From a68d5933a0e409592860229b35230c8e87155472 Mon Sep 17 00:00:00 2001
From: Chris Mason <chris.mason@oracle.com>
Date: Thu, 8 May 2008 14:11:56 -0400
Subject: [PATCH] Btrfs: Update nodatacow mode to support cloned single files
 and resizing

Before, nodatacow only checked to make sure multiple roots didn't have
references on a single extent.  This check makes sure that multiple
inodes don't have references.

nodatacow needed an extra check to see if the block group was currently
readonly.  This way cows forced by the chunk relocation code are honored.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
---
 fs/btrfs/ctree.h       |  2 +-
 fs/btrfs/extent-tree.c |  9 +++++++++
 fs/btrfs/inode.c       | 13 +++++++++----
 3 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index f4b4677bec77..6c2c2c4e4d2a 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1325,7 +1325,7 @@ static inline struct dentry *fdentry(struct file *file) {
 /* extent-tree.c */
 u32 btrfs_count_snapshots_in_path(struct btrfs_root *root,
 				  struct btrfs_path *count_path,
-				  u64 first_extent);
+				  u64 expected_owner, u64 first_extent);
 int btrfs_extent_post_op(struct btrfs_trans_handle *trans,
 			 struct btrfs_root *root);
 int btrfs_copy_pinned(struct btrfs_root *root, struct extent_io_tree *copy);
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 8e69b5acfeff..30a5094fffa7 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -721,12 +721,14 @@ static int lookup_extent_ref(struct btrfs_trans_handle *trans,
 
 u32 btrfs_count_snapshots_in_path(struct btrfs_root *root,
 				  struct btrfs_path *count_path,
+				  u64 expected_owner,
 				  u64 first_extent)
 {
 	struct btrfs_root *extent_root = root->fs_info->extent_root;
 	struct btrfs_path *path;
 	u64 bytenr;
 	u64 found_objectid;
+	u64 found_owner;
 	u64 root_objectid = root->root_key.objectid;
 	u32 total_count = 0;
 	u32 cur_count;
@@ -792,6 +794,13 @@ u32 btrfs_count_snapshots_in_path(struct btrfs_root *root,
 			total_count = 2;
 			goto out;
 		}
+		if (level == -1) {
+			found_owner = btrfs_ref_objectid(l, ref_item);
+			if (found_owner != expected_owner) {
+				total_count = 2;
+				goto out;
+			}
+		}
 		total_count = 1;
 		path->slots[0]++;
 	}
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index b437d3bdf95e..1bf37d15b174 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -172,6 +172,7 @@ static int run_delalloc_nocow(struct inode *inode, u64 start, u64 end)
 	u64 loops = 0;
 	u64 total_fs_bytes;
 	struct btrfs_root *root = BTRFS_I(inode)->root;
+	struct btrfs_block_group_cache *block_group;
 	struct extent_buffer *leaf;
 	int found_type;
 	struct btrfs_path *path;
@@ -230,16 +231,20 @@ static int run_delalloc_nocow(struct inode *inode, u64 start, u64 end)
 		if (bytenr == 0)
 			goto not_found;
 
+		if (btrfs_count_snapshots_in_path(root, path, inode->i_ino,
+						  bytenr) != 1) {
+			goto not_found;
+		}
+
 		/*
 		 * we may be called by the resizer, make sure we're inside
 		 * the limits of the FS
 		 */
-		if (bytenr + extent_num_bytes > total_fs_bytes)
+		block_group = btrfs_lookup_block_group(root->fs_info,
+						       bytenr);
+		if (!block_group || block_group->ro)
 			goto not_found;
 
-		if (btrfs_count_snapshots_in_path(root, path, bytenr) != 1) {
-			goto not_found;
-		}
 
 		start = extent_end;
 	} else {
-- 
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