NVMe: Handle bios that contain non-virtually contiguous addresses

NVMe scatterlists must be virtually contiguous, like almost all I/Os.
However, when the filesystem lays out files with a hole, it can be that
adjacent LBAs map to non-adjacent virtual addresses.  Handle this by
submitting one NVMe command at a time for each virtually discontiguous
range.

Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>

1 files changed, 29 insertions, 9 deletions

diff --git a/drivers/block/nvme.c b/drivers/block/nvme.c
index d99b400ccd79..240922706a93 100644
--- a/drivers/block/nvme.c
+++ b/drivers/block/nvme.c
@@ -315,7 +315,14 @@ static void bio_completion(struct nvme_queue *nvmeq, void *ctx,
         dma_unmap_sg(nvmeq->q_dmadev, nbio->sg, nbio->nents,
                         bio_data_dir(bio) ? DMA_TO_DEVICE : DMA_FROM_DEVICE);
         free_nbio(nvmeq, nbio);
-        bio_endio(bio, status ? -EIO : 0);
+        if (status)
+                bio_endio(bio, -EIO);
+        if (bio->bi_vcnt > bio->bi_idx) {
+                bio_list_add(&nvmeq->sq_cong, bio);
+                wake_up_process(nvme_thread);
+        } else {
+                bio_endio(bio, 0);
+        }
 }
 
 /* length is in bytes */
@@ -393,29 +400,41 @@ static struct nvme_prps *nvme_setup_prps(struct nvme_dev *dev,
         return prps;
 }
 
+/* NVMe scatterlists require no holes in the virtual address */
+#define BIOVEC_NOT_VIRT_MERGEABLE(vec1, vec2)   ((vec2)->bv_offset || \
+                        (((vec1)->bv_offset + (vec1)->bv_len) % PAGE_SIZE))
+
 static int nvme_map_bio(struct device *dev, struct nvme_bio *nbio,
                 struct bio *bio, enum dma_data_direction dma_dir, int psegs)
 {
         struct bio_vec *bvec, *bvprv = NULL;
         struct scatterlist *sg = NULL;
-        int i, nsegs = 0;
+        int i, old_idx, length = 0, nsegs = 0;
 
         sg_init_table(nbio->sg, psegs);
+        old_idx = bio->bi_idx;
         bio_for_each_segment(bvec, bio, i) {
                 if (bvprv && BIOVEC_PHYS_MERGEABLE(bvprv, bvec)) {
                         sg->length += bvec->bv_len;
                 } else {
-                        /* Check bvprv && offset == 0 */
+                        if (bvprv && BIOVEC_NOT_VIRT_MERGEABLE(bvprv, bvec))
+                                break;
                         sg = sg ? sg + 1 : nbio->sg;
                         sg_set_page(sg, bvec->bv_page, bvec->bv_len,
                                                         bvec->bv_offset);
                         nsegs++;
                 }
+                length += bvec->bv_len;
                 bvprv = bvec;
         }
+        bio->bi_idx = i;
         nbio->nents = nsegs;
         sg_mark_end(sg);
-        return dma_map_sg(dev, nbio->sg, nbio->nents, dma_dir);
+        if (dma_map_sg(dev, nbio->sg, nbio->nents, dma_dir) == 0) {
+                bio->bi_idx = old_idx;
+                return -ENOMEM;
+        }
+        return length;
 }
 
 static int nvme_submit_flush(struct nvme_queue *nvmeq, struct nvme_ns *ns,
@@ -451,7 +470,7 @@ static int nvme_submit_bio_queue(struct nvme_queue *nvmeq, struct nvme_ns *ns,
         struct nvme_command *cmnd;
         struct nvme_bio *nbio;
         enum dma_data_direction dma_dir;
-        int cmdid, result = -ENOMEM;
+        int cmdid, length, result = -ENOMEM;
         u16 control;
         u32 dsmgmt;
         int psegs = bio_phys_segments(ns->queue, bio);
@@ -496,16 +515,17 @@ static int nvme_submit_bio_queue(struct nvme_queue *nvmeq, struct nvme_ns *ns,
                 dma_dir = DMA_FROM_DEVICE;
         }
 
-        result = -ENOMEM;
-        if (nvme_map_bio(nvmeq->q_dmadev, nbio, bio, dma_dir, psegs) == 0)
+        result = nvme_map_bio(nvmeq->q_dmadev, nbio, bio, dma_dir, psegs);
+        if (result < 0)
                 goto free_nbio;
+        length = result;
 
         cmnd->rw.command_id = cmdid;
         cmnd->rw.nsid = cpu_to_le32(ns->ns_id);
         nbio->prps = nvme_setup_prps(nvmeq->dev, &cmnd->common, nbio->sg,
-                                                                bio->bi_size);
+                                                                length);
         cmnd->rw.slba = cpu_to_le64(bio->bi_sector >> (ns->lba_shift - 9));
-        cmnd->rw.length = cpu_to_le16((bio->bi_size >> ns->lba_shift) - 1);
+        cmnd->rw.length = cpu_to_le16((length >> ns->lba_shift) - 1);
         cmnd->rw.control = cpu_to_le16(control);
         cmnd->rw.dsmgmt = cpu_to_le32(dsmgmt);