maple_tree: reload mas before the second call for mas_empty_area

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

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

[Liam.Howlett@Oracle.com: fix mas_alloc_cyclic() second search]
Link: https://lore.kernel.org/all/20241216060600.287B4C4CED0@smtp.kernel.org/
Link: https://lkml.kernel.org/r/20241216190113.1226145-2-Liam.Howlett@oracle.com
Link: https://lkml.kernel.org/r/20241214093005.72284-1-yangerkun@huaweicloud.com
Fixes: 9b6713cc7522 ("maple_tree: Add mtree_alloc_cyclic()")
Signed-off-by: Yang Erkun <yangerkun@huawei.com>
Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Chuck Lever <chuck.lever@oracle.com> says:
Cc: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index d0ae808f3a14964941320c93d869741abe84cecc..047397136f15bfe9421f066e30c05ac6b42b7f6a 100644 (file)
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -4354,6 +4354,7 @@ int mas_alloc_cyclic(struct ma_state *mas, unsigned long *startp,
                ret = 1;
        }
        if (ret < 0 && range_lo > min) {
+               mas_reset(mas);
                ret = mas_empty_area(mas, min, range_hi, 1);
                if (ret == 0)
                        ret = 1;