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libdm: fix dm_stats_delete_region() backwards compat

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The dm_stats_delete_region() call removes a region from the bound
device, and, if the region is grouped, from the group leader
group descriptor stored in aux_data.

To do this requires a listed handle: previous versions of the
library do not since no dependencies exist between regions without
grouping.

This leads to strange behaviour when a command built against an old
version of the library is used with one supporting groups. Deleting
a region with dmstats succeeds, but logs errors:

  # dmstats list
  Name             RgID RgSta RgSiz #Areas ArSize ProgID
  vg_hex-root         0     0 1.00g      1  1.00g dmstats
  vg_hex-root         1 1.00g 1.00g      1  1.00g dmstats
  vg_hex-root         2 2.00g 1.00g      1  1.00g dmstats
  # dmstats delete --regionid 2 vg_hex/root
  Region ID 2 does not exist
  Could not delete statistics region.
  Command failed
  # dmstats list
  Name             RgID RgSta RgSiz #Areas ArSize ProgID
  vg_hex-root         0     0 1.00g      1  1.00g dmstats
  vg_hex-root         1 1.00g 1.00g      1  1.00g dmstats

This happens because the call to dm_stats_delete_region() is inside
a dm_stats_walk_*() iterator: upon entry to the call, the iterator
is at its end conditions and about to terminate. Due to the call to
dm_stats_list() inside the function, it returns with an iterator at
the beginning of a walk and performs a further iteration before
exiting. This final loop makes a further attempt to delete the
(already deleted) region, leading to the confusing error messages.
This commit is contained in:
Bryn M. Reeves 2016-09-27 17:46:52 +01:00
parent 6ec8854fdb
commit 56c90ffa5e
2 changed files with 40 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
WHATS_NEW_DM
View File

@ -1,5 +1,6 @@
Version 1.02.136 -
======================================
Fix 'dmstats delete' with dmsetup older than v1.02.129
Fix stats walk segfault with dmsetup older than v1.02.129
Version 1.02.135 - 26th September 2016

44
libdm/libdm-stats.c
View File

@ -1550,7 +1550,7 @@ out:
int dm_stats_walk_end(struct dm_stats *dms)
{
if (!dms || !dms->regions)
if (!dms)
return 1;
if (_stats_walk_end(dms, &dms->cur_flags,
@ -2020,26 +2020,47 @@ int dm_stats_delete_region(struct dm_stats *dms, uint64_t region_id)
{
char msg[STATS_MSG_BUF_LEN];
struct dm_task *dmt;
int listed = 0;
if (!_stats_bound(dms))
return_0;
if (!dms->regions && !dm_stats_list(dms, dms->program_id)) {
/*
* To correctly delete a region, that may be part of a group, a
* listed handle is required, since the region may need to be
* removed from another region's group descriptor; earlier
* versions of the region deletion interface do not have this
* requirement since there are no dependencies between regions.
*
* Listing a previously unlisted handle has numerous
* side-effects on other calls and operations (e.g. stats
* walks), especially when returning to a function that depends
* on the state of the region table, or statistics cursor.
*
* To avoid changing the semantics of the API, and the need for
* a versioned symbol, maintain a flag indicating when a listing
* has been carried out, and drop the region table before
* returning.
*
* This ensures compatibility with programs compiled against
* earlier versions of libdm.
*/
if (!dms->regions && !(listed = dm_stats_list(dms, dms->program_id))) {
log_error("Could not obtain region list while deleting "
"region ID " FMTu64, region_id);
return 0;
goto bad;
}
if (!dm_stats_get_nr_areas(dms)) {
log_error("Could not delete region ID " FMTu64 ": "
"no regions found", region_id);
return 0;
goto bad;
}
/* includes invalid and special region_id values */
if (!dm_stats_region_present(dms, region_id)) {
log_error("Region ID " FMTu64 " does not exist", region_id);
return 0;
goto bad;
}
if(_stats_region_is_grouped(dms, region_id))
@ -2047,12 +2068,12 @@ int dm_stats_delete_region(struct dm_stats *dms, uint64_t region_id)
log_error("Could not remove region ID " FMTu64 " from "
"group ID " FMTu64,
region_id, dms->regions[region_id].group_id);
return 0;
goto bad;
}
if (!dm_snprintf(msg, sizeof(msg), "@stats_delete " FMTu64, region_id)) {
log_error("Could not prepare @stats_delete message.");
return 0;
goto bad;
}
dmt = _stats_send_message(dms, msg);
@ -2060,10 +2081,19 @@ int dm_stats_delete_region(struct dm_stats *dms, uint64_t region_id)
return_0;
dm_task_destroy(dmt);
if (!listed)
/* wipe region and mark as not present */
_stats_region_destroy(&dms->regions[region_id]);
else
/* return handle to prior state */
_stats_regions_destroy(dms);
return 1;
bad:
if (listed)
_stats_regions_destroy(dms);
return 0;
}
int dm_stats_clear_region(struct dm_stats *dms, uint64_t region_id)