nfs: fix DIO good bytes calculation

For direct read that has IO size larger than rsize, we'll split
it into several READ requests and nfs_direct_good_bytes() would
count completed bytes incorrectly by eating last zero count reply.

Fix it by handling mirror and non-mirror cases differently such that
we only count mirrored writes differently.

This fixes 5fadeb47("nfs: count DIO good bytes correctly with mirroring").

Reported-by: Jean Spector <jean@primarydata.com>
Cc: <stable@vger.kernel.org> # v3.19+
Signed-off-by: Peng Tao <tao.peng@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

1 files changed, 17 insertions, 12 deletions

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index 018a06a062bd..e97a67e40b48 100644
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -131,20 +131,25 @@ nfs_direct_good_bytes(struct nfs_direct_req *dreq, struct nfs_pgio_header *hdr)
 
         WARN_ON_ONCE(hdr->pgio_mirror_idx >= dreq->mirror_count);
 
-        count = dreq->mirrors[hdr->pgio_mirror_idx].count;
-        if (count + dreq->io_start < hdr->io_start + hdr->good_bytes) {
-                count = hdr->io_start + hdr->good_bytes - dreq->io_start;
-                dreq->mirrors[hdr->pgio_mirror_idx].count = count;
-        }
-
-        /* update the dreq->count by finding the minimum agreed count from all
-         * mirrors */
-        count = dreq->mirrors[0].count;
+        if (dreq->mirror_count == 1) {
+                dreq->mirrors[hdr->pgio_mirror_idx].count += hdr->good_bytes;
+                dreq->count += hdr->good_bytes;
+        } else {
+                /* mirrored writes */
+                count = dreq->mirrors[hdr->pgio_mirror_idx].count;
+                if (count + dreq->io_start < hdr->io_start + hdr->good_bytes) {
+                        count = hdr->io_start + hdr->good_bytes - dreq->io_start;
+                        dreq->mirrors[hdr->pgio_mirror_idx].count = count;
+                }
+                /* update the dreq->count by finding the minimum agreed count from all
+                 * mirrors */
+                count = dreq->mirrors[0].count;
 
-        for (i = 1; i < dreq->mirror_count; i++)
-                count = min(count, dreq->mirrors[i].count);
+                for (i = 1; i < dreq->mirror_count; i++)
+                        count = min(count, dreq->mirrors[i].count);
 
-        dreq->count = count;
+                dreq->count = count;
+        }
 }
 
 /*