Thread: pgsql: Fix transient mdsync() errors of truncated relations due to 72a9
Fix transient mdsync() errors of truncated relations due to 72a98a6395. Unfortunately the segment size checks from 72a98a6395 had the negative side-effect of breaking a corner case in mdsync(): When processing a fsync request for a truncated away segment mdsync() could fail with "could not fsync file" (if previous segment < RELSEG_SIZE) because _mdfd_getseg() now wouldn't return the relevant segment anymore. The cleanest fix seems to be to allow the caller of _mdfd_getseg() to specify whether checks for RELSEG_SIZE are performed. To allow doing so, change the ExtensionBehavior enum into a bitmask. Besides allowing for the addition of EXTENSION_DONT_CHECK_SIZE, this makes for a nicer implementation of EXTENSION_REALLY_RETURN_NULL. Besides mdsync() the only callsite that should change behaviour due to this is mdprefetch() which now doesn't create segments anymore, even in recovery. Given the uses of mdprefetch() that seems better. Reported-By: Thom Brown Discussion: CAA-aLv72QazLvPdKZYpVn4a_Eh+i4_cxuB03k+iCuZM_xjc+6Q@mail.gmail.com Branch ------ master Details ------- http://git.postgresql.org/pg/commitdiff/a712487087c73eee880ff1a7c50528cbab2f1b90 Modified Files -------------- src/backend/storage/smgr/md.c | 81 +++++++++++++++++++++++++------------------ 1 file changed, 47 insertions(+), 34 deletions(-)
Re: [COMMITTERS] pgsql: Fix transient mdsync() errors of truncatedrelations due to 72a9
From
Peter Geoghegan
Date:
On Wed, May 4, 2016 at 1:59 AM, Andres Freund <andres@anarazel.de> wrote: > The cleanest fix seems to be to allow the caller of _mdfd_getseg() to > specify whether checks for RELSEG_SIZE are performed. To allow doing so, > change the ExtensionBehavior enum into a bitmask. Besides allowing for > the addition of EXTENSION_DONT_CHECK_SIZE, this makes for a nicer > implementation of EXTENSION_REALLY_RETURN_NULL. You missed a remaining reference to EXTENSION_REALLY_RETURN_NULL within _mdfd_getseg(). -- Peter Geoghegan -- Sent via pgsql-committers mailing list (pgsql-committers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-committers