(2011/08/11 10:58), Jeff Mahoney wrote:
> On 08/10/2011 09:27 PM, Tsutomu Itoh wrote:
>> Hi, Jeff,
>>
>> (2011/08/11 8:20), Jeff Mahoney wrote:
>>> This patch handles btrfs_start_transaction failures that don't occur
>>> in a loop and are obvious to simply push up. In all cases except the
>>> mark_garbage_root case, the error is already handled by BUG_ON in the
>>> caller.
>>>
>>> Signed-off-by: Jeff Mahoney<jeffm@xxxxxxxx>
>>> ---
>>> fs/btrfs/extent-tree.c | 6 +++++-
>>> fs/btrfs/relocation.c | 6 ++++--
>>> fs/btrfs/tree-log.c | 5 ++++-
>>> fs/btrfs/volumes.c | 3 ++-
>>> 4 files changed, 15 insertions(+), 5 deletions(-)
>>>
>>> --- a/fs/btrfs/extent-tree.c
>>> +++ b/fs/btrfs/extent-tree.c
>>> @@ -6319,7 +6319,11 @@ int btrfs_drop_snapshot(struct btrfs_roo
>>> }
>>>
>>> trans = btrfs_start_transaction(tree_root, 0);
>>> - BUG_ON(IS_ERR(trans));
>>> + if (IS_ERR(trans)) {
>>> + kfree(wc);
>>> + btrfs_free_path(path);
>>> + return PTR_ERR(trans);
>>> + }
>>
>> The caller of btrfs_drop_snapshot() ignore the error. So, I don't think
>> that it is significant even if the error is returned to the caller.
>
> I'd actually consider that a separate issue since btrfs_drop_snapshot
> also returns -ENOMEM. The errors should be properly caught or BUG_ON'd
> in the caller. My patchset usually catches cases like this but since
> btrfs_drop_snapshot already returned an error, I mistakenly assumed it
> was handled by the caller.
>
>> I think that it should make the filesystem readonly when becoming an error
>> in btrfs_start_transaction().
>
> For -ENOMEM, I don't think that's the way to handle it. Some transaction
> start failures can be caught and handled (e.g. just creating a file)
> easily by returning errors to the user. Other cases, deep in the code,
> may be too complex to unwind and recover from and then a ROFS is the
> next-best answer. The callers should be responsible for determining the
> correct course of action.
OK.
Could you please append BUG_ON() in the caller or correctly handle the error
of btrfs_start_transaction()?
-Tsutomu
>
> -Jeff
>
>> Thanks,
>> Tsutomu
>>
>>>
>>> if (block_rsv)
>>> trans->block_rsv = block_rsv;
>>> --- a/fs/btrfs/relocation.c
>>> +++ b/fs/btrfs/relocation.c
>>> @@ -4096,7 +4096,8 @@ static noinline_for_stack int mark_garba
>>> int ret;
>>>
>>> trans = btrfs_start_transaction(root->fs_info->tree_root, 0);
>>> - BUG_ON(IS_ERR(trans));
>>> + if (IS_ERR(trans))
>>> + return PTR_ERR(trans);
>>>
>>> memset(&root->root_item.drop_progress, 0,
>>> sizeof(root->root_item.drop_progress));
>>> @@ -4176,7 +4177,8 @@ int btrfs_recover_relocation(struct btrf
>>> err = ret;
>>> goto out;
>>> }
>>> - mark_garbage_root(reloc_root);
>>> + ret = mark_garbage_root(reloc_root);
>>> + BUG_ON(ret);
>>> }
>>> }
>>>
>>> --- a/fs/btrfs/tree-log.c
>>> +++ b/fs/btrfs/tree-log.c
>>> @@ -3151,7 +3151,10 @@ int btrfs_recover_log_trees(struct btrfs
>>> fs_info->log_root_recovering = 1;
>>>
>>> trans = btrfs_start_transaction(fs_info->tree_root, 0);
>>> - BUG_ON(IS_ERR(trans));
>>> + if (IS_ERR(trans)) {
>>> + btrfs_free_path(path);
>>> + return PTR_ERR(trans);
>>> + }
>>>
>>> wc.trans = trans;
>>> wc.pin = 1;
>>> --- a/fs/btrfs/volumes.c
>>> +++ b/fs/btrfs/volumes.c
>>> @@ -1876,7 +1876,8 @@ static int btrfs_relocate_chunk(struct b
>>> return ret;
>>>
>>> trans = btrfs_start_transaction(root, 0);
>>> - BUG_ON(IS_ERR(trans));
>>> + if (IS_ERR(trans))
>>> + return PTR_ERR(trans);
>>>
>>> lock_chunks(root);
>>>
>>
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