From 0f097f08c9b3c1fdb6cc9f2dd423abc17d13f1a2 Mon Sep 17 00:00:00 2001 From: Yishai Hadas Date: Wed, 11 Jan 2023 12:10:54 +0200 Subject: [PATCH] lib/scatterlist: Fix to calculate the last_pg properly The last_pg is wrong, it is actually the first page of the last scatterlist element. To get the last page of the last scatterlist element we have to add prv->length. So it is checking mergability against the wrong page, Further, a SG element is not guaranteed to end on a page boundary, so we have to check the sub page location also for merge eligibility. Fix the above by checking physical contiguity based on PFNs, compute the actual last page and then call pages_are_mergable(). Fixes: 1567b49d1a40 ("lib/scatterlist: add check when merging zone device pages") Link: https://lore.kernel.org/r/20230111101054.188136-1-yishaih@nvidia.com Reported-by: Jason Gunthorpe Signed-off-by: Yishai Hadas Reviewed-by: Chaitanya Kulkarni Signed-off-by: Jason Gunthorpe --- lib/scatterlist.c | 25 +++++++++++++++---------- 1 file changed, 15 insertions(+), 10 deletions(-) diff --git a/lib/scatterlist.c b/lib/scatterlist.c index f72aa50..8d7519a8 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -470,22 +470,27 @@ int sg_alloc_append_table_from_pages(struct sg_append_table *sgt_append, return -EOPNOTSUPP; if (sgt_append->prv) { + unsigned long next_pfn = (page_to_phys(sg_page(sgt_append->prv)) + + sgt_append->prv->offset + sgt_append->prv->length) / PAGE_SIZE; + if (WARN_ON(offset)) return -EINVAL; /* Merge contiguous pages into the last SG */ prv_len = sgt_append->prv->length; - last_pg = sg_page(sgt_append->prv); - while (n_pages && pages_are_mergeable(pages[0], last_pg)) { - if (sgt_append->prv->length + PAGE_SIZE > max_segment) - break; - sgt_append->prv->length += PAGE_SIZE; - last_pg = pages[0]; - pages++; - n_pages--; + if (page_to_pfn(pages[0]) == next_pfn) { + last_pg = pfn_to_page(next_pfn - 1); + while (n_pages && pages_are_mergeable(pages[0], last_pg)) { + if (sgt_append->prv->length + PAGE_SIZE > max_segment) + break; + sgt_append->prv->length += PAGE_SIZE; + last_pg = pages[0]; + pages++; + n_pages--; + } + if (!n_pages) + goto out; } - if (!n_pages) - goto out; } /* compute number of contiguous chunks */ -- 2.7.4