Btrfs: Add more synchronization before creating a snapshot
File data checksums are only done during writepage, so we have to make sure
all pages are written when the snapshot is taken. This also adds some
locking so that new writes don't race in and add new dirty pages.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 6b3e440..1ace6d1 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -686,6 +686,7 @@
if ((offset & (blocksize - 1)) == 0)
goto out;
+ down_read(&BTRFS_I(inode)->root->snap_sem);
ret = -ENOMEM;
page = grab_cache_page(mapping, index);
if (!page)
@@ -704,6 +705,7 @@
unlock_page(page);
page_cache_release(page);
+ up_read(&BTRFS_I(inode)->root->snap_sem);
out:
return ret;
}
@@ -1668,6 +1670,7 @@
int ret = -EINVAL;
u64 page_start;
+ down_read(&BTRFS_I(inode)->root->snap_sem);
lock_page(page);
wait_on_page_writeback(page);
size = i_size_read(inode);
@@ -1688,6 +1691,7 @@
ret = btrfs_cow_one_page(inode, page, end);
out_unlock:
+ up_read(&BTRFS_I(inode)->root->snap_sem);
unlock_page(page);
return ret;
}
@@ -1851,6 +1855,10 @@
if (!root->ref_cows)
return -EINVAL;
+ down_write(&root->snap_sem);
+ freeze_bdev(root->fs_info->sb->s_bdev);
+ thaw_bdev(root->fs_info->sb->s_bdev, root->fs_info->sb);
+
mutex_lock(&root->fs_info->fs_mutex);
trans = btrfs_start_transaction(root, 1);
BUG_ON(!trans);
@@ -1894,12 +1902,12 @@
ret = btrfs_inc_root_ref(trans, root);
if (ret)
goto fail;
-
fail:
err = btrfs_commit_transaction(trans, root);
if (err && !ret)
ret = err;
mutex_unlock(&root->fs_info->fs_mutex);
+ up_write(&root->snap_sem);
btrfs_btree_balance_dirty(root);
return ret;
}