libceph: remove MAX_EXTENTS check for sparse reads

There is no any limit for the extent array size and it's possible
that when reading with a large size contents the total number of
extents will exceed 4096. Then the messager will fail by reseting
the connection and keeps resending the inflight IOs infinitely.

[ idryomov: adjust error message ]

Link: https://tracker.ceph.com/issues/62081
Signed-off-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

net/ceph/osd_client.c

@@ -5850,8 +5850,6 @@ static inline void convert_extent_map(struct ceph_sparse_read *sr)
 }
 #endif
 
-#define MAX_EXTENTS 4096
-
 static int osd_sparse_read(struct ceph_connection *con,
 			   struct ceph_msg_data_cursor *cursor,
 			   char **pbuf)
@@ -5882,23 +5880,16 @@ static int osd_sparse_read(struct ceph_connection *con,
 
 		if (count > 0) {
 			if (!sr->sr_extent || count > sr->sr_ext_len) {
-				/*
-				 * Apply a hard cap to the number of extents.
-				 * If we have more, assume something is wrong.
-				 */
-				if (count > MAX_EXTENTS) {
-					dout("%s: OSD returned 0x%x extents in a single reply!\n",
-					     __func__, count);
-					return -EREMOTEIO;
-				}
-
 				/* no extent array provided, or too short */
 				kfree(sr->sr_extent);
 				sr->sr_extent = kmalloc_array(count,
 							      sizeof(*sr->sr_extent),
 							      GFP_NOIO);
-				if (!sr->sr_extent)
+				if (!sr->sr_extent) {
+					pr_err("%s: failed to allocate %u extents\n",
+					       __func__, count);
 					return -ENOMEM;
+				}
 				sr->sr_ext_len = count;
 			}
 			ret = count * sizeof(*sr->sr_extent);