[PATCH] maple_tree: reload mas before the second call for mas_empty_area

[Yang Erkun]

From: Yang Erkun <yangerkun at huawei.com>

Change the LONG_MAX in simple_offset_add to 1024, and do latter:

[root at fedora ~]# mkdir /tmp/dir
[root at fedora ~]# for i in {1..1024}; do touch /tmp/dir/$i; done
touch: cannot touch '/tmp/dir/1024': Device or resource busy
[root at fedora ~]# rm /tmp/dir/123
[root at fedora ~]# touch /tmp/dir/1024
[root at fedora ~]# rm /tmp/dir/100
[root at fedora ~]# touch /tmp/dir/1025
touch: cannot touch '/tmp/dir/1025': Device or resource busy

After we delete file 100, actually this is a empty entry, but the latter
create failed unexpected.

mas_alloc_cyclic has two chance to find empty entry. First find the
entry with range range_lo and range_hi, if no empty entry exist, and
range_lo > min, retry find with range min and range_hi. However, the
first call mas_empty_area may mark mas as EBUSY, and the second call for
mas_empty_area will return false directly. Fix this by reload mas before
second call for mas_empty_area.

Fixes: 9b6713cc7522 ("maple_tree: Add mtree_alloc_cyclic()")
Signed-off-by: Yang Erkun <yangerkun at huawei.com>
---
 lib/maple_tree.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index d0ae808f3a14..1fd02f4a05e6 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -4346,6 +4346,7 @@ int mas_alloc_cyclic(struct ma_state *mas, unsigned long *startp,
 {
 	unsigned long min = range_lo;
 	int ret = 0;
+	struct ma_state m = *mas;
 
 	range_lo = max(min, *next);
 	ret = mas_empty_area(mas, range_lo, range_hi, 1);
@@ -4354,6 +4355,7 @@ int mas_alloc_cyclic(struct ma_state *mas, unsigned long *startp,
 		ret = 1;
 	}
 	if (ret < 0 && range_lo > min) {
+		*mas = m;
 		ret = mas_empty_area(mas, min, range_hi, 1);
 		if (ret == 0)
 			ret = 1;
-- 
2.39.2