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mirror: Mirrored log should be fixed before mirror when double fault occurs

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This patch is intended to fix bug 825323 - FS turns read-only during a double
fault of a mirror leg and mirrored log's leg at the same time.  It only
affects a 2-way mirror with a mirrored log.  3+-way mirrors and mirrors
without a mirrored log are not affected.

The problem resulted from the fact that the top level mirror was not
using 'noflush' when suspending before its "down-convert".  When a
mirror image fails, the bios are queue until a suspend is recieved.  If
it is a 'noflush' suspend, the bios can be safely requeued in the DM
core.  If 'noflush' is not used, the bios must be pushed through the
target and if a device is failed for a mirror, that means issuing an
error.  When an error is received by a file system, it results in it
turning read-only (depending on the FS).

Part of the problem was is due to the nature of the stacking involved in
using a mirror as a mirror's log.  When an image in each fail, the top
level mirror stalls because it is waiting for a log flush.  The other
stalls waiting for corrective action.  When the repair command is issued,
the entire stacked arrangement is collapsed to a linear LV.  The log
flush then fails (somewhat uncleanly) and the top-level mirror is suspended
without 'noflush' because it is a linear device.

This patch allows the log to be repaired first, which in turn allows the
top-level mirror's log flush to complete cleanly.  The top-level mirror
is then secondarily reduced to a linear device - at which time this mirror
is suspended properly with 'noflush'.
This commit is contained in:
Jonathan Brassow 2012-11-14 14:58:47 -06:00
parent 7a34db0cfd
commit 54c73b7723
2 changed files with 3 additions and 6 deletions
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1
WHATS_NEW
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@ -1,5 +1,6 @@
Version 2.02.99 -
===================================
Mirrored log is now fixed before its mirror when double-fault occurs.
Add python-lvm unit test case
Exit pvscan --cache immediately if cluster locking used or lvmetad not used.
Don't use lvmetad in lvm2-monitor.service ExecStop to avoid a systemd issue.

8
tools/lvconvert.c
View File

@ -1341,10 +1341,6 @@ int mirror_remove_missing(struct cmd_context *cmd,
if (!(failed_pvs = _failed_pv_list(lv->vg)))
return_0;
/* No point in keeping a log if the result is not a mirror */
if (_failed_mirrors_count(lv) + 1 >= lv_mirror_count(lv))
log_count = 0;
if (force && _failed_mirrors_count(lv) == lv_mirror_count(lv)) {
log_error("No usable images left in %s.", lv->name);
return lv_remove_with_dependencies(cmd, lv, DONT_PROMPT, 0);
@ -1363,8 +1359,8 @@ int mirror_remove_missing(struct cmd_context *cmd,
_is_partial_lv, NULL, 0))
return 0;
if (!_lv_update_log_type(cmd, NULL, lv, failed_pvs,
log_count))
if (lv_is_mirrored(lv) &&
!_lv_update_log_type(cmd, NULL, lv, failed_pvs, log_count))
return 0;
if (!_reload_lv(cmd, lv->vg, lv))