[PATCH] f2fs: introduce f2fs_reserve_blocks to speedup fallocate

[Chao Yu <yuchao0@huawei.com>]

Preallocation operation in ->fallocate seems quite slow, since for all
new preallocated blocks, f2fs will update them one by one in direct nodes,

This patch introduces f2fs_reserve_blocks to make all preallocated blocks
belongs to one direct node updating in batch, so it can save a lot of
cpu cycle.

In virtual machine, with 32g loop device:

1. touch file
2. time fallocate -l 24G file

Before:
real	0m3.881s
user	0m0.000s
sys	0m3.881s

After:
real	0m0.054s
user	0m0.000s
sys	0m0.041s

Signed-off-by: Chao Yu <yuchao0@huawei.com>
---
 fs/f2fs/data.c              | 87 ++++++++++++++++++++++++++++++++++++++-------
 fs/f2fs/f2fs.h              |  1 +
 fs/f2fs/file.c              |  5 +--
 include/trace/events/f2fs.h | 12 ++++---
 4 files changed, 86 insertions(+), 19 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 96b0353..a2e7629 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -278,6 +278,16 @@ alloc_new:
 	trace_f2fs_submit_page_mbio(fio->page, fio);
 }
 
+void __set_data_blkaddr(struct dnode_of_data *dn)
+{
+	struct f2fs_node *rn = F2FS_NODE(dn->node_page);
+	__le32 *addr_array;
+
+	/* Get physical address of data block */
+	addr_array = blkaddr_in_node(rn);
+	addr_array[dn->ofs_in_node] = cpu_to_le32(dn->data_blkaddr);
+}
+
 /*
  * Lock ordering for the change of data block address:
  * ->data_page
@@ -286,19 +296,10 @@ alloc_new:
  */
 void set_data_blkaddr(struct dnode_of_data *dn)
 {
-	struct f2fs_node *rn;
-	__le32 *addr_array;
-	struct page *node_page = dn->node_page;
-	unsigned int ofs_in_node = dn->ofs_in_node;
-
-	f2fs_wait_on_page_writeback(node_page, NODE, true);
+	f2fs_wait_on_page_writeback(dn->node_page, NODE, true);
 
-	rn = F2FS_NODE(node_page);
-
-	/* Get physical address of data block */
-	addr_array = blkaddr_in_node(rn);
-	addr_array[ofs_in_node] = cpu_to_le32(dn->data_blkaddr);
-	if (set_page_dirty(node_page))
+	__set_data_blkaddr(dn);
+	if (set_page_dirty(dn->node_page))
 		dn->node_changed = true;
 }
 
@@ -318,7 +319,7 @@ int reserve_new_block(struct dnode_of_data *dn)
 	if (unlikely(!inc_valid_block_count(sbi, dn->inode, 1)))
 		return -ENOSPC;
 
-	trace_f2fs_reserve_new_block(dn->inode, dn->nid, dn->ofs_in_node);
+	trace_f2fs_reserve_new_block(dn->inode, dn->nid, dn->ofs_in_node, 1);
 
 	dn->data_blkaddr = NEW_ADDR;
 	set_data_blkaddr(dn);
@@ -343,6 +344,66 @@ int f2fs_reserve_block(struct dnode_of_data *dn, pgoff_t index)
 	return err;
 }
 
+int f2fs_reserve_blocks(struct dnode_of_data *dn, pgoff_t *start, pgoff_t end)
+{
+	struct f2fs_sb_info *sbi = F2FS_I_SB(dn->inode);
+	pgoff_t end_offset, index = *start;
+	unsigned int max_blocks, count = 0, i, ofs_in_node;
+	int err;
+
+	err = get_dnode_of_data(dn, index, ALLOC_NODE);
+	if (err)
+		return err;
+
+	if (unlikely(is_inode_flag_set(F2FS_I(dn->inode), FI_NO_ALLOC))) {
+		err = -EPERM;
+		goto out;
+	}
+
+	end_offset = ADDRS_PER_PAGE(dn->node_page, dn->inode);
+	max_blocks = min(end_offset - dn->ofs_in_node, end - index + 1);
+	ofs_in_node = dn->ofs_in_node;
+
+	for (i = 0; i < max_blocks; i++, ofs_in_node++) {
+		if (datablock_addr(dn->node_page, ofs_in_node) == NULL_ADDR)
+			count++;
+	}
+
+	if (!count)
+		goto out_update;
+
+	if (unlikely(!inc_valid_block_count(sbi, dn->inode, count))) {
+		err = -ENOSPC;
+		goto out;
+	}
+
+	trace_f2fs_reserve_new_block(dn->inode, dn->nid,
+						dn->ofs_in_node, count);
+
+	f2fs_wait_on_page_writeback(dn->node_page, NODE, true);
+
+	for (i = 0; i < max_blocks; i++, dn->ofs_in_node++) {
+		dn->data_blkaddr =
+			datablock_addr(dn->node_page, dn->ofs_in_node);
+
+		if (dn->data_blkaddr == NULL_ADDR) {
+			dn->data_blkaddr = NEW_ADDR;
+			__set_data_blkaddr(dn);
+		}
+	}
+
+	if (set_page_dirty(dn->node_page))
+		dn->node_changed = true;
+
+	mark_inode_dirty(dn->inode);
+	sync_inode_page(dn);
+out_update:
+	*start = index + max_blocks - 1;
+out:
+	f2fs_put_dnode(dn);
+	return err;
+}
+
 int f2fs_get_block(struct dnode_of_data *dn, pgoff_t index)
 {
 	struct extent_info ei;
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 75b0084..5654d0e 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1969,6 +1969,7 @@ int reserve_new_block(struct dnode_of_data *);
 int f2fs_get_block(struct dnode_of_data *, pgoff_t);
 ssize_t f2fs_preallocate_blocks(struct kiocb *, struct iov_iter *);
 int f2fs_reserve_block(struct dnode_of_data *, pgoff_t);
+int f2fs_reserve_blocks(struct dnode_of_data *, pgoff_t *, pgoff_t);
 struct page *get_read_data_page(struct inode *, pgoff_t, int, bool);
 struct page *find_data_page(struct inode *, pgoff_t);
 struct page *get_lock_data_page(struct inode *, pgoff_t, bool);
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 00af85f..071fe2b 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1226,7 +1226,8 @@ static int expand_inode_data(struct inode *inode, loff_t offset,
 			goto noalloc;
 
 		set_new_dnode(&dn, inode, NULL, NULL, 0);
-		ret = f2fs_reserve_block(&dn, index);
+		ret = f2fs_reserve_blocks(&dn, &index,
+					off_end ? pg_end : pg_end - 1);
 		if (ret)
 			break;
 noalloc:
@@ -1238,7 +1239,7 @@ noalloc:
 			new_size = ((loff_t)index << PAGE_SHIFT) +
 								off_end;
 		else
-			new_size += PAGE_SIZE;
+			new_size = (loff_t)index << PAGE_SHIFT;
 	}
 
 	if (!(mode & FALLOC_FL_KEEP_SIZE) &&
diff --git a/include/trace/events/f2fs.h b/include/trace/events/f2fs.h
index 0f56584..8b8dd9e 100644
--- a/include/trace/events/f2fs.h
+++ b/include/trace/events/f2fs.h
@@ -696,26 +696,30 @@ TRACE_EVENT(f2fs_direct_IO_exit,
 
 TRACE_EVENT(f2fs_reserve_new_block,
 
-	TP_PROTO(struct inode *inode, nid_t nid, unsigned int ofs_in_node),
+	TP_PROTO(struct inode *inode, nid_t nid, unsigned int ofs_in_node,
+						unsigned int count),
 
-	TP_ARGS(inode, nid, ofs_in_node),
+	TP_ARGS(inode, nid, ofs_in_node, count),
 
 	TP_STRUCT__entry(
 		__field(dev_t,	dev)
 		__field(nid_t, nid)
 		__field(unsigned int, ofs_in_node)
+		__field(unsigned int, count)
 	),
 
 	TP_fast_assign(
 		__entry->dev	= inode->i_sb->s_dev;
 		__entry->nid	= nid;
 		__entry->ofs_in_node = ofs_in_node;
+		__entry->count = count;
 	),
 
-	TP_printk("dev = (%d,%d), nid = %u, ofs_in_node = %u",
+	TP_printk("dev = (%d,%d), nid = %u, ofs_in_node = %u, count = %u",
 		show_dev(__entry),
 		(unsigned int)__entry->nid,
-		__entry->ofs_in_node)
+		__entry->ofs_in_node,
+		__entry->count)
 );
 
 DECLARE_EVENT_CLASS(f2fs__submit_page_bio,
-- 
2.8.2.311.gee88674