Commit 34f8ac6d authored Jan 27, 2012 by Jonathan Brassow Committed by NeilBrown Jan 31, 2012

Prevent DM RAID from loading bitmap twice.



The life cycle of a device-mapper target is:
1) create
2) resume
3) suspend
*) possibly repeat from 2
4) destroy

The dm-raid target is unconditionally calling MD's bitmap_load function upon
every resume.  If steps 2 & 3 above are repeated, bitmap_load is called
multiple times.  It is only written to be called once; otherwise, it allocates
new memory for the bitmap (without freeing the old) and incrementing the number
of pages it thinks it has without zeroing first.  This ultimately leads to
access beyond allocated memory and lost memory.

Simply avoiding the bitmap_load call upon resume is not sufficient.  If the
target was suspended while the initial recovery was only partially complete,
it needs to be restarted when the target is resumed.  This is why
'md_wakeup_thread' is called before issuing the 'mddev_resume'.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.de>

parent 307729c8

drivers/md/dm-raid.c

+9 −3

Original line number	Diff line number	Diff line
		@@ -56,7 +56,8 @@ struct raid_dev {
		struct raid_set {
		struct dm_target *ti;

		uint64_t print_flags;
		uint32_t bitmap_loaded;
		uint32_t print_flags;

		struct mddev md;
		struct raid_type *raid_type;
		@@ -1085,7 +1086,7 @@ static int raid_status(struct dm_target *ti, status_type_t type,
		raid_param_cnt += 2;
		}

		raid_param_cnt += (hweight64(rs->print_flags & ~DMPF_REBUILD) * 2);
		raid_param_cnt += (hweight32(rs->print_flags & ~DMPF_REBUILD) * 2);
		if (rs->print_flags & (DMPF_SYNC \| DMPF_NOSYNC))
		raid_param_cnt--;

		@@ -1197,7 +1198,12 @@ static void raid_resume(struct dm_target *ti)
		{
		struct raid_set *rs = ti->private;

		if (!rs->bitmap_loaded) {
		bitmap_load(&rs->md);
		rs->bitmap_loaded = 1;
		} else
		md_wakeup_thread(rs->md.thread);

		mddev_resume(&rs->md);
		}

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