On 8/19/21 4:55 PM, Christoph Hellwig wrote:
On Wed, Aug 18, 2021 at 03:37:38PM +0800, Guoqing Jiang wrote:
quoted
for (i = 0; i < disks; i++) {
struct md_rdev *rdev = rcu_dereference(conf->mirrors[i].rdev);
+
+ if (test_bit(WriteMostly, &mirror->rdev->flags))
+ write_behind = true;
How does this condition relate to the ones used for actually calling
alloc_behind_master_bio? It looks related, but as someone not familiar
with the code I can't really verify if this is correct, so a comment
explaining it might be useful.
How about this?
+ /*
+ * The write-behind io is only attempted on drives marked as
+ * write-mostly, which means we will allocate write behind
+ * bio later.
+ */
if (test_bit(WriteMostly, &mirror->rdev->flags))
write_behind = true;
quoted
+ /*
+ * When using a bitmap, we may call alloc_behind_master_bio below.
+ * alloc_behind_master_bio allocates a copy of the data payload a page
+ * at a time and thus needs a new bio that can fit the whole payload
+ * this bio in page sized chunks.
+ */
+ if (write_behind && bitmap)
+ max_sectors = min_t(int, max_sectors, BIO_MAX_VECS * PAGE_SECTORS);
Overly long line here.
I can change it given you still prefer the limitation is 80 characters.
Thanks,
Guoqing