Split the recursion prevention loop into its own little helpers.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
block/blk-core.c | 160 ++++++++++++++++++++++++++---------------------
1 file changed, 88 insertions(+), 72 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index 7f11560bfddbb..732d5b8d3cd25 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1008,6 +1008,85 @@ generic_make_request_checks(struct bio *bio)
return false;
}
+static blk_qc_t do_make_request(struct bio *bio,
+ struct bio_list bio_list_on_stack[2])
+{
+ struct request_queue *q = bio->bi_disk->queue;
+ struct bio_list lower, same;
+ blk_qc_t ret;
+
+ /*
+ * Create a fresh bio_list for all subordinate requests.
+ */
+ bio_list_on_stack[1] = bio_list_on_stack[0];
+ bio_list_init(&bio_list_on_stack[0]);
+
+ if (unlikely(bio_queue_enter(bio) != 0))
+ return BLK_QC_T_NONE;
+ if (q->make_request_fn)
+ ret = q->make_request_fn(q, bio);
+ else
+ ret = blk_mq_make_request(q, bio);
+ blk_queue_exit(q);
+
+ /*
+ * Sort new bios into those for a lower level and those for the same
+ * level.
+ */
+ bio_list_init(&lower);
+ bio_list_init(&same);
+ while ((bio = bio_list_pop(&bio_list_on_stack[0])) != NULL)
+ if (q == bio->bi_disk->queue)
+ bio_list_add(&same, bio);
+ else
+ bio_list_add(&lower, bio);
+
+ /*
+ * Now assemble so we handle the lowest level first.
+ */
+ bio_list_merge(&bio_list_on_stack[0], &lower);
+ bio_list_merge(&bio_list_on_stack[0], &same);
+ bio_list_merge(&bio_list_on_stack[0], &bio_list_on_stack[1]);
+ return ret;
+}
+
+static blk_qc_t __generic_make_request(struct bio *bio)
+{
+ /*
+ * bio_list_on_stack[0] contains bios submitted by the current
+ * make_request_fn.
+ * bio_list_on_stack[1] contains bios that were submitted before the
+ * current make_request_fn, but that haven't been processed yet.
+ */
+ struct bio_list bio_list_on_stack[2];
+ blk_qc_t ret = BLK_QC_T_NONE;
+
+ BUG_ON(bio->bi_next);
+
+ /*
+ * The following loop may be a bit non-obvious, and so deserves some
+ * explanation: Before entering the loop, bio->bi_next is NULL (as all
+ * callers ensure that) so we have a list with a single bio. We pretend
+ * that we have just taken it off a longer list, so we assign bio_list
+ * to a pointer to the bio_list_on_stack, thus initialising the bio_list
+ * of new bios to be added. ->make_request() may indeed add some more
+ * bios through a recursive call to generic_make_request. If it did, we
+ * find a non-NULL value in bio_list and re-enter the loop from the top.
+ * In this case we really did just take the bio of the top of the list
+ * (no pretending) and so remove it from bio_list, and call into
+ * ->make_request() again.
+ */
+ bio_list_init(&bio_list_on_stack[0]);
+
+ current->bio_list = bio_list_on_stack;
+ do {
+ ret = do_make_request(bio, bio_list_on_stack);
+ } while ((bio = bio_list_pop(&bio_list_on_stack[0])));
+ current->bio_list = NULL; /* deactivate */
+
+ return ret;
+}
+
/**
* generic_make_request - re-submit a bio to the block device layer for I/O
* @bio: The bio describing the location in memory and on the device.
@@ -1019,88 +1098,25 @@ generic_make_request_checks(struct bio *bio)
*/
blk_qc_t generic_make_request(struct bio *bio)
{
- /*
- * bio_list_on_stack[0] contains bios submitted by the current
- * make_request_fn.
- * bio_list_on_stack[1] contains bios that were submitted before
- * the current make_request_fn, but that haven't been processed
- * yet.
- */
- struct bio_list bio_list_on_stack[2];
- blk_qc_t ret = BLK_QC_T_NONE;
-
if (!generic_make_request_checks(bio))
- goto out;
+ return BLK_QC_T_NONE;
/*
* We only want one ->make_request_fn to be active at a time, else
* stack usage with stacked devices could be a problem. So use
- * current->bio_list to keep a list of requests submited by a
- * make_request_fn function. current->bio_list is also used as a
- * flag to say if generic_make_request is currently active in this
- * task or not. If it is NULL, then no make_request is active. If
- * it is non-NULL, then a make_request is active, and new requests
- * should be added at the tail
+ * current->bio_list to keep a list of requests submitted by a
+ * make_request_fn function. current->bio_list is also used as a flag
+ * to say if generic_make_request is currently active in this thread or
+ * not. If it is NULL, then no make_request is active. If it is
+ * non-NULL, then a make_request is active, and new requests should be
+ * added at the tail
*/
if (current->bio_list) {
bio_list_add(¤t->bio_list[0], bio);
- goto out;
+ return BLK_QC_T_NONE;
}
- /* following loop may be a bit non-obvious, and so deserves some
- * explanation.
- * Before entering the loop, bio->bi_next is NULL (as all callers
- * ensure that) so we have a list with a single bio.
- * We pretend that we have just taken it off a longer list, so
- * we assign bio_list to a pointer to the bio_list_on_stack,
- * thus initialising the bio_list of new bios to be
- * added. ->make_request() may indeed add some more bios
- * through a recursive call to generic_make_request. If it
- * did, we find a non-NULL value in bio_list and re-enter the loop
- * from the top. In this case we really did just take the bio
- * of the top of the list (no pretending) and so remove it from
- * bio_list, and call into ->make_request() again.
- */
- BUG_ON(bio->bi_next);
- bio_list_init(&bio_list_on_stack[0]);
- current->bio_list = bio_list_on_stack;
- do {
- struct request_queue *q = bio->bi_disk->queue;
-
- if (likely(bio_queue_enter(bio) == 0)) {
- struct bio_list lower, same;
-
- /* Create a fresh bio_list for all subordinate requests */
- bio_list_on_stack[1] = bio_list_on_stack[0];
- bio_list_init(&bio_list_on_stack[0]);
- if (q->make_request_fn)
- ret = q->make_request_fn(q, bio);
- else
- ret = blk_mq_make_request(q, bio);
-
- blk_queue_exit(q);
-
- /* sort new bios into those for a lower level
- * and those for the same level
- */
- bio_list_init(&lower);
- bio_list_init(&same);
- while ((bio = bio_list_pop(&bio_list_on_stack[0])) != NULL)
- if (q == bio->bi_disk->queue)
- bio_list_add(&same, bio);
- else
- bio_list_add(&lower, bio);
- /* now assemble so we handle the lowest level first */
- bio_list_merge(&bio_list_on_stack[0], &lower);
- bio_list_merge(&bio_list_on_stack[0], &same);
- bio_list_merge(&bio_list_on_stack[0], &bio_list_on_stack[1]);
- }
- bio = bio_list_pop(&bio_list_on_stack[0]);
- } while (bio);
- current->bio_list = NULL; /* deactivate */
-
-out:
- return ret;
+ return __generic_make_request(bio);
}
EXPORT_SYMBOL(generic_make_request);
--
2.26.1
