Btrfs: Add mount -o ssd, which includes optimizations for seek free storage

Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/ctree.h

@@ -351,6 +351,7 @@ struct btrfs_fs_info {
 	spinlock_t delalloc_lock;
 	spinlock_t new_trans_lock;
 	u64 delalloc_bytes;
+	u64 last_alloc;
 };
 /*
  * in ram representation of the tree.  extent_root is used for all allocations
@@ -444,6 +445,7 @@ struct btrfs_root {
 #define BTRFS_MOUNT_NODATASUM		(1 << 0)
 #define BTRFS_MOUNT_NODATACOW		(1 << 1)
 #define BTRFS_MOUNT_NOBARRIER		(1 << 2)
+#define BTRFS_MOUNT_SSD			(1 << 3)
 
 #define btrfs_clear_opt(o, opt)		((o) &= ~BTRFS_MOUNT_##opt)
 #define btrfs_set_opt(o, opt)		((o) |= BTRFS_MOUNT_##opt)

fs/btrfs/disk-io.c

@@ -193,6 +193,7 @@ int csum_dirty_buffer(struct btrfs_root *root, struct page *page)
 	}
 	eb = alloc_extent_buffer(tree, start, len, page, GFP_NOFS);
 	read_extent_buffer_pages(tree, eb, start + PAGE_CACHE_SIZE, 1);
+	btrfs_clear_buffer_defrag(eb);
 	found_start = btrfs_header_bytenr(eb);
 	if (found_start != start) {
 		printk("warning: eb start incorrect %Lu buffer %Lu len %lu\n",
@@ -676,6 +677,8 @@ struct btrfs_root *open_ctree(struct super_block *sb)
 	fs_info->do_barriers = 1;
 	fs_info->closing = 0;
 	fs_info->total_pinned = 0;
+	fs_info->last_alloc = 0;
+
 #if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,18)
 	INIT_WORK(&fs_info->trans_work, btrfs_transaction_cleaner, fs_info);
 #else

fs/btrfs/extent-tree.c

@@ -1431,6 +1431,19 @@ static int noinline find_free_extent(struct btrfs_trans_handle *trans,
 		data = BTRFS_BLOCK_GROUP_MIXED;
 	}
 
+	/* for SSD, cluster allocations together as much as possible */
+	if (btrfs_test_opt(root, SSD)) {
+		if (!data) {
+			if (root->fs_info->last_alloc)
+				hint_byte = root->fs_info->last_alloc;
+			else {
+				hint_byte = hint_byte &
+					~((u64)BTRFS_BLOCK_GROUP_SIZE - 1);
+				empty_size += 16 * 1024 * 1024;
+			}
+		}
+	}
+
 	search_end = min(search_end,
 			 btrfs_super_total_bytes(&info->super_copy));
 	if (hint_byte) {
@@ -1456,6 +1469,19 @@ static int noinline find_free_extent(struct btrfs_trans_handle *trans,
 	}
 	search_start = find_search_start(root, &block_group, search_start,
 					 total_needed, data);
+
+	if (!data && btrfs_test_opt(root, SSD) && info->last_alloc &&
+	    search_start != info->last_alloc) {
+		info->last_alloc = 0;
+		if (!empty_size) {
+			empty_size += 16 * 1024 * 1024;
+			total_needed += empty_size;
+		}
+		search_start = find_search_start(root, &block_group,
+						 search_start, total_needed,
+						 data);
+	}
+
 	search_start = stripe_align(root, search_start);
 	cached_start = search_start;
 	btrfs_init_path(path);
@@ -1610,6 +1636,8 @@ static int noinline find_free_extent(struct btrfs_trans_handle *trans,
 error:
 	btrfs_release_path(root, path);
 	btrfs_free_path(path);
+	if (btrfs_test_opt(root, SSD) && !ret && !data)
+		info->last_alloc = ins->objectid + ins->offset;
 	return ret;
 }
 /*
@@ -1778,7 +1806,8 @@ struct extent_buffer *__btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
 			buf->start, buf->start + buf->len - 1,
 			EXTENT_CSUM, GFP_NOFS);
 	buf->flags |= EXTENT_CSUM;
-	btrfs_set_buffer_defrag(buf);
+	if (!btrfs_test_opt(root, SSD))
+		btrfs_set_buffer_defrag(buf);
 	trans->blocks_used++;
 	return buf;
 }

fs/btrfs/super.c

@@ -64,7 +64,7 @@ static void btrfs_put_super (struct super_block * sb)
 
 enum {
 	Opt_subvol, Opt_nodatasum, Opt_nodatacow, Opt_max_extent,
-	Opt_alloc_start, Opt_nobarrier, Opt_err,
+	Opt_alloc_start, Opt_nobarrier, Opt_ssd, Opt_err,
 };
 
 static match_table_t tokens = {
@@ -74,6 +74,7 @@ static match_table_t tokens = {
 	{Opt_nobarrier, "nobarrier"},
 	{Opt_max_extent, "max_extent=%s"},
 	{Opt_alloc_start, "alloc_start=%s"},
+	{Opt_ssd, "ssd"},
 	{Opt_err, NULL}
 };
 
@@ -149,6 +150,12 @@ static int parse_options (char * options,
 				btrfs_set_opt(info->mount_opt, NODATASUM);
 			}
 			break;
+		case Opt_ssd:
+			if (info) {
+				printk("btrfs: use ssd allocation scheme\n");
+				btrfs_set_opt(info->mount_opt, SSD);
+			}
+			break;
 		case Opt_nobarrier:
 			if (info) {
 				printk("btrfs: turning off barriers\n");

fs/btrfs/transaction.c

@@ -57,6 +57,7 @@ static int join_transaction(struct btrfs_root *root)
 		BUG_ON(!cur_trans);
 		root->fs_info->generation++;
 		root->fs_info->running_transaction = cur_trans;
+		root->fs_info->last_alloc = 0;
 		cur_trans->num_writers = 1;
 		cur_trans->num_joined = 0;
 		cur_trans->transid = root->fs_info->generation;

fs/btrfs/tree-defrag.c

@@ -179,6 +179,9 @@ int btrfs_defrag_leaves(struct btrfs_trans_handle *trans,
 	if (root->ref_cows == 0 && !is_extent)
 		goto out;
 
+	if (btrfs_test_opt(root, SSD))
+		goto out;
+
 	path = btrfs_alloc_path();
 	if (!path)
 		return -ENOMEM;