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.
-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);
>>
>
--
Jeff Mahoney
SuSE Labs
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