[LU-14727] incorrect locking order in ofd_preprw_write()

Blocker — Fri, 15 Apr 2022 18:29:28 +0000

found in one customer report:

Call Trace:
[<ffffffffac5bd474>] __lock_page+0x74/0x90				objlock - lockpage
[<ffffffffac5be1e4>] __find_lock_page+0x54/0x70
[<ffffffffac5bee64>] find_or_create_page+0x34/0xa0
[<ffffffffc131be97>] osd_bufs_get+0x487/0xb20 [osd_ldiskfs]
[<ffffffffc16c6266>] ofd_preprw_write.isra.27+0x536/0x10c0 [ofd]
[<ffffffffc16c720e>] ofd_preprw+0x41e/0x8c0 [ofd]
[<ffffffffc0e74ddc>] tgt_brw_write+0xd2c/0x1d60 [ptlrpc]

Call Trace:
[<ffffffffac797dc7>] call_rwsem_down_write_failed+0x17/0x30		trunc - start - objlock
[<ffffffffc12f0e9c>] osd_write_lock+0x5c/0xe0 [osd_ldiskfs]
[<ffffffffc16bfb04>] ofd_object_punch+0x6c4/0xcb0 [ofd]
[<ffffffffc16aa3cf>] ofd_punch_hdl+0x4df/0xa90 [ofd]

Call Trace:
[<ffffffffacb88e79>] schedule+0x29/0x70
[<ffffffffc0442085>] wait_transaction_locked+0x85/0xd0 [jbd2]		lockpage - trunc - start
[<ffffffffc0442378>] add_transaction_credits+0x278/0x310 [jbd2]
[<ffffffffc0442601>] start_this_handle+0x1a1/0x430 [jbd2]
[<ffffffffc0442ab3>] jbd2__journal_start+0xf3/0x1f0 [jbd2]
[<ffffffffc12fd0de>] osd_trans_start+0x20e/0x4e0 [osd_ldiskfs]
[<ffffffffc16c32bc>] ofd_commitrw_write+0x11dc/0x1da0 [ofd]
[<ffffffffc16c7b29>] ofd_commitrw+0x479/0xe20 [ofd]
[<ffffffffc0e750d6>] tgt_brw_write+0x1026/0x1d60 [ptlrpc]

the root cause is that ofd_preprw_write() takes a lock on the object first, then locks pages.

introduced with ~~LU-10048~~ ofd: take local locks within transaction

Whamcloud Community JIRA

[LU-14727] incorrect locking order in ofd_preprw_write()