On 2017年12月08日 21:05, Austin S. Hemmelgarn wrote:
> On 2017-12-08 07:59, Qu Wenruo wrote:
>>
>>
>> On 2017年12月08日 20:51, Austin S. Hemmelgarn wrote:
>>> On 2017-12-08 02:57, Anand Jain wrote:
>>>> -EXPERIMENTAL-
>>>> As of now when primary SB fails we won't self heal and would fail
>>>> mount,
>>>> this is an experimental patch which thinks why not go and read backup
>>>> copy.
>>> I like the concept, and actually think this should be default behavior
>>> on a filesystem that's already mounted (we fix other errors, why not
>>> SB's), but I don't think it should be default behavior at mount time for
>>> the reasons Qu has outlined (picking up old BTRFS SB's after
>>> reformatting is bad). However, I do think it's useful to be able to ask
>>> for this behavior on mount, so that you don't need to fight with the
>>> programs to get a filesystem to mount when the first SB is missing
>>> (perhaps add a 'usebackupsb' option to mirror 'usebackuproot'?).
>>
>> Yeah, I also like the idea of 'usebackupsuper'/'usebackupsuper=n' mount
>> option than do it automatically.
> I still think there should be an option to do automatic detection (it's
> not particularly hard, and it's not likely to do the wrong thing in most
> cases), but being able to explicitly specify a particular superblock for
> a mount is definitely a step in the right direction.
usebackupsuper <- Auto
usebackupsuper=n <- Manual
usebackupsuper=n,m <- Manual multi, in given order
(The last one seems a little overkilled though)
Thanks,
Qu
>>
>> Thanks,
>> Qu
>>
>>>>
>>>> Signed-off-by: Anand Jain <anand.jain@xxxxxxxxxx>
>>>> ---
>>>> fs/btrfs/disk-io.c | 8 +++++++-
>>>> fs/btrfs/volumes.c | 10 +++++++---
>>>> 2 files changed, 14 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
>>>> index 9b20c1f3563b..a791b8dfe8a8 100644
>>>> --- a/fs/btrfs/disk-io.c
>>>> +++ b/fs/btrfs/disk-io.c
>>>> @@ -3190,7 +3190,7 @@ struct buffer_head *btrfs_read_dev_super(struct
>>>> block_device *bdev)
>>>> * So, we need to add a special mount option to scan for
>>>> * later supers, using BTRFS_SUPER_MIRROR_MAX instead
>>>> */
>>>> - for (i = 0; i < 1; i++) {
>>>> + for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; i++) {
>>>> ret = btrfs_read_dev_one_super(bdev, i, &bh);
>>>> if (ret)
>>>> continue;
>>>> @@ -4015,11 +4015,17 @@ static int btrfs_check_super_valid(struct
>>>> btrfs_fs_info *fs_info)
>>>> ret = -EINVAL;
>>>> }
>>>> +#if 0
>>>> + /*
>>>> + * Need a way to check for any copy of SB, as its not a
>>>> + * strong check, just ignore this for now.
>>>> + */
>>>> if (btrfs_super_bytenr(sb) != BTRFS_SUPER_INFO_OFFSET) {
>>>> btrfs_err(fs_info, "super offset mismatch %llu != %u",
>>>> btrfs_super_bytenr(sb), BTRFS_SUPER_INFO_OFFSET);
>>>> ret = -EINVAL;
>>>> }
>>>> +#endif
>>>> /*
>>>> * Obvious sys_chunk_array corruptions, it must hold at least
>>>> one key
>>>> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
>>>> index 9fa2539a8493..f368db94d62b 100644
>>>> --- a/fs/btrfs/volumes.c
>>>> +++ b/fs/btrfs/volumes.c
>>>> @@ -1369,7 +1369,7 @@ int btrfs_scan_one_device(const char *path,
>>>> fmode_t flags, void *holder,
>>>> {
>>>> struct btrfs_super_block *disk_super;
>>>> struct block_device *bdev;
>>>> - struct page *page;
>>>> + struct buffer_head *sb_bh;
>>>> int ret = -EINVAL;
>>>> u64 devid;
>>>> u64 transid;
>>>> @@ -1392,8 +1392,12 @@ int btrfs_scan_one_device(const char *path,
>>>> fmode_t flags, void *holder,
>>>> goto error;
>>>> }
>>>> - if (btrfs_read_disk_super(bdev, bytenr, &page, &disk_super))
>>>> + sb_bh = btrfs_read_dev_super(bdev);
>>>> + if (IS_ERR(sb_bh)) {
>>>> + ret = PTR_ERR(sb_bh);
>>>> goto error_bdev_put;
>>>> + }
>>>> + disk_super = (struct btrfs_super_block *) sb_bh->b_data;
>>>> devid = btrfs_stack_device_id(&disk_super->dev_item);
>>>> transid = btrfs_super_generation(disk_super);
>>>> @@ -1413,7 +1417,7 @@ int btrfs_scan_one_device(const char *path,
>>>> fmode_t flags, void *holder,
>>>> if (!ret && fs_devices_ret)
>>>> (*fs_devices_ret)->total_devices = total_devices;
>>>> - btrfs_release_disk_super(page);
>>>> + brelse(sb_bh);
>>>> error_bdev_put:
>>>> blkdev_put(bdev, flags);
>>>>
> --
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