Btrfs: write out free space cache

This is a simple bit, just dump the free space cache out to our preallocated
inode when we're writing out dirty block groups.  There are a bunch of changes
in inode.c in order to account for special cases.  Mostly when we're doing the
writeout we're holding trans_mutex, so we need to use the nolock transacation
functions.  Also we can't do asynchronous completions since the async thread
could be blocked on already completed IO waiting for the transaction lock.  This
has been tested with xfstests and btrfs filesystem balance, as well as my ENOSPC
tests.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>

1 files changed, 302 insertions, 0 deletions

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 05efcc7061a..7f972e59cc0 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -28,6 +28,11 @@
 #define BITS_PER_BITMAP		(PAGE_CACHE_SIZE * 8)
 #define MAX_CACHE_BYTES_PER_GIG	(32 * 1024)
 
+static void recalculate_thresholds(struct btrfs_block_group_cache
+				   *block_group);
+static int link_free_space(struct btrfs_block_group_cache *block_group,
+			   struct btrfs_free_space *info);
+
 struct inode *lookup_free_space_inode(struct btrfs_root *root,
 				      struct btrfs_block_group_cache
 				      *block_group, struct btrfs_path *path)
@@ -182,6 +187,303 @@ int btrfs_truncate_free_space_cache(struct btrfs_root *root,
 	return btrfs_update_inode(trans, root, inode);
 }
 
+int btrfs_write_out_cache(struct btrfs_root *root,
+			  struct btrfs_trans_handle *trans,
+			  struct btrfs_block_group_cache *block_group,
+			  struct btrfs_path *path)
+{
+	struct btrfs_free_space_header *header;
+	struct extent_buffer *leaf;
+	struct inode *inode;
+	struct rb_node *node;
+	struct list_head *pos, *n;
+	struct page *page;
+	struct extent_state *cached_state = NULL;
+	struct list_head bitmap_list;
+	struct btrfs_key key;
+	u64 bytes = 0;
+	u32 *crc, *checksums;
+	pgoff_t index = 0, last_index = 0;
+	unsigned long first_page_offset;
+	int num_checksums;
+	int entries = 0;
+	int bitmaps = 0;
+	int ret = 0;
+
+	root = root->fs_info->tree_root;
+
+	INIT_LIST_HEAD(&bitmap_list);
+
+	spin_lock(&block_group->lock);
+	if (block_group->disk_cache_state < BTRFS_DC_SETUP) {
+		spin_unlock(&block_group->lock);
+		return 0;
+	}
+	spin_unlock(&block_group->lock);
+
+	inode = lookup_free_space_inode(root, block_group, path);
+	if (IS_ERR(inode))
+		return 0;
+
+	if (!i_size_read(inode)) {
+		iput(inode);
+		return 0;
+	}
+
+	last_index = (i_size_read(inode) - 1) >> PAGE_CACHE_SHIFT;
+	filemap_write_and_wait(inode->i_mapping);
+	btrfs_wait_ordered_range(inode, inode->i_size &
+				 ~(root->sectorsize - 1), (u64)-1);
+
+	/* We need a checksum per page. */
+	num_checksums = i_size_read(inode) / PAGE_CACHE_SIZE;
+	crc = checksums  = kzalloc(sizeof(u32) * num_checksums, GFP_NOFS);
+	if (!crc) {
+		iput(inode);
+		return 0;
+	}
+
+	/* Since the first page has all of our checksums and our generation we
+	 * need to calculate the offset into the page that we can start writing
+	 * our entries.
+	 */
+	first_page_offset = (sizeof(u32) * num_checksums) + sizeof(u64);
+
+	node = rb_first(&block_group->free_space_offset);
+	if (!node)
+		goto out_free;
+
+	/*
+	 * Lock all pages first so we can lock the extent safely.
+	 *
+	 * NOTE: Because we hold the ref the entire time we're going to write to
+	 * the page find_get_page should never fail, so we don't do a check
+	 * after find_get_page at this point.  Just putting this here so people
+	 * know and don't freak out.
+	 */
+	while (index <= last_index) {
+		page = grab_cache_page(inode->i_mapping, index);
+		if (!page) {
+			pgoff_t i = 0;
+
+			while (i < index) {
+				page = find_get_page(inode->i_mapping, i);
+				unlock_page(page);
+				page_cache_release(page);
+				page_cache_release(page);
+				i++;
+			}
+			goto out_free;
+		}
+		index++;
+	}
+
+	index = 0;
+	lock_extent_bits(&BTRFS_I(inode)->io_tree, 0, i_size_read(inode) - 1,
+			 0, &cached_state, GFP_NOFS);
+
+	/* Write out the extent entries */
+	do {
+		struct btrfs_free_space_entry *entry;
+		void *addr;
+		unsigned long offset = 0;
+		unsigned long start_offset = 0;
+
+		if (index == 0) {
+			start_offset = first_page_offset;
+			offset = start_offset;
+		}
+
+		page = find_get_page(inode->i_mapping, index);
+
+		addr = kmap(page);
+		entry = addr + start_offset;
+
+		memset(addr, 0, PAGE_CACHE_SIZE);
+		while (1) {
+			struct btrfs_free_space *e;
+
+			e = rb_entry(node, struct btrfs_free_space, offset_index);
+			entries++;
+
+			entry->offset = cpu_to_le64(e->offset);
+			entry->bytes = cpu_to_le64(e->bytes);
+			if (e->bitmap) {
+				entry->type = BTRFS_FREE_SPACE_BITMAP;
+				list_add_tail(&e->list, &bitmap_list);
+				bitmaps++;
+			} else {
+				entry->type = BTRFS_FREE_SPACE_EXTENT;
+			}
+			node = rb_next(node);
+			if (!node)
+				break;
+			offset += sizeof(struct btrfs_free_space_entry);
+			if (offset + sizeof(struct btrfs_free_space_entry) >=
+			    PAGE_CACHE_SIZE)
+				break;
+			entry++;
+		}
+		*crc = ~(u32)0;
+		*crc = btrfs_csum_data(root, addr + start_offset, *crc,
+				       PAGE_CACHE_SIZE - start_offset);
+		kunmap(page);
+
+		btrfs_csum_final(*crc, (char *)crc);
+		crc++;
+
+		bytes += PAGE_CACHE_SIZE;
+
+		ClearPageChecked(page);
+		set_page_extent_mapped(page);
+		SetPageUptodate(page);
+		set_page_dirty(page);
+
+		/*
+		 * We need to release our reference we got for grab_cache_page,
+		 * except for the first page which will hold our checksums, we
+		 * do that below.
+		 */
+		if (index != 0) {
+			unlock_page(page);
+			page_cache_release(page);
+		}
+
+		page_cache_release(page);
+
+		index++;
+	} while (node);
+
+	/* Write out the bitmaps */
+	list_for_each_safe(pos, n, &bitmap_list) {
+		void *addr;
+		struct btrfs_free_space *entry =
+			list_entry(pos, struct btrfs_free_space, list);
+
+		page = find_get_page(inode->i_mapping, index);
+
+		addr = kmap(page);
+		memcpy(addr, entry->bitmap, PAGE_CACHE_SIZE);
+		*crc = ~(u32)0;
+		*crc = btrfs_csum_data(root, addr, *crc, PAGE_CACHE_SIZE);
+		kunmap(page);
+		btrfs_csum_final(*crc, (char *)crc);
+		crc++;
+		bytes += PAGE_CACHE_SIZE;
+
+		ClearPageChecked(page);
+		set_page_extent_mapped(page);
+		SetPageUptodate(page);
+		set_page_dirty(page);
+		unlock_page(page);
+		page_cache_release(page);
+		page_cache_release(page);
+		list_del_init(&entry->list);
+		index++;
+	}
+
+	/* Zero out the rest of the pages just to make sure */
+	while (index <= last_index) {
+		void *addr;
+
+		page = find_get_page(inode->i_mapping, index);
+
+		addr = kmap(page);
+		memset(addr, 0, PAGE_CACHE_SIZE);
+		kunmap(page);
+		ClearPageChecked(page);
+		set_page_extent_mapped(page);
+		SetPageUptodate(page);
+		set_page_dirty(page);
+		unlock_page(page);
+		page_cache_release(page);
+		page_cache_release(page);
+		bytes += PAGE_CACHE_SIZE;
+		index++;
+	}
+
+	btrfs_set_extent_delalloc(inode, 0, bytes - 1, &cached_state);
+
+	/* Write the checksums and trans id to the first page */
+	{
+		void *addr;
+		u64 *gen;
+
+		page = find_get_page(inode->i_mapping, 0);
+
+		addr = kmap(page);
+		memcpy(addr, checksums, sizeof(u32) * num_checksums);
+		gen = addr + (sizeof(u32) * num_checksums);
+		*gen = trans->transid;
+		kunmap(page);
+		ClearPageChecked(page);
+		set_page_extent_mapped(page);
+		SetPageUptodate(page);
+		set_page_dirty(page);
+		unlock_page(page);
+		page_cache_release(page);
+		page_cache_release(page);
+	}
+	BTRFS_I(inode)->generation = trans->transid;
+
+	unlock_extent_cached(&BTRFS_I(inode)->io_tree, 0,
+			     i_size_read(inode) - 1, &cached_state, GFP_NOFS);
+
+	filemap_write_and_wait(inode->i_mapping);
+
+	key.objectid = BTRFS_FREE_SPACE_OBJECTID;
+	key.offset = block_group->key.objectid;
+	key.type = 0;
+
+	ret = btrfs_search_slot(trans, root, &key, path, 1, 1);
+	if (ret < 0) {
+		ret = 0;
+		clear_extent_bit(&BTRFS_I(inode)->io_tree, 0, bytes - 1,
+				 EXTENT_DIRTY | EXTENT_DELALLOC |
+				 EXTENT_DO_ACCOUNTING, 0, 0, NULL, GFP_NOFS);
+		goto out_free;
+	}
+	leaf = path->nodes[0];
+	if (ret > 0) {
+		struct btrfs_key found_key;
+		BUG_ON(!path->slots[0]);
+		path->slots[0]--;
+		btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+		if (found_key.objectid != BTRFS_FREE_SPACE_OBJECTID ||
+		    found_key.offset != block_group->key.objectid) {
+			ret = 0;
+			clear_extent_bit(&BTRFS_I(inode)->io_tree, 0, bytes - 1,
+					 EXTENT_DIRTY | EXTENT_DELALLOC |
+					 EXTENT_DO_ACCOUNTING, 0, 0, NULL,
+					 GFP_NOFS);
+			btrfs_release_path(root, path);
+			goto out_free;
+		}
+	}
+	header = btrfs_item_ptr(leaf, path->slots[0],
+				struct btrfs_free_space_header);
+	btrfs_set_free_space_entries(leaf, header, entries);
+	btrfs_set_free_space_bitmaps(leaf, header, bitmaps);
+	btrfs_set_free_space_generation(leaf, header, trans->transid);
+	btrfs_mark_buffer_dirty(leaf);
+	btrfs_release_path(root, path);
+
+	ret = 1;
+
+out_free:
+	if (ret == 0) {
+		invalidate_inode_pages2_range(inode->i_mapping, 0, index);
+		spin_lock(&block_group->lock);
+		block_group->disk_cache_state = BTRFS_DC_ERROR;
+		spin_unlock(&block_group->lock);
+		BTRFS_I(inode)->generation = 0;
+	}
+	kfree(checksums);
+	btrfs_update_inode(trans, root, inode);
+	iput(inode);
+	return ret;
+}
+
 static inline unsigned long offset_to_bit(u64 bitmap_start, u64 sectorsize,
 					  u64 offset)
 {