pmem: fail io-requests to known bad blocks

Check the sectors specified in a read bio to see if they hit a known bad
block, and return an error code pmem_do_bvec().

Note that the ->rw_page() is not in a position to return errors.  For
now, copy the same layering violation present in zram_rw_page() to avoid
crashes of the form:

 kernel BUG at mm/filemap.c:822!
 [..]
 Call Trace:
  [<ffffffff811c540e>] page_endio+0x1e/0x60
  [<ffffffff81290d29>] mpage_end_io+0x39/0x60
  [<ffffffff8141c4ef>] bio_endio+0x3f/0x60
  [<ffffffffa005c491>] pmem_make_request+0x111/0x230 [nd_pmem]

...i.e. unlock a page that was already unlocked via pmem_rw_page() =>
page_endio().

Reported-by: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 39 insertions, 7 deletions

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 2b1f3009f827..d00c659d1304 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -47,7 +47,20 @@ struct pmem_device {
 
 static int pmem_major;
 
-static void pmem_do_bvec(struct pmem_device *pmem, struct page *page,
+static bool is_bad_pmem(struct badblocks *bb, sector_t sector, unsigned int len)
+{
+        if (bb->count) {
+                sector_t first_bad;
+                int num_bad;
+
+                return !!badblocks_check(bb, sector, len / 512, &first_bad,
+                                &num_bad);
+        }
+
+        return false;
+}
+
+static int pmem_do_bvec(struct pmem_device *pmem, struct page *page,
                         unsigned int len, unsigned int off, int rw,
                         sector_t sector)
 {
@@ -56,6 +69,8 @@ static void pmem_do_bvec(struct pmem_device *pmem, struct page *page,
         void __pmem *pmem_addr = pmem->virt_addr + pmem_off;
 
         if (rw == READ) {
+                if (unlikely(is_bad_pmem(&pmem->bb, sector, len)))
+                        return -EIO;
                 memcpy_from_pmem(mem + off, pmem_addr, len);
                 flush_dcache_page(page);
         } else {
@@ -64,10 +79,12 @@ static void pmem_do_bvec(struct pmem_device *pmem, struct page *page,
         }
 
         kunmap_atomic(mem);
+        return 0;
 }
 
 static blk_qc_t pmem_make_request(struct request_queue *q, struct bio *bio)
 {
+        int rc = 0;
         bool do_acct;
         unsigned long start;
         struct bio_vec bvec;
@@ -76,9 +93,15 @@ static blk_qc_t pmem_make_request(struct request_queue *q, struct bio *bio)
         struct pmem_device *pmem = bdev->bd_disk->private_data;
 
         do_acct = nd_iostat_start(bio, &start);
-        bio_for_each_segment(bvec, bio, iter)
-                pmem_do_bvec(pmem, bvec.bv_page, bvec.bv_len, bvec.bv_offset,
-                                bio_data_dir(bio), iter.bi_sector);
+        bio_for_each_segment(bvec, bio, iter) {
+                rc = pmem_do_bvec(pmem, bvec.bv_page, bvec.bv_len,
+                                bvec.bv_offset, bio_data_dir(bio),
+                                iter.bi_sector);
+                if (rc) {
+                        bio->bi_error = rc;
+                        break;
+                }
+        }
         if (do_acct)
                 nd_iostat_end(bio, start);
 
@@ -93,13 +116,22 @@ static int pmem_rw_page(struct block_device *bdev, sector_t sector,
                        struct page *page, int rw)
 {
         struct pmem_device *pmem = bdev->bd_disk->private_data;
+        int rc;
 
-        pmem_do_bvec(pmem, page, PAGE_CACHE_SIZE, 0, rw, sector);
+        rc = pmem_do_bvec(pmem, page, PAGE_CACHE_SIZE, 0, rw, sector);
         if (rw & WRITE)
                 wmb_pmem();
-        page_endio(page, rw & WRITE, 0);
 
-        return 0;
+        /*
+         * The ->rw_page interface is subtle and tricky.  The core
+         * retries on any error, so we can only invoke page_endio() in
+         * the successful completion case.  Otherwise, we'll see crashes
+         * caused by double completion.
+         */
+        if (rc == 0)
+                page_endio(page, rw & WRITE, 0);
+
+        return rc;
 }
 
 static long pmem_direct_access(struct block_device *bdev, sector_t sector,