memfd_wait_for

函数名称：Setting SEAL_WRITE requires us to verify there's no pending writer. However,* via get_user_pages(), drivers might have some pending I/O without any active* user-space mappings (eg., direct-IO, AIO). Therefore, we look at all pages

函数原型：static int memfd_wait_for_pins(struct address_space *mapping)

返回类型：int

参数：

类型	参数	名称
struct address_space *	mapping

tagged等于0

如果非xas_marked( & xas, We need a tag: a new tag would expand every xa_node by 8 bytes,* so reuse a tag which we firmly believe is never set or cleared on tmpfs* or hugetlbfs because they are memory only filesystems.)则退出

如果非scan则lru_add_drain_all()

否则如果schedule_timeout_killable((HZ << scan) / 200)则scan等于about 150ms max

xas_set() - Set up XArray operation state for a different index

xas_lock_irq( & xas)

bool clear = true

如果xa_is_value() - Determine if an entry is a value.*@entry: XArray entry.* Context: Any context.* Return: True if the entry is a value, false if it is a pointer.则继续下一循环

page等于find_subpage(page, xa_index)

如果page_count(page)减page_mapcount(page)不等于1则

如果scan恒等于about 150ms max 则error等于负EBUSY

101

否则clear = false

104

如果clear则xas_clear_mark() - Clears the mark on this entry and its parents.*@xas: XArray operation state.*@mark: Mark number.* Clears the specified mark on this entry, and walks back to the head* attempting to clear it on all the ancestor entries. Does nothing if

106

如果tagged先自加取模XA_CHECK_SCHED则继续下一循环

109

xas_pause() - Pause a walk to drop a lock.*@xas: XArray operation state.* Some users need to pause a walk and drop the lock they're holding in* order to yield to a higher priority thread or carry out an operation* on an entry

110

xas_unlock_irq( & xas)

111

cond_resched()

112

xas_lock_irq( & xas)

函数逻辑报告