nfs: take i_mutex during direct I/O reads

We'll need the i_mutex to prevent i_dio_count from incrementing while
truncate is waiting for it to reach zero, and protects against having
the pagecache repopulated after we flushed it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

1 files changed, 12 insertions, 2 deletions

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index cbfbd17eae85..85e4e4be401a 100644
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -500,16 +500,17 @@ ssize_t nfs_file_direct_read(struct kiocb *iocb, const struct iovec *iov,
         if (!count)
                 goto out;
 
+        mutex_lock(&inode->i_mutex);
         result = nfs_sync_mapping(mapping);
         if (result)
-                goto out;
+                goto out_unlock;
 
         task_io_account_read(count);
 
         result = -ENOMEM;
         dreq = nfs_direct_req_alloc();
         if (dreq == NULL)
-                goto out;
+                goto out_unlock;
 
         dreq->inode = inode;
         dreq->bytes_left = iov_length(iov, nr_segs);
@@ -525,13 +526,22 @@ ssize_t nfs_file_direct_read(struct kiocb *iocb, const struct iovec *iov,
 
         NFS_I(inode)->read_io += iov_length(iov, nr_segs);
         result = nfs_direct_read_schedule_iovec(dreq, iov, nr_segs, pos, uio);
+
+        mutex_unlock(&inode->i_mutex);
+
         if (!result) {
                 result = nfs_direct_wait(dreq);
                 if (result > 0)
                         iocb->ki_pos = pos + result;
         }
+
+        nfs_direct_req_release(dreq);
+        return result;
+
 out_release:
         nfs_direct_req_release(dreq);
+out_unlock:
+        mutex_unlock(&inode->i_mutex);
 out:
         return result;
 }