Revert Btrfs ro snapshot commit that causes filesystem corruption

1 files changed, 105 insertions, 0 deletions

diff --git a/Revert-Btrfs-race-free-update-of-commit-root-for-ro-.patch b/Revert-Btrfs-race-free-update-of-commit-root-for-ro-.patch
new file mode 100644
index 000000000..bc78069b5
--- /dev/null
+++ b/Revert-Btrfs-race-free-update-of-commit-root-for-ro-.patch
@@ -0,0 +1,105 @@
+From: Josh Boyer <jwboyer@fedoraproject.org>
+Date: Wed, 15 Oct 2014 10:09:50 -0400
+Subject: [PATCH] Revert "Btrfs: race free update of commit root for ro
+ snapshots"
+
+This reverts commit 9c3b306e1c9e6be4be09e99a8fe2227d1005effc.
+---
+ fs/btrfs/inode.c | 36 ------------------------------------
+ fs/btrfs/ioctl.c | 33 +++++++++++++++++++++++++++++++++
+ 2 files changed, 33 insertions(+), 36 deletions(-)
+
+diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
+index fc9c0439caa3..d23362f4464e 100644
+--- a/fs/btrfs/inode.c
++++ b/fs/btrfs/inode.c
+@@ -5261,42 +5261,6 @@ struct inode *btrfs_lookup_dentry(struct inode *dir, struct dentry *dentry)
+ 			iput(inode);
+ 			inode = ERR_PTR(ret);
+ 		}
+-		/*
+-		 * If orphan cleanup did remove any orphans, it means the tree
+-		 * was modified and therefore the commit root is not the same as
+-		 * the current root anymore. This is a problem, because send
+-		 * uses the commit root and therefore can see inode items that
+-		 * don't exist in the current root anymore, and for example make
+-		 * calls to btrfs_iget, which will do tree lookups based on the
+-		 * current root and not on the commit root. Those lookups will
+-		 * fail, returning a -ESTALE error, and making send fail with
+-		 * that error. So make sure a send does not see any orphans we
+-		 * have just removed, and that it will see the same inodes
+-		 * regardless of whether a transaction commit happened before
+-		 * it started (meaning that the commit root will be the same as
+-		 * the current root) or not.
+-		 */
+-		if (sub_root->node != sub_root->commit_root) {
+-			u64 sub_flags = btrfs_root_flags(&sub_root->root_item);
+-
+-			if (sub_flags & BTRFS_ROOT_SUBVOL_RDONLY) {
+-				struct extent_buffer *eb;
+-
+-				/*
+-				 * Assert we can't have races between dentry
+-				 * lookup called through the snapshot creation
+-				 * ioctl and the VFS.
+-				 */
+-				ASSERT(mutex_is_locked(&dir->i_mutex));
+-
+-				down_write(&root->fs_info->commit_root_sem);
+-				eb = sub_root->commit_root;
+-				sub_root->commit_root =
+-					btrfs_root_node(sub_root);
+-				up_write(&root->fs_info->commit_root_sem);
+-				free_extent_buffer(eb);
+-			}
+-		}
+ 	}
+ 
+ 	return inode;
+diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
+index 0fe1aa047f15..8d2b76e29d3b 100644
+--- a/fs/btrfs/ioctl.c
++++ b/fs/btrfs/ioctl.c
+@@ -713,6 +713,39 @@ static int create_snapshot(struct btrfs_root *root, struct inode *dir,
+ 	if (ret)
+ 		goto fail;
+ 
++	ret = btrfs_orphan_cleanup(pending_snapshot->snap);
++	if (ret)
++		goto fail;
++
++	/*
++	 * If orphan cleanup did remove any orphans, it means the tree was
++	 * modified and therefore the commit root is not the same as the
++	 * current root anymore. This is a problem, because send uses the
++	 * commit root and therefore can see inode items that don't exist
++	 * in the current root anymore, and for example make calls to
++	 * btrfs_iget, which will do tree lookups based on the current root
++	 * and not on the commit root. Those lookups will fail, returning a
++	 * -ESTALE error, and making send fail with that error. So make sure
++	 * a send does not see any orphans we have just removed, and that it
++	 * will see the same inodes regardless of whether a transaction
++	 * commit happened before it started (meaning that the commit root
++	 * will be the same as the current root) or not.
++	 */
++	if (readonly && pending_snapshot->snap->node !=
++	    pending_snapshot->snap->commit_root) {
++		trans = btrfs_join_transaction(pending_snapshot->snap);
++		if (IS_ERR(trans) && PTR_ERR(trans) != -ENOENT) {
++			ret = PTR_ERR(trans);
++			goto fail;
++		}
++		if (!IS_ERR(trans)) {
++			ret = btrfs_commit_transaction(trans,
++						       pending_snapshot->snap);
++			if (ret)
++				goto fail;
++		}
++	}
++
+ 	inode = btrfs_lookup_dentry(dentry->d_parent->d_inode, dentry);
+ 	if (IS_ERR(inode)) {
+ 		ret = PTR_ERR(inode);
+-- 
+1.9.3
+