On Thu, Jun 25, 2015 at 12:41:04PM -0400, Brian Foster wrote: > On Wed, Jun 03, 2015 at 04:04:50PM +1000, Dave Chinner wrote: > > From: Dave Chinner <dchinner@xxxxxxxxxx> > > > > The rmap btree is allocated from the AGFL, which means we have to > > ensure ENOSPC is reported to userspace before we run out of free > > space in each AG. The last allocation in an AG can cause a full > > height rmap btree split, and that means we have to reserve at least > > this many blocks *in each AG* to be placed on the AGFL at ENOSPC. > > Update the various space calculation functiosn to handle this. > > > > Also, because the macros are now executing conditional code and are called quite > > frequently, convert them to functions that initialise varaibles in the struct > > xfs_mount, use the new variables everywhere and document the calculations > > better. > > > > Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx> ..... > > + * so we set the number of set-aside blocks to 4 + 4*agcount when not using rmap > > + * btrees. > > + * > > + * When rmap btrees are active, we have to consider that using the last block in > > + * the AG can cause a full height rmap btree split and we need enough blocks on > > + * the AGFL to be able to handle this. That means we have, in addition to the > > + * above consideration, another (2 * mp->m_ag_levels) - 1 blocks required to be > > + * available to the free list. > > + */ > > BTW, I think I get the 2 block per level log requirement in that a split > requires logging the two blocks involved. Where does the 2nd block per > level come in as an allocation requirement? Yup, you are right, I've mixed the two conditions up. Split only requires an extra block per level, plus a new root block. e.g. see xfs_alloc_min_freelist()... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
