Re: [PATCH v2 01/10] maple_tree: Rework mtree_alloc_{range,rrange}()
From: Peng Zhang
Date: Thu May 18 2023 - 02:10:43 EST
在 2023/5/18 02:17, Liam R. Howlett 写道:
* Peng Zhang <zhangpeng.00@xxxxxxxxxxxxx> [230517 04:58]:
Use mas_empty_area{_rev}() to refactor mtree_alloc_{range,rrange}()
Signed-off-by: Peng Zhang <zhangpeng.00@xxxxxxxxxxxxx>
---
lib/maple_tree.c | 63 ++++++++++++++++++++++++------------------------
1 file changed, 32 insertions(+), 31 deletions(-)
diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 4eb220008f72..e1820e90f167 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -6493,32 +6493,31 @@ int mtree_alloc_range(struct maple_tree *mt, unsigned long *startp,
{
int ret = 0;
- MA_STATE(mas, mt, min, min);
+ MA_STATE(mas, mt, 0, 0);
if (!mt_is_alloc(mt))
return -EINVAL;
if (WARN_ON_ONCE(mt_is_reserved(entry)))
return -EINVAL;
- if (min > max)
- return -EINVAL;
-
- if (max < size)
- return -EINVAL;
-
- if (!size)
- return -EINVAL;
-
mtree_lock(mt);
retry:
- mas.offset = 0;
- mas.index = min;
- mas.last = max - size + 1;
- ret = mas_alloc(&mas, entry, size, startp);
- if (mas_nomem(&mas, gfp))
- goto retry;
-
+ ret = mas_empty_area(&mas, min, max, size);
+ if (!ret) {
+ mas_insert(&mas, entry);
+ /*
+ * mas_nomem() may release the lock, causing the allocated area
+ * to be unavailable, so try to allocate a free area again.
+ */
+ if (mas_nomem(&mas, gfp))
+ goto retry;
+ }
mtree_unlock(mt);
+ if (!ret) {
Checking for a mas_is_err() should probably be outside if (!ret)
statement. If mas_insert() returns something besides ENOMEM, we will
not detect the error. I'm not sure if this is possible today since this
should never return an -EEXISTS, but having it this way doesn't add much
to the overhead.
I don't think there will be error that can't be detected here.
In fact, there are two sources of errors:
1. mas_empty_area(), the error number is in the variable ret,
and may also be in mas->node, but ret must contain all errors.
2. mas_insert(), the error number is in mas->node
When we check errors, we should first check errors from
mas_empty_area(). If there is no error in mas_empty_area(), we
will check errors from mas_insert().
So, mas_is_err() is inside the if (!ret) statement, no problem here.
Of course, even if mas_insert() returns -EEXISTS, it can be detected
under the current encoding, because "if (!ret)" is true in this case.
But I don't think this can happen, if it happens, it's a bug of maple
tree.
I don't think it's good to put mas_is_err() outside, because the error
number stored in mas->node may come from mas_empty_area(). We should use
the ret variable to detect the error from mas_empty_area() first.
+ if (mas_is_err(&mas))
+ return xa_err(mas.node);
+ *startp = mas.index;
+ }
return ret;
}
EXPORT_SYMBOL(mtree_alloc_range);
@@ -6529,29 +6528,31 @@ int mtree_alloc_rrange(struct maple_tree *mt, unsigned long *startp,
{
int ret = 0;
- MA_STATE(mas, mt, min, max - size + 1);
+ MA_STATE(mas, mt, 0, 0);
if (!mt_is_alloc(mt))
return -EINVAL;
if (WARN_ON_ONCE(mt_is_reserved(entry)))
return -EINVAL;
- if (min > max)
- return -EINVAL;
-
- if (max < size - 1)
- return -EINVAL;
-
- if (!size)
- return -EINVAL;
-
mtree_lock(mt);
retry:
- ret = mas_rev_alloc(&mas, min, max, entry, size, startp);
- if (mas_nomem(&mas, gfp))
- goto retry;
-
+ ret = mas_empty_area_rev(&mas, min, max, size);
+ if (!ret) {
+ mas_insert(&mas, entry);
+ /*
+ * mas_nomem() may release the lock, causing the allocated area
+ * to be unavailable, so try to allocate a free area again.
+ */
+ if (mas_nomem(&mas, gfp))
+ goto retry;
+ }
mtree_unlock(mt);
+ if (!ret) {
Same here.
+ if (mas_is_err(&mas))
+ return xa_err(mas.node);
+ *startp = mas.index;
+ }
return ret;
}
EXPORT_SYMBOL(mtree_alloc_rrange);
--
2.20.1