[PATCH 5.18 051/102] lib/sbitmap: Fix invalid loop in __sbitmap_queue_get_batch()

Greg Kroah-Hartman
2022-07-05T12:35:24Z

From: wuchi <wuchi.zero@gmail.com>

commit fbb564a557809466c171b95f8d593a0972450ff2 upstream.

1. Getting next index before continue branch.
2. Checking free bits when setting the target bits. Otherwise,
it may reuse the busying bits.

Signed-off-by: wuchi <wuchi.zero@gmail.com>
Reviewed-by: Martin Wilck <mwilck@suse.com>
Link: https://lore.kernel.org/r/20220605145835.26916-1-wuchi.zero@gmail.com
Fixes: 9672b0d43782 ("sbitmap: add __sbitmap_queue_get_batch()")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
lib/sbitmap.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/lib/sbitmap.c b/lib/sbitmap.c
index ae4fd4de9ebe..29eb0484215a 100644
--- a/lib/sbitmap.c
+++ b/lib/sbitmap.c
@@ -528,7 +528,7 @@ unsigned long __sbitmap_queue_get_batch(struct sbitmap_queue *sbq, int nr_tags,

sbitmap_deferred_clear(map);
if (map->word == (1UL << (map_depth - 1)) - 1)
- continue;
+ goto next;

nr = find_first_zero_bit(&map->word, map_depth);
if (nr + nr_tags <= map_depth) {
@@ -539,6 +539,8 @@ unsigned long __sbitmap_queue_get_batch(struct sbitmap_queue *sbq, int nr_tags,
get_mask = ((1UL << map_tags) - 1) << nr;
do {
val = READ_ONCE(map->word);
+ if ((val & ~get_mask) != val)
+ goto next;
ret = atomic_long_cmpxchg(ptr, val, get_mask | val);
} while (ret != val);
get_mask = (get_mask & ~ret) >> nr;
@@ -549,6 +551,7 @@ unsigned long __sbitmap_queue_get_batch(struct sbitmap_queue *sbq, int nr_tags,
return get_mask;
}
}
+next:
/* Jump to next index. */
if (++index >= sb->map_nr)
index = 0;
--
2.37.0