libceph: fix broken data length assertions

It's OK for the result of a read to come back with fewer bytes than
were requested.  So don't trigger a BUG() in that case when
initializing the data cursor.

This resolves the first problem described in:
    http://tracker.ceph.com/issues/4598

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>

diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index d4e46d8..24f3aba 100644 (file)
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -833,7 +833,7 @@ static void ceph_msg_data_pages_cursor_init(struct ceph_msg_data *data,
 
        BUG_ON(!data->pages);
        BUG_ON(!data->length);
-       BUG_ON(length != data->length);
+       BUG_ON(length > data->length);  /* short reads are OK */
 
        cursor->resid = length;
        page_count = calc_pages_for(data->alignment, (u64)data->length);
@@ -905,7 +905,7 @@ static void ceph_msg_data_pagelist_cursor_init(struct ceph_msg_data *data,
 
        pagelist = data->pagelist;
        BUG_ON(!pagelist);
-       BUG_ON(length != pagelist->length);
+       BUG_ON(length > pagelist->length);      /* short reads are OK */
 
        if (!length)
                return;         /* pagelist can be assigned but empty */