diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/access/transam/multixact.c | 24 |
1 files changed, 19 insertions, 5 deletions
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c index 60c3370ece2..e2b31ee441f 100644 --- a/src/backend/access/transam/multixact.c +++ b/src/backend/access/transam/multixact.c @@ -2259,7 +2259,6 @@ ExtendMultiXactMember(MultiXactOffset offset, int nmembers) { int flagsoff; int flagsbit; - int difference; /* * Only zero when at first entry of a page. @@ -2280,10 +2279,25 @@ ExtendMultiXactMember(MultiXactOffset offset, int nmembers) LWLockRelease(MultiXactMemberControlLock); } - /* Advance to next page (OK if nmembers goes negative) */ - difference = MULTIXACT_MEMBERS_PER_PAGE - offset % MULTIXACT_MEMBERS_PER_PAGE; - offset += difference; - nmembers -= difference; + /* + * Advance to next page, taking care to properly handle the wraparound + * case. OK if nmembers goes negative. + */ + if ((unsigned int) (offset + nmembers) < offset) + { + uint32 difference = offset + MULTIXACT_MEMBERS_PER_PAGE; + + nmembers -= (unsigned int) (MULTIXACT_MEMBERS_PER_PAGE - difference); + offset = 0; + } + else + { + int difference; + + difference = MULTIXACT_MEMBERS_PER_PAGE - offset % MULTIXACT_MEMBERS_PER_PAGE; + nmembers -= difference; + offset += difference; + } } } |