(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).
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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