io_uring: defer alloc_hint update to io_file_bitmap_set()

io_file_bitmap_get() returns a free bitmap slot, but if it isn't
used later, such as io_queue_rsrc_removal() returns error, in this
case, we should not update alloc_hint at all, which still should
be considered as a valid candidate for next io_file_bitmap_get()
calls.

To fix this issue, only update alloc_hint in io_file_bitmap_set().
Signed-off-by: Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com>
Link: https://lore.kernel.org/r/20220528015109.48039-1-xiaoguang.wang@linux.alibaba.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -5419,15 +5419,11 @@ static int io_file_bitmap_get(struct io_ring_ctx *ctx)
 	unsigned long nr = ctx->nr_user_files;
 	int ret;
 
-	if (table->alloc_hint >= nr)
-		table->alloc_hint = 0;
-
 	do {
 		ret = find_next_zero_bit(table->bitmap, nr, table->alloc_hint);
-		if (ret != nr) {
-			table->alloc_hint = ret + 1;
+		if (ret != nr)
 			return ret;
-		}
+
 		if (!table->alloc_hint)
 			break;
 
@@ -9682,8 +9678,7 @@ static inline void io_file_bitmap_set(struct io_file_table *table, int bit)
 {
 	WARN_ON_ONCE(test_bit(bit, table->bitmap));
 	__set_bit(bit, table->bitmap);
-	if (bit == table->alloc_hint)
-		table->alloc_hint++;
+	table->alloc_hint = bit + 1;
 }
 
 static inline void io_file_bitmap_clear(struct io_file_table *table, int bit)