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Revert initial solution to bug 733114 - I/O error message during splitmirror

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The original commit comments can be located via this git commit ID:
	7d8e615c0b30fc2ef300c90378a51f01c328128c

There were three possible solutions to the original problem proposed in the
initial check-in.  The one chosen was as follows:
    2) Do like _remove_mirror_images does and suspend the original, then suspend
    the sub-lv (the error target), then resume the sub-lv, and finally resume the
    original LV.  This seems like extra pointless operations to me, but it doesn't
    produce the error message (although, I'm not sure why) and it allows us to
    leave the visible flag in place.
Turns out, the cluster also views the extra suspend/resume operations as
pointless too and ignores them.  So, this solution doesn't work in a cluster.
Further, I've noticed that in addition to the remote cluster nodes still getting
I/O errors from scanning the error target, they also have a different LVM and
DM views of the same LV.  IOW, while the LVM level (gotten from the LVM metadata)
sees the correct name for the newly split LV, device-mapper still maintains the
old names.

Because the original fix failed to completely fix the problem (or work-around it)
and because a better solution must be found to address the additional cluster
issue of device renaming, I am reverting the above mentioned commit.
This commit is contained in:
Jonathan Earl Brassow 2011-10-06 14:49:16 +00:00
parent 83c606ae30
commit 6c0b0e5d9a
2 changed files with 0 additions and 41 deletions
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1
WHATS_NEW
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@ -42,7 +42,6 @@ Version 2.02.89 -
Fix failure to down-convert a mirror to linear due to udev "dev open" conflict
Fix mirrored log creation when PE size is small - force log_size >= region_size
Fix log size calculation when only a log is being added to a mirror.
Work around resume_lv causing error LV scanning during splitmirror operation.
Add 7th lv_attr char to show the related kernel target.
Terminate pv_attr field correctly. (2.02.86)
Fix 'not not' typo in pvcreate man page.

40
lib/metadata/mirror.c
View File

@ -673,10 +673,6 @@ static int _split_mirror_images(struct logical_volume *lv,
return 0;
}
/* Suspend temporary error target (see FIXME for resume below) */
if (sub_lv && !suspend_lv(sub_lv->vg->cmd, sub_lv))
return_0;
if (!vg_commit(mirrored_seg->lv->vg)) {
resume_lv(cmd, mirrored_seg->lv);
return 0;
@ -684,42 +680,6 @@ static int _split_mirror_images(struct logical_volume *lv,
log_very_verbose("Updating \"%s\" in kernel", mirrored_seg->lv->name);
/*
* FIXME:
When an image is split from a 2-way mirror, the original mirror is converted to
a linear device. To do this, the top "layer" must be removed. The segments
are transferred from the sub-lv to the top-level LV and the link is severed.
The former sub-lv - having its segments transferred - now contains a temporary
error target.
When the original LV is resumed, the old sub-lv that now contains an error
segment is activated and scanned. This causes I/O error messages. There are
three ways to fix this problem:
1) Do not set the sub-lv which contains the error target as "visible" before
suspending the original LV. This way, when the original is resumed, the sub-lv
device node is not created and it is not scanned - avoiding the error messages.
The problem with this approach is that if the machine crashes after the
resume, it leaves the *hidden* LV in place and the user has a more difficult
time noticing that it needs to be cleaned up. Thus, this type of processing is
frowned upon.
2) Do like _remove_mirror_images does and suspend the original, then suspend
the sub-lv (the error target), then resume the sub-lv, and finally resume the
original LV. This seems like extra pointless operations to me, but it does not
produce the error message (although, I'm not sure why) and it allows us to
leave the visible flag in place. ** THIS IS THE CHOSEN SOLUTION HERE **
3) Flag the sub-lv (error target) with a "do not scan" flag. This seems like
the cleanest approach, but I have been unable to find the method for doing
this. LVs get tagged in such a way by _get_udev_flags, but in this case the
resume of the original LV also resumes the error target LV without running it
through _get_udev_flags (likely because they are no longer linked). Could
there be something wrong in resume_lv?
*/
if (sub_lv && !resume_lv(sub_lv->vg->cmd, sub_lv))
return_0;
/*
* Resume the mirror - this also activates the visible, independent
* soon-to-be-split sub-LVs