| /* |
| * 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/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; |
| int for_kupdate:1; |
| int range_cyclic:1; |
| int for_background: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) |
| { |
| 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); |
| } 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, |
| }; |
| 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 |
| * @nr_pages: the number of pages to write |
| * |
| * Description: |
| * This does WB_SYNC_NONE opportunistic writeback. The IO is only |
| * started when this function returns, we make no guarentees on |
| * completion. Caller need not hold sb s_umount semaphore. |
| * |
| */ |
| void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages) |
| { |
| struct wb_writeback_args args = { |
| .sync_mode = WB_SYNC_NONE, |
| .nr_pages = nr_pages, |
| .range_cyclic = 1, |
| }; |
| |
| /* |
| * 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); |
| } |
| |
| /* |
| * 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 pdflush 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) |
| { |
| while (!list_empty(delaying_queue)) { |
| struct inode *inode = list_entry(delaying_queue->prev, |
| struct inode, i_list); |
| if (older_than_this && |
| inode_dirtied_after(inode, *older_than_this)) |
| break; |
| 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, int sync) |
| { |
| if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode)) |
| return inode->i_sb->s_op->write_inode(inode, sync); |
| 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); |
| do { |
| spin_unlock(&inode_lock); |
| __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE); |
| spin_lock(&inode_lock); |
| } while (inode->i_state & I_SYNC); |
| } |
| |
| /* |
| * 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; |
| int wait = wbc->sync_mode == WB_SYNC_ALL; |
| 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 (!wait) { |
| 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 */ |
| dirty = inode->i_state & I_DIRTY; |
| inode->i_state |= I_SYNC; |
| inode->i_state &= ~I_DIRTY; |
| |
| spin_unlock(&inode_lock); |
| |
| ret = do_writepages(mapping, wbc); |
| |
| /* 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, wait); |
| if (ret == 0) |
| ret = err; |
| } |
| |
| if (wait) { |
| int err = filemap_fdatawait(mapping); |
| 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) { |
| /* |
| * Someone redirtied the inode while were writing back |
| * the pages. |
| */ |
| 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; |
| 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; |
| } |
| |
| /* |
| * 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. |
| * |
| * Returns 0 if the super was successfully pinned (or pinning wasn't needed), |
| * 1 if we failed. |
| */ |
| static int pin_sb_for_writeback(struct writeback_control *wbc, |
| struct inode *inode) |
| { |
| struct super_block *sb = inode->i_sb; |
| |
| /* |
| * Caller must already hold the ref for this |
| */ |
| if (wbc->sync_mode == WB_SYNC_ALL) { |
| WARN_ON(!rwsem_is_locked(&sb->s_umount)); |
| return 0; |
| } |
| |
| spin_lock(&sb_lock); |
| sb->s_count++; |
| if (down_read_trylock(&sb->s_umount)) { |
| if (sb->s_root) { |
| spin_unlock(&sb_lock); |
| return 0; |
| } |
| /* |
| * umounted, drop rwsem again and fall through to failure |
| */ |
| up_read(&sb->s_umount); |
| } |
| |
| sb->s_count--; |
| spin_unlock(&sb_lock); |
| return 1; |
| } |
| |
| static void unpin_sb_for_writeback(struct writeback_control *wbc, |
| struct inode *inode) |
| { |
| struct super_block *sb = inode->i_sb; |
| |
| if (wbc->sync_mode == WB_SYNC_ALL) |
| return; |
| |
| up_read(&sb->s_umount); |
| put_super(sb); |
| } |
| |
| static void writeback_inodes_wb(struct bdi_writeback *wb, |
| struct writeback_control *wbc) |
| { |
| struct super_block *sb = wbc->sb; |
| const int is_blkdev_sb = sb_is_blkdev_sb(sb); |
| const unsigned long 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); |
| long pages_skipped; |
| |
| /* |
| * super block given and doesn't match, skip this inode |
| */ |
| if (sb && sb != inode->i_sb) { |
| redirty_tail(inode); |
| continue; |
| } |
| |
| if (!bdi_cap_writeback_dirty(wb->bdi)) { |
| redirty_tail(inode); |
| if (is_blkdev_sb) { |
| /* |
| * Dirty memory-backed blockdev: the ramdisk |
| * driver does this. Skip just this inode |
| */ |
| continue; |
| } |
| /* |
| * Dirty memory-backed inode against a filesystem other |
| * than the kernel-internal bdev filesystem. Skip the |
| * entire superblock. |
| */ |
| break; |
| } |
| |
| if (inode->i_state & (I_NEW | I_WILL_FREE)) { |
| requeue_io(inode); |
| continue; |
| } |
| |
| if (wbc->nonblocking && bdi_write_congested(wb->bdi)) { |
| wbc->encountered_congestion = 1; |
| if (!is_blkdev_sb) |
| break; /* Skip a congested fs */ |
| requeue_io(inode); |
| continue; /* Skip a congested blockdev */ |
| } |
| |
| /* |
| * Was this inode dirtied after sync_sb_inodes was called? |
| * This keeps sync from extra jobs and livelock. |
| */ |
| if (inode_dirtied_after(inode, start)) |
| break; |
| |
| if (pin_sb_for_writeback(wbc, inode)) { |
| requeue_io(inode); |
| continue; |
| } |
| |
| BUG_ON(inode->i_state & (I_FREEING | I_CLEAR)); |
| __iget(inode); |
| pages_skipped = wbc->pages_skipped; |
| writeback_single_inode(inode, wbc); |
| unpin_sb_for_writeback(wbc, inode); |
| 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; |
| break; |
| } |
| if (!list_empty(&wb->b_more_io)) |
| wbc->more_io = 1; |
| } |
| |
| 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, |
| .range_cyclic = args->range_cyclic, |
| }; |
| 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.encountered_congestion = 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; |
| |
| 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; |
| |
| /* |
| * Override sync mode, in case we must wait for completion |
| */ |
| if (force_wait) |
| work->args.sync_mode = args.sync_mode = WB_SYNC_ALL; |
| |
| /* |
| * If this isn't a data integrity operation, just notify |
| * that we have seen this work and we are now starting it. |
| */ |
| if (args.sync_mode == WB_SYNC_NONE) |
| 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 (args.sync_mode == WB_SYNC_ALL) |
| 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; |
| } |
| |
| wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10); |
| schedule_timeout_interruptible(wait_jiffies); |
| 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); |
| } |
| |
| 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 we're a pdlfush thread, then implement pdflush collision avoidance |
| * against the entire list. |
| * |
| * 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); |
| } |
| |
| /** |
| * 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) |
| { |
| 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_writeback_all(sb, nr_to_write); |
| } |
| EXPORT_SYMBOL(writeback_inodes_sb); |
| |
| /** |
| * 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); |