[LU-12800] mdd_is_parent() goes into infinite loop

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.13.0
• Severity: 3
• Assignee: Andriy Skulysh
• Reporter: Andriy Skulysh

Description

mdd_parent_fid() reads xattrs without taking a lock, so the xattr cache can be populated with stale data. So link_ea data forms a cycle :

        osp <struct osp_object 0xffff8800852091e0>
         b'trusted.link' <struct osp_xattr_entry 0xffff880085836d80>
         <struct link_ea_entry 0xffff880085836dde> b'16' [0x2c0000400:0x21:0x0]

         osp <struct osp_object 0xffff880085208420>
         b'trusted.link' <struct osp_xattr_entry 0xffff8801246c1780>
         <struct link_ea_entry 0xffff8801246c17de> b'[0x2c0000400:0x21:0x0]:0' [0x2c0000404:0x720:0x0]

        osp <struct osp_object 0xffff880085209080>
         b'trusted.link' <struct osp_xattr_entry 0xffff880085836700>
         <struct link_ea_entry 0xffff88008583675e> b'8' [0x280000403:0x7:0x0]

        osp <struct osp_object 0xffff8800852082c0>
         b'trusted.link' <struct osp_xattr_entry 0xffff880083db1300>
         <struct link_ea_entry 0xffff880083db135e> b'[0x280000403:0x7:0x0]:3' [0x2c0000409:0x729:0x0]

It is reproduced by racer.