On Mon, Sep 25, 2017 at 12:44:18PM -0700, Richard Wareing wrote:
> - For FSes which have a realtime device configured, rt_fallback_pct forces
> allocations to the realtime device after data device usage reaches
> rt_fallback_pct.
> - Useful for realtime device users to help prevent ENOSPC errors when
> selectively storing some files (e.g. small files) on data device, while
> others are stored on realtime block device.
> - Set via the "rt_fallback_pct" sysfs value which is available if
> the kernel is compiled with CONFIG_XFS_RT.
>
> Signed-off-by: Richard Wareing <rwareing@xxxxxx>
> ---
> Changes since v4:
> * Refactored to align with xfs_inode_select_target change
> * Fallback percentage reworked to trigger on % space used on data device.
> I find this a bit more intuitive as it aligns well with "df" output.
> * mp->m_rt_min_fdblocks now assigned via function call
> * Better consistency on sysfs options
>
> Changes since v3:
> * None, new patch to patch set
>
> fs/xfs/xfs_fsops.c | 2 ++
> fs/xfs/xfs_mount.c | 24 ++++++++++++++++++++++++
> fs/xfs/xfs_mount.h | 8 ++++++++
> fs/xfs/xfs_rtalloc.c | 32 ++++++++++++++++++++++++++++++++
> fs/xfs/xfs_sysfs.c | 38 ++++++++++++++++++++++++++++++++++++++
> 5 files changed, 104 insertions(+)
>
> diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
> index 6ccaae9..80ccb14 100644
> --- a/fs/xfs/xfs_fsops.c
> +++ b/fs/xfs/xfs_fsops.c
> @@ -610,6 +610,8 @@ xfs_growfs_data_private(
> xfs_set_low_space_thresholds(mp);
> mp->m_alloc_set_aside = xfs_alloc_set_aside(mp);
>
> + mp->m_rt_min_free_dblocks = xfs_rt_calc_min_free_dblocks(mp);
> +
> /*
> * If we expanded the last AG, free the per-AG reservation
> * so we can reinitialize it with the new size.
> diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
> index 2eaf818..e8bae5e 100644
> --- a/fs/xfs/xfs_mount.c
> +++ b/fs/xfs/xfs_mount.c
> @@ -1396,3 +1396,27 @@ xfs_dev_is_read_only(
> }
> return 0;
> }
> +
> +/*
> + * precalculate minimum of data blocks required, if we fall
> + * below this value, we will fallback to the real-time device.
> + *
> + * m_rt_fallback_pct can only be non-zero if a real-time device
> + * is configured.
> + */
> +uint64_t
> +xfs_rt_calc_min_free_dblocks(
> + struct xfs_mount *mp)
> +{
> + uint64_t min_free_dblocks = 0;
> +
> + if (!XFS_IS_REALTIME_MOUNT(mp))
> + return 0;
> +
> + /* Pre-compute minimum data blocks required before
> + * falling back to RT device for allocations
> + */
> + min_free_dblocks = mp->m_sb.sb_dblocks * (100 - mp->m_rt_fallback_pct);
> + do_div(min_free_dblocks, 100);
> + return min_free_dblocks;
> +}
> diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
> index 2adc701..74dcdc3 100644
> --- a/fs/xfs/xfs_mount.h
> +++ b/fs/xfs/xfs_mount.h
> @@ -198,6 +198,13 @@ typedef struct xfs_mount {
>
> bool m_fail_unmount;
> uint m_rt_alloc_min; /* Min RT allocation */
> + uint32_t m_rt_fallback_pct; /* Fallback to realtime device if data
> + * device usage above rt_fallback_pct
> + */
uint? Surely we'll never see a fallback_pct > 100...
> + uint64_t m_rt_min_free_dblocks; /* Use realtime device if free data
xfs_rfsblock_t, since that's what we use for blocks used?
> + * device blocks falls below this;
> + * computed from m_rt_fallback_pct.
> + */
These comments could go above the field, rather than being jammed
together at the right edge of the screen.
> #ifdef DEBUG
> /*
> * DEBUG mode instrumentation to test and/or trigger delayed allocation
> @@ -463,4 +470,5 @@ int xfs_zero_extent(struct xfs_inode *ip, xfs_fsblock_t start_fsb,
> struct xfs_error_cfg * xfs_error_get_cfg(struct xfs_mount *mp,
> int error_class, int error);
>
> +uint64_t xfs_rt_calc_min_free_dblocks(struct xfs_mount *mp);
> #endif /* __XFS_MOUNT_H__ */
> diff --git a/fs/xfs/xfs_rtalloc.c b/fs/xfs/xfs_rtalloc.c
> index 421f860..c197b95 100644
> --- a/fs/xfs/xfs_rtalloc.c
> +++ b/fs/xfs/xfs_rtalloc.c
> @@ -1305,6 +1305,35 @@ void xfs_rt_alloc_min(
> }
>
> /*
> + * m_rt_min_free_dblocks is a pre-computed threshold, which controls target
> + * selection based on how many free blocks are available on the data device.
> + *
> + * If the number of free data device blocks falls below
> + * mp->m_rt_min_free_dblocks, the realtime device is selected as the target
> + * device. If this value is not set, this target policy is in-active.
> + *
> + */
> +void xfs_rt_min_free_dblocks(
> + struct xfs_mount *mp,
> + struct xfs_inode *ip,
> + xfs_off_t len)
> +{
> + /* Disabled */
> + if (!mp->m_rt_fallback_pct)
> + return;
> +
> + /* If inode target is already realtime device, nothing to do here */
> + if(!XFS_IS_REALTIME_INODE(ip)) {
> + uint64_t free_dblocks;
Spacing after the variable, indentation on the if test, indentation on
the overflow line below...
> + free_dblocks = percpu_counter_sum(&mp->m_fdblocks) -
> + mp->m_alloc_set_aside;
> + if (free_dblocks < mp->m_rt_min_free_dblocks) {
> + ip->i_d.di_flags |= XFS_DIFLAG_REALTIME;
> + }
More of the thing where we set flags but we don't log the inode core?
> + }
> +}
> +
> +/*
> * Select the target device for the inode based on either the size of the
> * initial allocation, or the amount of space available on the data device.
> *
> @@ -1333,4 +1362,7 @@ void xfs_inode_select_target(
> * not valid if not set.
> */
> xfs_rt_alloc_min(mp, ip, len);
> +
> + /* Select target based on remaining free blocks on data device */
> + xfs_rt_min_free_dblocks(mp, ip, len);
Ok, /me retracts his comment from the previous reply; these helpers
decide if we set the flag, so why don't they return boolean? That's
much easier to figure out than a bunch of helpers that may or may not
tweak the realtime flag:
if (xfs_first_alloc_short_enough(...) && !xfs_data_dev_has_free(...))
ip->i_d.di_flags |= XFS_DIFLAG_REALTIME;
else
ip->i_d.di_flags &= ~XFS_DIFLAG_REALTIME;
xfs_log_inode_core(tp, ip, ...);
> }
> diff --git a/fs/xfs/xfs_sysfs.c b/fs/xfs/xfs_sysfs.c
> index 1e202a1..889b006 100644
> --- a/fs/xfs/xfs_sysfs.c
> +++ b/fs/xfs/xfs_sysfs.c
> @@ -166,11 +166,49 @@ rt_alloc_min_show(
> }
> XFS_SYSFS_ATTR_RW(rt_alloc_min);
>
> +STATIC ssize_t
> +rt_fallback_pct_store(
> + struct kobject *kobject,
> + const char *buf,
> + size_t count)
> +{
> + struct xfs_mount *mp = to_mp(kobject);
> + int ret;
> + int val;
> +
> + ret = kstrtoint(buf, 0, &val);
> + if (ret)
> + return ret;
> +
> + if (!XFS_IS_REALTIME_MOUNT(mp))
> + return -EINVAL;
> +
> + if (val < 0)
> + return -EINVAL;
> +
> + /* Only valid if using a real-time device */
> + mp->m_rt_fallback_pct = val;
echo 30000000 > rt_fallback_pct is ok? Why?
--D
> + mp->m_rt_min_free_dblocks = xfs_rt_calc_min_free_dblocks(mp);
> + return count;
> +}
> +
> +STATIC ssize_t
> +rt_fallback_pct_show(
> + struct kobject *kobject,
> + char *buf)
> +{
> + struct xfs_mount *mp = to_mp(kobject);
> +
> + return snprintf(buf, PAGE_SIZE, "%d\n", mp->m_rt_fallback_pct);
> +}
> +XFS_SYSFS_ATTR_RW(rt_fallback_pct);
> +
> static struct attribute *xfs_mp_attrs[] = {
> #ifdef DEBUG
> ATTR_LIST(drop_writes),
> #endif
> ATTR_LIST(rt_alloc_min),
> + ATTR_LIST(rt_fallback_pct),
> NULL,
> };
>
> --
> 2.9.5
>
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