On 9.04.2018 14:58, David Sterba wrote:
> We really want to know to which filesystem the extent map events belong,
> but as it cannot be reached from the extent_map pointers, we need to
> pass it down the callchain.
I really dislike propagating arguments solely for tracepoints purposes,
but if we don't have any other choice then I guess we should go with it.
However...
>
> Signed-off-by: David Sterba <dsterba@xxxxxxxx>
> ---
> fs/btrfs/extent_map.c | 6 ++++--
> fs/btrfs/extent_map.h | 3 ++-
> fs/btrfs/inode.c | 2 +-
> fs/btrfs/tests/extent-map-tests.c | 8 ++++----
> include/trace/events/btrfs.h | 12 +++++++-----
> 5 files changed, 18 insertions(+), 13 deletions(-)
>
> diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
> index 53a0633c6ef7..581b42d23e0d 100644
> --- a/fs/btrfs/extent_map.c
> +++ b/fs/btrfs/extent_map.c
> @@ -517,6 +517,7 @@ static noinline int merge_extent_mapping(struct extent_map_tree *em_tree,
>
> /**
> * btrfs_add_extent_mapping - add extent mapping into em_tree
> + * @fs_info - used for tracepoint
> * @em_tree - the extent tree into which we want to insert the extent mapping
> * @em_in - extent we are inserting
> * @start - start of the logical range btrfs_get_extent() is requesting
> @@ -534,7 +535,8 @@ static noinline int merge_extent_mapping(struct extent_map_tree *em_tree,
> * Return 0 on success, otherwise -EEXIST.
> *
> */
> -int btrfs_add_extent_mapping(struct extent_map_tree *em_tree,
> +int btrfs_add_extent_mapping(struct btrfs_fs_info *fs_info,
> + struct extent_map_tree *em_tree,
> struct extent_map **em_in, u64 start, u64 len)
> {
> int ret;
> @@ -552,7 +554,7 @@ int btrfs_add_extent_mapping(struct extent_map_tree *em_tree,
>
> existing = search_extent_mapping(em_tree, start, len);
>
> - trace_btrfs_handle_em_exist(existing, em, start, len);
> + trace_btrfs_handle_em_exist(fs_info, existing, em, start, len);
>
> /*
> * existing will always be non-NULL, since there must be
> diff --git a/fs/btrfs/extent_map.h b/fs/btrfs/extent_map.h
> index f6f8ba114977..f55c8b4ef120 100644
> --- a/fs/btrfs/extent_map.h
> +++ b/fs/btrfs/extent_map.h
> @@ -91,6 +91,7 @@ int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len, u64 gen
> void clear_em_logging(struct extent_map_tree *tree, struct extent_map *em);
> struct extent_map *search_extent_mapping(struct extent_map_tree *tree,
> u64 start, u64 len);
> -int btrfs_add_extent_mapping(struct extent_map_tree *em_tree,
> +int btrfs_add_extent_mapping(struct btrfs_fs_info *fs_info,
> + struct extent_map_tree *em_tree,
> struct extent_map **em_in, u64 start, u64 len);
> #endif
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 1f091c2358a4..18c31006865f 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -7092,7 +7092,7 @@ struct extent_map *btrfs_get_extent(struct btrfs_inode *inode,
>
> err = 0;
> write_lock(&em_tree->lock);
> - err = btrfs_add_extent_mapping(em_tree, &em, start, len);
> + err = btrfs_add_extent_mapping(fs_info, em_tree, &em, start, len);
This function is called only here, and we know that em_tree passed
points to a struct, stored in btrfs_inode. So can't we use container_of
to get the btrfs_inode in this function, from where we can reference the
fs_info? I guess it could be a problem for tests.
Admittedly this feels somewhat hacky and I guess is not very
future-proof, but it's still a viable alternative.
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