/* * fs/fs-writeback.c * * Copyright (C) 2002, Linus Torvalds. * * Contains all the functions related to writing back and waiting * upon dirty inodes against superblocks, and writing back dirty * pages against inodes. ie: data writeback. Writeout of the * inode itself is not handled here. * * 10Apr2002 Andrew Morton * Split out of fs/inode.c * Additions for address_space-based writeback */ #include <linux/kernel.h> #include <linux/module.h> #include <linux/spinlock.h> #include <linux/slab.h> #include <linux/sched.h> #include <linux/fs.h> #include <linux/mm.h> #include <linux/kthread.h> #include <linux/freezer.h> #include <linux/writeback.h> #include <linux/blkdev.h> #include <linux/backing-dev.h> #include <linux/buffer_head.h> #include "internal.h" #define inode_to_bdi(inode) ((inode)->i_mapping->backing_dev_info) /* * We don't actually have pdflush, but this one is exported though /proc... */ int nr_pdflush_threads; /* * Passed into wb_writeback(), essentially a subset of writeback_control */ struct wb_writeback_args { long nr_pages; struct super_block *sb; enum writeback_sync_modes sync_mode; unsigned int for_kupdate:1; unsigned int range_cyclic:1; unsigned int for_background:1; unsigned int sb_pinned:1; }; /* * Work items for the bdi_writeback threads */ struct bdi_work { struct list_head list; /* pending work list */ struct rcu_head rcu_head; /* for RCU free/clear of work */ unsigned long seen; /* threads that have seen this work */ atomic_t pending; /* number of threads still to do work */ struct wb_writeback_args args; /* writeback arguments */ unsigned long state; /* flag bits, see WS_* */ }; enum { WS_USED_B = 0, WS_ONSTACK_B, }; #define WS_USED (1 << WS_USED_B) #define WS_ONSTACK (1 << WS_ONSTACK_B) static inline bool bdi_work_on_stack(struct bdi_work *work) { return test_bit(WS_ONSTACK_B, &work->state); } static inline void bdi_work_init(struct bdi_work *work, struct wb_writeback_args *args) { INIT_RCU_HEAD(&work->rcu_head); work->args = *args; work->state = WS_USED; } /** * writeback_in_progress - determine whether there is writeback in progress * @bdi: the device's backing_dev_info structure. * * Determine whether there is writeback waiting to be handled against a * backing device. */ int writeback_in_progress(struct backing_dev_info *bdi) { return !list_empty(&bdi->work_list); } static void bdi_work_clear(struct bdi_work *work) { clear_bit(WS_USED_B, &work->state); smp_mb__after_clear_bit(); /* * work can have disappeared at this point. bit waitq functions * should be able to tolerate this, provided bdi_sched_wait does * not dereference it's pointer argument. */ wake_up_bit(&work->state, WS_USED_B); } static void bdi_work_free(struct rcu_head *head) { struct bdi_work *work = container_of(head, struct bdi_work, rcu_head); if (!bdi_work_on_stack(work)) kfree(work); else bdi_work_clear(work); } static void wb_work_complete(struct bdi_work *work) { const enum writeback_sync_modes sync_mode = work->args.sync_mode; int onstack = bdi_work_on_stack(work); /* * For allocated work, we can clear the done/seen bit right here. * For on-stack work, we need to postpone both the clear and free * to after the RCU grace period, since the stack could be invalidated * as soon as bdi_work_clear() has done the wakeup. */ if (!onstack) bdi_work_clear(work); if (sync_mode == WB_SYNC_NONE || onstack) call_rcu(&work->rcu_head, bdi_work_free); } static void wb_clear_pending(struct bdi_writeback *wb, struct bdi_work *work) { /* * The caller has retrieved the work arguments from this work, * drop our reference. If this is the last ref, delete and free it */ if (atomic_dec_and_test(&work->pending)) { struct backing_dev_info *bdi = wb->bdi; spin_lock(&bdi->wb_lock); list_del_rcu(&work->list); spin_unlock(&bdi->wb_lock); wb_work_complete(work); } } static void bdi_queue_work(struct backing_dev_info *bdi, struct bdi_work *work) { work->seen = bdi->wb_mask; BUG_ON(!work->seen); atomic_set(&work->pending, bdi->wb_cnt); BUG_ON(!bdi->wb_cnt); /* * list_add_tail_rcu() contains the necessary barriers to * make sure the above stores are seen before the item is * noticed on the list */ spin_lock(&bdi->wb_lock); list_add_tail_rcu(&work->list, &bdi->work_list); spin_unlock(&bdi->wb_lock); /* * If the default thread isn't there, make sure we add it. When * it gets created and wakes up, we'll run this work. */ if (unlikely(list_empty_careful(&bdi->wb_list))) wake_up_process(default_backing_dev_info.wb.task); else { struct bdi_writeback *wb = &bdi->wb; if (wb->task) wake_up_process(wb->task); } } /* * Used for on-stack allocated work items. The caller needs to wait until * the wb threads have acked the work before it's safe to continue. */ static void bdi_wait_on_work_clear(struct bdi_work *work) { wait_on_bit(&work->state, WS_USED_B, bdi_sched_wait, TASK_UNINTERRUPTIBLE); } static void bdi_alloc_queue_work(struct backing_dev_info *bdi, struct wb_writeback_args *args, int wait) { struct bdi_work *work; /* * This is WB_SYNC_NONE writeback, so if allocation fails just * wakeup the thread for old dirty data writeback */ work = kmalloc(sizeof(*work), GFP_ATOMIC); if (work) { bdi_work_init(work, args); bdi_queue_work(bdi, work); if (wait) bdi_wait_on_work_clear(work); } else { struct bdi_writeback *wb = &bdi->wb; if (wb->task) wake_up_process(wb->task); } } /** * bdi_sync_writeback - start and wait for writeback * @bdi: the backing device to write from * @sb: write inodes from this super_block * * Description: * This does WB_SYNC_ALL data integrity writeback and waits for the * IO to complete. Callers must hold the sb s_umount semaphore for * reading, to avoid having the super disappear before we are done. */ static void bdi_sync_writeback(struct backing_dev_info *bdi, struct super_block *sb) { struct wb_writeback_args args = { .sb = sb, .sync_mode = WB_SYNC_ALL, .nr_pages = LONG_MAX, .range_cyclic = 0, /* * Setting sb_pinned is not necessary for WB_SYNC_ALL, but * lets make it explicitly clear. */ .sb_pinned = 1, }; struct bdi_work work; bdi_work_init(&work, &args); work.state |= WS_ONSTACK; bdi_queue_work(bdi, &work); bdi_wait_on_work_clear(&work); } /** * bdi_start_writeback - start writeback * @bdi: the backing device to write from * @sb: write inodes from this super_block * @nr_pages: the number of pages to write * @sb_locked: caller already holds sb umount sem. * * Description: * This does WB_SYNC_NONE opportunistic writeback. The IO is only * started when this function returns, we make no guarentees on * completion. Caller specifies whether sb umount sem is held already or not. * */ void bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb, long nr_pages, int sb_locked) { struct wb_writeback_args args = { .sb = sb, .sync_mode = WB_SYNC_NONE, .nr_pages = nr_pages, .range_cyclic = 1, .sb_pinned = sb_locked, }; /* * We treat @nr_pages=0 as the special case to do background writeback, * ie. to sync pages until the background dirty threshold is reached. */ if (!nr_pages) { args.nr_pages = LONG_MAX; args.for_background = 1; } bdi_alloc_queue_work(bdi, &args, sb_locked); } /* * Redirty an inode: set its when-it-was dirtied timestamp and move it to the * furthest end of its superblock's dirty-inode list. * * Before stamping the inode's ->dirtied_when, we check to see whether it is * already the most-recently-dirtied inode on the b_dirty list. If that is * the case then the inode must have been redirtied while it was being written * out and we don't reset its dirtied_when. */ static void redirty_tail(struct inode *inode) { struct bdi_writeback *wb = &inode_to_bdi(inode)->wb; if (!list_empty(&wb->b_dirty)) { struct inode *tail; tail = list_entry(wb->b_dirty.next, struct inode, i_list); if (time_before(inode->dirtied_when, tail->dirtied_when)) inode->dirtied_when = jiffies; } list_move(&inode->i_list, &wb->b_dirty); } /* * requeue inode for re-scanning after bdi->b_io list is exhausted. */ static void requeue_io(struct inode *inode) { struct bdi_writeback *wb = &inode_to_bdi(inode)->wb; list_move(&inode->i_list, &wb->b_more_io); } static void inode_sync_complete(struct inode *inode) { /* * Prevent speculative execution through spin_unlock(&inode_lock); */ smp_mb(); wake_up_bit(&inode->i_state, __I_SYNC); } static bool inode_dirtied_after(struct inode *inode, unsigned long t) { bool ret = time_after(inode->dirtied_when, t); #ifndef CONFIG_64BIT /* * For inodes being constantly redirtied, dirtied_when can get stuck. * It _appears_ to be in the future, but is actually in distant past. * This test is necessary to prevent such wrapped-around relative times * from permanently stopping the whole bdi writeback. */ ret = ret && time_before_eq(inode->dirtied_when, jiffies); #endif return ret; } /* * Move expired dirty inodes from @delaying_queue to @dispatch_queue. */ static void move_expired_inodes(struct list_head *delaying_queue, struct list_head *dispatch_queue, unsigned long *older_than_this) { LIST_HEAD(tmp); struct list_head *pos, *node; struct super_block *sb = NULL; struct inode *inode; int do_sb_sort = 0; while (!list_empty(delaying_queue)) { inode = list_entry(delaying_queue->prev, struct inode, i_list); if (older_than_this && inode_dirtied_after(inode, *older_than_this)) break; if (sb && sb != inode->i_sb) do_sb_sort = 1; sb = inode->i_sb; list_move(&inode->i_list, &tmp); } /* just one sb in list, splice to dispatch_queue and we're done */ if (!do_sb_sort) { list_splice(&tmp, dispatch_queue); return; } /* Move inodes from one superblock together */ while (!list_empty(&tmp)) { inode = list_entry(tmp.prev, struct inode, i_list); sb = inode->i_sb; list_for_each_prev_safe(pos, node, &tmp) { inode = list_entry(pos, struct inode, i_list); if (inode->i_sb == sb) list_move(&inode->i_list, dispatch_queue); } } } /* * Queue all expired dirty inodes for io, eldest first. */ static void queue_io(struct bdi_writeback *wb, unsigned long *older_than_this) { list_splice_init(&wb->b_more_io, wb->b_io.prev); move_expired_inodes(&wb->b_dirty, &wb->b_io, older_than_this); } static int write_inode(struct inode *inode, struct writeback_control *wbc) { if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode)) return inode->i_sb->s_op->write_inode(inode, wbc); return 0; } /* * Wait for writeback on an inode to complete. */ static void inode_wait_for_writeback(struct inode *inode) { DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC); wait_queue_head_t *wqh; wqh = bit_waitqueue(&inode->i_state, __I_SYNC); while (inode->i_state & I_SYNC) { spin_unlock(&inode_lock); __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE); spin_lock(&inode_lock); } } /* * Write out an inode's dirty pages. Called under inode_lock. Either the * caller has ref on the inode (either via __iget or via syscall against an fd) * or the inode has I_WILL_FREE set (via generic_forget_inode) * * If `wait' is set, wait on the writeout. * * The whole writeout design is quite complex and fragile. We want to avoid * starvation of particular inodes when others are being redirtied, prevent * livelocks, etc. * * Called under inode_lock. */ static int writeback_single_inode(struct inode *inode, struct writeback_control *wbc) { struct address_space *mapping = inode->i_mapping; unsigned dirty; int ret; if (!atomic_read(&inode->i_count)) WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING))); else WARN_ON(inode->i_state & I_WILL_FREE); if (inode->i_state & I_SYNC) { /* * If this inode is locked for writeback and we are not doing * writeback-for-data-integrity, move it to b_more_io so that * writeback can proceed with the other inodes on s_io. * * We'll have another go at writing back this inode when we * completed a full scan of b_io. */ if (wbc->sync_mode != WB_SYNC_ALL) { requeue_io(inode); return 0; } /* * It's a data-integrity sync. We must wait. */ inode_wait_for_writeback(inode); } BUG_ON(inode->i_state & I_SYNC); /* Set I_SYNC, reset I_DIRTY_PAGES */ inode->i_state |= I_SYNC; inode->i_state &= ~I_DIRTY_PAGES; spin_unlock(&inode_lock); ret = do_writepages(mapping, wbc); /* * Make sure to wait on the data before writing out the metadata. * This is important for filesystems that modify metadata on data * I/O completion. */ if (wbc->sync_mode == WB_SYNC_ALL) { int err = filemap_fdatawait(mapping); if (ret == 0) ret = err; } /* * Some filesystems may redirty the inode during the writeback * due to delalloc, clear dirty metadata flags right before * write_inode() */ spin_lock(&inode_lock); dirty = inode->i_state & I_DIRTY; inode->i_state &= ~(I_DIRTY_SYNC | I_DIRTY_DATASYNC); spin_unlock(&inode_lock); /* Don't write the inode if only I_DIRTY_PAGES was set */ if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) { int err = write_inode(inode, wbc); if (ret == 0) ret = err; } spin_lock(&inode_lock); inode->i_state &= ~I_SYNC; if (!(inode->i_state & (I_FREEING | I_CLEAR))) { if ((inode->i_state & I_DIRTY_PAGES) && wbc->for_kupdate) { /* * More pages get dirtied by a fast dirtier. */ goto select_queue; } else if (inode->i_state & I_DIRTY) { /* * At least XFS will redirty the inode during the * writeback (delalloc) and on io completion (isize). */ redirty_tail(inode); } else if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) { /* * We didn't write back all the pages. nfs_writepages() * sometimes bales out without doing anything. Redirty * the inode; Move it from b_io onto b_more_io/b_dirty. */ /* * akpm: if the caller was the kupdate function we put * this inode at the head of b_dirty so it gets first * consideration. Otherwise, move it to the tail, for * the reasons described there. I'm not really sure * how much sense this makes. Presumably I had a good * reasons for doing it this way, and I'd rather not * muck with it at present. */ if (wbc->for_kupdate) { /* * For the kupdate function we move the inode * to b_more_io so it will get more writeout as * soon as the queue becomes uncongested. */ inode->i_state |= I_DIRTY_PAGES; select_queue: if (wbc->nr_to_write <= 0) { /* * slice used up: queue for next turn */ requeue_io(inode); } else { /* * somehow blocked: retry later */ redirty_tail(inode); } } else { /* * Otherwise fully redirty the inode so that * other inodes on this superblock will get some * writeout. Otherwise heavy writing to one * file would indefinitely suspend writeout of * all the other files. */ inode->i_state |= I_DIRTY_PAGES; redirty_tail(inode); } } else if (atomic_read(&inode->i_count)) { /* * The inode is clean, inuse */ list_move(&inode->i_list, &inode_in_use); } else { /* * The inode is clean, unused */ list_move(&inode->i_list, &inode_unused); } } inode_sync_complete(inode); return ret; } static void unpin_sb_for_writeback(struct super_block *sb) { up_read(&sb->s_umount); put_super(sb); } enum sb_pin_state { SB_PINNED, SB_NOT_PINNED, SB_PIN_FAILED }; /* * For WB_SYNC_NONE writeback, the caller does not have the sb pinned * before calling writeback. So make sure that we do pin it, so it doesn't * go away while we are writing inodes from it. */ static enum sb_pin_state pin_sb_for_writeback(struct writeback_control *wbc, struct super_block *sb) { /* * Caller must already hold the ref for this */ if (wbc->sync_mode == WB_SYNC_ALL || wbc->sb_pinned) { WARN_ON(!rwsem_is_locked(&sb->s_umount)); return SB_NOT_PINNED; } spin_lock(&sb_lock); sb->s_count++; if (down_read_trylock(&sb->s_umount)) { if (sb->s_root) { spin_unlock(&sb_lock); return SB_PINNED; } /* * umounted, drop rwsem again and fall through to failure */ up_read(&sb->s_umount); } sb->s_count--; spin_unlock(&sb_lock); return SB_PIN_FAILED; } /* * Write a portion of b_io inodes which belong to @sb. * If @wbc->sb != NULL, then find and write all such * inodes. Otherwise write only ones which go sequentially * in reverse order. * Return 1, if the caller writeback routine should be * interrupted. Otherwise return 0. */ static int writeback_sb_inodes(struct super_block *sb, struct bdi_writeback *wb, struct writeback_control *wbc) { while (!list_empty(&wb->b_io)) { long pages_skipped; struct inode *inode = list_entry(wb->b_io.prev, struct inode, i_list); if (wbc->sb && sb != inode->i_sb) { /* super block given and doesn't match, skip this inode */ redirty_tail(inode); continue; } if (sb != inode->i_sb) /* finish with this superblock */ return 0; if (inode->i_state & (I_NEW | I_WILL_FREE)) { requeue_io(inode); continue; } /* * Was this inode dirtied after sync_sb_inodes was called? * This keeps sync from extra jobs and livelock. */ if (inode_dirtied_after(inode, wbc->wb_start)) return 1; BUG_ON(inode->i_state & (I_FREEING | I_CLEAR)); __iget(inode); pages_skipped = wbc->pages_skipped; writeback_single_inode(inode, wbc); if (wbc->pages_skipped != pages_skipped) { /* * writeback is not making progress due to locked * buffers. Skip this inode for now. */ redirty_tail(inode); } spin_unlock(&inode_lock); iput(inode); cond_resched(); spin_lock(&inode_lock); if (wbc->nr_to_write <= 0) { wbc->more_io = 1; return 1; } if (!list_empty(&wb->b_more_io)) wbc->more_io = 1; } /* b_io is empty */ return 1; } static void writeback_inodes_wb(struct bdi_writeback *wb, struct writeback_control *wbc) { int ret = 0; wbc->wb_start = jiffies; /* livelock avoidance */ spin_lock(&inode_lock); if (!wbc->for_kupdate || list_empty(&wb->b_io)) queue_io(wb, wbc->older_than_this); while (!list_empty(&wb->b_io)) { struct inode *inode = list_entry(wb->b_io.prev, struct inode, i_list); struct super_block *sb = inode->i_sb; enum sb_pin_state state; if (wbc->sb && sb != wbc->sb) { /* super block given and doesn't match, skip this inode */ redirty_tail(inode); continue; } state = pin_sb_for_writeback(wbc, sb); if (state == SB_PIN_FAILED) { requeue_io(inode); continue; } ret = writeback_sb_inodes(sb, wb, wbc); if (state == SB_PINNED) unpin_sb_for_writeback(sb); if (ret) break; } spin_unlock(&inode_lock); /* Leave any unwritten inodes on b_io */ } void writeback_inodes_wbc(struct writeback_control *wbc) { struct backing_dev_info *bdi = wbc->bdi; writeback_inodes_wb(&bdi->wb, wbc); } /* * The maximum number of pages to writeout in a single bdi flush/kupdate * operation. We do this so we don't hold I_SYNC against an inode for * enormous amounts of time, which would block a userspace task which has * been forced to throttle against that inode. Also, the code reevaluates * the dirty each time it has written this many pages. */ #define MAX_WRITEBACK_PAGES 1024 static inline bool over_bground_thresh(void) { unsigned long background_thresh, dirty_thresh; get_dirty_limits(&background_thresh, &dirty_thresh, NULL, NULL); return (global_page_state(NR_FILE_DIRTY) + global_page_state(NR_UNSTABLE_NFS) >= background_thresh); } /* * Explicit flushing or periodic writeback of "old" data. * * Define "old": the first time one of an inode's pages is dirtied, we mark the * dirtying-time in the inode's address_space. So this periodic writeback code * just walks the superblock inode list, writing back any inodes which are * older than a specific point in time. * * Try to run once per dirty_writeback_interval. But if a writeback event * takes longer than a dirty_writeback_interval interval, then leave a * one-second gap. * * older_than_this takes precedence over nr_to_write. So we'll only write back * all dirty pages if they are all attached to "old" mappings. */ static long wb_writeback(struct bdi_writeback *wb, struct wb_writeback_args *args) { struct writeback_control wbc = { .bdi = wb->bdi, .sb = args->sb, .sync_mode = args->sync_mode, .older_than_this = NULL, .for_kupdate = args->for_kupdate, .for_background = args->for_background, .range_cyclic = args->range_cyclic, .sb_pinned = args->sb_pinned, }; unsigned long oldest_jif; long wrote = 0; struct inode *inode; if (wbc.for_kupdate) { wbc.older_than_this = &oldest_jif; oldest_jif = jiffies - msecs_to_jiffies(dirty_expire_interval * 10); } if (!wbc.range_cyclic) { wbc.range_start = 0; wbc.range_end = LLONG_MAX; } for (;;) { /* * Stop writeback when nr_pages has been consumed */ if (args->nr_pages <= 0) break; /* * For background writeout, stop when we are below the * background dirty threshold */ if (args->for_background && !over_bground_thresh()) break; wbc.more_io = 0; wbc.nr_to_write = MAX_WRITEBACK_PAGES; wbc.pages_skipped = 0; writeback_inodes_wb(wb, &wbc); args->nr_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write; wrote += MAX_WRITEBACK_PAGES - wbc.nr_to_write; /* * If we consumed everything, see if we have more */ if (wbc.nr_to_write <= 0) continue; /* * Didn't write everything and we don't have more IO, bail */ if (!wbc.more_io) break; /* * Did we write something? Try for more */ if (wbc.nr_to_write < MAX_WRITEBACK_PAGES) continue; /* * Nothing written. Wait for some inode to * become available for writeback. Otherwise * we'll just busyloop. */ spin_lock(&inode_lock); if (!list_empty(&wb->b_more_io)) { inode = list_entry(wb->b_more_io.prev, struct inode, i_list); inode_wait_for_writeback(inode); } spin_unlock(&inode_lock); } return wrote; } /* * Return the next bdi_work struct that hasn't been processed by this * wb thread yet. ->seen is initially set for each thread that exists * for this device, when a thread first notices a piece of work it * clears its bit. Depending on writeback type, the thread will notify * completion on either receiving the work (WB_SYNC_NONE) or after * it is done (WB_SYNC_ALL). */ static struct bdi_work *get_next_work_item(struct backing_dev_info *bdi, struct bdi_writeback *wb) { struct bdi_work *work, *ret = NULL; rcu_read_lock(); list_for_each_entry_rcu(work, &bdi->work_list, list) { if (!test_bit(wb->nr, &work->seen)) continue; clear_bit(wb->nr, &work->seen); ret = work; break; } rcu_read_unlock(); return ret; } static long wb_check_old_data_flush(struct bdi_writeback *wb) { unsigned long expired; long nr_pages; /* * When set to zero, disable periodic writeback */ if (!dirty_writeback_interval) return 0; expired = wb->last_old_flush + msecs_to_jiffies(dirty_writeback_interval * 10); if (time_before(jiffies, expired)) return 0; wb->last_old_flush = jiffies; nr_pages = global_page_state(NR_FILE_DIRTY) + global_page_state(NR_UNSTABLE_NFS) + (inodes_stat.nr_inodes - inodes_stat.nr_unused); if (nr_pages) { struct wb_writeback_args args = { .nr_pages = nr_pages, .sync_mode = WB_SYNC_NONE, .for_kupdate = 1, .range_cyclic = 1, }; return wb_writeback(wb, &args); } return 0; } /* * Retrieve work items and do the writeback they describe */ long wb_do_writeback(struct bdi_writeback *wb, int force_wait) { struct backing_dev_info *bdi = wb->bdi; struct bdi_work *work; long wrote = 0; while ((work = get_next_work_item(bdi, wb)) != NULL) { struct wb_writeback_args args = work->args; int post_clear; /* * Override sync mode, in case we must wait for completion */ if (force_wait) work->args.sync_mode = args.sync_mode = WB_SYNC_ALL; post_clear = WB_SYNC_ALL || args.sb_pinned; /* * If this isn't a data integrity operation, just notify * that we have seen this work and we are now starting it. */ if (!post_clear) wb_clear_pending(wb, work); wrote += wb_writeback(wb, &args); /* * This is a data integrity writeback, so only do the * notification when we have completed the work. */ if (post_clear) wb_clear_pending(wb, work); } /* * Check for periodic writeback, kupdated() style */ wrote += wb_check_old_data_flush(wb); return wrote; } /* * Handle writeback of dirty data for the device backed by this bdi. Also * wakes up periodically and does kupdated style flushing. */ int bdi_writeback_task(struct bdi_writeback *wb) { unsigned long last_active = jiffies; unsigned long wait_jiffies = -1UL; long pages_written; while (!kthread_should_stop()) { pages_written = wb_do_writeback(wb, 0); if (pages_written) last_active = jiffies; else if (wait_jiffies != -1UL) { unsigned long max_idle; /* * Longest period of inactivity that we tolerate. If we * see dirty data again later, the task will get * recreated automatically. */ max_idle = max(5UL * 60 * HZ, wait_jiffies); if (time_after(jiffies, max_idle + last_active)) break; } if (dirty_writeback_interval) { wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10); schedule_timeout_interruptible(wait_jiffies); } else { set_current_state(TASK_INTERRUPTIBLE); if (list_empty_careful(&wb->bdi->work_list) && !kthread_should_stop()) schedule(); __set_current_state(TASK_RUNNING); } try_to_freeze(); } return 0; } /* * Schedule writeback for all backing devices. This does WB_SYNC_NONE * writeback, for integrity writeback see bdi_sync_writeback(). */ static void bdi_writeback_all(struct super_block *sb, long nr_pages) { struct wb_writeback_args args = { .sb = sb, .nr_pages = nr_pages, .sync_mode = WB_SYNC_NONE, }; struct backing_dev_info *bdi; rcu_read_lock(); list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) { if (!bdi_has_dirty_io(bdi)) continue; bdi_alloc_queue_work(bdi, &args, 0); } rcu_read_unlock(); } /* * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back * the whole world. */ void wakeup_flusher_threads(long nr_pages) { if (nr_pages == 0) nr_pages = global_page_state(NR_FILE_DIRTY) + global_page_state(NR_UNSTABLE_NFS); bdi_writeback_all(NULL, nr_pages); } static noinline void block_dump___mark_inode_dirty(struct inode *inode) { if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) { struct dentry *dentry; const char *name = "?"; dentry = d_find_alias(inode); if (dentry) { spin_lock(&dentry->d_lock); name = (const char *) dentry->d_name.name; } printk(KERN_DEBUG "%s(%d): dirtied inode %lu (%s) on %s\n", current->comm, task_pid_nr(current), inode->i_ino, name, inode->i_sb->s_id); if (dentry) { spin_unlock(&dentry->d_lock); dput(dentry); } } } /** * __mark_inode_dirty - internal function * @inode: inode to mark * @flags: what kind of dirty (i.e. I_DIRTY_SYNC) * Mark an inode as dirty. Callers should use mark_inode_dirty or * mark_inode_dirty_sync. * * Put the inode on the super block's dirty list. * * CAREFUL! We mark it dirty unconditionally, but move it onto the * dirty list only if it is hashed or if it refers to a blockdev. * If it was not hashed, it will never be added to the dirty list * even if it is later hashed, as it will have been marked dirty already. * * In short, make sure you hash any inodes _before_ you start marking * them dirty. * * This function *must* be atomic for the I_DIRTY_PAGES case - * set_page_dirty() is called under spinlock in several places. * * Note that for blockdevs, inode->dirtied_when represents the dirtying time of * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of * the kernel-internal blockdev inode represents the dirtying time of the * blockdev's pages. This is why for I_DIRTY_PAGES we always use * page->mapping->host, so the page-dirtying time is recorded in the internal * blockdev inode. */ void __mark_inode_dirty(struct inode *inode, int flags) { struct super_block *sb = inode->i_sb; /* * Don't do this for I_DIRTY_PAGES - that doesn't actually * dirty the inode itself */ if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) { if (sb->s_op->dirty_inode) sb->s_op->dirty_inode(inode); } /* * make sure that changes are seen by all cpus before we test i_state * -- mikulas */ smp_mb(); /* avoid the locking if we can */ if ((inode->i_state & flags) == flags) return; if (unlikely(block_dump)) block_dump___mark_inode_dirty(inode); spin_lock(&inode_lock); if ((inode->i_state & flags) != flags) { const int was_dirty = inode->i_state & I_DIRTY; inode->i_state |= flags; /* * If the inode is being synced, just update its dirty state. * The unlocker will place the inode on the appropriate * superblock list, based upon its state. */ if (inode->i_state & I_SYNC) goto out; /* * Only add valid (hashed) inodes to the superblock's * dirty list. Add blockdev inodes as well. */ if (!S_ISBLK(inode->i_mode)) { if (hlist_unhashed(&inode->i_hash)) goto out; } if (inode->i_state & (I_FREEING|I_CLEAR)) goto out; /* * If the inode was already on b_dirty/b_io/b_more_io, don't * reposition it (that would break b_dirty time-ordering). */ if (!was_dirty) { struct bdi_writeback *wb = &inode_to_bdi(inode)->wb; struct backing_dev_info *bdi = wb->bdi; if (bdi_cap_writeback_dirty(bdi) && !test_bit(BDI_registered, &bdi->state)) { WARN_ON(1); printk(KERN_ERR "bdi-%s not registered\n", bdi->name); } inode->dirtied_when = jiffies; list_move(&inode->i_list, &wb->b_dirty); } } out: spin_unlock(&inode_lock); } EXPORT_SYMBOL(__mark_inode_dirty); /* * Write out a superblock's list of dirty inodes. A wait will be performed * upon no inodes, all inodes or the final one, depending upon sync_mode. * * If older_than_this is non-NULL, then only write out inodes which * had their first dirtying at a time earlier than *older_than_this. * * If `bdi' is non-zero then we're being asked to writeback a specific queue. * This function assumes that the blockdev superblock's inodes are backed by * a variety of queues, so all inodes are searched. For other superblocks, * assume that all inodes are backed by the same queue. * * The inodes to be written are parked on bdi->b_io. They are moved back onto * bdi->b_dirty as they are selected for writing. This way, none can be missed * on the writer throttling path, and we get decent balancing between many * throttled threads: we don't want them all piling up on inode_sync_wait. */ static void wait_sb_inodes(struct super_block *sb) { struct inode *inode, *old_inode = NULL; /* * We need to be protected against the filesystem going from * r/o to r/w or vice versa. */ WARN_ON(!rwsem_is_locked(&sb->s_umount)); spin_lock(&inode_lock); /* * Data integrity sync. Must wait for all pages under writeback, * because there may have been pages dirtied before our sync * call, but which had writeout started before we write it out. * In which case, the inode may not be on the dirty list, but * we still have to wait for that writeout. */ list_for_each_entry(inode, &sb->s_inodes, i_sb_list) { struct address_space *mapping; if (inode->i_state & (I_FREEING|I_CLEAR|I_WILL_FREE|I_NEW)) continue; mapping = inode->i_mapping; if (mapping->nrpages == 0) continue; __iget(inode); spin_unlock(&inode_lock); /* * We hold a reference to 'inode' so it couldn't have * been removed from s_inodes list while we dropped the * inode_lock. We cannot iput the inode now as we can * be holding the last reference and we cannot iput it * under inode_lock. So we keep the reference and iput * it later. */ iput(old_inode); old_inode = inode; filemap_fdatawait(mapping); cond_resched(); spin_lock(&inode_lock); } spin_unlock(&inode_lock); iput(old_inode); } static void __writeback_inodes_sb(struct super_block *sb, int sb_locked) { unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY); unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS); long nr_to_write; nr_to_write = nr_dirty + nr_unstable + (inodes_stat.nr_inodes - inodes_stat.nr_unused); bdi_start_writeback(sb->s_bdi, sb, nr_to_write, sb_locked); } /** * writeback_inodes_sb - writeback dirty inodes from given super_block * @sb: the superblock * * Start writeback on some inodes on this super_block. No guarantees are made * on how many (if any) will be written, and this function does not wait * for IO completion of submitted IO. The number of pages submitted is * returned. */ void writeback_inodes_sb(struct super_block *sb) { __writeback_inodes_sb(sb, 0); } EXPORT_SYMBOL(writeback_inodes_sb); /** * writeback_inodes_sb_locked - writeback dirty inodes from given super_block * @sb: the superblock * * Like writeback_inodes_sb(), except the caller already holds the * sb umount sem. */ void writeback_inodes_sb_locked(struct super_block *sb) { __writeback_inodes_sb(sb, 1); } /** * writeback_inodes_sb_if_idle - start writeback if none underway * @sb: the superblock * * Invoke writeback_inodes_sb if no writeback is currently underway. * Returns 1 if writeback was started, 0 if not. */ int writeback_inodes_sb_if_idle(struct super_block *sb) { if (!writeback_in_progress(sb->s_bdi)) { writeback_inodes_sb(sb); return 1; } else return 0; } EXPORT_SYMBOL(writeback_inodes_sb_if_idle); /** * sync_inodes_sb - sync sb inode pages * @sb: the superblock * * This function writes and waits on any dirty inode belonging to this * super_block. The number of pages synced is returned. */ void sync_inodes_sb(struct super_block *sb) { bdi_sync_writeback(sb->s_bdi, sb); wait_sb_inodes(sb); } EXPORT_SYMBOL(sync_inodes_sb); /** * write_inode_now - write an inode to disk * @inode: inode to write to disk * @sync: whether the write should be synchronous or not * * This function commits an inode to disk immediately if it is dirty. This is * primarily needed by knfsd. * * The caller must either have a ref on the inode or must have set I_WILL_FREE. */ int write_inode_now(struct inode *inode, int sync) { int ret; struct writeback_control wbc = { .nr_to_write = LONG_MAX, .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE, .range_start = 0, .range_end = LLONG_MAX, }; if (!mapping_cap_writeback_dirty(inode->i_mapping)) wbc.nr_to_write = 0; might_sleep(); spin_lock(&inode_lock); ret = writeback_single_inode(inode, &wbc); spin_unlock(&inode_lock); if (sync) inode_sync_wait(inode); return ret; } EXPORT_SYMBOL(write_inode_now); /** * sync_inode - write an inode and its pages to disk. * @inode: the inode to sync * @wbc: controls the writeback mode * * sync_inode() will write an inode and its pages to disk. It will also * correctly update the inode on its superblock's dirty inode lists and will * update inode->i_state. * * The caller must have a ref on the inode. */ int sync_inode(struct inode *inode, struct writeback_control *wbc) { int ret; spin_lock(&inode_lock); ret = writeback_single_inode(inode, wbc); spin_unlock(&inode_lock); return ret; } EXPORT_SYMBOL(sync_inode);