On 8/21/20 11:37 AM, Christoph Hellwig wrote:
On Wed, Aug 19, 2020 at 03:58:41PM +0530, Anju T Sudhakar wrote:
From: Ritesh Harjani <riteshh@xxxxxxxxxxxxx>
__bio_try_merge_page() may return same_page = 1 and merged = 0.
This could happen when bio->bi_iter.bi_size + len > UINT_MAX.
Handle this case in iomap_add_to_ioend() by incrementing write_count.
This scenario mostly happens where we have too much dirty data accumulated.
w/o the patch we hit below kernel warning,
I think this is better fixed in the block layer rather than working
around the problem in the callers. Something like this:
diff --git a/block/bio.c b/block/bio.c
index c63ba04bd62967..ef321cd1072e4e 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -879,8 +879,10 @@ bool __bio_try_merge_page(struct bio *bio, struct page *page,
struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt - 1];
if (page_is_mergeable(bv, page, len, off, same_page)) {
- if (bio->bi_iter.bi_size > UINT_MAX - len)
+ if (bio->bi_iter.bi_size > UINT_MAX - len) {
+ *same_page = false;
return false;
+ }
bv->bv_len += len;
bio->bi_iter.bi_size += len;
return true;
Ya, we had think of that. But what we then thought was, maybe the
API does return the right thing. Meaning, what API says is, same_page is
true, but the page couldn't be merged hence it returned ret = false.
With that thought, we fixed this in the caller.
But agree with you that with ret = false, there is no meaning of
same_page being true. Ok, so let linux-block comment on whether
above also looks good. If yes, I can spin out an official patch with
all details.
-ritesh
