On Tue, Apr 17, 2018 at 09:47:19AM +0800, Qu Wenruo wrote:
> @@ -2680,7 +2681,7 @@ int open_ctree(struct super_block *sb,
>
> memcpy(fs_info->fsid, fs_info->super_copy->fsid, BTRFS_FSID_SIZE);
>
> - ret = btrfs_check_super_valid(fs_info);
> + ret = btrfs_check_super_valid(fs_info, fs_info->super_copy);
> if (ret) {
> btrfs_err(fs_info, "superblock contains fatal errors");
> err = -EINVAL;
> @@ -3310,6 +3311,27 @@ static int write_dev_supers(struct btrfs_device
> *device,
This is in write_dev_supers, so the superblock is checked
number-of-devices times. The caller write_all_supers rewrites the device
item so it matches the device it's going to write to. But,
btrfs_check_super_valid does not validate the dev_item so all the
validation does not bring much benefit, as it repeatedly checks the same
data.
So, what if the validation is done only once in write_all_supers? Lock
the devices, validate, if it fails, report that and unlock devices and
go readonly.
There's a differnce to what you implemented: if the in-memory superblock
corruption happens between writing to the devices, there are some left
with the new superblock and some with the old.
Although this sounds quite improbable, I think that doing the check in
advance would save some trouble if that happens. The superblocks on all
devices will match.
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