On 4.09.19 г. 11:30 ч., Qu Wenruo wrote:
>
>
> On 2019/9/4 下午3:37, Nikolay Borisov wrote:
>>
>>
>> On 3.09.19 г. 11:24 ч., Qu Wenruo wrote:
>>> Before this patch, repair_imode_common() can only handle two types of
>>> inodes:
>>> - Free space cache inodes
>>> - ROOT DIR inodes
>>>
>>> For inodes in subvolume trees, the problem is how to determine the
>>> correct imode, thus it was not implemented.
>>>
>>> However there are more reports of incorrect imode in subvolume trees, we
>>> need to support such fix.
>>>
>>> So this patch adds a new function, detect_imode(), to detect (or call it
>>> educated guess) imode for inodes in subvolume trees.
>>>
>>> Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
>>> ---
>>> check/mode-common.c | 96 +++++++++++++++++++++++++++++++++++++++------
>>> 1 file changed, 83 insertions(+), 13 deletions(-)
>>>
>>> diff --git a/check/mode-common.c b/check/mode-common.c
>>> index 195b6efaa7aa..807d7daf98a6 100644
>>> --- a/check/mode-common.c
>>> +++ b/check/mode-common.c
>>> @@ -836,6 +836,80 @@ int reset_imode(struct btrfs_trans_handle *trans, struct btrfs_root *root,
>>> return ret;
>>> }
>>>
>>> +static int detect_imode(struct btrfs_root *root, struct btrfs_path *path,
>>> + u32 *imode_ret)
>>> +{
>>> + struct btrfs_key key;
>>> + struct btrfs_inode_item *iitem;
>>> + const u32 priv = 0700;
>>> + u64 ino;
>>> + u32 imode = S_IFREG;
>>> + int ret = 0;
>>> +
>>> + btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
>>> + ino = key.objectid;
>>> + iitem = btrfs_item_ptr(path->nodes[0], path->slots[0],
>>> + struct btrfs_inode_item);
>>> +
>>> + /*
>>> + * Both CHR and BLK uses rdev, no way to distinguish them, so fall back
>>> + * to BLK.
>>> + */
>>> + if (btrfs_inode_rdev(path->nodes[0], iitem) != 0) {
>>> + imode = S_IFBLK;
>>> + goto out;
>>> + }
>>> +
>>> + /* root inode */
>>> + if (ino == BTRFS_FIRST_FREE_OBJECTID) {
>>> + imode = S_IFDIR;
>>> + goto out;
>>> + }
>>> +
>>> + while (1) {
>>> + ret = btrfs_next_item(root, path);
>>> + if (ret > 0) {
>>> + /* No determining result found, falls back to REG */
>>> + ret = 0;
>>> + goto out;
>>> + }
>>> + if (ret < 0)
>>> + goto out;
>>> + btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
>>> + if (key.objectid != ino)
>>> + goto out;
>>> +
>>> + /*
>>> + * We ignore some types to make life easier:
>>> + * - INODE_REF
>>> + * We need to do a full tree search, which can fail for
>>> + * corrupted fs, but not worthy compared to other easier
>>> + * to determine types.
>>> + * - XATTR
>>> + * Both REG and DIR can have xattr, so not useful
>>> + */
>>> + switch (key.type) {
>>> + case BTRFS_DIR_ITEM_KEY:
>>> + case BTRFS_DIR_INDEX_KEY:
>>> + imode = S_IFDIR;
>>> + goto out;
>>> + case BTRFS_EXTENT_DATA_KEY:
>>> + /*
>>> + * Both REG and LINK could have EXTENT_DATA.
>>> + * We just fall back to REG as user can inspect the
>>> + * content.
>>> + */
>>> + imode = S_IFREG;
>>> + goto out;
>>> + }
>>> + }
>>> +
>>> +out:
>>> + /* Set default value even when something wrong happened */
>>> + *imode_ret = (imode | priv);
>>> + return ret;
>>> +}
>>> +
>>> /*
>>> * Reset the inode mode of the inode specified by @path.
>>> *
>>> @@ -852,22 +926,18 @@ int repair_imode_common(struct btrfs_root *root, struct btrfs_path *path)
>>> u32 imode;
>>> int ret;
>>>
>>> - if (root->root_key.objectid != BTRFS_ROOT_TREE_OBJECTID) {
>>> - error(
>>> - "repair inode mode outside of root tree is not supported yet");
>>> - return -ENOTTY;
>>> - }
>>> btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
>>> ASSERT(key.type == BTRFS_INODE_ITEM_KEY);
>>> - if (key.objectid != BTRFS_ROOT_TREE_DIR_OBJECTID &&
>>> - !is_fstree(key.objectid)) {
>>> - error("unsupported ino %llu", key.objectid);
>>> - return -ENOTTY;
>>> + if (root->objectid == BTRFS_ROOT_TREE_OBJECTID) {
>>> + /* In root tree we only have two possible imode */
>>> + if (key.objectid == BTRFS_ROOT_TREE_OBJECTID)
>>> + imode = S_IFDIR | 0755;
>>> + else
>>> + imode = S_IFREG | 0600;
>>> + } else {
>>> + detect_imode(root, path, &imode);
>>> + /* Ignore error returned, just use the default value returned */
>>
>> Is this safe enough though?
>
> It depends. But I'd say if we failed in detect_imode(), then it doesn't
> matter whatever the type we're putting here.
>
>> What if due to an error a directory is
>> corrected to be file?
>
> If a failure happens, it means btrfs-progs fails to read the next leaf.
> Then it really doesn't make much sense whatever the type is.
>
> But I get your point, indeed we should error out without trying out to
> fix the inode.
>
> I'll change this behavior in next version.
IMO the goal of btrfs-progs should be to make a broken filesystem better
and not replace one type of breakage with potentially another. In such
cases we ought to break out gracefully.
>
> Thanks,
> Qu
>
>> Let's not forget the context we are oprating here
>> - a broken fs so it's possible (if not likely) that any of the search
>> functions inside detect_imode could return negative error value. OTOH
>> I'd expect the transaction commit to fail if that's the case e.g. faulty
>> device.
>>
>>> }
>>> - if (key.objectid == BTRFS_ROOT_TREE_DIR_OBJECTID)
>>> - imode = 040755;
>>> - else
>>> - imode = 0100600;
>>>
>>> trans = btrfs_start_transaction(root, 1);
>>> if (IS_ERR(trans)) {
>>>
>
