On Tue, Oct 10, 2017 at 09:57:46AM +0300, Nikolay Borisov wrote:
>
>
> On 9.10.2017 21:01, Liu Bo wrote:
> > We've avoided data losing raid profile when doing balance, but it
> > turns out that deleting a device could also result in the same
> > problem.
> >
> > This fixes the problem by creating an empty data chunk before
> > relocating the data chunk.
> >
> > Metadata/System chunk are supposed to have non-zero bytes all the time
> > so their raid profile is persistent.
>
> This patch introduces new warning:
>
> fs/btrfs/volumes.c:3523:29: note: ‘trans’ was declared here
> struct btrfs_trans_handle *trans;
>
Not sure how I missed this, thanks for pointing it out.
>
> >
> > Reported-by: James Alandt <james.ala...@wdc.com>
> > Signed-off-by: Liu Bo <bo.li....@oracle.com>
> > ---
> > fs/btrfs/volumes.c | 87
> > ++++++++++++++++++++++++++++++++++++++++++------------
> > 1 file changed, 68 insertions(+), 19 deletions(-)
> >
> > diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> > index 4a72c45..3f48bcd 100644
> > --- a/fs/btrfs/volumes.c
> > +++ b/fs/btrfs/volumes.c
> > @@ -144,6 +144,8 @@ static int __btrfs_map_block(struct btrfs_fs_info
> > *fs_info,
> > u64 logical, u64 *length,
> > struct btrfs_bio **bbio_ret,
> > int mirror_num, int need_raid_map);
> > +static int btrfs_may_alloc_data_chunk(struct btrfs_fs_info *fs_info,
> > + u64 chunk_offset);
>
> Also there is no need to have this forward declaration, the function can
> just as well be put right before __btrfs_balance. Let's try and keep
> changes minimal.
>
OK.
> >
> > DEFINE_MUTEX(uuid_mutex);
> > static LIST_HEAD(fs_uuids);
> > @@ -3476,7 +3478,6 @@ static int __btrfs_balance(struct btrfs_fs_info
> > *fs_info)
> > u32 count_meta = 0;
> > u32 count_sys = 0;
> > int chunk_reserved = 0;
> > - u64 bytes_used = 0;
> >
> > /* step one make some room on all the devices */
> > devices = &fs_info->fs_devices->devices;
> > @@ -3635,28 +3636,22 @@ static int __btrfs_balance(struct btrfs_fs_info
> > *fs_info)
> > goto loop;
> > }
> >
> > - ASSERT(fs_info->data_sinfo);
> > - spin_lock(&fs_info->data_sinfo->lock);
> > - bytes_used = fs_info->data_sinfo->bytes_used;
> > - spin_unlock(&fs_info->data_sinfo->lock);
> > -
> > - if ((chunk_type & BTRFS_BLOCK_GROUP_DATA) &&
> > - !chunk_reserved && !bytes_used) {
> > - trans = btrfs_start_transaction(chunk_root, 0);
> > - if (IS_ERR(trans)) {
> > - mutex_unlock(&fs_info->delete_unused_bgs_mutex);
> > - ret = PTR_ERR(trans);
> > - goto error;
> > - }
> > -
> > - ret = btrfs_force_chunk_alloc(trans, fs_info,
> > - BTRFS_BLOCK_GROUP_DATA);
> > - btrfs_end_transaction(trans);
> > + if (!chunk_reserved) {
> > + /*
> > + * We may be relocating the only data chunk we have,
> > + * which could potentially end up with losing data's
> > + * raid profile, so lets allocate an empty one in
> > + * advance.
> > + */
> > + ret = btrfs_may_alloc_data_chunk(fs_info,
> > + found_key.offset);
> > if (ret < 0) {
> > mutex_unlock(&fs_info->delete_unused_bgs_mutex);
> > + ret = PTR_ERR(trans);
I'll remove this ret = PTR_ERR(trans);
-liubo
> > goto error;
> > + } else if (ret == 1) {
> > + chunk_reserved = 1;
> > }
> > - chunk_reserved = 1;
> > }
> >
> > ret = btrfs_relocate_chunk(fs_info, found_key.offset);
> > @@ -4327,6 +4322,48 @@ int btrfs_check_uuid_tree(struct btrfs_fs_info
> > *fs_info)
> > }
> >
> > /*
> > + * return 1 : allocate a data chunk successfully,
> > + * return <0: errors during allocating a data chunk,
> > + * return 0 : no need to allocate a data chunk.
> > + */
> > +static int btrfs_may_alloc_data_chunk(struct btrfs_fs_info *fs_info,
> > + u64 chunk_offset)
> > +{
> > + struct btrfs_block_group_cache *cache;
> > + u64 bytes_used;
> > + u64 chunk_type;
> > +
> > + cache = btrfs_lookup_block_group(fs_info, chunk_offset);
> > + ASSERT(cache);
> > + chunk_type = cache->flags;
> > + btrfs_put_block_group(cache);
> > +
> > + if (chunk_type & BTRFS_BLOCK_GROUP_DATA) {
> > + spin_lock(&fs_info->data_sinfo->lock);
> > + bytes_used = fs_info->data_sinfo->bytes_used;
> > + spin_unlock(&fs_info->data_sinfo->lock);
> > +
> > + if (!bytes_used) {
> > + struct btrfs_trans_handle *trans;
> > + int ret;
> > +
> > + trans = btrfs_join_transaction(fs_info->tree_root);
> > + if (IS_ERR(trans))
> > + return PTR_ERR(trans);
> > +
> > + ret = btrfs_force_chunk_alloc(trans, fs_info,
> > + BTRFS_BLOCK_GROUP_DATA);
> > + btrfs_end_transaction(trans);
> > + if (ret < 0)
> > + return ret;
> > +
> > + return 1;
> > + }
> > + }
> > + return 0;
> > +}
> > +
> > +/*
> > * shrinking a device means finding all of the device extents past
> > * the new size, and then following the back refs to the chunks.
> > * The chunk relocation code actually frees the device extent
> > @@ -4419,6 +4456,18 @@ int btrfs_shrink_device(struct btrfs_device *device,
> > u64 new_size)
> > chunk_offset = btrfs_dev_extent_chunk_offset(l, dev_extent);
> > btrfs_release_path(path);
> >
> > + /*
> > + * We may be relocating the only data chunk we have,
> > + * which could potentially end up with losing data's
> > + * raid profile, so lets allocate an empty one in
> > + * advance.
> > + */
> > + ret = btrfs_may_alloc_data_chunk(fs_info, chunk_offset);
> > + if (ret < 0) {
> > + mutex_unlock(&fs_info->delete_unused_bgs_mutex);
> > + goto done;
> > + }
> > +
> > ret = btrfs_relocate_chunk(fs_info, chunk_offset);
> > mutex_unlock(&fs_info->delete_unused_bgs_mutex);
> > if (ret && ret != -ENOSPC)
> >
> --
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