On Fri, Sep 30, 2016 at 12:46:35PM -0400, Brian Foster wrote:
> (Dropping fsdevel CC from future replies to reduce review spam.)
>
> On Thu, Sep 29, 2016 at 08:07:26PM -0700, Darrick J. Wong wrote:
> > The reference count btree is allocated from the free space, which
> > means that we have to ensure that an AG can't run out of free space
> > while performing a refcount operation. In the pathological case each
> > AG block has its own refcntbt record, so we have to keep that much
> > space available.
> >
> > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> > ---
> > v2: Calculate the maximum possible size of the rmap and refcount
> > btrees based on minimally-full btree blocks. This increases the
> > per-AG block reservations to handle the worst case btree size.
> > ---
>
> The code seems fine but I'm thrown off a bit by the commit log
> description because the patch doesn't actually change behavior (wrt to
> keeping space available for the refcountbt), but rather adds support
> functions for such a mechanism to come (I presume).
Ah, right, this patch is a leftover from before the per-AG reservation
thing. I think the xfs_refcount_btree.c hunks can go into the patch
that sets up the reservations for the refcountbt, and I'll change the
description to match the remaining piece.
--D
>
> Brian
>
> > fs/xfs/libxfs/xfs_alloc.c | 3 +++
> > fs/xfs/libxfs/xfs_refcount_btree.c | 23 +++++++++++++++++++++++
> > fs/xfs/libxfs/xfs_refcount_btree.h | 4 ++++
> > 3 files changed, 30 insertions(+)
> >
> >
> > diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
> > index be7e3fc..9d9a46e 100644
> > --- a/fs/xfs/libxfs/xfs_alloc.c
> > +++ b/fs/xfs/libxfs/xfs_alloc.c
> > @@ -38,6 +38,7 @@
> > #include "xfs_buf_item.h"
> > #include "xfs_log.h"
> > #include "xfs_ag_resv.h"
> > +#include "xfs_refcount_btree.h"
> >
> > struct workqueue_struct *xfs_alloc_wq;
> >
> > @@ -128,6 +129,8 @@ xfs_alloc_ag_max_usable(
> > blocks++; /* finobt root block */
> > if (xfs_sb_version_hasrmapbt(&mp->m_sb))
> > blocks++; /* rmap root block */
> > + if (xfs_sb_version_hasreflink(&mp->m_sb))
> > + blocks++; /* refcount root block */
> >
> > return mp->m_sb.sb_agblocks - blocks;
> > }
> > diff --git a/fs/xfs/libxfs/xfs_refcount_btree.c b/fs/xfs/libxfs/xfs_refcount_btree.c
> > index 81d58b0..6b5e82b9 100644
> > --- a/fs/xfs/libxfs/xfs_refcount_btree.c
> > +++ b/fs/xfs/libxfs/xfs_refcount_btree.c
> > @@ -387,3 +387,26 @@ xfs_refcountbt_compute_maxlevels(
> > mp->m_refc_maxlevels = xfs_btree_compute_maxlevels(mp,
> > mp->m_refc_mnr, mp->m_sb.sb_agblocks);
> > }
> > +
> > +/* Calculate the refcount btree size for some records. */
> > +xfs_extlen_t
> > +xfs_refcountbt_calc_size(
> > + struct xfs_mount *mp,
> > + unsigned long long len)
> > +{
> > + return xfs_btree_calc_size(mp, mp->m_refc_mnr, len);
> > +}
> > +
> > +/*
> > + * Calculate the maximum refcount btree size.
> > + */
> > +xfs_extlen_t
> > +xfs_refcountbt_max_size(
> > + struct xfs_mount *mp)
> > +{
> > + /* Bail out if we're uninitialized, which can happen in mkfs. */
> > + if (mp->m_refc_mxr[0] == 0)
> > + return 0;
> > +
> > + return xfs_refcountbt_calc_size(mp, mp->m_sb.sb_agblocks);
> > +}
> > diff --git a/fs/xfs/libxfs/xfs_refcount_btree.h b/fs/xfs/libxfs/xfs_refcount_btree.h
> > index 9e9ad7c..780b02f 100644
> > --- a/fs/xfs/libxfs/xfs_refcount_btree.h
> > +++ b/fs/xfs/libxfs/xfs_refcount_btree.h
> > @@ -64,4 +64,8 @@ extern int xfs_refcountbt_maxrecs(struct xfs_mount *mp, int blocklen,
> > bool leaf);
> > extern void xfs_refcountbt_compute_maxlevels(struct xfs_mount *mp);
> >
> > +extern xfs_extlen_t xfs_refcountbt_calc_size(struct xfs_mount *mp,
> > + unsigned long long len);
> > +extern xfs_extlen_t xfs_refcountbt_max_size(struct xfs_mount *mp);
> > +
> > #endif /* __XFS_REFCOUNT_BTREE_H__ */
> >
> > --
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