[LU-8680] replay-single test_20b: BUG: soft lockup - osc_makes_rpc()

• Type: Bug
• Resolution: Fixed
• Priority: Blocker
• Fix Version/s: Lustre 2.9.0
• Affects Version/s: Lustre 2.9.0
• Severity: 3
• Assignee: Zhenyu Xu
• Reporter: Maloo

Description

This issue was created by maloo for Niu Yawei <[e-mail]>

This issue relates to the following test suite run: https://testing.hpdd.intel.com/test_sets/a265b3dc-8b49-11e6-ad53-5254006e85c2.

The sub-test test_20b failed with the following error:

test failed to respond and timed out

Please provide additional information about the failure here.

Info required for matching: replay-single 20b

Comments

[Peter Jones]

Landed for 2.9

[Gerrit Updater]

Oleg Drokin ([e-mail]) merged in patch http://review.whamcloud.com/23326/
Subject: LU-8680 osc: soft lock - osc_makes_rpc()
Project: fs/lustre-release
Branch: master
Current Patch Set:
Commit: a687000d2400fee88f122526444700502cb57fe4

[Gerrit Updater]

Bobi Jam ([e-mail]) uploaded a new patch: http://review.whamcloud.com/23326
Subject: LU-8680 osc: soft lock - osc_makes_rpc()
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: 4b891b4752273c0852bec39e188a6aecfec800de

[Jinshan Xiong (Inactive)]

Indeed. It occurred to me why I would like to have

osc_max_write_chunks()
{
        return PTLRPC_MAX_BRW_SIZE >> cli->cl_chunkbits;
}

instead of the current implementation.

[Niu Yawei (Inactive)]

One thing I can't see from the patch of LU-8135 is that: when will the large extent (exceeding chunk limitation) being flushed back?

[Niu Yawei (Inactive)]

This could be a regression caused by LU-8135, that patch limited chunk number in a write RPC, so for a extent with large number of chunk, osc_check_rpcs() will run into a loop and never break.

see osc_check_rpcs()

                if (osc_makes_rpc(cli, osc, OBD_BRW_WRITE)) {
                        rc = osc_send_write_rpc(env, cli, osc);
                        if (rc < 0) {
                                CERROR("Write request failed with %d\n", rc);

                                /* osc_send_write_rpc failed, mostly because of
                                 * memory pressure.
                                 *
                                 * It can't break here, because if:
                                 *  - a page was submitted by osc_io_submit, so
                                 *    page locked;
                                 *  - no request in flight
                                 *  - no subsequent request
                                 * The system will be in live-lock state,
                                 * because there is no chance to call
                                 * osc_io_unplug() and osc_check_rpcs() any
                                 * more. pdflush can't help in this case,
                                 * because it might be blocked at grabbing
                                 * the page lock as we mentioned.
                                 *
                                 * Anyway, continue to drain pages. */
                                /* break; */
                        }
                }

With the fix of LU-8135, osc_send_write_rpc() will do nothing when the extent is too large, and osc_check_rpcs() won't break loop but continue to try on the same object.