mm/page_io.c
static struct bio *get_swap_bio(gfp_t gfp_flags,
struct page *page, bio_end_io_t end_io)
{
bio = bio_alloc(gfp_flags, 1);
if (bio) {
bio->bi_iter.bi_sector = map_swap_page(page, &bio->bi_bdev);
bio->bi_iter.bi_sector <<= PAGE_SHIFT - 9;
bio->bi_iter.bi_size = PAGE_SIZE;
bio->bi_end_io = end_io;
}
return bio;
}
bi_endio() calls bio->bi_end_io. One should assign a routine to bio->bi_end_io.
One can wake up the thread waiting for IO in bi_end_io. For example: direct IO
has assigned dio_bio_end_io routine to bio->bi_end_io
fs/direct-io.c
/*
* The BIO completion handler simply queues the BIO up for the process-context
* handler.
*
* During I/O bi_private points at the dio. After I/O, bi_private is used to
* implement a singly-linked list of completed BIOs, at dio->bio_list.
*/
static void dio_bio_end_io(struct bio *bio, int error)
{
struct dio *dio = bio->bi_private;
bio->bi_private = dio->bio_list;
dio->bio_list = bio;
if (--dio->refcount == 1 && dio->waiter)
wake_up_process(dio->waiter);
}
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