131 lines
6.7 KiB
Diff
131 lines
6.7 KiB
Diff
From aefff389c4d11bd69180db7177135c4645a9b1bd Mon Sep 17 00:00:00 2001
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From: Sergio Lopez Pascual <slp@redhat.com>
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Date: Fri, 7 Feb 2020 11:27:46 +0000
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Subject: [PATCH 13/18] block/backup-top: Don't acquire context while dropping
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top
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RH-Author: Sergio Lopez Pascual <slp@redhat.com>
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Message-id: <20200207112749.25073-7-slp@redhat.com>
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Patchwork-id: 93759
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O-Subject: [RHEL-AV-8.2.0 qemu-kvm PATCH v2 6/9] block/backup-top: Don't acquire context while dropping top
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Bugzilla: 1745606 1746217 1773517 1779036 1782111 1782175 1783965
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RH-Acked-by: Stefano Garzarella <sgarzare@redhat.com>
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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RH-Acked-by: Max Reitz <mreitz@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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All paths that lead to bdrv_backup_top_drop(), except for the call
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from backup_clean(), imply that the BDS AioContext has already been
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acquired, so doing it there too can potentially lead to QEMU hanging
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on AIO_WAIT_WHILE().
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An easy way to trigger this situation is by issuing a two actions
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transaction, with a proper and a bogus blockdev-backup, so the second
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one will trigger a rollback. This will trigger a hang with an stack
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trace like this one:
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#0 0x00007fb680c75016 in __GI_ppoll (fds=0x55e74580f7c0, nfds=1, timeout=<optimized out>,
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timeout@entry=0x0, sigmask=sigmask@entry=0x0) at ../sysdeps/unix/sysv/linux/ppoll.c:39
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#1 0x000055e743386e09 in ppoll (__ss=0x0, __timeout=0x0, __nfds=<optimized out>, __fds=<optimized out>)
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at /usr/include/bits/poll2.h:77
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#2 0x000055e743386e09 in qemu_poll_ns
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(fds=<optimized out>, nfds=<optimized out>, timeout=<optimized out>) at util/qemu-timer.c:336
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#3 0x000055e743388dc4 in aio_poll (ctx=0x55e7458925d0, blocking=blocking@entry=true)
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at util/aio-posix.c:669
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#4 0x000055e743305dea in bdrv_flush (bs=bs@entry=0x55e74593c0d0) at block/io.c:2878
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#5 0x000055e7432be58e in bdrv_close (bs=0x55e74593c0d0) at block.c:4017
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#6 0x000055e7432be58e in bdrv_delete (bs=<optimized out>) at block.c:4262
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#7 0x000055e7432be58e in bdrv_unref (bs=bs@entry=0x55e74593c0d0) at block.c:5644
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#8 0x000055e743316b9b in bdrv_backup_top_drop (bs=bs@entry=0x55e74593c0d0) at block/backup-top.c:273
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#9 0x000055e74331461f in backup_job_create
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(job_id=0x0, bs=bs@entry=0x55e7458d5820, target=target@entry=0x55e74589f640, speed=0, sync_mode=MIRROR_SYNC_MODE_FULL, sync_bitmap=sync_bitmap@entry=0x0, bitmap_mode=BITMAP_SYNC_MODE_ON_SUCCESS, compress=false, filter_node_name=0x0, on_source_error=BLOCKDEV_ON_ERROR_REPORT, on_target_error=BLOCKDEV_ON_ERROR_REPORT, creation_flags=0, cb=0x0, opaque=0x0, txn=0x0, errp=0x7ffddfd1efb0) at block/backup.c:478
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#10 0x000055e74315bc52 in do_backup_common
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(backup=backup@entry=0x55e746c066d0, bs=bs@entry=0x55e7458d5820, target_bs=target_bs@entry=0x55e74589f640, aio_context=aio_context@entry=0x55e7458a91e0, txn=txn@entry=0x0, errp=errp@entry=0x7ffddfd1efb0)
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at blockdev.c:3580
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#11 0x000055e74315c37c in do_blockdev_backup
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(backup=backup@entry=0x55e746c066d0, txn=0x0, errp=errp@entry=0x7ffddfd1efb0)
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at /usr/src/debug/qemu-kvm-4.2.0-2.module+el8.2.0+5135+ed3b2489.x86_64/./qapi/qapi-types-block-core.h:1492
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#12 0x000055e74315c449 in blockdev_backup_prepare (common=0x55e746a8de90, errp=0x7ffddfd1f018)
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at blockdev.c:1885
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#13 0x000055e743160152 in qmp_transaction
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(dev_list=<optimized out>, has_props=<optimized out>, props=0x55e7467fe2c0, errp=errp@entry=0x7ffddfd1f088) at blockdev.c:2340
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#14 0x000055e743287ff5 in qmp_marshal_transaction
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(args=<optimized out>, ret=<optimized out>, errp=0x7ffddfd1f0f8)
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at qapi/qapi-commands-transaction.c:44
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#15 0x000055e74333de6c in do_qmp_dispatch
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(errp=0x7ffddfd1f0f0, allow_oob=<optimized out>, request=<optimized out>, cmds=0x55e743c28d60 <qmp_commands>) at qapi/qmp-dispatch.c:132
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#16 0x000055e74333de6c in qmp_dispatch
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(cmds=0x55e743c28d60 <qmp_commands>, request=<optimized out>, allow_oob=<optimized out>)
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at qapi/qmp-dispatch.c:175
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#17 0x000055e74325c061 in monitor_qmp_dispatch (mon=0x55e745908030, req=<optimized out>)
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at monitor/qmp.c:145
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#18 0x000055e74325c6fa in monitor_qmp_bh_dispatcher (data=<optimized out>) at monitor/qmp.c:234
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#19 0x000055e743385866 in aio_bh_call (bh=0x55e745807ae0) at util/async.c:117
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#20 0x000055e743385866 in aio_bh_poll (ctx=ctx@entry=0x55e7458067a0) at util/async.c:117
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#21 0x000055e743388c54 in aio_dispatch (ctx=0x55e7458067a0) at util/aio-posix.c:459
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#22 0x000055e743385742 in aio_ctx_dispatch
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(source=<optimized out>, callback=<optimized out>, user_data=<optimized out>) at util/async.c:260
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#23 0x00007fb68543e67d in g_main_dispatch (context=0x55e745893a40) at gmain.c:3176
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#24 0x00007fb68543e67d in g_main_context_dispatch (context=context@entry=0x55e745893a40) at gmain.c:3829
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#25 0x000055e743387d08 in glib_pollfds_poll () at util/main-loop.c:219
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#26 0x000055e743387d08 in os_host_main_loop_wait (timeout=<optimized out>) at util/main-loop.c:242
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#27 0x000055e743387d08 in main_loop_wait (nonblocking=<optimized out>) at util/main-loop.c:518
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#28 0x000055e74316a3c1 in main_loop () at vl.c:1828
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#29 0x000055e743016a72 in main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>)
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at vl.c:4504
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Fix this by not acquiring the AioContext there, and ensuring all paths
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leading to it have it already acquired (backup_clean()).
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RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1782111
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Signed-off-by: Sergio Lopez <slp@redhat.com>
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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(cherry picked from commit 0abf2581717a19d9749d5c2ff8acd0ac203452c2)
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Signed-off-by: Sergio Lopez <slp@redhat.com>
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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block/backup-top.c | 5 -----
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block/backup.c | 3 +++
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2 files changed, 3 insertions(+), 5 deletions(-)
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diff --git a/block/backup-top.c b/block/backup-top.c
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index 818d3f2..b8d863f 100644
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--- a/block/backup-top.c
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+++ b/block/backup-top.c
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@@ -255,9 +255,6 @@ append_failed:
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void bdrv_backup_top_drop(BlockDriverState *bs)
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{
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BDRVBackupTopState *s = bs->opaque;
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- AioContext *aio_context = bdrv_get_aio_context(bs);
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-
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- aio_context_acquire(aio_context);
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bdrv_drained_begin(bs);
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@@ -271,6 +268,4 @@ void bdrv_backup_top_drop(BlockDriverState *bs)
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bdrv_drained_end(bs);
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bdrv_unref(bs);
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-
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- aio_context_release(aio_context);
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}
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diff --git a/block/backup.c b/block/backup.c
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index cf62b1a..1383e21 100644
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--- a/block/backup.c
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+++ b/block/backup.c
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@@ -135,8 +135,11 @@ static void backup_abort(Job *job)
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static void backup_clean(Job *job)
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{
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BackupBlockJob *s = container_of(job, BackupBlockJob, common.job);
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+ AioContext *aio_context = bdrv_get_aio_context(s->backup_top);
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+ aio_context_acquire(aio_context);
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bdrv_backup_top_drop(s->backup_top);
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+ aio_context_release(aio_context);
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}
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void backup_do_checkpoint(BlockJob *job, Error **errp)
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--
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1.8.3.1
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