On Thu, Sep 29, 2016 at 02:18:23PM -0700, Darrick J. Wong wrote: > On Wed, Sep 28, 2016 at 12:20:05PM -0400, Brian Foster wrote: > > On Tue, Sep 27, 2016 at 07:54:20PM -0700, Darrick J. Wong wrote: > > > Every time we allocate or free an extent, we might need to split the > > > refcount btree. Reserve some blocks in the transaction to handle > > > this possibility. > > > > > > > I'm probably not far along enough to grok how this all works, but I'm a > > bit confused by the requirement here. Why is generic block > > allocation/free a refcountbt matter? E.g., the function below is used > > for things like inode chunk allocation and whatnot, aren't those > > irrelevant to the refcountbt? > > Overnight tests seem to run ok, so I'll remove this patch. If it > becomes a problem we can always put it back in. I spoke too soon. Running the (upcoming) xfs/900 test with a block size of 1k actually /does/ cause a perfect storm wherein a refcount adjustment of a large range of blocks causes full tree splits in two separate extents in two separate refcount tree blocks; allocating new refcount tree blocks causes rmap btree splits; and all the allocation activity causes the freespace btrees to split. By the time we finish running around doing all that we've blown the reservation. So I guess I'll put this patch back in, with a better explanation in the changelog. --D > --D > > > > > Brian > > > > > (Reproduced by generic/167 over NFS atop XFS) > > > > > > Signed-off-by: Christoph Hellwig <hch@xxxxxx> > > > [darrick.wong@xxxxxxxxxx: add commit message] > > > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> > > > --- > > > fs/xfs/libxfs/xfs_trans_resv.c | 5 ++++- > > > 1 file changed, 4 insertions(+), 1 deletion(-) > > > > > > > > > diff --git a/fs/xfs/libxfs/xfs_trans_resv.c b/fs/xfs/libxfs/xfs_trans_resv.c > > > index 7c840e1..a59838f 100644 > > > --- a/fs/xfs/libxfs/xfs_trans_resv.c > > > +++ b/fs/xfs/libxfs/xfs_trans_resv.c > > > @@ -67,7 +67,8 @@ xfs_calc_buf_res( > > > * Per-extent log reservation for the btree changes involved in freeing or > > > * allocating an extent. In classic XFS there were two trees that will be > > > * modified (bnobt + cntbt). With rmap enabled, there are three trees > > > - * (rmapbt). The number of blocks reserved is based on the formula: > > > + * (rmapbt). With reflink, there are four trees (refcountbt). The number of > > > + * blocks reserved is based on the formula: > > > * > > > * num trees * ((2 blocks/level * max depth) - 1) > > > * > > > @@ -83,6 +84,8 @@ xfs_allocfree_log_count( > > > blocks = num_ops * 2 * (2 * mp->m_ag_maxlevels - 1); > > > if (xfs_sb_version_hasrmapbt(&mp->m_sb)) > > > blocks += num_ops * (2 * mp->m_rmap_maxlevels - 1); > > > + if (xfs_sb_version_hasreflink(&mp->m_sb)) > > > + blocks += num_ops * (2 * mp->m_refc_maxlevels - 1); > > > > > > return blocks; > > > } > > > > > > -- > > > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
