NFS: nfs_set_pgio_error sometimes misses errors

We should ensure that we always set the pgio_header's error field
if a READ or WRITE RPC call returns an error. The current code depends
on 'hdr->good_bytes' always being initialised to a large value, which
is not always done correctly by callers.
When this happens, applications may end up missing important errors.

Cc: stable@vger.kernel.org
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index 4984bbe55ff1eed1623df2196bc0de0de41a4304..7c5718ba625e28ff661868dd2d32fb438042a7bb 100644 (file)
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -77,8 +77,8 @@ EXPORT_SYMBOL_GPL(nfs_pgheader_init);
 void nfs_set_pgio_error(struct nfs_pgio_header *hdr, int error, loff_t pos)
 {
        spin_lock(&hdr->lock);
-       if (pos < hdr->io_start + hdr->good_bytes) {
-               set_bit(NFS_IOHDR_ERROR, &hdr->flags);
+       if (!test_and_set_bit(NFS_IOHDR_ERROR, &hdr->flags)
+           || pos < hdr->io_start + hdr->good_bytes) {
                clear_bit(NFS_IOHDR_EOF, &hdr->flags);
                hdr->good_bytes = pos - hdr->io_start;
                hdr->error = error;