGES case -
881 * set_page_dirty() is called under spinlock in several places.
882 *
883 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
884 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
885 * the kernel-internal blockdev inode represents the dirtying time of the
886 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
887 * page->mapping->host, so the page-dirtying time is recorded in the internal
888 * blockdev inode.
889 */
890void __mark_inode_dirty(struct inode *inode, int flags)
891{
892 struct super_block *sb = inode->i_sb;
893
894 /*
895 * Don't do this for I_DIRTY_PAGES - that doesn't actually
896 * dirty the inode itself
897 */
898 if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
899 if (sb->s_op->dirty_inode)
900 sb->s_op->dirty_inode(inode);
901 }
902
903 /*
904 * make sure that changes are seen by all cpus before we test i_state
905 * -- mikulas
906 */
907 smp_mb();
908
909 /* avoid the locking if we can */
910 if ((inode->i_state & flags) == flags)
911 return;
912
913 if (unlikely(block_dump))
914 block_dump___mark_inode_dirty(inode);
915
916 spin_lock(&inode_lock);
917 if ((inode->i_state & flags) != flags) {
918 const int was_dirty = inode->i_state & I_DIRTY;
919
920 inode->i_state |= flags;
921
922 /*
923 * If the inode is being synced, just update its dirty state.
924 * The unlocker will place the inode on the appropriate
925 * superblock list, based upon its state.
926 */
927 if (inode->i_state & I_SYNC)
928 goto out;
929
930 /*
931 * Only add valid (hashed) inodes to the superblock's
932 * dirty list. Add blockdev inodes as well.
933 */
934 if (!S_ISBLK(inode->i_mode)) {
935 if (hlist_unhashed(&inode->i_hash))
936 goto out;
937 }
938 if (inode->i_state & (I_FREEING|I_CLEAR))
939 goto out;
940
941 /*
942 * If the inode was already on b_dirty/b_io/b_more_io, don't
943 * reposition it (that would break b_dirty time-ordering).
944 */
945 if (!was_dirty) {
946 struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
Jens Axboe500b0672009-09-09 09:10:25 +0200947 struct backing_dev_info *bdi = wb->bdi;
948
949 if (bdi_cap_writeback_dirty(bdi) &&
950 !test_bit(BDI_registered, &bdi->state)) {
951 WARN_ON(1);
952 printk(KERN_ERR "bdi-%s not registered\n",
953 bdi->name);
954 }
Jens Axboe03ba3782009-09-09 09:08:54 +0200955
956 inode->dirtied_when = jiffies;
957 list_move(&inode->i_list, &wb->b_dirty);
958 }
959 }
960out:
961 spin_unlock(&inode_lock);
962}
963EXPORT_SYMBOL(__mark_inode_dirty);
964
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200965/*
966 * Write out a superblock's list of dirty inodes. A wait will be performed
967 * upon no inodes, all inodes or the final one, depending upon sync_mode.
968 *
969 * If older_than_this is non-NULL, then only write out inodes which
970 * had their first dirtying at a time earlier than *older_than_this.
971 *
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200972 * If `bdi' is non-zero then we're being asked to writeback a specific queue.
973 * This function assumes that the blockdev superblock's inodes are backed by
974 * a variety of queues, so all inodes are searched. For other superblocks,
975 * assume that all inodes are backed by the same queue.
976 *
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200977 * The inodes to be written are parked on bdi->b_io. They are moved back onto
978 * bdi->b_dirty as they are selected for writing. This way, none can be missed
979 * on the writer throttling path, and we get decent balancing between many
980 * throttled threads: we don't want them all piling up on inode_sync_wait.
981 */
Jens Axboeb6e51312009-09-16 15:13:54 +0200982static void wait_sb_inodes(struct super_block *sb)
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200983{
Jens Axboe03ba3782009-09-09 09:08:54 +0200984 struct inode *inode, *old_inode = NULL;
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200985
Jens Axboe03ba3782009-09-09 09:08:54 +0200986 /*
987 * We need to be protected against the filesystem going from
988 * r/o to r/w or vice versa.
989 */
Jens Axboeb6e51312009-09-16 15:13:54 +0200990 WARN_ON(!rwsem_is_locked(&sb->s_umount));
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200991
Jens Axboe03ba3782009-09-09 09:08:54 +0200992 spin_lock(&inode_lock);
993
994 /*
995 * Data integrity sync. Must wait for all pages under writeback,
996 * because there may have been pages dirtied before our sync
997 * call, but which had writeout started before we write it out.
998 * In which case, the inode may not be on the dirty list, but
999 * we still have to wait for that writeout.
1000 */
Jens Axboeb6e51312009-09-16 15:13:54 +02001001 list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
Jens Axboe03ba3782009-09-09 09:08:54 +02001002 struct address_space *mapping;
1003
1004 if (inode->i_state & (I_FREEING|I_CLEAR|I_WILL_FREE|I_NEW))
1005 continue;
1006 mapping = inode->i_mapping;
1007 if (mapping->nrpages == 0)
1008 continue;
1009 __iget(inode);
1010 spin_unlock(&inode_lock);
1011 /*
1012 * We hold a reference to 'inode' so it couldn't have
1013 * been removed from s_inodes list while we dropped the
1014 * inode_lock. We cannot iput the inode now as we can
1015 * be holding the last reference and we cannot iput it
1016 * under inode_lock. So we keep the reference and iput
1017 * it later.
1018 */
1019 iput(old_inode);
1020 old_inode = inode;
1021
1022 filemap_fdatawait(mapping);
1023
1024 cond_resched();
Nick Piggin38f21972009-01-06 14:40:25 -08001025
Jens Axboe66f3b8e2009-09-02 09:19:46 +02001026 spin_lock(&inode_lock);
Jens Axboe66f3b8e2009-09-02 09:19:46 +02001027 }
Jens Axboe03ba3782009-09-09 09:08:54 +02001028 spin_unlock(&inode_lock);
1029 iput(old_inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001030}
1031
Jens Axboed8a85592009-09-02 12:34:32 +02001032/**
1033 * writeback_inodes_sb - writeback dirty inodes from given super_block
1034 * @sb: the superblock
Linus Torvalds1da177e2005-04-16 15:20:36 -07001035 *
Jens Axboed8a85592009-09-02 12:34:32 +02001036 * Start writeback on some inodes on this super_block. No guarantees are made
1037 * on how many (if any) will be written, and this function does not wait
1038 * for IO completion of submitted IO. The number of pages submitted is
1039 * returned.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001040 */
Jens Axboeb6e51312009-09-16 15:13:54 +02001041void writeback_inodes_sb(struct super_block *sb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001042{
Jens Axboe0e3c9a22010-06-01 11:08:43 +02001043 unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY);
1044 unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS);
Christoph Hellwig83ba7b02010-07-06 08:59:53 +02001045 DECLARE_COMPLETION_ONSTACK(done);
1046 struct wb_writeback_work work = {
Christoph Hellwig3c4d7162010-06-08 18:14:43 +02001047 .sb = sb,
1048 .sync_mode = WB_SYNC_NONE,
Christoph Hellwig83ba7b02010-07-06 08:59:53 +02001049 .done = &done,
Christoph Hellwig3c4d7162010-06-08 18:14:43 +02001050 };
Jens Axboe0e3c9a22010-06-01 11:08:43 +02001051
Christoph Hellwigcf37e972010-06-08 18:14:51 +02001052 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1053
Christoph Hellwig83ba7b02010-07-06 08:59:53 +02001054 work.nr_pages = nr_dirty + nr_unstable +
Jens Axboe0e3c9a22010-06-01 11:08:43 +02001055 (inodes_stat.nr_inodes - inodes_stat.nr_unused);
1056
Christoph Hellwig83ba7b02010-07-06 08:59:53 +02001057 bdi_queue_work(sb->s_bdi, &work);
1058 wait_for_completion(&done);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001059}
Jens Axboed8a85592009-09-02 12:34:32 +02001060EXPORT_SYMBOL(writeback_inodes_sb);
1061
1062/**
Eric Sandeen17bd55d2009-12-23 07:57:07 -05001063 * writeback_inodes_sb_if_idle - start writeback if none underway
1064 * @sb: the superblock
1065 *
1066 * Invoke writeback_inodes_sb if no writeback is currently underway.
1067 * Returns 1 if writeback was started, 0 if not.
1068 */
1069int writeback_inodes_sb_if_idle(struct super_block *sb)
1070{
1071 if (!writeback_in_progress(sb->s_bdi)) {
Christoph Hellwigcf37e972010-06-08 18:14:51 +02001072 down_read(&sb->s_umount);
Eric Sandeen17bd55d2009-12-23 07:57:07 -05001073 writeback_inodes_sb(sb);
Christoph Hellwigcf37e972010-06-08 18:14:51 +02001074 up_read(&sb->s_umount);
Eric Sandeen17bd55d2009-12-23 07:57:07 -05001075 return 1;
1076 } else
1077 return 0;
1078}
1079EXPORT_SYMBOL(writeback_inodes_sb_if_idle);
1080
1081/**
Jens Axboed8a85592009-09-02 12:34:32 +02001082 * sync_inodes_sb - sync sb inode pages
1083 * @sb: the superblock
1084 *
1085 * This function writes and waits on any dirty inode belonging to this
1086 * super_block. The number of pages synced is returned.
1087 */
Jens Axboeb6e51312009-09-16 15:13:54 +02001088void sync_inodes_sb(struct super_block *sb)
Jens Axboed8a85592009-09-02 12:34:32 +02001089{
Christoph Hellwig83ba7b02010-07-06 08:59:53 +02001090 DECLARE_COMPLETION_ONSTACK(done);
1091 struct wb_writeback_work work = {
Christoph Hellwig3c4d7162010-06-08 18:14:43 +02001092 .sb = sb,
1093 .sync_mode = WB_SYNC_ALL,
1094 .nr_pages = LONG_MAX,
1095 .range_cyclic = 0,
Christoph Hellwig83ba7b02010-07-06 08:59:53 +02001096 .done = &done,
Christoph Hellwig3c4d7162010-06-08 18:14:43 +02001097 };
1098
Christoph Hellwigcf37e972010-06-08 18:14:51 +02001099 WARN_ON(!rwsem_is_locked(&sb->s_umount));
1100
Christoph Hellwig83ba7b02010-07-06 08:59:53 +02001101 bdi_queue_work(sb->s_bdi, &work);
1102 wait_for_completion(&done);
1103
Jens Axboeb6e51312009-09-16 15:13:54 +02001104 wait_sb_inodes(sb);
Jens Axboed8a85592009-09-02 12:34:32 +02001105}
1106EXPORT_SYMBOL(sync_inodes_sb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001107
Linus Torvalds1da177e2005-04-16 15:20:36 -07001108/**
Andrea Arcangeli7f04c262005-10-30 15:03:05 -08001109 * write_inode_now - write an inode to disk
1110 * @inode: inode to write to disk
1111 * @sync: whether the write should be synchronous or not
Linus Torvalds1da177e2005-04-16 15:20:36 -07001112 *
Andrea Arcangeli7f04c262005-10-30 15:03:05 -08001113 * This function commits an inode to disk immediately if it is dirty. This is
1114 * primarily needed by knfsd.
1115 *
1116 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001117 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001118int write_inode_now(struct inode *inode, int sync)
1119{
1120 int ret;
1121 struct writeback_control wbc = {
1122 .nr_to_write = LONG_MAX,
Mike Galbraith18914b12008-02-08 04:20:23 -08001123 .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
OGAWA Hirofumi111ebb62006-06-23 02:03:26 -07001124 .range_start = 0,
1125 .range_end = LLONG_MAX,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001126 };
1127
1128 if (!mapping_cap_writeback_dirty(inode->i_mapping))
Andrew Morton49364ce2005-11-07 00:59:15 -08001129 wbc.nr_to_write = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001130
1131 might_sleep();
1132 spin_lock(&inode_lock);
Christoph Hellwig01c03192009-06-08 13:35:40 +02001133 ret = writeback_single_inode(inode, &wbc);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001134 spin_unlock(&inode_lock);
1135 if (sync)
Joern Engel1c0eeaf2007-10-16 23:30:44 -07001136 inode_sync_wait(inode);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001137 return ret;
1138}
1139EXPORT_SYMBOL(write_inode_now);
1140
1141/**
1142 * sync_inode - write an inode and its pages to disk.
1143 * @inode: the inode to sync
1144 * @wbc: controls the writeback mode
1145 *
1146 * sync_inode() will write an inode and its pages to disk. It will also
1147 * correctly update the inode on its superblock's dirty inode lists and will
1148 * update inode->i_state.
1149 *
1150 * The caller must have a ref on the inode.
1151 */
1152int sync_inode(struct inode *inode, struct writeback_control *wbc)
1153{
1154 int ret;
1155
1156 spin_lock(&inode_lock);
Christoph Hellwig01c03192009-06-08 13:35:40 +02001157 ret = writeback_single_inode(inode, wbc);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001158 spin_unlock(&inode_lock);
1159 return ret;
1160}
1161EXPORT_SYMBOL(sync_inode);