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author | Jonathan Earl Brassow <jbrassow@redhat.com> | 2010-08-04 18:18:18 +0000 |
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committer | Jonathan Earl Brassow <jbrassow@redhat.com> | 2010-08-04 18:18:18 +0000 |
commit | 498747d792c93d8f98cdd08631c367d84ec8bdc2 (patch) | |
tree | 71b29dcc75c9387a8e718da8410c8a7ece50f84c /daemons/cmirrord | |
parent | 851aaf4ecc55235f4a4ba6911abcee666007a067 (diff) | |
download | lvm2-498747d792c93d8f98cdd08631c367d84ec8bdc2.tar.gz |
A misunderstanding of the return value of 'dm_bit' has been causing a data
corruption bug in cmirror. 'dm_bit' is only ever used as a boolean operation
within LVM, but it can return a range of values. If the bit is set, a power of
2 is returned. If the bit is unset, 0 is returned.
'log_test_bit' (a function in the cluster mirror log daemon code) has switched
to using the dm bit operations in rhel6. There are two places in the daemon
code where 'log_test_bit' is not used merely as a boolean, but rather the
return value is used as the return value for the log functions 'is_clean' and
'in_sync' - having assumed that 'dm_bit' was returning 0 or 1 only.
One place the 'in_sync' function is utilized is in 'dm_rh_get_state' - a
function that informs the mirroring code how to treat I/O and which devices to
read/write from. 'dm_rh_get_state' was checking if the return value of
'in_sync' was 1 to determine if the region was DM_RH_CLEAN. Since 'dm_bit'
(and by extension 'log_test_bit' and 'in_sync') was returning powers of 2,
DM_RH_CLEAN was rarely being reported as it should have been. Thinking the
region was out-of-sync, the mirroring code would write only to the primary
device. When the primary device was failed, all of those writes were lost -
leaving the entire mirror corrupted.
Diffstat (limited to 'daemons/cmirrord')
-rw-r--r-- | daemons/cmirrord/functions.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/daemons/cmirrord/functions.c b/daemons/cmirrord/functions.c index 2ecd6b335..991762594 100644 --- a/daemons/cmirrord/functions.c +++ b/daemons/cmirrord/functions.c @@ -106,7 +106,7 @@ static DM_LIST_INIT(log_pending_list); static int log_test_bit(dm_bitset_t bs, int bit) { - return dm_bit(bs, bit); + return dm_bit(bs, bit) ? 1 : 0; } static void log_set_bit(struct log_c *lc, dm_bitset_t bs, int bit) |