nfs: mirroring support for direct io

The current mirroring code only notices short writes to the first
mirror. This patch keeps per-mirror byte counts and only considers
a byte to be written once all mirrors report so.

Signed-off-by: Weston Andros Adamson <dros@primarydata.com>

1 files changed, 57 insertions, 14 deletions

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index 0178d4fe8ab7..651387bbfd9f 100644
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -66,6 +66,10 @@ static struct kmem_cache *nfs_direct_cachep;
 /*
  * This represents a set of asynchronous requests that we're waiting on
  */
+struct nfs_direct_mirror {
+        ssize_t count;
+};
+
 struct nfs_direct_req {
         struct kref             kref;           /* release manager */
 
@@ -78,6 +82,10 @@ struct nfs_direct_req {
         /* completion state */
         atomic_t                io_count;       /* i/os we're waiting for */
         spinlock_t              lock;           /* protect completion state */
+
+        struct nfs_direct_mirror mirrors[NFS_PAGEIO_DESCRIPTOR_MIRROR_MAX];
+        int                     mirror_count;
+
         ssize_t                 count,          /* bytes actually processed */
                                 bytes_left,     /* bytes left to be sent */
                                 error;          /* any reported error */
@@ -108,6 +116,29 @@ static inline int put_dreq(struct nfs_direct_req *dreq)
         return atomic_dec_and_test(&dreq->io_count);
 }
 
+static void
+nfs_direct_good_bytes(struct nfs_direct_req *dreq, struct nfs_pgio_header *hdr)
+{
+        int i;
+        ssize_t count;
+
+        WARN_ON_ONCE(hdr->pgio_mirror_idx >= dreq->mirror_count);
+
+        dreq->mirrors[hdr->pgio_mirror_idx].count += hdr->good_bytes;
+
+        if (hdr->pgio_mirror_idx == 0)
+                dreq->count += hdr->good_bytes;
+
+        /* 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);
+
+        dreq->count = count;
+}
+
 /*
  * nfs_direct_select_verf - select the right verifier
  * @dreq - direct request possibly spanning multiple servers
@@ -241,6 +272,18 @@ void nfs_init_cinfo_from_dreq(struct nfs_commit_info *cinfo,
         cinfo->completion_ops = &nfs_direct_commit_completion_ops;
 }
 
+static inline void nfs_direct_setup_mirroring(struct nfs_direct_req *dreq,
+                                             struct nfs_pageio_descriptor *pgio,
+                                             struct nfs_page *req)
+{
+        int mirror_count = 1;
+
+        if (pgio->pg_ops->pg_get_mirror_count)
+                mirror_count = pgio->pg_ops->pg_get_mirror_count(pgio, req);
+
+        dreq->mirror_count = mirror_count;
+}
+
 static inline struct nfs_direct_req *nfs_direct_req_alloc(void)
 {
         struct nfs_direct_req *dreq;
@@ -255,6 +298,7 @@ static inline struct nfs_direct_req *nfs_direct_req_alloc(void)
         INIT_LIST_HEAD(&dreq->mds_cinfo.list);
         dreq->verf.committed = NFS_INVALID_STABLE_HOW;  /* not set yet */
         INIT_WORK(&dreq->work, nfs_direct_write_schedule_work);
+        dreq->mirror_count = 1;
         spin_lock_init(&dreq->lock);
 
         return dreq;
@@ -360,14 +404,9 @@ static void nfs_direct_read_completion(struct nfs_pgio_header *hdr)
         spin_lock(&dreq->lock);
         if (test_bit(NFS_IOHDR_ERROR, &hdr->flags) && (hdr->good_bytes == 0))
                 dreq->error = hdr->error;
-        else {
-                /*
-                 * FIXME: right now this only accounts for bytes written
-                 *        to the first mirror
-                 */
-                if (hdr->pgio_mirror_idx == 0)
-                        dreq->count += hdr->good_bytes;
-        }
+        else
+                nfs_direct_good_bytes(dreq, hdr);
+
         spin_unlock(&dreq->lock);
 
         while (!list_empty(&hdr->pages)) {
@@ -598,17 +637,23 @@ static void nfs_direct_write_reschedule(struct nfs_direct_req *dreq)
         LIST_HEAD(reqs);
         struct nfs_commit_info cinfo;
         LIST_HEAD(failed);
+        int i;
 
         nfs_init_cinfo_from_dreq(&cinfo, dreq);
         nfs_direct_write_scan_commit_list(dreq->inode, &reqs, &cinfo);
 
         dreq->count = 0;
+        for (i = 0; i < dreq->mirror_count; i++)
+                dreq->mirrors[i].count = 0;
         get_dreq(dreq);
 
         nfs_pageio_init_write(&desc, dreq->inode, FLUSH_STABLE, false,
                               &nfs_direct_write_completion_ops);
         desc.pg_dreq = dreq;
 
+        req = nfs_list_entry(reqs.next);
+        nfs_direct_setup_mirroring(dreq, &desc, req);
+
         list_for_each_entry_safe(req, tmp, &reqs, wb_list) {
                 if (!nfs_pageio_add_request(&desc, req)) {
                         nfs_list_remove_request(req);
@@ -730,12 +775,7 @@ static void nfs_direct_write_completion(struct nfs_pgio_header *hdr)
                 dreq->error = hdr->error;
         }
         if (dreq->error == 0) {
-                /*
-                 * FIXME: right now this only accounts for bytes written
-                 *        to the first mirror
-                 */
-                if (hdr->pgio_mirror_idx == 0)
-                        dreq->count += hdr->good_bytes;
+                nfs_direct_good_bytes(dreq, hdr);
                 if (nfs_write_need_commit(hdr)) {
                         if (dreq->flags == NFS_ODIRECT_RESCHED_WRITES)
                                 request_commit = true;
@@ -841,6 +881,9 @@ static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq,
                                 result = PTR_ERR(req);
                                 break;
                         }
+
+                        nfs_direct_setup_mirroring(dreq, &desc, req);
+
                         nfs_lock_request(req);
                         req->wb_index = pos >> PAGE_SHIFT;
                         req->wb_offset = pos & ~PAGE_MASK;