* [PATCH] rbtree: fix jffs2 build issue due to renamed __rb_parent_color field
@ 2012-07-18 11:31 ` Michel Lespinasse
0 siblings, 0 replies; 4+ messages in thread
From: Michel Lespinasse @ 2012-07-18 11:31 UTC (permalink / raw)
To: aarcange, dwmw2, riel, peterz, daniel.santos, axboe, ebiederm, akpm
Cc: linux-mm, linux-kernel, torvalds
When renaming rb_parent_color into __rb_parent_color to highlight the
fact that people aren't expected to directly manipulate this, I broke
the jffs2 build which was doing such direct manipulation in
fs/jffs2/readinode.c . Fix this and add a comment explaining why
this direct use is safe here.
Signed-off-by: Michel Lespinasse <walken@google.com>
---
fs/jffs2/readinode.c | 6 ++++--
1 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/fs/jffs2/readinode.c b/fs/jffs2/readinode.c
index dc0437e..b00fc50 100644
--- a/fs/jffs2/readinode.c
+++ b/fs/jffs2/readinode.c
@@ -395,7 +395,9 @@ static int jffs2_add_tn_to_tree(struct jffs2_sb_info *c,
/* Trivial function to remove the last node in the tree. Which by definition
has no right-hand -- so can be removed just by making its only child (if
- any) take its place under its parent. */
+ any) take its place under its parent. Note that we don't maintain the
+ usual rbtree invariants as there won't be further insert or erase
+ operations on the tree.*/
static void eat_last(struct rb_root *root, struct rb_node *node)
{
struct rb_node *parent = rb_parent(node);
@@ -414,7 +416,7 @@ static void eat_last(struct rb_root *root, struct rb_node *node)
*link = node->rb_left;
/* Colour doesn't matter now. Only the parent pointer. */
if (node->rb_left)
- node->rb_left->rb_parent_color = node->rb_parent_color;
+ node->rb_left->__rb_parent_color = node->__rb_parent_color;
}
/* We put this in reverse order, so we can just use eat_last */
--
1.7.7.3
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH] rbtree: fix jffs2 build issue due to renamed __rb_parent_color field
@ 2012-07-18 11:31 ` Michel Lespinasse
0 siblings, 0 replies; 4+ messages in thread
From: Michel Lespinasse @ 2012-07-18 11:31 UTC (permalink / raw)
To: aarcange, dwmw2, riel, peterz, daniel.santos, axboe, ebiederm, akpm
Cc: linux-mm, linux-kernel, torvalds
When renaming rb_parent_color into __rb_parent_color to highlight the
fact that people aren't expected to directly manipulate this, I broke
the jffs2 build which was doing such direct manipulation in
fs/jffs2/readinode.c . Fix this and add a comment explaining why
this direct use is safe here.
Signed-off-by: Michel Lespinasse <walken@google.com>
---
fs/jffs2/readinode.c | 6 ++++--
1 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/fs/jffs2/readinode.c b/fs/jffs2/readinode.c
index dc0437e..b00fc50 100644
--- a/fs/jffs2/readinode.c
+++ b/fs/jffs2/readinode.c
@@ -395,7 +395,9 @@ static int jffs2_add_tn_to_tree(struct jffs2_sb_info *c,
/* Trivial function to remove the last node in the tree. Which by definition
has no right-hand -- so can be removed just by making its only child (if
- any) take its place under its parent. */
+ any) take its place under its parent. Note that we don't maintain the
+ usual rbtree invariants as there won't be further insert or erase
+ operations on the tree.*/
static void eat_last(struct rb_root *root, struct rb_node *node)
{
struct rb_node *parent = rb_parent(node);
@@ -414,7 +416,7 @@ static void eat_last(struct rb_root *root, struct rb_node *node)
*link = node->rb_left;
/* Colour doesn't matter now. Only the parent pointer. */
if (node->rb_left)
- node->rb_left->rb_parent_color = node->rb_parent_color;
+ node->rb_left->__rb_parent_color = node->__rb_parent_color;
}
/* We put this in reverse order, so we can just use eat_last */
--
1.7.7.3
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^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] rbtree: fix jffs2 build issue due to renamed __rb_parent_color field
2012-07-18 11:31 ` Michel Lespinasse
(?)
@ 2012-07-18 11:40 ` David Woodhouse
2012-07-18 15:16 ` David Woodhouse
-1 siblings, 1 reply; 4+ messages in thread
From: David Woodhouse @ 2012-07-18 11:40 UTC (permalink / raw)
To: Michel Lespinasse
Cc: aarcange, riel, peterz, daniel.santos, axboe, ebiederm, akpm,
linux-mm, linux-kernel, torvalds
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On Wed, 2012-07-18 at 04:31 -0700, Michel Lespinasse wrote:
> Fix this and add a comment explaining why this direct use is safe
> here.
Note that there was already a comment which was *intended* to have that
effect, right before the assignment:
/* Colour doesn't matter now. Only the parent pointer. */
If you're going to make that comment redundant, you might as well remove
it. And you might as well say that the trees are being *destroyed*
(consumed) at this point, rather than just that there will be no further
insert or erase operations.
--
dwmw2
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^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH] rbtree: fix jffs2 build issue due to renamed __rb_parent_color field
2012-07-18 11:40 ` David Woodhouse
@ 2012-07-18 15:16 ` David Woodhouse
0 siblings, 0 replies; 4+ messages in thread
From: David Woodhouse @ 2012-07-18 15:16 UTC (permalink / raw)
To: Michel Lespinasse
Cc: aarcange, riel, peterz, daniel.santos, axboe, ebiederm, akpm,
linux-mm, linux-kernel, torvalds
[-- Attachment #1: Type: text/plain, Size: 2466 bytes --]
... and clean up the comments to better explain why it's acceptable to
do it this way instead of using rb_erase() "properly".
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
---
On Wed, 2012-07-18 at 12:40 +0100, David Woodhouse wrote:
> If you're going to make that comment redundant, you might as well remove
> it. And you might as well say that the trees are being *destroyed*
> (consumed) at this point, rather than just that there will be no further
> insert or erase operations.
The comment on ver_insert() confused me too while I was looking at this,
so I've improved that as well.
A quick and dirty benchmark shows about a 10% performance improvement
when mounting a RAM-backed JFFS2 file system on Westmere. Thanks.
Acked-By: David Woodhouse <David.Woodhouse@intel.com> for the rest of
the series.
diff --git a/fs/jffs2/readinode.c b/fs/jffs2/readinode.c
index 1ea349f..ae81b01 100644
--- a/fs/jffs2/readinode.c
+++ b/fs/jffs2/readinode.c
@@ -394,8 +394,11 @@ static int jffs2_add_tn_to_tree(struct jffs2_sb_info *c,
}
/* Trivial function to remove the last node in the tree. Which by definition
- has no right-hand -- so can be removed just by making its only child (if
- any) take its place under its parent. */
+ has no right-hand child — so can be removed just by making its left-hand
+ child (if any) take its place under its parent. Since this is only done
+ when we're consuming the whole tree, there's no need to use rb_erase()
+ and let it worry about adjusting colours and balancing the tree. That
+ would just be a waste of time. */
static void eat_last(struct rb_root *root, struct rb_node *node)
{
struct rb_node *parent = rb_parent(node);
@@ -412,12 +415,12 @@ static void eat_last(struct rb_root *root, struct rb_node *node)
link = &parent->rb_right;
*link = node->rb_left;
- /* Colour doesn't matter now. Only the parent pointer. */
if (node->rb_left)
- node->rb_left->rb_parent_color = node->rb_parent_color;
+ node->rb_left->__rb_parent_color = node->__rb_parent_color;
}
-/* We put this in reverse order, so we can just use eat_last */
+/* We put the version tree in reverse order, so we can use the same eat_last()
+ function that we use to consume the tmpnode tree (tn_root). */
static void ver_insert(struct rb_root *ver_root, struct jffs2_tmp_dnode_info *tn)
{
struct rb_node **link = &ver_root->rb_node;
--
dwmw2
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^ permalink raw reply related [flat|nested] 4+ messages in thread
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2012-07-18 11:31 [PATCH] rbtree: fix jffs2 build issue due to renamed __rb_parent_color field Michel Lespinasse
2012-07-18 11:31 ` Michel Lespinasse
2012-07-18 11:40 ` David Woodhouse
2012-07-18 15:16 ` David Woodhouse
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