1 files changed, 27 insertions, 4 deletions

diff --git a/drivers/gpu/nvgpu/os/linux/swap.h b/drivers/gpu/nvgpu/os/linux/swap.h
index 1e986095..3a648b26 100644
--- a/drivers/gpu/nvgpu/os/linux/swap.h
+++ b/drivers/gpu/nvgpu/os/linux/swap.h
@@ -1,8 +1,12 @@
 #include <linux/scatterlist.h>
 #include <linux/bio.h>
-//#include <nvgpu/bug.h>
+#include <linux/blkdev.h> // For SECTOR_SHIFT
+
+// Next sector to assign a mapped_buf to. Skip first disk block
+atomic64_t nvgpu_swap_next_sector = {4};
 
 // Callback for completion of the I/O chain
+// TODO: Error checking and handling
 static void complete_swap_io(struct bio *bio) {
   struct nvgpu_mapped_buf *m = bio->bi_private;
   bio_put(bio);
@@ -11,21 +15,38 @@ static void complete_swap_io(struct bio *bio) {
 
 // Queue a command to copy out an SGT to disk
 // TODO: Cache bdev
-// TODO: Don't hardcode sector 0
-// TODO: Figure out if submit_bio() can fail, and what to do then
+// TODO: Track, allocate, and recycle individual swap buffers on disk instead
+//       of only supporting a global reset
 int copy(struct sg_table *sgt, int op, struct nvgpu_mapped_buf *m) {
   unsigned int i;
   struct scatterlist *sg;
   struct bio *bio;
   int err = 0;
   int sg_cnt = sgt->nents;
-  sector_t sector = 0; // XXX: For testing
+  sector_t sector = m->os_priv.swap_sector;
   // Find and open the block device
   struct block_device *bdev = blkdev_get_by_path("/dev/nvme0n1", FMODE_READ | FMODE_WRITE, copy);
   if (unlikely(IS_ERR(bdev))) {
     printk(KERN_WARNING "Unabled to find `nvme0`, err %ld!\n", PTR_ERR(bdev));
     return -ENODEV;
   }
+  // Assign a sector on-disk (0 indicates unassigned, we start at 4)
+  if (sector == 0) {
+    // Read block device size in sectors, and fail if we'd use more than 1/3rd
+    // of the disk (to stay in SLC-emulation-mode).
+    // TODO: Issue NVMe DSM commands to try to manage this better? Read-only
+    //       regions should be able to be moved to TLC safely, whereas other
+    //       data should be kept in the SLC cache to reduce wear.
+    if (atomic64_read(&nvgpu_swap_next_sector) >= i_size_read(bdev->bd_inode)/3) {
+      err = -ENOMEM;
+      goto out_put;
+    }
+    // Hand out sectors sequentially, and statically
+    // TODO: Intelligent sector allocation
+    sector = atomic64_add_return(m->size >> SECTOR_SHIFT, &nvgpu_swap_next_sector);
+    sector -= (m->size >> SECTOR_SHIFT);
+    m->os_priv.swap_sector = sector;
+  }
   // Reset the .done variable in the completion
   reinit_completion(&m->os_priv.swap_io_done);
   // bio_alloc() will never fail when allocating <= BIO_MAX_PAGES
@@ -58,8 +79,10 @@ int copy(struct sg_table *sgt, int op, struct nvgpu_mapped_buf *m) {
   }
 
   // Async submit. Caller should wait_for_completion_io(&m->os_priv.swap_io_done);
+  // Does not fail. Error reported via completion handler.
   submit_bio(bio);
 
+out_put:
   // Release our block device handle
   blkdev_put(bdev, FMODE_WRITE | FMODE_READ); // Is this safe?
   return err;