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Btrfs: fix broken nocow after balance 

Balance will create reloc_root for each fs root, and it's going to
record last_snapshot to filter shared blocks.  The side effect of
setting last_snapshot is to break nocow attributes of files.

Since the extents are not shared by the relocation tree after the balance,
we can recover the old last_snapshot safely if no one snapshoted the
source tree. We fix the above problem by this way.

Reported-by: Kyle Gates <kylegates@hotmail.com>
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
This commit is contained in:
Miao Xie 2013-06-06 03:28:03 +00:00 committed by Josef Bacik
parent 8c2a1a3028
commit 5bc7247ac4
1 changed files with 44 additions and 0 deletions
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44
fs/btrfs/relocation.c
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@ -1305,6 +1305,7 @@ static struct btrfs_root *create_reloc_root(struct btrfs_trans_handle *trans,
struct extent_buffer *eb;
struct btrfs_root_item *root_item;
struct btrfs_key root_key;
u64 last_snap = 0;
int ret;
root_item = kmalloc(sizeof(*root_item), GFP_NOFS);
@ -1320,6 +1321,7 @@ static struct btrfs_root *create_reloc_root(struct btrfs_trans_handle *trans,
BTRFS_TREE_RELOC_OBJECTID);
BUG_ON(ret);
last_snap = btrfs_root_last_snapshot(&root->root_item);
btrfs_set_root_last_snapshot(&root->root_item,
trans->transid - 1);
} else {
@ -1345,6 +1347,12 @@ static struct btrfs_root *create_reloc_root(struct btrfs_trans_handle *trans,
memset(&root_item->drop_progress, 0,
sizeof(struct btrfs_disk_key));
root_item->drop_level = 0;
/*
* abuse rtransid, it is safe because it is impossible to
* receive data into a relocation tree.
*/
btrfs_set_root_rtransid(root_item, last_snap);
btrfs_set_root_otransid(root_item, trans->transid);
}
btrfs_tree_unlock(eb);
@ -2272,8 +2280,12 @@ void free_reloc_roots(struct list_head *list)
static noinline_for_stack
int merge_reloc_roots(struct reloc_control *rc)
{
struct btrfs_trans_handle *trans;
struct btrfs_root *root;
struct btrfs_root *reloc_root;
u64 last_snap;
u64 otransid;
u64 objectid;
LIST_HEAD(reloc_roots);
int found = 0;
int ret = 0;
@ -2307,12 +2319,44 @@ again:
} else {
list_del_init(&reloc_root->root_list);
}
/*
* we keep the old last snapshod transid in rtranid when we
* created the relocation tree.
*/
last_snap = btrfs_root_rtransid(&reloc_root->root_item);
otransid = btrfs_root_otransid(&reloc_root->root_item);
objectid = reloc_root->root_key.offset;
ret = btrfs_drop_snapshot(reloc_root, rc->block_rsv, 0, 1);
if (ret < 0) {
if (list_empty(&reloc_root->root_list))
list_add_tail(&reloc_root->root_list,
&reloc_roots);
goto out;
} else if (!ret) {
/*
* recover the last snapshot tranid to avoid
* the space balance break NOCOW.
*/
root = read_fs_root(rc->extent_root->fs_info,
objectid);
if (IS_ERR(root))
continue;
if (btrfs_root_refs(&root->root_item) == 0)
continue;
trans = btrfs_join_transaction(root);
BUG_ON(IS_ERR(trans));
/* Check if the fs/file tree was snapshoted or not. */
if (btrfs_root_last_snapshot(&root->root_item) ==
otransid - 1)
btrfs_set_root_last_snapshot(&root->root_item,
last_snap);
btrfs_end_transaction(trans, root);
}
}