[LU-15779] do not hold object's lock over read bulk

• Type: Improvement
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.16.0, Lustre 2.15.2
• Assignee: Alex Zhuravlev
• Reporter: Alex Zhuravlev

Description

as a stuck bulk can block OUT's (e.g. out_tx_xattr_set_exec taking an exclusive object's lock), then all shared object's locks are blocked and finally all transactions are blocked:

Call Trace:
[<0>] call_rwsem_down_write_failed+0x17/0x30
[<0>] osd_write_lock+0x5c/0xe0 [osd_ldiskfs]
[<0>] out_tx_xattr_set_exec+0xdb/0x840 [ptlrpc]
[<0>] out_tx_end+0xe1/0x5c0 [ptlrpc]
[<0>] out_handle+0x1452/0x1bc0 [ptlrpc]
[<0>] tgt_request_handle+0xaee/0x15f0 [ptlrpc]
[<0>] ptlrpc_server_handle_request+0x24b/0xab0 [ptlrpc]

Call Trace:
[<0>] wait_transaction_locked+0x85/0xd0 [jbd2]
[<0>] add_transaction_credits+0x278/0x310 [jbd2]
[<0>] start_this_handle+0x1a1/0x430 [jbd2]
[<0>] jbd2__journal_start+0xf3/0x1f0 [jbd2]
[<0>] __ldiskfs_journal_start_sb+0x69/0xe0 [ldiskfs]
[<0>] osd_trans_start+0x20e/0x4e0 [osd_ldiskfs]
[<0>] ofd_commitrw_write+0x11dc/0x1da0 [ofd]
[<0>] ofd_commitrw+0x53f/0xf70 [ofd]
[<0>] tgt_brw_write+0xffb/0x1dc0 [ptlrpc]
[<0>] tgt_request_handle+0xaee/0x15f0 [ptlrpc]
[<0>] ptlrpc_server_handle_request+0x24b/0xab0 [ptlrpc]