From f1bb01ab48f1bed95d7d1b3376da33d99a580beb Mon Sep 17 00:00:00 2001
From: Tom Marshall <tdm.code@gmail.com>
Date: Sun, 17 Nov 2019 04:59:54 +0100
Subject: [PATCH] Use bio_chain instead of rolling our own

---
 dm-compress/util.c | 64 +++++++++++++---------------------------------
 1 file changed, 18 insertions(+), 46 deletions(-)

diff --git a/dm-compress/util.c b/dm-compress/util.c
index 160bfee..fc86548 100644
--- a/dm-compress/util.c
+++ b/dm-compress/util.c
@@ -230,53 +230,21 @@ pblk_write(struct compress_params* kparams,
     submit_bio(bio);
 }
 
-struct pblk_iov
-{
-    struct compress_params*     kparams;
-    atomic_t                    remain;
-};
-
-void
-pblk_writev_endio(struct bio* bio)
-{
-    struct pblk_iov* iov = bio->bi_private;
-    struct compress_params* kparams = iov->kparams;
-    struct page* page = bio->bi_io_vec[0].bv_page;
-
-    if (bio->bi_status != BLK_STS_OK) {
-        printk(KERN_ERR "%s: I/O error\n", __func__);
-        kparams->params.flags |= CBD_FLAG_ERROR;
-        SetPageError(page);
-    }
-    if (atomic_dec_and_test(&iov->remain)) {
-        ClearPageDirty(page);
-        unlock_page(page);
-        kfree(iov);
-    }
-    bio_put(bio);
-}
-
 void
 pblk_writev(struct compress_params* kparams,
         u64* pblkv, u32 count, struct page* page)
 {
     u32 pblk_len = pblk_size(&kparams->params);
-    struct pblk_iov* iov;
     u32 idx;
     u32 page_off;
     u32 nr_bio;
     u64 pblk;
     u32 iov_nr_pblk;
+    struct bio* parent_bio;
     struct bio* bio;
 
     BUG_ON(pblk_len * count > PAGE_SIZE);
-    iov = kmalloc(sizeof(struct pblk_iov), GFP_KERNEL);
-    if (!iov) {
-        printk(KERN_ERR "%s: out of memory\n", __func__);
-        goto err;
-    }
-    iov->kparams = kparams;
-    atomic_set(&iov->remain, count);
+    parent_bio = NULL;
     idx = 0;
     page_off = 0;
     nr_bio = 0;
@@ -292,25 +260,29 @@ pblk_writev(struct compress_params* kparams,
             pblk_len, pblk, iov_nr_pblk, page, page_off);
         if (!bio) {
             printk(KERN_ERR "%s: out of memory\n", __func__);
-            goto err_free;
+            goto err;
+        }
+        if (!parent_bio) {
+            bio->bi_end_io = pblk_write_endio;
+            bio->bi_private = kparams;
+            parent_bio = bio;
+        }
+        else {
+            bio_chain(bio, parent_bio);
+            parent_bio = bio;
         }
-        ++nr_bio;
-        bio->bi_end_io = pblk_writev_endio;
-        bio->bi_private = iov;
-        submit_bio(bio);
         page_off += pblk_len * iov_nr_pblk;
-    }
-    if (atomic_sub_and_test(count - nr_bio, &iov->remain)) {
-        ClearPageDirty(page);
-        unlock_page(page);
-        kfree(iov);
+        submit_bio(bio);
     }
 
     return;
 
-err_free:
-    kfree(iov);
 err:
+    while (parent_bio) {
+        bio = parent_bio;
+        parent_bio = bio->bi_private;
+        bio_put(bio);
+    }
     kparams->params.flags |= CBD_FLAG_ERROR;
     SetPageError(page);
     unlock_page(page);