On Thu 15-12-16 15:07:12, Michal Hocko wrote:
> From: Michal Hocko <mhocko@xxxxxxxx>
>
> now that we have memalloc_nofs_{save,restore} api we can mark the whole
> transaction context as implicitly GFP_NOFS. All allocations will
> automatically inherit GFP_NOFS this way. This means that we do not have
> to mark any of those requests with GFP_NOFS and moreover all the
> ext4_kv[mz]alloc(GFP_NOFS) are also safe now because even the hardcoded
> GFP_KERNEL allocations deep inside the vmalloc will be NOFS now.
>
> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
Looks good to me. You can add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> fs/jbd2/transaction.c | 11 +++++++++++
> include/linux/jbd2.h | 2 ++
> 2 files changed, 13 insertions(+)
>
> diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
> index e1652665bd93..35a5d3d76182 100644
> --- a/fs/jbd2/transaction.c
> +++ b/fs/jbd2/transaction.c
> @@ -388,6 +388,11 @@ static int start_this_handle(journal_t *journal, handle_t *handle,
>
> rwsem_acquire_read(&journal->j_trans_commit_map, 0, 0, _THIS_IP_);
> jbd2_journal_free_transaction(new_transaction);
> + /*
> + * Make sure that no allocations done while the transaction is
> + * open is going to recurse back to the fs layer.
> + */
> + handle->saved_alloc_context = memalloc_nofs_save();
> return 0;
> }
>
> @@ -466,6 +471,7 @@ handle_t *jbd2__journal_start(journal_t *journal, int nblocks, int rsv_blocks,
> trace_jbd2_handle_start(journal->j_fs_dev->bd_dev,
> handle->h_transaction->t_tid, type,
> line_no, nblocks);
> +
> return handle;
> }
> EXPORT_SYMBOL(jbd2__journal_start);
> @@ -1760,6 +1766,11 @@ int jbd2_journal_stop(handle_t *handle)
> if (handle->h_rsv_handle)
> jbd2_journal_free_reserved(handle->h_rsv_handle);
> free_and_exit:
> + /*
> + * scope of th GFP_NOFS context is over here and so we can
> + * restore the original alloc context.
> + */
> + memalloc_nofs_restore(handle->saved_alloc_context);
> jbd2_free_handle(handle);
> return err;
> }
> diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
> index dfaa1f4dcb0c..606b6bce3a5b 100644
> --- a/include/linux/jbd2.h
> +++ b/include/linux/jbd2.h
> @@ -491,6 +491,8 @@ struct jbd2_journal_handle
>
> unsigned long h_start_jiffies;
> unsigned int h_requested_credits;
> +
> + unsigned int saved_alloc_context;
> };
>
>
> --
> 2.10.2
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
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