Struct bio has a reference count that controls when it can be freed.
Most uses cases is allocating the bio, which then returns with a
single reference to it, doing IO, and then dropping that single
reference. We can remove this atomic_dec_and_test() in the completion
path, if nobody else is holding a reference to the bio.
If someone does call bio_get() on the bio, then we flag the bio as
now having valid count and that we must properly honor the reference
count when it's being put.
Tested-by: Robert Elliott <elliott@hp.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
memset(bio, 0, sizeof(*bio));
bio->bi_flags = 1 << BIO_UPTODATE;
atomic_set(&bio->__bi_remaining, 1);
- atomic_set(&bio->bi_cnt, 1);
+ atomic_set(&bio->__bi_cnt, 1);
}
EXPORT_SYMBOL(bio_init);
**/
void bio_put(struct bio *bio)
{
- BIO_BUG_ON(!atomic_read(&bio->bi_cnt));
-
- /*
- * last put frees it
- */
- if (atomic_dec_and_test(&bio->bi_cnt))
+ if (!bio_flagged(bio, BIO_REFFED))
bio_free(bio);
+ else {
+ BIO_BUG_ON(!atomic_read(&bio->__bi_cnt));
+
+ /*
+ * last put frees it
+ */
+ if (atomic_dec_and_test(&bio->__bi_cnt))
+ bio_free(bio);
+ }
}
EXPORT_SYMBOL(bio_put);
bio->bi_end_io = request_endio;
bio->bi_private = &s->cl;
- atomic_set(&bio->bi_cnt, 3);
+ bio_cnt_set(bio, 3);
}
static void search_free(struct closure *cl)
waitqueue_active(&fs_info->async_submit_wait))
wake_up(&fs_info->async_submit_wait);
- BUG_ON(atomic_read(&cur->bi_cnt) == 0);
+ BUG_ON(atomic_read(&cur->__bi_cnt) == 0);
/*
* if we're doing the sync list, record that our
{
xfs_ioend_t *ioend = bio->bi_private;
- ASSERT(atomic_read(&bio->bi_cnt) >= 1);
ioend->io_error = test_bit(BIO_UPTODATE, &bio->bi_flags) ? 0 : error;
/* Toss bio and pass work off to an xfsdatad thread */
* returns. and then bio would be freed memory when if (bio->bi_flags ...)
* runs
*/
-#define bio_get(bio) atomic_inc(&(bio)->bi_cnt)
+static inline void bio_get(struct bio *bio)
+{
+ bio->bi_flags |= (1 << BIO_REFFED);
+ smp_mb__before_atomic();
+ atomic_inc(&bio->__bi_cnt);
+}
+
+static inline void bio_cnt_set(struct bio *bio, unsigned int count)
+{
+ if (count != 1) {
+ bio->bi_flags |= (1 << BIO_REFFED);
+ smp_mb__before_atomic();
+ }
+ atomic_set(&bio->__bi_cnt, count);
+}
enum bip_flags {
BIP_BLOCK_INTEGRITY = 1 << 0, /* block layer owns integrity data */
unsigned short bi_max_vecs; /* max bvl_vecs we can hold */
- atomic_t bi_cnt; /* pin count */
+ atomic_t __bi_cnt; /* pin count */
struct bio_vec *bi_io_vec; /* the actual vec list */
#define BIO_QUIET 9 /* Make BIO Quiet */
#define BIO_SNAP_STABLE 10 /* bio data must be snapshotted during write */
#define BIO_CHAIN 11 /* chained bio, ->bi_remaining in effect */
+#define BIO_REFFED 12 /* bio has elevated ->bi_cnt */
/*
* Flags starting here get preserved by bio_reset() - this includes