NFS: Fix O_DIRECT accounting of number of bytes read/written

When a series of O_DIRECT reads or writes are truncated, either due to
eof or due to an error, then we should return the number of contiguous
bytes that were received/sent starting at the offset specified by the
application.

Currently, we are failing to correctly check contiguity, and so we're
failing the generic/465 in xfstests when the race between the read
and write RPCs causes the file to get extended while the 2 reads are
outstanding. If the first read RPC call wins the race and returns with
eof set, we should treat the second read RPC as being truncated.

Reported-by: Su Yanjun <suyj.fnst@cn.fujitsu.com>
Fixes: 1ccbad9f9f9bd ("nfs: fix DIO good bytes calculation")
Cc: stable@vger.kernel.org # 4.1+
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index 222d711..98a9a0b 100644 (file)
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -123,32 +123,49 @@ static inline int put_dreq(struct nfs_direct_req *dreq)
 }
 
 static void
-nfs_direct_good_bytes(struct nfs_direct_req *dreq, struct nfs_pgio_header *hdr)
+nfs_direct_handle_truncated(struct nfs_direct_req *dreq,
+                           const struct nfs_pgio_header *hdr,
+                           ssize_t dreq_len)
 {
-       int i;
-       ssize_t count;
+       struct nfs_direct_mirror *mirror = &dreq->mirrors[hdr->pgio_mirror_idx];
+
+       if (!(test_bit(NFS_IOHDR_ERROR, &hdr->flags) ||
+             test_bit(NFS_IOHDR_EOF, &hdr->flags)))
+               return;
+       if (dreq->max_count >= dreq_len) {
+               dreq->max_count = dreq_len;
+               if (dreq->count > dreq_len)
+                       dreq->count = dreq_len;
+
+               if (test_bit(NFS_IOHDR_ERROR, &hdr->flags))
+                       dreq->error = hdr->error;
+               else /* Clear outstanding error if this is EOF */
+                       dreq->error = 0;
+       }
+       if (mirror->count > dreq_len)
+               mirror->count = dreq_len;
+}
 
-       WARN_ON_ONCE(dreq->count >= dreq->max_count);
+static void
+nfs_direct_count_bytes(struct nfs_direct_req *dreq,
+                      const struct nfs_pgio_header *hdr)
+{
+       struct nfs_direct_mirror *mirror = &dreq->mirrors[hdr->pgio_mirror_idx];
+       loff_t hdr_end = hdr->io_start + hdr->good_bytes;
+       ssize_t dreq_len = 0;
 
-       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;
+       if (hdr_end > dreq->io_start)
+               dreq_len = hdr_end - dreq->io_start;
 
-               for (i = 1; i < dreq->mirror_count; i++)
-                       count = min(count, dreq->mirrors[i].count);
+       nfs_direct_handle_truncated(dreq, hdr, dreq_len);
 
-               dreq->count = count;
-       }
+       if (dreq_len > dreq->max_count)
+               dreq_len = dreq->max_count;
+
+       if (mirror->count < dreq_len)
+               mirror->count = dreq_len;
+       if (dreq->count < dreq_len)
+               dreq->count = dreq_len;
 }
 
 /*
@@ -402,20 +419,12 @@ static void nfs_direct_read_completion(struct nfs_pgio_header *hdr)
        struct nfs_direct_req *dreq = hdr->dreq;
 
        spin_lock(&dreq->lock);
-       if (test_bit(NFS_IOHDR_ERROR, &hdr->flags))
-               dreq->error = hdr->error;
-
        if (test_bit(NFS_IOHDR_REDO, &hdr->flags)) {
                spin_unlock(&dreq->lock);
                goto out_put;
        }
 
-       if (hdr->good_bytes != 0)
-               nfs_direct_good_bytes(dreq, hdr);
-
-       if (test_bit(NFS_IOHDR_EOF, &hdr->flags))
-               dreq->error = 0;
-
+       nfs_direct_count_bytes(dreq, hdr);
        spin_unlock(&dreq->lock);
 
        while (!list_empty(&hdr->pages)) {
@@ -652,6 +661,9 @@ static void nfs_direct_write_reschedule(struct nfs_direct_req *dreq)
        nfs_direct_write_scan_commit_list(dreq->inode, &reqs, &cinfo);
 
        dreq->count = 0;
+       dreq->max_count = 0;
+       list_for_each_entry(req, &reqs, wb_list)
+               dreq->max_count += req->wb_bytes;
        dreq->verf.committed = NFS_INVALID_STABLE_HOW;
        nfs_clear_pnfs_ds_commit_verifiers(&dreq->ds_cinfo);
        for (i = 0; i < dreq->mirror_count; i++)
@@ -791,17 +803,13 @@ static void nfs_direct_write_completion(struct nfs_pgio_header *hdr)
        nfs_init_cinfo_from_dreq(&cinfo, dreq);
 
        spin_lock(&dreq->lock);
-
-       if (test_bit(NFS_IOHDR_ERROR, &hdr->flags))
-               dreq->error = hdr->error;
-
        if (test_bit(NFS_IOHDR_REDO, &hdr->flags)) {
                spin_unlock(&dreq->lock);
                goto out_put;
        }
 
+       nfs_direct_count_bytes(dreq, hdr);
        if (hdr->good_bytes != 0) {
-               nfs_direct_good_bytes(dreq, hdr);
                if (nfs_write_need_commit(hdr)) {
                        if (dreq->flags == NFS_ODIRECT_RESCHED_WRITES)
                                request_commit = true;