Btrfs: Shrink delay allocated space in a synchronized

Shrink delayed allocation space in a synchronized manner is more
controllable than flushing all delay allocated space in an async
thread.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

4 files changed, 88 insertions, 121 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index a68f34603b9d..85c7b95dd2fe 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -700,10 +700,6 @@ struct btrfs_space_info {
 
         struct list_head list;
 
-        /* for controlling how we free up space for allocations */
-        wait_queue_head_t flush_wait;
-        int flushing;
-
         /* for block groups in our same type */
         struct list_head block_groups[BTRFS_NR_RAID_TYPES];
         spinlock_t lock;
@@ -928,7 +924,6 @@ struct btrfs_fs_info {
         struct btrfs_workers endio_meta_write_workers;
         struct btrfs_workers endio_write_workers;
         struct btrfs_workers submit_workers;
-        struct btrfs_workers enospc_workers;
         /*
          * fixup workers take dirty pages that didn't properly go through
          * the cow mechanism and make them safe to write.  It happens
@@ -2312,6 +2307,7 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
                                u32 min_type);
 
 int btrfs_start_delalloc_inodes(struct btrfs_root *root, int delay_iput);
+int btrfs_start_one_delalloc_inode(struct btrfs_root *root, int delay_iput);
 int btrfs_set_extent_delalloc(struct inode *inode, u64 start, u64 end,
                               struct extent_state **cached_state);
 int btrfs_writepages(struct address_space *mapping,
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index feca04197d02..05f26acfd070 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1759,9 +1759,6 @@ struct btrfs_root *open_ctree(struct super_block *sb,
                            min_t(u64, fs_devices->num_devices,
                            fs_info->thread_pool_size),
                            &fs_info->generic_worker);
-        btrfs_init_workers(&fs_info->enospc_workers, "enospc",
-                           fs_info->thread_pool_size,
-                           &fs_info->generic_worker);
 
         /* a higher idle thresh on the submit workers makes it much more
          * likely that bios will be send down in a sane order to the
@@ -1809,7 +1806,6 @@ struct btrfs_root *open_ctree(struct super_block *sb,
         btrfs_start_workers(&fs_info->endio_meta_workers, 1);
         btrfs_start_workers(&fs_info->endio_meta_write_workers, 1);
         btrfs_start_workers(&fs_info->endio_write_workers, 1);
-        btrfs_start_workers(&fs_info->enospc_workers, 1);
 
         fs_info->bdi.ra_pages *= btrfs_super_num_devices(disk_super);
         fs_info->bdi.ra_pages = max(fs_info->bdi.ra_pages,
@@ -2040,7 +2036,6 @@ fail_sb_buffer:
         btrfs_stop_workers(&fs_info->endio_meta_write_workers);
         btrfs_stop_workers(&fs_info->endio_write_workers);
         btrfs_stop_workers(&fs_info->submit_workers);
-        btrfs_stop_workers(&fs_info->enospc_workers);
 fail_iput:
         invalidate_inode_pages2(fs_info->btree_inode->i_mapping);
         iput(fs_info->btree_inode);
@@ -2473,7 +2468,6 @@ int close_ctree(struct btrfs_root *root)
         btrfs_stop_workers(&fs_info->endio_meta_write_workers);
         btrfs_stop_workers(&fs_info->endio_write_workers);
         btrfs_stop_workers(&fs_info->submit_workers);
-        btrfs_stop_workers(&fs_info->enospc_workers);
 
         btrfs_close_devices(fs_info->fs_devices);
         btrfs_mapping_tree_free(&fs_info->mapping_tree);
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 2c95507c9abb..f32b1618ee6d 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -74,6 +74,9 @@ static void dump_space_info(struct btrfs_space_info *info, u64 bytes,
 static int maybe_allocate_chunk(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
                                 struct btrfs_space_info *sinfo, u64 num_bytes);
+static int shrink_delalloc(struct btrfs_trans_handle *trans,
+                           struct btrfs_root *root,
+                           struct btrfs_space_info *sinfo, u64 to_reclaim);
 
 static noinline int
 block_group_cache_done(struct btrfs_block_group_cache *cache)
@@ -2693,7 +2696,6 @@ static int update_space_info(struct btrfs_fs_info *info, u64 flags,
         for (i = 0; i < BTRFS_NR_RAID_TYPES; i++)
                 INIT_LIST_HEAD(&found->block_groups[i]);
         init_rwsem(&found->groups_sem);
-        init_waitqueue_head(&found->flush_wait);
         spin_lock_init(&found->lock);
         found->flags = flags & (BTRFS_BLOCK_GROUP_DATA |
                                 BTRFS_BLOCK_GROUP_SYSTEM |
@@ -2907,105 +2909,6 @@ static void check_force_delalloc(struct btrfs_space_info *meta_sinfo)
                 meta_sinfo->force_delalloc = 0;
 }
 
-struct async_flush {
-        struct btrfs_root *root;
-        struct btrfs_space_info *info;
-        struct btrfs_work work;
-};
-
-static noinline void flush_delalloc_async(struct btrfs_work *work)
-{
-        struct async_flush *async;
-        struct btrfs_root *root;
-        struct btrfs_space_info *info;
-
-        async = container_of(work, struct async_flush, work);
-        root = async->root;
-        info = async->info;
-
-        btrfs_start_delalloc_inodes(root, 0);
-        wake_up(&info->flush_wait);
-        btrfs_wait_ordered_extents(root, 0, 0);
-
-        spin_lock(&info->lock);
-        info->flushing = 0;
-        spin_unlock(&info->lock);
-        wake_up(&info->flush_wait);
-
-        kfree(async);
-}
-
-static void wait_on_flush(struct btrfs_space_info *info)
-{
-        DEFINE_WAIT(wait);
-        u64 used;
-
-        while (1) {
-                prepare_to_wait(&info->flush_wait, &wait,
-                                TASK_UNINTERRUPTIBLE);
-                spin_lock(&info->lock);
-                if (!info->flushing) {
-                        spin_unlock(&info->lock);
-                        break;
-                }
-
-                used = info->bytes_used + info->bytes_reserved +
-                        info->bytes_pinned + info->bytes_readonly +
-                        info->bytes_super + info->bytes_root +
-                        info->bytes_may_use + info->bytes_delalloc;
-                if (used < info->total_bytes) {
-                        spin_unlock(&info->lock);
-                        break;
-                }
-                spin_unlock(&info->lock);
-                schedule();
-        }
-        finish_wait(&info->flush_wait, &wait);
-}
-
-static void flush_delalloc(struct btrfs_root *root,
-                                 struct btrfs_space_info *info)
-{
-        struct async_flush *async;
-        bool wait = false;
-
-        spin_lock(&info->lock);
-
-        if (!info->flushing)
-                info->flushing = 1;
-        else
-                wait = true;
-
-        spin_unlock(&info->lock);
-
-        if (wait) {
-                wait_on_flush(info);
-                return;
-        }
-
-        async = kzalloc(sizeof(*async), GFP_NOFS);
-        if (!async)
-                goto flush;
-
-        async->root = root;
-        async->info = info;
-        async->work.func = flush_delalloc_async;
-
-        btrfs_queue_worker(&root->fs_info->enospc_workers,
-                           &async->work);
-        wait_on_flush(info);
-        return;
-
-flush:
-        btrfs_start_delalloc_inodes(root, 0);
-        btrfs_wait_ordered_extents(root, 0, 0);
-
-        spin_lock(&info->lock);
-        info->flushing = 0;
-        spin_unlock(&info->lock);
-        wake_up(&info->flush_wait);
-}
-
 /*
  * Reserve metadata space for delalloc.
  */
@@ -3058,7 +2961,7 @@ again:
                         filemap_flush(inode->i_mapping);
                         goto again;
                 } else if (flushed == 3) {
-                        flush_delalloc(root, meta_sinfo);
+                        shrink_delalloc(NULL, root, meta_sinfo, num_bytes);
                         goto again;
                 }
                 spin_lock(&meta_sinfo->lock);
@@ -3171,7 +3074,7 @@ again:
                 }
 
                 if (retries == 2) {
-                        flush_delalloc(root, meta_sinfo);
+                        shrink_delalloc(NULL, root, meta_sinfo, num_bytes);
                         goto again;
                 }
                 spin_lock(&meta_sinfo->lock);
@@ -3197,7 +3100,7 @@ int btrfs_check_data_free_space(struct btrfs_root *root, struct inode *inode,
 {
         struct btrfs_space_info *data_sinfo;
         u64 used;
-        int ret = 0, committed = 0, flushed = 0;
+        int ret = 0, committed = 0;
 
         /* make sure bytes are sectorsize aligned */
         bytes = (bytes + root->sectorsize - 1) & ~((u64)root->sectorsize - 1);
@@ -3217,13 +3120,6 @@ again:
         if (used + bytes > data_sinfo->total_bytes) {
                 struct btrfs_trans_handle *trans;
 
-                if (!flushed) {
-                        spin_unlock(&data_sinfo->lock);
-                        flush_delalloc(root, data_sinfo);
-                        flushed = 1;
-                        goto again;
-                }
-
                 /*
                  * if we don't have enough free bytes in this space then we need
                  * to alloc a new chunk.
@@ -3467,6 +3363,55 @@ static int maybe_allocate_chunk(struct btrfs_trans_handle *trans,
         return ret == 1 ? 1 : 0;
 }
 
+/*
+ * shrink metadata reservation for delalloc
+ */
+static int shrink_delalloc(struct btrfs_trans_handle *trans,
+                           struct btrfs_root *root,
+                           struct btrfs_space_info *sinfo, u64 to_reclaim)
+{
+        u64 reserved;
+        u64 max_reclaim;
+        u64 reclaimed = 0;
+        int pause = 1;
+        int ret;
+
+        spin_lock(&sinfo->lock);
+        reserved = sinfo->bytes_delalloc;
+        spin_unlock(&sinfo->lock);
+
+        if (reserved == 0)
+                return 0;
+
+        max_reclaim = min(reserved, to_reclaim);
+
+        while (1) {
+                ret = btrfs_start_one_delalloc_inode(root, trans ? 1 : 0);
+                if (!ret) {
+                        __set_current_state(TASK_INTERRUPTIBLE);
+                        schedule_timeout(pause);
+                        pause <<= 1;
+                        if (pause > HZ / 10)
+                                pause = HZ / 10;
+                } else {
+                        pause = 1;
+                }
+
+                spin_lock(&sinfo->lock);
+                if (reserved > sinfo->bytes_delalloc)
+                        reclaimed = reserved - sinfo->bytes_delalloc;
+                reserved = sinfo->bytes_delalloc;
+                spin_unlock(&sinfo->lock);
+
+                if (reserved == 0 || reclaimed >= max_reclaim)
+                        break;
+
+                if (trans && trans->transaction->blocked)
+                        return -EAGAIN;
+        }
+        return reclaimed >= to_reclaim;
+}
+
 static int update_block_group(struct btrfs_trans_handle *trans,
                               struct btrfs_root *root,
                               u64 bytenr, u64 num_bytes, int alloc,
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 2bfdc641d4e3..d53cad1afe26 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -5611,6 +5611,38 @@ int btrfs_start_delalloc_inodes(struct btrfs_root *root, int delay_iput)
         return 0;
 }
 
+int btrfs_start_one_delalloc_inode(struct btrfs_root *root, int delay_iput)
+{
+        struct btrfs_inode *binode;
+        struct inode *inode = NULL;
+
+        spin_lock(&root->fs_info->delalloc_lock);
+        while (!list_empty(&root->fs_info->delalloc_inodes)) {
+                binode = list_entry(root->fs_info->delalloc_inodes.next,
+                                    struct btrfs_inode, delalloc_inodes);
+                inode = igrab(&binode->vfs_inode);
+                if (inode) {
+                        list_move_tail(&binode->delalloc_inodes,
+                                       &root->fs_info->delalloc_inodes);
+                        break;
+                }
+
+                list_del_init(&binode->delalloc_inodes);
+                cond_resched_lock(&root->fs_info->delalloc_lock);
+        }
+        spin_unlock(&root->fs_info->delalloc_lock);
+
+        if (inode) {
+                write_inode_now(inode, 0);
+                if (delay_iput)
+                        btrfs_add_delayed_iput(inode);
+                else
+                        iput(inode);
+                return 1;
+        }
+        return 0;
+}
+
 static int btrfs_symlink(struct inode *dir, struct dentry *dentry,
                          const char *symname)
 {