[PATCH 0/3] Cleanups around extent increment

[PATCH 0/3] Cleanups around extent increment

[Nikolay Borisov]

Hello, 

This series improves the functions involved around extent reference increment. 
The first patch just removes a redundant argument, the second one documents the 
parameters of __btrfs_inc_extent_ref. It can be considered v2 of the standalone
version which Jeff had some input to. The final patch fixes a comment in 
lookup_inline_extent_backref which transpired while Jeff was revieweing the 
documentation patch. 

Nikolay Borisov (3):
  btrfs: Remove fs_info argument from __btrfs_inc_extent_ref
  btrfs: Document __btrfs_inc_extent_ref
  btrfs: Fix comment in lookup_inline_extent_backref

 fs/btrfs/extent-tree.c | 51 ++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 41 insertions(+), 10 deletions(-)

-- 
2.7.4

[PATCH 1/3] btrfs: Remove fs_info argument from __btrfs_inc_extent_ref

[Nikolay Borisov]

This function already takes a transaction which holds a reference to
the fs_info struct. Use that reference and remove the extra arg. No
functional changes.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
---
 fs/btrfs/extent-tree.c | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 4850e538ab10..59645ced6fbc 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2208,12 +2208,12 @@ int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
 }
 
 static int __btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
-				  struct btrfs_fs_info *fs_info,
 				  struct btrfs_delayed_ref_node *node,
 				  u64 parent, u64 root_objectid,
 				  u64 owner, u64 offset, int refs_to_add,
 				  struct btrfs_delayed_extent_op *extent_op)
 {
+	struct btrfs_fs_info *fs_info = trans->fs_info;
 	struct btrfs_path *path;
 	struct extent_buffer *leaf;
 	struct btrfs_extent_item *item;
@@ -2297,10 +2297,9 @@ static int run_delayed_data_ref(struct btrfs_trans_handle *trans,
 						 ref->objectid, ref->offset,
 						 &ins, node->ref_mod);
 	} else if (node->action == BTRFS_ADD_DELAYED_REF) {
-		ret = __btrfs_inc_extent_ref(trans, fs_info, node, parent,
-					     ref_root, ref->objectid,
-					     ref->offset, node->ref_mod,
-					     extent_op);
+		ret = __btrfs_inc_extent_ref(trans, node, parent, ref_root,
+					     ref->objectid, ref->offset,
+					     node->ref_mod, extent_op);
 	} else if (node->action == BTRFS_DROP_DELAYED_REF) {
 		ret = __btrfs_free_extent(trans, fs_info, node, parent,
 					  ref_root, ref->objectid,
@@ -2450,10 +2449,8 @@ static int run_delayed_tree_ref(struct btrfs_trans_handle *trans,
 		BUG_ON(!extent_op || !extent_op->update_flags);
 		ret = alloc_reserved_tree_block(trans, node, extent_op);
 	} else if (node->action == BTRFS_ADD_DELAYED_REF) {
-		ret = __btrfs_inc_extent_ref(trans, fs_info, node,
-					     parent, ref_root,
-					     ref->level, 0, 1,
-					     extent_op);
+		ret = __btrfs_inc_extent_ref(trans, node, parent, ref_root,
+					     ref->level, 0, 1, extent_op);
 	} else if (node->action == BTRFS_DROP_DELAYED_REF) {
 		ret = __btrfs_free_extent(trans, fs_info, node,
 					  parent, ref_root,
-- 
2.7.4

[PATCH 2/3] btrfs: Document __btrfs_inc_extent_ref

[Nikolay Borisov]

Here is a doc-only patch which tires to deobfuscate the terra-incognita
that arguments for delayed refs are.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
---
 fs/btrfs/extent-tree.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 59645ced6fbc..39d0652bf3f3 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2207,6 +2207,40 @@ int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
 	return ret;
 }
 
+/*
+ * __btrfs_inc_extent_ref - insert backreference for a given extent
+ *
+ * @trans:	    Handle of transaction
+ *
+ * @node:	    The delayed ref node used to get the bytenr/length for
+ *		    extent whose references are incremented.
+ *
+ * @parent:	    If this is a shared extent (BTRFS_SHARED_DATA_REF_KEY/
+ *		    BTRFS_SHARED_BLOCK_REF_KEY) then it holds the logical
+ *		    bytenr of the parent block. Since new extents are always
+ *		    created with indirect references, this will only be the case
+ *		    when relocating a shared extent. In that case, root_objectid
+ *		    will be BTRFS_TREE_RELOC_OBJECTID. Otheriwse, parent must
+ *		    be 0
+ *
+ * @root_objectid:  The id of the root where this modification has originated,
+ *		    this can be either one of the well-known metadata trees or
+ *		    the subvolume id which references this extent.
+ *
+ * @owner:	    For data extents it is the inode number of the owning file.
+ *		    For metadata extents this parameter holds the level in the
+ *		    tree of the extent.
+ *
+ * @offset:	    For metadata extents the offset is ignored and is currently
+ *		    always passed as 0. For data extents it is the fileoffset
+ *		    this extent belongs to.
+ *
+ * @refs_to_add     Number of references to add
+ *
+ * @extent_op       Pointer to a structure, holding information necessary when
+ *                  updating a tree block's flags
+ *
+ */
 static int __btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
 				  struct btrfs_delayed_ref_node *node,
 				  u64 parent, u64 root_objectid,
-- 
2.7.4

[PATCH 3/3] btrfs: Fix comment in lookup_inline_extent_backref

[Nikolay Borisov]

The comment wrongfully states that the owner parameter is the level of
the parent block. In fact owner is the level of the current block and
by adding 1 to it we can eventually get to the parent/root.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
---
 fs/btrfs/extent-tree.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 39d0652bf3f3..a470a07d4f2a 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -1635,7 +1635,7 @@ int lookup_inline_extent_backref(struct btrfs_trans_handle *trans,
 		extra_size = -1;
 
 	/*
-	 * Owner is our parent level, so we can just add one to get the level
+	 * Owner is our level, so we can just add one to get the level
 	 * for the block we are interested in.
 	 */
 	if (skinny_metadata && owner < BTRFS_FIRST_FREE_OBJECTID) {
-- 
2.7.4

Re: [PATCH 1/3] btrfs: Remove fs_info argument from __btrfs_inc_extent_ref

[Qu Wenruo]

On 2018年06月18日 19:59, Nikolay Borisov wrote:
> This function already takes a transaction which holds a reference to
> the fs_info struct. Use that reference and remove the extra arg. No
> functional changes.
> 
> Signed-off-by: Nikolay Borisov <nborisov@suse.com>

Reviewed-by: Qu Wenruo <wqu@suse.com>

Thanks,
Qu

> ---
>  fs/btrfs/extent-tree.c | 15 ++++++---------
>  1 file changed, 6 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index 4850e538ab10..59645ced6fbc 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -2208,12 +2208,12 @@ int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
>  }
>  
>  static int __btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
> -				  struct btrfs_fs_info *fs_info,
>  				  struct btrfs_delayed_ref_node *node,
>  				  u64 parent, u64 root_objectid,
>  				  u64 owner, u64 offset, int refs_to_add,
>  				  struct btrfs_delayed_extent_op *extent_op)
>  {
> +	struct btrfs_fs_info *fs_info = trans->fs_info;
>  	struct btrfs_path *path;
>  	struct extent_buffer *leaf;
>  	struct btrfs_extent_item *item;
> @@ -2297,10 +2297,9 @@ static int run_delayed_data_ref(struct btrfs_trans_handle *trans,
>  						 ref->objectid, ref->offset,
>  						 &ins, node->ref_mod);
>  	} else if (node->action == BTRFS_ADD_DELAYED_REF) {
> -		ret = __btrfs_inc_extent_ref(trans, fs_info, node, parent,
> -					     ref_root, ref->objectid,
> -					     ref->offset, node->ref_mod,
> -					     extent_op);
> +		ret = __btrfs_inc_extent_ref(trans, node, parent, ref_root,
> +					     ref->objectid, ref->offset,
> +					     node->ref_mod, extent_op);
>  	} else if (node->action == BTRFS_DROP_DELAYED_REF) {
>  		ret = __btrfs_free_extent(trans, fs_info, node, parent,
>  					  ref_root, ref->objectid,
> @@ -2450,10 +2449,8 @@ static int run_delayed_tree_ref(struct btrfs_trans_handle *trans,
>  		BUG_ON(!extent_op || !extent_op->update_flags);
>  		ret = alloc_reserved_tree_block(trans, node, extent_op);
>  	} else if (node->action == BTRFS_ADD_DELAYED_REF) {
> -		ret = __btrfs_inc_extent_ref(trans, fs_info, node,
> -					     parent, ref_root,
> -					     ref->level, 0, 1,
> -					     extent_op);
> +		ret = __btrfs_inc_extent_ref(trans, node, parent, ref_root,
> +					     ref->level, 0, 1, extent_op);
>  	} else if (node->action == BTRFS_DROP_DELAYED_REF) {
>  		ret = __btrfs_free_extent(trans, fs_info, node,
>  					  parent, ref_root,
> 

Re: [PATCH 2/3] btrfs: Document __btrfs_inc_extent_ref

[Qu Wenruo]

On 2018年06月18日 19:59, Nikolay Borisov wrote:
> Here is a doc-only patch which tires to deobfuscate the terra-incognita
> that arguments for delayed refs are.
> 
> Signed-off-by: Nikolay Borisov <nborisov@suse.com>

Reviewed-by: Qu Wenruo <wqu@suse.com>

> ---
>  fs/btrfs/extent-tree.c | 34 ++++++++++++++++++++++++++++++++++
>  1 file changed, 34 insertions(+)
> 
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index 59645ced6fbc..39d0652bf3f3 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -2207,6 +2207,40 @@ int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
>  	return ret;
>  }
>  
> +/*
> + * __btrfs_inc_extent_ref - insert backreference for a given extent
> + *
> + * @trans:	    Handle of transaction
> + *
> + * @node:	    The delayed ref node used to get the bytenr/length for
> + *		    extent whose references are incremented.
> + *
> + * @parent:	    If this is a shared extent (BTRFS_SHARED_DATA_REF_KEY/
> + *		    BTRFS_SHARED_BLOCK_REF_KEY) then it holds the logical
> + *		    bytenr of the parent block. Since new extents are always
> + *		    created with indirect references, this will only be the case
> + *		    when relocating a shared extent. In that case, root_objectid
> + *		    will be BTRFS_TREE_RELOC_OBJECTID. Otheriwse, parent must
> + *		    be 0
> + *
> + * @root_objectid:  The id of the root where this modification has originated,
> + *		    this can be either one of the well-known metadata trees or
> + *		    the subvolume id which references this extent.
> + *
> + * @owner:	    For data extents it is the inode number of the owning file.
> + *		    For metadata extents this parameter holds the level in the
> + *		    tree of the extent.

@owner the naming itself is a little confusing, but it's the necessary evil.
Or we will have too many parameters.

Thanks,
Qu

> + *
> + * @offset:	    For metadata extents the offset is ignored and is currently
> + *		    always passed as 0. For data extents it is the fileoffset
> + *		    this extent belongs to.
> + *
> + * @refs_to_add     Number of references to add
> + *
> + * @extent_op       Pointer to a structure, holding information necessary when
> + *                  updating a tree block's flags
> + *
> + */
>  static int __btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
>  				  struct btrfs_delayed_ref_node *node,
>  				  u64 parent, u64 root_objectid,
> 

Re: [PATCH 1/3] btrfs: Remove fs_info argument from __btrfs_inc_extent_ref

[Nikolay Borisov]

On 18.06.2018 14:59, Nikolay Borisov wrote:
> This function already takes a transaction which holds a reference to
> the fs_info struct. Use that reference and remove the extra arg. No
> functional changes.
> 
> Signed-off-by: Nikolay Borisov <nborisov@suse.com>
> --- 

Please ignore this patch, since I'm going to re-send it as apart of a
larger series dealing specifically with fs_info cleanup. The other 2 are
good.

<snip>

Re: [PATCH 0/3] Cleanups around extent increment

[David Sterba]

On Mon, Jun 18, 2018 at 02:59:23PM +0300, Nikolay Borisov wrote:
> This series improves the functions involved around extent reference increment. 
> The first patch just removes a redundant argument, the second one documents the 
> parameters of __btrfs_inc_extent_ref. It can be considered v2 of the standalone
> version which Jeff had some input to. The final patch fixes a comment in 
> lookup_inline_extent_backref which transpired while Jeff was revieweing the 
> documentation patch. 
> 
> Nikolay Borisov (3):
>   btrfs: Remove fs_info argument from __btrfs_inc_extent_ref

>   btrfs: Document __btrfs_inc_extent_ref
>   btrfs: Fix comment in lookup_inline_extent_backref

2 and 3 added to misc-next, thanks.

Re: [PATCH 1/3] btrfs: Remove fs_info argument from __btrfs_inc_extent_ref

[Jeff Mahoney]

[-- Attachment #1.1: Type: text/plain, Size: 2855 bytes --]

On 6/18/18 7:59 AM, Nikolay Borisov wrote:
> This function already takes a transaction which holds a reference to
> the fs_info struct. Use that reference and remove the extra arg. No
> functional changes.

I like the idea here.  I wasn't sold at first, but I think if we can
standardize on taking only a trans handle when one is required and both
a trans and fs_info when it's optional, it'll make the code clearer.
This cleanup can percolate up the stack to cover pretty much all of
delayed refs.

Reviewed-by: Jeff Mahoney <jeffm@suse.com>

> Signed-off-by: Nikolay Borisov <nborisov@suse.com>
> ---
>  fs/btrfs/extent-tree.c | 15 ++++++---------
>  1 file changed, 6 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index 4850e538ab10..59645ced6fbc 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -2208,12 +2208,12 @@ int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
>  }
>  
>  static int __btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
> -				  struct btrfs_fs_info *fs_info,
>  				  struct btrfs_delayed_ref_node *node,
>  				  u64 parent, u64 root_objectid,
>  				  u64 owner, u64 offset, int refs_to_add,
>  				  struct btrfs_delayed_extent_op *extent_op)
>  {
> +	struct btrfs_fs_info *fs_info = trans->fs_info;
>  	struct btrfs_path *path;
>  	struct extent_buffer *leaf;
>  	struct btrfs_extent_item *item;
> @@ -2297,10 +2297,9 @@ static int run_delayed_data_ref(struct btrfs_trans_handle *trans,
>  						 ref->objectid, ref->offset,
>  						 &ins, node->ref_mod);
>  	} else if (node->action == BTRFS_ADD_DELAYED_REF) {
> -		ret = __btrfs_inc_extent_ref(trans, fs_info, node, parent,
> -					     ref_root, ref->objectid,
> -					     ref->offset, node->ref_mod,
> -					     extent_op);
> +		ret = __btrfs_inc_extent_ref(trans, node, parent, ref_root,
> +					     ref->objectid, ref->offset,
> +					     node->ref_mod, extent_op);
>  	} else if (node->action == BTRFS_DROP_DELAYED_REF) {
>  		ret = __btrfs_free_extent(trans, fs_info, node, parent,
>  					  ref_root, ref->objectid,
> @@ -2450,10 +2449,8 @@ static int run_delayed_tree_ref(struct btrfs_trans_handle *trans,
>  		BUG_ON(!extent_op || !extent_op->update_flags);
>  		ret = alloc_reserved_tree_block(trans, node, extent_op);
>  	} else if (node->action == BTRFS_ADD_DELAYED_REF) {
> -		ret = __btrfs_inc_extent_ref(trans, fs_info, node,
> -					     parent, ref_root,
> -					     ref->level, 0, 1,
> -					     extent_op);
> +		ret = __btrfs_inc_extent_ref(trans, node, parent, ref_root,
> +					     ref->level, 0, 1, extent_op);
>  	} else if (node->action == BTRFS_DROP_DELAYED_REF) {
>  		ret = __btrfs_free_extent(trans, fs_info, node,
>  					  parent, ref_root,
> 


-- 
Jeff Mahoney
SUSE Labs


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Re: [PATCH 1/3] btrfs: Remove fs_info argument from __btrfs_inc_extent_ref

[Nikolay Borisov]

On 19.06.2018 22:31, Jeff Mahoney wrote:
> I like the idea here.  I wasn't sold at first, but I think if we can
> standardize on taking only a trans handle when one is required and both
> a trans and fs_info when it's optional, it'll make the code clearer.
> This cleanup can percolate up the stack to cover pretty much all of
> delayed refs.

I have a 25-something patches which do exactly this. Still WIP, will
likely send it tomorrow.