@@ -42,6 +42,9 @@ static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
goto new_segment;
if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
goto new_segment;
+ if ((bvprv->bv_page != bv->bv_page) &&
+ (bvprv->bv_page + 1) != bv->bv_page)
+ goto new_segment;
seg_size += bv->bv_len;
bvprv = bv;
@@ -126,6 +129,9 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
goto new_segment;
if (!BIOVEC_SEG_BOUNDARY(q, *bvprv, bvec))
goto new_segment;
+ if ((bvprv->bv_page != bvec->bv_page) &&
+ ((bvprv->bv_page + 1) != bvec->bv_page))
+ goto new_segment;
(*sg)->length += nbytes;
} else {
blk_rq_map_sg() function merges the physically contiguous pages to use same scatter-gather node without checking if their page descriptors are contiguous or not. Now when dma_map_sg() is called on the scatter gather list, it would take the base page pointer from each node (one by one) and iterates through all of the pages in same sg node by keep incrementing the base page pointer with the assumption that physically contiguous pages will have their page descriptor address contiguous which may not be true if SPARSEMEM config is enabled. So here we may end referring to invalid page descriptor. Following table shows the example of physically contiguous pages but their page descriptor addresses non-contiguous. ------------------------------------------- | Page Descriptor | Physical Address | ------------------------------------------ | 0xc1e43fdc | 0xdffff000 | | 0xc2052000 | 0xe0000000 | ------------------------------------------- With this patch, relevant blk-merge functions will also check if the physically contiguous pages are having page descriptors address contiguous or not? If not then, these pages are separated to be in different scatter-gather nodes. Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org> --- block/blk-merge.c | 6 ++++++ 1 files changed, 6 insertions(+), 0 deletions(-)