| /* |
| * 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 <linux/tracepoint.h> |
| #include "internal.h" |
| |
| /* |
| * Passed into wb_writeback(), essentially a subset of writeback_control |
| */ |
| struct wb_writeback_work { |
| long nr_pages; |
| struct super_block *sb; |
| enum writeback_sync_modes sync_mode; |
| unsigned int tagged_writepages:1; |
| unsigned int for_kupdate:1; |
| unsigned int range_cyclic:1; |
| unsigned int for_background:1; |
| |
| struct list_head list; /* pending work list */ |
| struct completion *done; /* set if the caller waits */ |
| }; |
| |
| /* |
| * Include the creation of the trace points after defining the |
| * wb_writeback_work structure so that the definition remains local to this |
| * file. |
| */ |
| #define CREATE_TRACE_POINTS |
| #include <trace/events/writeback.h> |
| |
| /* |
| * We don't actually have pdflush, but this one is exported though /proc... |
| */ |
| int nr_pdflush_threads; |
| |
| /** |
| * 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 test_bit(BDI_writeback_running, &bdi->state); |
| } |
| |
| static inline struct backing_dev_info *inode_to_bdi(struct inode *inode) |
| { |
| struct super_block *sb = inode->i_sb; |
| |
| if (strcmp(sb->s_type->name, "bdev") == 0) |
| return inode->i_mapping->backing_dev_info; |
| |
| return sb->s_bdi; |
| } |
| |
| static inline struct inode *wb_inode(struct list_head *head) |
| { |
| return list_entry(head, struct inode, i_wb_list); |
| } |
| |
| /* Wakeup flusher thread or forker thread to fork it. Requires bdi->wb_lock. */ |
| static void bdi_wakeup_flusher(struct backing_dev_info *bdi) |
| { |
| if (bdi->wb.task) { |
| wake_up_process(bdi->wb.task); |
| } else { |
| /* |
| * The bdi thread isn't there, wake up the forker thread which |
| * will create and run it. |
| */ |
| wake_up_process(default_backing_dev_info.wb.task); |
| } |
| } |
| |
| static void bdi_queue_work(struct backing_dev_info *bdi, |
| struct wb_writeback_work *work) |
| { |
| trace_writeback_queue(bdi, work); |
| |
| spin_lock_bh(&bdi->wb_lock); |
| list_add_tail(&work->list, &bdi->work_list); |
| if (!bdi->wb.task) |
| trace_writeback_nothread(bdi, work); |
| bdi_wakeup_flusher(bdi); |
| spin_unlock_bh(&bdi->wb_lock); |
| } |
| |
| static void |
| __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages, |
| bool range_cyclic) |
| { |
| struct wb_writeback_work *work; |
| |
| /* |
| * This is WB_SYNC_NONE writeback, so if allocation fails just |
| * wakeup the thread for old dirty data writeback |
| */ |
| work = kzalloc(sizeof(*work), GFP_ATOMIC); |
| if (!work) { |
| if (bdi->wb.task) { |
| trace_writeback_nowork(bdi); |
| wake_up_process(bdi->wb.task); |
| } |
| return; |
| } |
| |
| work->sync_mode = WB_SYNC_NONE; |
| work->nr_pages = nr_pages; |
| work->range_cyclic = range_cyclic; |
| |
| bdi_queue_work(bdi, 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 guarantees on |
| * completion. Caller need not hold sb s_umount semaphore. |
| * |
| */ |
| void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages) |
| { |
| __bdi_start_writeback(bdi, nr_pages, true); |
| } |
| |
| /** |
| * bdi_start_background_writeback - start background writeback |
| * @bdi: the backing device to write from |
| * |
| * Description: |
| * This makes sure WB_SYNC_NONE background writeback happens. When |
| * this function returns, it is only guaranteed that for given BDI |
| * some IO is happening if we are over background dirty threshold. |
| * Caller need not hold sb s_umount semaphore. |
| */ |
| void bdi_start_background_writeback(struct backing_dev_info *bdi) |
| { |
| /* |
| * We just wake up the flusher thread. It will perform background |
| * writeback as soon as there is no other work to do. |
| */ |
| trace_writeback_wake_background(bdi); |
| spin_lock_bh(&bdi->wb_lock); |
| bdi_wakeup_flusher(bdi); |
| spin_unlock_bh(&bdi->wb_lock); |
| } |
| |
| /* |
| * Remove the inode from the writeback list it is on. |
| */ |
| void inode_wb_list_del(struct inode *inode) |
| { |
| struct backing_dev_info *bdi = inode_to_bdi(inode); |
| |
| spin_lock(&bdi->wb.list_lock); |
| list_del_init(&inode->i_wb_list); |
| spin_unlock(&bdi->wb.list_lock); |
| } |
| |
| /* |
| * 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) |
| { |
| assert_spin_locked(&wb->list_lock); |
| if (!list_empty(&wb->b_dirty)) { |
| struct inode *tail; |
| |
| tail = wb_inode(wb->b_dirty.next); |
| if (time_before(inode->dirtied_when, tail->dirtied_when)) |
| inode->dirtied_when = jiffies; |
| } |
| list_move(&inode->i_wb_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) |
| { |
| assert_spin_locked(&wb->list_lock); |
| list_move(&inode->i_wb_list, &wb->b_more_io); |
| } |
| |
| static void inode_sync_complete(struct inode *inode) |
| { |
| /* |
| * Prevent speculative execution through |
| * spin_unlock(&wb->list_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 = wb_inode(delaying_queue->prev); |
| 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_wb_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)) { |
| sb = wb_inode(tmp.prev)->i_sb; |
| list_for_each_prev_safe(pos, node, &tmp) { |
| inode = wb_inode(pos); |
| if (inode->i_sb == sb) |
| list_move(&inode->i_wb_list, dispatch_queue); |
| } |
| } |
| } |
| |
| /* |
| * Queue all expired dirty inodes for io, eldest first. |
| * Before |
| * newly dirtied b_dirty b_io b_more_io |
| * =============> gf edc BA |
| * After |
| * newly dirtied b_dirty b_io b_more_io |
| * =============> g fBAedc |
| * | |
| * +--> dequeue for IO |
| */ |
| static void queue_io(struct bdi_writeback *wb, unsigned long *older_than_this) |
| { |
| assert_spin_locked(&wb->list_lock); |
| list_splice_init(&wb->b_more_io, &wb->b_io); |
| 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, |
| struct bdi_writeback *wb) |
| { |
| 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->i_lock); |
| spin_unlock(&wb->list_lock); |
| __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE); |
| spin_lock(&wb->list_lock); |
| spin_lock(&inode->i_lock); |
| } |
| } |
| |
| /* |
| * Write out an inode's dirty pages. Called under wb->list_lock and |
| * inode->i_lock. Either the caller has an active reference on the inode or |
| * the inode has I_WILL_FREE set. |
| * |
| * 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. |
| */ |
| static int |
| writeback_single_inode(struct inode *inode, struct bdi_writeback *wb, |
| struct writeback_control *wbc) |
| { |
| struct address_space *mapping = inode->i_mapping; |
| long nr_to_write = wbc->nr_to_write; |
| unsigned dirty; |
| int ret; |
| |
| assert_spin_locked(&wb->list_lock); |
| assert_spin_locked(&inode->i_lock); |
| |
| 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, wb); |
| trace_writeback_single_inode_requeue(inode, wbc, |
| nr_to_write); |
| return 0; |
| } |
| |
| /* |
| * It's a data-integrity sync. We must wait. |
| */ |
| inode_wait_for_writeback(inode, wb); |
| } |
| |
| 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->i_lock); |
| spin_unlock(&wb->list_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->i_lock); |
| dirty = inode->i_state & I_DIRTY; |
| inode->i_state &= ~(I_DIRTY_SYNC | I_DIRTY_DATASYNC); |
| spin_unlock(&inode->i_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(&wb->list_lock); |
| spin_lock(&inode->i_lock); |
| inode->i_state &= ~I_SYNC; |
| if (!(inode->i_state & I_FREEING)) { |
| /* |
| * Sync livelock prevention. Each inode is tagged and synced in |
| * one shot. If still dirty, it will be redirty_tail()'ed below. |
| * Update the dirty time to prevent enqueue and sync it again. |
| */ |
| if ((inode->i_state & I_DIRTY) && |
| (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)) |
| inode->dirtied_when = jiffies; |
| |
| if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) { |
| /* |
| * We didn't write back all the pages. nfs_writepages() |
| * sometimes bales out without doing anything. |
| */ |
| inode->i_state |= I_DIRTY_PAGES; |
| if (wbc->nr_to_write <= 0) { |
| /* |
| * slice used up: queue for next turn |
| */ |
| requeue_io(inode, wb); |
| } else { |
| /* |
| * Writeback blocked by something other than |
| * congestion. Delay the inode for some time to |
| * avoid spinning on the CPU (100% iowait) |
| * retrying writeback of the dirty page/inode |
| * that cannot be performed immediately. |
| */ |
| redirty_tail(inode, wb); |
| } |
| } else if (inode->i_state & I_DIRTY) { |
| /* |
| * Filesystems can dirty the inode during writeback |
| * operations, such as delayed allocation during |
| * submission or metadata updates after data IO |
| * completion. |
| */ |
| redirty_tail(inode, wb); |
| } else { |
| /* |
| * The inode is clean. At this point we either have |
| * a reference to the inode or it's on it's way out. |
| * No need to add it back to the LRU. |
| */ |
| list_del_init(&inode->i_wb_list); |
| wbc->inodes_written++; |
| } |
| } |
| inode_sync_complete(inode); |
| trace_writeback_single_inode(inode, wbc, nr_to_write); |
| return ret; |
| } |
| |
| /* |
| * For background 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 bool pin_sb_for_writeback(struct super_block *sb) |
| { |
| spin_lock(&sb_lock); |
| if (list_empty(&sb->s_instances)) { |
| spin_unlock(&sb_lock); |
| return false; |
| } |
| |
| sb->s_count++; |
| spin_unlock(&sb_lock); |
| |
| if (down_read_trylock(&sb->s_umount)) { |
| if (sb->s_root) |
| return true; |
| up_read(&sb->s_umount); |
| } |
| |
| put_super(sb); |
| return false; |
| } |
| |
| /* |
| * Write a portion of b_io inodes which belong to @sb. |
| * |
| * If @only_this_sb is true, 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, bool only_this_sb) |
| { |
| while (!list_empty(&wb->b_io)) { |
| long pages_skipped; |
| struct inode *inode = wb_inode(wb->b_io.prev); |
| |
| if (inode->i_sb != sb) { |
| if (only_this_sb) { |
| /* |
| * We only want to write back data for this |
| * superblock, move all inodes not belonging |
| * to it back onto the dirty list. |
| */ |
| redirty_tail(inode, wb); |
| continue; |
| } |
| |
| /* |
| * The inode belongs to a different superblock. |
| * Bounce back to the caller to unpin this and |
| * pin the next superblock. |
| */ |
| return 0; |
| } |
| |
| /* |
| * Don't bother with new inodes or inodes beeing freed, first |
| * kind does not need peridic writeout yet, and for the latter |
| * kind writeout is handled by the freer. |
| */ |
| spin_lock(&inode->i_lock); |
| if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) { |
| spin_unlock(&inode->i_lock); |
| requeue_io(inode, wb); |
| continue; |
| } |
| |
| __iget(inode); |
| |
| pages_skipped = wbc->pages_skipped; |
| writeback_single_inode(inode, wb, wbc); |
| if (wbc->pages_skipped != pages_skipped) { |
| /* |
| * writeback is not making progress due to locked |
| * buffers. Skip this inode for now. |
| */ |
| redirty_tail(inode, wb); |
| } |
| spin_unlock(&inode->i_lock); |
| spin_unlock(&wb->list_lock); |
| iput(inode); |
| cond_resched(); |
| spin_lock(&wb->list_lock); |
| if (wbc->nr_to_write <= 0) |
| return 1; |
| } |
| /* b_io is empty */ |
| return 1; |
| } |
| |
| static void __writeback_inodes_wb(struct bdi_writeback *wb, |
| struct writeback_control *wbc) |
| { |
| int ret = 0; |
| |
| while (!list_empty(&wb->b_io)) { |
| struct inode *inode = wb_inode(wb->b_io.prev); |
| struct super_block *sb = inode->i_sb; |
| |
| if (!pin_sb_for_writeback(sb)) { |
| requeue_io(inode, wb); |
| continue; |
| } |
| ret = writeback_sb_inodes(sb, wb, wbc, false); |
| drop_super(sb); |
| |
| if (ret) |
| break; |
| } |
| /* Leave any unwritten inodes on b_io */ |
| } |
| |
| void writeback_inodes_wb(struct bdi_writeback *wb, |
| struct writeback_control *wbc) |
| { |
| spin_lock(&wb->list_lock); |
| if (list_empty(&wb->b_io)) |
| queue_io(wb, wbc->older_than_this); |
| __writeback_inodes_wb(wb, wbc); |
| spin_unlock(&wb->list_lock); |
| } |
| |
| /* |
| * 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; |
| |
| global_dirty_limits(&background_thresh, &dirty_thresh); |
| |
| 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_work *work) |
| { |
| struct writeback_control wbc = { |
| .sync_mode = work->sync_mode, |
| .tagged_writepages = work->tagged_writepages, |
| .older_than_this = NULL, |
| .for_kupdate = work->for_kupdate, |
| .for_background = work->for_background, |
| .range_cyclic = work->range_cyclic, |
| }; |
| unsigned long oldest_jif; |
| long wrote = 0; |
| long write_chunk = MAX_WRITEBACK_PAGES; |
| struct inode *inode; |
| |
| if (!wbc.range_cyclic) { |
| wbc.range_start = 0; |
| wbc.range_end = LLONG_MAX; |
| } |
| |
| /* |
| * WB_SYNC_ALL mode does livelock avoidance by syncing dirty |
| * inodes/pages in one big loop. Setting wbc.nr_to_write=LONG_MAX |
| * here avoids calling into writeback_inodes_wb() more than once. |
| * |
| * The intended call sequence for WB_SYNC_ALL writeback is: |
| * |
| * wb_writeback() |
| * writeback_sb_inodes() <== called only once |
| * write_cache_pages() <== called once for each inode |
| * (quickly) tag currently dirty pages |
| * (maybe slowly) sync all tagged pages |
| */ |
| if (wbc.sync_mode == WB_SYNC_ALL || wbc.tagged_writepages) |
| write_chunk = LONG_MAX; |
| |
| oldest_jif = jiffies; |
| wbc.older_than_this = &oldest_jif; |
| |
| spin_lock(&wb->list_lock); |
| for (;;) { |
| /* |
| * Stop writeback when nr_pages has been consumed |
| */ |
| if (work->nr_pages <= 0) |
| break; |
| |
| /* |
| * Background writeout and kupdate-style writeback may |
| * run forever. Stop them if there is other work to do |
| * so that e.g. sync can proceed. They'll be restarted |
| * after the other works are all done. |
| */ |
| if ((work->for_background || work->for_kupdate) && |
| !list_empty(&wb->bdi->work_list)) |
| break; |
| |
| /* |
| * For background writeout, stop when we are below the |
| * background dirty threshold |
| */ |
| if (work->for_background && !over_bground_thresh()) |
| break; |
| |
| if (work->for_kupdate) { |
| oldest_jif = jiffies - |
| msecs_to_jiffies(dirty_expire_interval * 10); |
| wbc.older_than_this = &oldest_jif; |
| } |
| |
| wbc.nr_to_write = write_chunk; |
| wbc.pages_skipped = 0; |
| wbc.inodes_written = 0; |
| |
| trace_wbc_writeback_start(&wbc, wb->bdi); |
| if (list_empty(&wb->b_io)) |
| queue_io(wb, wbc.older_than_this); |
| if (work->sb) |
| writeback_sb_inodes(work->sb, wb, &wbc, true); |
| else |
| __writeback_inodes_wb(wb, &wbc); |
| trace_wbc_writeback_written(&wbc, wb->bdi); |
| |
| work->nr_pages -= write_chunk - wbc.nr_to_write; |
| wrote += write_chunk - wbc.nr_to_write; |
| |
| /* |
| * Did we write something? Try for more |
| * |
| * Dirty inodes are moved to b_io for writeback in batches. |
| * The completion of the current batch does not necessarily |
| * mean the overall work is done. So we keep looping as long |
| * as made some progress on cleaning pages or inodes. |
| */ |
| if (wbc.nr_to_write < write_chunk) |
| continue; |
| if (wbc.inodes_written) |
| continue; |
| /* |
| * No more inodes for IO, bail |
| */ |
| if (list_empty(&wb->b_more_io)) |
| break; |
| /* |
| * Nothing written. Wait for some inode to |
| * become available for writeback. Otherwise |
| * we'll just busyloop. |
| */ |
| if (!list_empty(&wb->b_more_io)) { |
| inode = wb_inode(wb->b_more_io.prev); |
| trace_wbc_writeback_wait(&wbc, wb->bdi); |
| spin_lock(&inode->i_lock); |
| inode_wait_for_writeback(inode, wb); |
| spin_unlock(&inode->i_lock); |
| } |
| } |
| spin_unlock(&wb->list_lock); |
| |
| return wrote; |
| } |
| |
| /* |
| * Return the next wb_writeback_work struct that hasn't been processed yet. |
| */ |
| static struct wb_writeback_work * |
| get_next_work_item(struct backing_dev_info *bdi) |
| { |
| struct wb_writeback_work *work = NULL; |
| |
| spin_lock_bh(&bdi->wb_lock); |
| if (!list_empty(&bdi->work_list)) { |
| work = list_entry(bdi->work_list.next, |
| struct wb_writeback_work, list); |
| list_del_init(&work->list); |
| } |
| spin_unlock_bh(&bdi->wb_lock); |
| return work; |
| } |
| |
| /* |
| * Add in the number of potentially dirty inodes, because each inode |
| * write can dirty pagecache in the underlying blockdev. |
| */ |
| static unsigned long get_nr_dirty_pages(void) |
| { |
| return global_page_state(NR_FILE_DIRTY) + |
| global_page_state(NR_UNSTABLE_NFS) + |
| get_nr_dirty_inodes(); |
| } |
| |
| static long wb_check_background_flush(struct bdi_writeback *wb) |
| { |
| if (over_bground_thresh()) { |
| |
| struct wb_writeback_work work = { |
| .nr_pages = LONG_MAX, |
| .sync_mode = WB_SYNC_NONE, |
| .for_background = 1, |
| .range_cyclic = 1, |
| }; |
| |
| return wb_writeback(wb, &work); |
| } |
| |
| return 0; |
| } |
| |
| 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 = get_nr_dirty_pages(); |
| |
| if (nr_pages) { |
| struct wb_writeback_work work = { |
| .nr_pages = nr_pages, |
| .sync_mode = WB_SYNC_NONE, |
| .for_kupdate = 1, |
| .range_cyclic = 1, |
| }; |
| |
| return wb_writeback(wb, &work); |
| } |
| |
| 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 wb_writeback_work *work; |
| long wrote = 0; |
| |
| set_bit(BDI_writeback_running, &wb->bdi->state); |
| while ((work = get_next_work_item(bdi)) != NULL) { |
| /* |
| * Override sync mode, in case we must wait for completion |
| * because this thread is exiting now. |
| */ |
| if (force_wait) |
| work->sync_mode = WB_SYNC_ALL; |
| |
| trace_writeback_exec(bdi, work); |
| |
| wrote += wb_writeback(wb, work); |
| |
| /* |
| * Notify the caller of completion if this is a synchronous |
| * work item, otherwise just free it. |
| */ |
| if (work->done) |
| complete(work->done); |
| else |
| kfree(work); |
| } |
| |
| /* |
| * Check for periodic writeback, kupdated() style |
| */ |
| wrote += wb_check_old_data_flush(wb); |
| wrote += wb_check_background_flush(wb); |
| clear_bit(BDI_writeback_running, &wb->bdi->state); |
| |
| 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_thread(void *data) |
| { |
| struct bdi_writeback *wb = data; |
| struct backing_dev_info *bdi = wb->bdi; |
| long pages_written; |
| |
| current->flags |= PF_SWAPWRITE; |
| set_freezable(); |
| wb->last_active = jiffies; |
| |
| /* |
| * Our parent may run at a different priority, just set us to normal |
| */ |
| set_user_nice(current, 0); |
| |
| trace_writeback_thread_start(bdi); |
| |
| while (!kthread_should_stop()) { |
| /* |
| * Remove own delayed wake-up timer, since we are already awake |
| * and we'll take care of the preriodic write-back. |
| */ |
| del_timer(&wb->wakeup_timer); |
| |
| pages_written = wb_do_writeback(wb, 0); |
| |
| trace_writeback_pages_written(pages_written); |
| |
| if (pages_written) |
| wb->last_active = jiffies; |
| |
| set_current_state(TASK_INTERRUPTIBLE); |
| if (!list_empty(&bdi->work_list) || kthread_should_stop()) { |
| __set_current_state(TASK_RUNNING); |
| continue; |
| } |
| |
| if (wb_has_dirty_io(wb) && dirty_writeback_interval) |
| schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10)); |
| else { |
| /* |
| * We have nothing to do, so can go sleep without any |
| * timeout and save power. When a work is queued or |
| * something is made dirty - we will be woken up. |
| */ |
| schedule(); |
| } |
| |
| try_to_freeze(); |
| } |
| |
| /* Flush any work that raced with us exiting */ |
| if (!list_empty(&bdi->work_list)) |
| wb_do_writeback(wb, 1); |
| |
| trace_writeback_thread_stop(bdi); |
| return 0; |
| } |
| |
| |
| /* |
| * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back |
| * the whole world. |
| */ |
| void wakeup_flusher_threads(long nr_pages) |
| { |
| struct backing_dev_info *bdi; |
| |
| if (!nr_pages) { |
| nr_pages = global_page_state(NR_FILE_DIRTY) + |
| global_page_state(NR_UNSTABLE_NFS); |
| } |
| |
| rcu_read_lock(); |
| list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) { |
| if (!bdi_has_dirty_io(bdi)) |
| continue; |
| __bdi_start_writeback(bdi, nr_pages, false); |
| } |
| rcu_read_unlock(); |
| } |
| |
| 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. |
| * |
| * 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; |
| struct backing_dev_info *bdi = NULL; |
| |
| /* |
| * 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, flags); |
| } |
| |
| /* |
| * 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->i_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_unlock_inode; |
| |
| /* |
| * Only add valid (hashed) inodes to the superblock's |
| * dirty list. Add blockdev inodes as well. |
| */ |
| if (!S_ISBLK(inode->i_mode)) { |
| if (inode_unhashed(inode)) |
| goto out_unlock_inode; |
| } |
| if (inode->i_state & I_FREEING) |
| goto out_unlock_inode; |
| |
| /* |
| * 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) { |
| bool wakeup_bdi = false; |
| bdi = inode_to_bdi(inode); |
| |
| if (bdi_cap_writeback_dirty(bdi)) { |
| WARN(!test_bit(BDI_registered, &bdi->state), |
| "bdi-%s not registered\n", bdi->name); |
| |
| /* |
| * If this is the first dirty inode for this |
| * bdi, we have to wake-up the corresponding |
| * bdi thread to make sure background |
| * write-back happens later. |
| */ |
| if (!wb_has_dirty_io(&bdi->wb)) |
| wakeup_bdi = true; |
| } |
| |
| spin_unlock(&inode->i_lock); |
| spin_lock(&bdi->wb.list_lock); |
| inode->dirtied_when = jiffies; |
| list_move(&inode->i_wb_list, &bdi->wb.b_dirty); |
| spin_unlock(&bdi->wb.list_lock); |
| |
| if (wakeup_bdi) |
| bdi_wakeup_thread_delayed(bdi); |
| return; |
| } |
| } |
| out_unlock_inode: |
| spin_unlock(&inode->i_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_sb_list_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 = inode->i_mapping; |
| |
| spin_lock(&inode->i_lock); |
| if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) || |
| (mapping->nrpages == 0)) { |
| spin_unlock(&inode->i_lock); |
| continue; |
| } |
| __iget(inode); |
| spin_unlock(&inode->i_lock); |
| spin_unlock(&inode_sb_list_lock); |
| |
| /* |
| * We hold a reference to 'inode' so it couldn't have been |
| * removed from s_inodes list while we dropped the |
| * inode_sb_list_lock. We cannot iput the inode now as we can |
| * be holding the last reference and we cannot iput it under |
| * inode_sb_list_lock. So we keep the reference and iput it |
| * later. |
| */ |
| iput(old_inode); |
| old_inode = inode; |
| |
| filemap_fdatawait(mapping); |
| |
| cond_resched(); |
| |
| spin_lock(&inode_sb_list_lock); |
| } |
| spin_unlock(&inode_sb_list_lock); |
| iput(old_inode); |
| } |
| |
| /** |
| * writeback_inodes_sb_nr - writeback dirty inodes from given super_block |
| * @sb: the superblock |
| * @nr: the number of pages to write |
| * |
| * 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. |
| */ |
| void writeback_inodes_sb_nr(struct super_block *sb, unsigned long nr) |
| { |
| DECLARE_COMPLETION_ONSTACK(done); |
| struct wb_writeback_work work = { |
| .sb = sb, |
| .sync_mode = WB_SYNC_NONE, |
| .tagged_writepages = 1, |
| .done = &done, |
| .nr_pages = nr, |
| }; |
| |
| WARN_ON(!rwsem_is_locked(&sb->s_umount)); |
| bdi_queue_work(sb->s_bdi, &work); |
| wait_for_completion(&done); |
| } |
| EXPORT_SYMBOL(writeback_inodes_sb_nr); |
| |
| /** |
| * 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. |
| */ |
| void writeback_inodes_sb(struct super_block *sb) |
| { |
| return writeback_inodes_sb_nr(sb, get_nr_dirty_pages()); |
| } |
| EXPORT_SYMBOL(writeback_inodes_sb); |
| |
| /** |
| * 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)) { |
| down_read(&sb->s_umount); |
| writeback_inodes_sb(sb); |
| up_read(&sb->s_umount); |
| return 1; |
| } else |
| return 0; |
| } |
| EXPORT_SYMBOL(writeback_inodes_sb_if_idle); |
| |
| /** |
| * writeback_inodes_sb_if_idle - start writeback if none underway |
| * @sb: the superblock |
| * @nr: the number of pages to write |
| * |
| * Invoke writeback_inodes_sb if no writeback is currently underway. |
| * Returns 1 if writeback was started, 0 if not. |
| */ |
| int writeback_inodes_sb_nr_if_idle(struct super_block *sb, |
| unsigned long nr) |
| { |
| if (!writeback_in_progress(sb->s_bdi)) { |
| down_read(&sb->s_umount); |
| writeback_inodes_sb_nr(sb, nr); |
| up_read(&sb->s_umount); |
| return 1; |
| } else |
| return 0; |
| } |
| EXPORT_SYMBOL(writeback_inodes_sb_nr_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. |
| */ |
| void sync_inodes_sb(struct super_block *sb) |
| { |
| DECLARE_COMPLETION_ONSTACK(done); |
| struct wb_writeback_work work = { |
| .sb = sb, |
| .sync_mode = WB_SYNC_ALL, |
| .nr_pages = LONG_MAX, |
| .range_cyclic = 0, |
| .done = &done, |
| }; |
| |
| WARN_ON(!rwsem_is_locked(&sb->s_umount)); |
| |
| bdi_queue_work(sb->s_bdi, &work); |
| wait_for_completion(&done); |
| |
| 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) |
| { |
| struct bdi_writeback *wb = &inode_to_bdi(inode)->wb; |
| 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(&wb->list_lock); |
| spin_lock(&inode->i_lock); |
| ret = writeback_single_inode(inode, wb, &wbc); |
| spin_unlock(&inode->i_lock); |
| spin_unlock(&wb->list_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) |
| { |
| struct bdi_writeback *wb = &inode_to_bdi(inode)->wb; |
| int ret; |
| |
| spin_lock(&wb->list_lock); |
| spin_lock(&inode->i_lock); |
| ret = writeback_single_inode(inode, wb, wbc); |
| spin_unlock(&inode->i_lock); |
| spin_unlock(&wb->list_lock); |
| return ret; |
| } |
| EXPORT_SYMBOL(sync_inode); |
| |
| /** |
| * sync_inode_metadata - write an inode to disk |
| * @inode: the inode to sync |
| * @wait: wait for I/O to complete. |
| * |
| * Write an inode to disk and adjust its dirty state after completion. |
| * |
| * Note: only writes the actual inode, no associated data or other metadata. |
| */ |
| int sync_inode_metadata(struct inode *inode, int wait) |
| { |
| struct writeback_control wbc = { |
| .sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_NONE, |
| .nr_to_write = 0, /* metadata-only */ |
| }; |
| |
| return sync_inode(inode, &wbc); |
| } |
| EXPORT_SYMBOL(sync_inode_metadata); |