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blockdev: Acquire AioContext on dirty bitmap functions
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Dirty map addition and removal functions are not acquiring to BDS
AioContext, while they may call to code that expects it to be
acquired.

This may trigger a crash with a stack trace like this one:

 #0  0x00007f0ef146370f in __GI_raise (sig=sig@entry=6)
     at ../sysdeps/unix/sysv/linux/raise.c:50
 qemu#1  0x00007f0ef144db25 in __GI_abort () at abort.c:79
 qemu#2  0x0000565022294dce in error_exit
     (err=<optimized out>, msg=msg@entry=0x56502243a730 <__func__.16350> "qemu_mutex_unlock_impl") at util/qemu-thread-posix.c:36
 qemu#3  0x00005650222950ba in qemu_mutex_unlock_impl
     (mutex=mutex@entry=0x5650244b0240, file=file@entry=0x565022439adf "util/async.c", line=line@entry=526) at util/qemu-thread-posix.c:108
 qemu#4  0x0000565022290029 in aio_context_release
     (ctx=ctx@entry=0x5650244b01e0) at util/async.c:526
 qemu#5  0x000056502221cd08 in bdrv_can_store_new_dirty_bitmap
     (bs=bs@entry=0x5650244dc820, name=name@entry=0x56502481d360 "bitmap1", granularity=granularity@entry=65536, errp=errp@entry=0x7fff22831718)
     at block/dirty-bitmap.c:542
 qemu#6  0x000056502206ae53 in qmp_block_dirty_bitmap_add
     (errp=0x7fff22831718, disabled=false, has_disabled=<optimized out>, persistent=<optimized out>, has_persistent=true, granularity=65536, has_granularity=<optimized out>, name=0x56502481d360 "bitmap1", node=<optimized out>) at blockdev.c:2894
 qemu#7  0x000056502206ae53 in qmp_block_dirty_bitmap_add
     (node=<optimized out>, name=0x56502481d360 "bitmap1", has_granularity=<optimized out>, granularity=<optimized out>, has_persistent=true, persistent=<optimized out>, has_disabled=false, disabled=false, errp=0x7fff22831718) at blockdev.c:2856
 qemu#8  0x00005650221847a3 in qmp_marshal_block_dirty_bitmap_add
     (args=<optimized out>, ret=<optimized out>, errp=0x7fff22831798)
     at qapi/qapi-commands-block-core.c:651
 qemu#9  0x0000565022247e6c in do_qmp_dispatch
     (errp=0x7fff22831790, allow_oob=<optimized out>, request=<optimized out>, cmds=0x565022b32d60 <qmp_commands>) at qapi/qmp-dispatch.c:132
 qemu#10 0x0000565022247e6c in qmp_dispatch
     (cmds=0x565022b32d60 <qmp_commands>, request=<optimized out>, allow_oob=<optimized out>) at qapi/qmp-dispatch.c:175
 qemu#11 0x0000565022166061 in monitor_qmp_dispatch
     (mon=0x56502450faa0, req=<optimized out>) at monitor/qmp.c:145
 qemu#12 0x00005650221666fa in monitor_qmp_bh_dispatcher
     (data=<optimized out>) at monitor/qmp.c:234
 qemu#13 0x000056502228f866 in aio_bh_call (bh=0x56502440eae0)
     at util/async.c:117
 qemu#14 0x000056502228f866 in aio_bh_poll (ctx=ctx@entry=0x56502440d7a0)
     at util/async.c:117
 qemu#15 0x0000565022292c54 in aio_dispatch (ctx=0x56502440d7a0)
     at util/aio-posix.c:459
 qemu#16 0x000056502228f742 in aio_ctx_dispatch
     (source=<optimized out>, callback=<optimized out>, user_data=<optimized out>) at util/async.c:260
 qemu#17 0x00007f0ef5ce667d in g_main_dispatch (context=0x56502449aa40)
     at gmain.c:3176
 qemu#18 0x00007f0ef5ce667d in g_main_context_dispatch
     (context=context@entry=0x56502449aa40) at gmain.c:3829
 qemu#19 0x0000565022291d08 in glib_pollfds_poll () at util/main-loop.c:219
 qemu#20 0x0000565022291d08 in os_host_main_loop_wait
     (timeout=<optimized out>) at util/main-loop.c:242
 qemu#21 0x0000565022291d08 in main_loop_wait (nonblocking=<optimized out>)
     at util/main-loop.c:518
 qemu#22 0x00005650220743c1 in main_loop () at vl.c:1828
 qemu#23 0x0000565021f20a72 in main
     (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>)
     at vl.c:4504

Fix this by acquiring the AioContext at qmp_block_dirty_bitmap_add()
and qmp_block_dirty_bitmap_add().

RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1782175
Signed-off-by: Sergio Lopez <slp@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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@slp @kevmw
slp authored and kevmw committed Jan 27, 2020
1 parent 0abf258 commit 91005a4
Showing 1 changed file with 18 additions and 4 deletions.
22 changes: 18 additions & 4 deletions blockdev.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2984,6 +2984,7 @@ void qmp_block_dirty_bitmap_add(const char *node, const char *name,
{
BlockDriverState *bs;
BdrvDirtyBitmap *bitmap;
AioContext *aio_context;

if (!name || name[0] == '\0') {
error_setg(errp, "Bitmap name cannot be empty");
Expand All @@ -2995,11 +2996,14 @@ void qmp_block_dirty_bitmap_add(const char *node, const char *name,
return;
}

aio_context = bdrv_get_aio_context(bs);
aio_context_acquire(aio_context);

if (has_granularity) {
if (granularity < 512 || !is_power_of_2(granularity)) {
error_setg(errp, "Granularity must be power of 2 "
"and at least 512");
return;
goto out;
}
} else {
/* Default to cluster size, if available: */
Expand All @@ -3017,19 +3021,22 @@ void qmp_block_dirty_bitmap_add(const char *node, const char *name,
if (persistent &&
!bdrv_can_store_new_dirty_bitmap(bs, name, granularity, errp))
{
return;
goto out;
}

bitmap = bdrv_create_dirty_bitmap(bs, granularity, name, errp);
if (bitmap == NULL) {
return;
goto out;
}

if (disabled) {
bdrv_disable_dirty_bitmap(bitmap);
}

bdrv_dirty_bitmap_set_persistence(bitmap, persistent);

out:
aio_context_release(aio_context);
}

static BdrvDirtyBitmap *do_block_dirty_bitmap_remove(
Expand All @@ -3038,21 +3045,27 @@ static BdrvDirtyBitmap *do_block_dirty_bitmap_remove(
{
BlockDriverState *bs;
BdrvDirtyBitmap *bitmap;
AioContext *aio_context;

bitmap = block_dirty_bitmap_lookup(node, name, &bs, errp);
if (!bitmap || !bs) {
return NULL;
}

aio_context = bdrv_get_aio_context(bs);
aio_context_acquire(aio_context);

if (bdrv_dirty_bitmap_check(bitmap, BDRV_BITMAP_BUSY | BDRV_BITMAP_RO,
errp)) {
aio_context_release(aio_context);
return NULL;
}

if (bdrv_dirty_bitmap_get_persistence(bitmap) &&
bdrv_remove_persistent_dirty_bitmap(bs, name, errp) < 0)
{
return NULL;
aio_context_release(aio_context);
return NULL;
}

if (release) {
Expand All @@ -3063,6 +3076,7 @@ static BdrvDirtyBitmap *do_block_dirty_bitmap_remove(
*bitmap_bs = bs;
}

aio_context_release(aio_context);
return release ? NULL : bitmap;
}

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