[LU-7409] llog declares write region that don't match actually write region later for osd_zfs

• Type: Bug
• Resolution: Won't Fix
• Priority: Minor
• Labels: zfs
• Severity: 3
• Assignee: Alex Zhuravlev
• Reporter: Jinshan Xiong (Inactive)

Description

The typical stack trace is as follows:

Call Trace:
 [<ffffffff8156bf13>] ? panic+0xac/0x179
 [<ffffffffa0f4e5cc>] ? zio_wait+0x21c/0x3e0 [zfs]
 [<ffffffffa0e7ef87>] ? dmu_tx_dirty_buf+0x247/0x3d0 [zfs]
 [<ffffffffa0f4e2f3>] ? zio_destroy+0xb3/0x170 [zfs]
 [<ffffffffa0e5e55f>] ? dbuf_dirty+0x5f/0x16d0 [zfs]
 [<ffffffff8157156b>] ? _spin_unlock+0x2b/0x40
 [<ffffffffa0e848ea>] ? dnode_rele+0x5a/0xa0 [zfs]
 [<ffffffffa0e61501>] ? dmu_buf_will_dirty+0x91/0x100 [zfs]
 [<ffffffffa0e6cc70>] ? dmu_write+0xa0/0x230 [zfs]
 [<ffffffffa08444c1>] ? osd_write+0x1d1/0x3a0 [osd_zfs]
 [<ffffffffa06b9bdd>] ? dt_record_write+0x3d/0x130 [obdclass]
 [<ffffffffa067955a>] ? llog_osd_write_rec+0xd6a/0x1b70 [obdclass]
 [<ffffffffa06673f6>] ? llog_write_rec+0xb6/0x270 [obdclass]
 [<ffffffffa066c1b8>] ? llog_write+0x298/0x430 [obdclass]
 [<ffffffffa066c1cf>] ? llog_write+0x2af/0x430 [obdclass]
 [<ffffffffa14780a1>] ? record_marker+0x1c1/0x1e0 [mgs]
 [<ffffffffa14779ea>] ? record_start_log+0x38a/0x4a0 [mgs]
 [<ffffffffa14787cf>] ? mgs_write_log_lov+0x38f/0x6b0 [mgs]
 [<ffffffffa148a5c6>] ? mgs_write_log_mdt+0x326/0x1630 [mgs]
 [<ffffffff810c156d>] ? trace_hardirqs_on+0xd/0x10
 [<ffffffffa148d475>] ? mgs_write_log_target+0xb55/0x1980 [mgs]
 [<ffffffff810c156d>] ? trace_hardirqs_on+0xd/0x10
 [<ffffffffa057cc11>] ? libcfs_debug_msg+0x41/0x50 [libcfs]
 [<ffffffffa1471d89>] ? mgs_target_reg+0xa19/0xe50 [mgs]
 [<ffffffffa0940b3f>] ? tgt_request_handle+0x8cf/0x1300 [ptlrpc]
 [<ffffffffa08eb85a>] ? ptlrpc_main+0xdaa/0x18b0 [ptlrpc]
 [<ffffffffa08eaab0>] ? ptlrpc_main+0x0/0x18b0 [ptlrpc]
 [<ffffffff810a728e>] ? kthread+0x9e/0xc0
 [<ffffffff8100c38a>] ? child_rip+0xa/0x20
 [<ffffffff815714b0>] ? _spin_unlock_irq+0x30/0x40
 [<ffffffff8100bb90>] ? restore_args+0x0/0x30
 [<ffffffff810a71f0>] ? kthread+0x0/0xc0
 [<ffffffff8100c380>] ? child_rip+0x0/0x20

Patch will be submitted shortly

Issue Links

• duplicates: LU-2160 Implement ZFS dmu_tx_hold_append() declarations for llog
• is related to: LU-7408 multislot RPC support didn't declare write for reply_data object

Comments

[Alex Zhuravlev]

I didn't see the patch, but in theory - yes. it should be consisting of two pieces:
1) recognize a special (like -1) offset and reserve slightly more credits like we're going to write at huge offset resulting in a deep tree
2) changes to the debugging code so that such a "undefined" write can be satisfied with that special declaration at (1)

my original point was that we can't land this patch.

[Andreas Dilger]

Alex, I recall that the actual patch to the ZFS declare code is not very complex? How hard would it be to recreate that patch?

[Jinshan Xiong (Inactive)]

it can allow me to mount my MDS after debug enabled.

[Alex Zhuravlev]

well, then what's the purpose of the ticket? looks like a duplication of LU-2160 ?

[Jinshan Xiong (Inactive)]

Yes, this is with debug enabled, and it failed at file system mount time. I saw there is a discussion about llog append therefore this patch is not a final solution, but simply an attempt to pass the check so that I can do some real test.

[Alex Zhuravlev]

Ricardo developed a patch to allow append declaration, but I have no idea where that patch is. is your zfs build configured with debug enabled?

[Alex Zhuravlev]

LLOG can't declare exact region as actual size is choosed after dmu_tx_assign() - it's append, essentially.

[Gerrit Updater]

Jinshan Xiong ([e-mail]) uploaded a new patch: http://review.whamcloud.com/17085
Subject: LDEV-239 osd-zfs: declare exact object region to write
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: d0ee25c74f33cb99a0a7c2564e6112ca267ff06e