Re: [PATCH 4/5] xfs: convert perag lookup to xarray

Darrick J. Wong
2024-08-21T16:28:11Z

On Wed, Aug 21, 2024 at 08:38:31AM +0200, Christoph Hellwig wrote:
> Convert the perag lookup from the legacy radix tree to the xarray,
> which allows for much nicer iteration and bulk lookup semantics.

Looks like a pretty straightforward covnersion. Is there a good
justification for converting the ici radix tree too? Or is it too
sparse to be worth doing?

Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> fs/xfs/libxfs/xfs_ag.c | 31 +++++++-------------------
> fs/xfs/xfs_icache.c | 50 +++++++++++++++++++++---------------------
> fs/xfs/xfs_mount.h | 3 +--
> fs/xfs/xfs_super.c | 3 +--
> 4 files changed, 35 insertions(+), 52 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_ag.c b/fs/xfs/libxfs/xfs_ag.c
> index 87f00f0180846f..5f0494702e0b55 100644
> --- a/fs/xfs/libxfs/xfs_ag.c
> +++ b/fs/xfs/libxfs/xfs_ag.c
> @@ -46,7 +46,7 @@ xfs_perag_get(
> struct xfs_perag *pag;
>
> rcu_read_lock();
> - pag = radix_tree_lookup(&mp->m_perag_tree, agno);
> + pag = xa_load(&mp->m_perags, agno);
> if (pag) {
> trace_xfs_perag_get(pag, _RET_IP_);
> ASSERT(atomic_read(&pag->pag_ref) >= 0);
> @@ -92,7 +92,7 @@ xfs_perag_grab(
> struct xfs_perag *pag;
>
> rcu_read_lock();
> - pag = radix_tree_lookup(&mp->m_perag_tree, agno);
> + pag = xa_load(&mp->m_perags, agno);
> if (pag) {
> trace_xfs_perag_grab(pag, _RET_IP_);
> if (!atomic_inc_not_zero(&pag->pag_active_ref))
> @@ -195,9 +195,7 @@ xfs_free_perag(
> xfs_agnumber_t agno;
>
> for (agno = 0; agno < mp->m_sb.sb_agcount; agno++) {
> - spin_lock(&mp->m_perag_lock);
> - pag = radix_tree_delete(&mp->m_perag_tree, agno);
> - spin_unlock(&mp->m_perag_lock);
> + pag = xa_erase(&mp->m_perags, agno);
> ASSERT(pag);
> XFS_IS_CORRUPT(pag->pag_mount, atomic_read(&pag->pag_ref) != 0);
> xfs_defer_drain_free(&pag->pag_intents_drain);
> @@ -286,9 +284,7 @@ xfs_free_unused_perag_range(
> xfs_agnumber_t index;
>
> for (index = agstart; index < agend; index++) {
> - spin_lock(&mp->m_perag_lock);
> - pag = radix_tree_delete(&mp->m_perag_tree, index);
> - spin_unlock(&mp->m_perag_lock);
> + pag = xa_erase(&mp->m_perags, index);
> if (!pag)
> break;
> xfs_buf_cache_destroy(&pag->pag_bcache);
> @@ -329,20 +325,11 @@ xfs_initialize_perag(
> pag->pag_agno = index;
> pag->pag_mount = mp;
>
> - error = radix_tree_preload(GFP_KERNEL | __GFP_RETRY_MAYFAIL);
> - if (error)
> - goto out_free_pag;
> -
> - spin_lock(&mp->m_perag_lock);
> - if (radix_tree_insert(&mp->m_perag_tree, index, pag)) {
> - WARN_ON_ONCE(1);
> - spin_unlock(&mp->m_perag_lock);
> - radix_tree_preload_end();
> - error = -EEXIST;
> + error = xa_insert(&mp->m_perags, index, pag, GFP_KERNEL);
> + if (error) {
> + WARN_ON_ONCE(error == -EBUSY);
> goto out_free_pag;
> }
> - spin_unlock(&mp->m_perag_lock);
> - radix_tree_preload_end();
>
> #ifdef __KERNEL__
> /* Place kernel structure only init below this point. */
> @@ -390,9 +377,7 @@ xfs_initialize_perag(
>
> out_remove_pag:
> xfs_defer_drain_free(&pag->pag_intents_drain);
> - spin_lock(&mp->m_perag_lock);
> - radix_tree_delete(&mp->m_perag_tree, index);
> - spin_unlock(&mp->m_perag_lock);
> + pag = xa_erase(&mp->m_perags, index);
> out_free_pag:
> kfree(pag);
> out_unwind_new_pags:
> diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
> index 4d71fbfe71299a..5bca845e702f1d 100644
> --- a/fs/xfs/xfs_icache.c
> +++ b/fs/xfs/xfs_icache.c
> @@ -65,6 +65,18 @@ static int xfs_icwalk_ag(struct xfs_perag *pag,
> XFS_ICWALK_FLAG_RECLAIM_SICK | \
> XFS_ICWALK_FLAG_UNION)
>
> +/* Marks for the perag xarray */
> +#define XFS_PERAG_RECLAIM_MARK XA_MARK_0
> +#define XFS_PERAG_BLOCKGC_MARK XA_MARK_1
> +
> +static inline xa_mark_t ici_tag_to_mark(unsigned int tag)
> +{
> + if (tag == XFS_ICI_RECLAIM_TAG)
> + return XFS_PERAG_RECLAIM_MARK;
> + ASSERT(tag == XFS_ICI_BLOCKGC_TAG);
> + return XFS_PERAG_BLOCKGC_MARK;
> +}
> +
> /*
> * Allocate and initialise an xfs_inode.
> */
> @@ -191,7 +203,7 @@ xfs_reclaim_work_queue(
> {
>
> rcu_read_lock();
> - if (radix_tree_tagged(&mp->m_perag_tree, XFS_ICI_RECLAIM_TAG)) {
> + if (xa_marked(&mp->m_perags, XFS_PERAG_RECLAIM_MARK)) {
> queue_delayed_work(mp->m_reclaim_workqueue, &mp->m_reclaim_work,
> msecs_to_jiffies(xfs_syncd_centisecs / 6 * 10));
> }
> @@ -241,9 +253,7 @@ xfs_perag_set_inode_tag(
> return;
>
> /* propagate the tag up into the perag radix tree */
> - spin_lock(&mp->m_perag_lock);
> - radix_tree_tag_set(&mp->m_perag_tree, pag->pag_agno, tag);
> - spin_unlock(&mp->m_perag_lock);
> + xa_set_mark(&mp->m_perags, pag->pag_agno, ici_tag_to_mark(tag));
>
> /* start background work */
> switch (tag) {
> @@ -285,9 +295,7 @@ xfs_perag_clear_inode_tag(
> return;
>
> /* clear the tag from the perag radix tree */
> - spin_lock(&mp->m_perag_lock);
> - radix_tree_tag_clear(&mp->m_perag_tree, pag->pag_agno, tag);
> - spin_unlock(&mp->m_perag_lock);
> + xa_clear_mark(&mp->m_perags, pag->pag_agno, ici_tag_to_mark(tag));
>
> trace_xfs_perag_clear_inode_tag(pag, _RET_IP_);
> }
> @@ -302,7 +310,6 @@ xfs_perag_get_next_tag(
> unsigned int tag)
> {
> unsigned long index = 0;
> - int found;
>
> if (pag) {
> index = pag->pag_agno + 1;
> @@ -310,14 +317,11 @@ xfs_perag_get_next_tag(
> }
>
> rcu_read_lock();
> - found = radix_tree_gang_lookup_tag(&mp->m_perag_tree,
> - (void **)&pag, index, 1, tag);
> - if (found <= 0) {
> - rcu_read_unlock();
> - return NULL;
> + pag = xa_find(&mp->m_perags, &index, ULONG_MAX, ici_tag_to_mark(tag));
> + if (pag) {
> + trace_xfs_perag_get_next_tag(pag, _RET_IP_);
> + atomic_inc(&pag->pag_ref);
> }
> - trace_xfs_perag_get_next_tag(pag, _RET_IP_);
> - atomic_inc(&pag->pag_ref);
> rcu_read_unlock();
> return pag;
> }
> @@ -332,7 +336,6 @@ xfs_perag_grab_next_tag(
> int tag)
> {
> unsigned long index = 0;
> - int found;
>
> if (pag) {
> index = pag->pag_agno + 1;
> @@ -340,15 +343,12 @@ xfs_perag_grab_next_tag(
> }
>
> rcu_read_lock();
> - found = radix_tree_gang_lookup_tag(&mp->m_perag_tree,
> - (void **)&pag, index, 1, tag);
> - if (found <= 0) {
> - rcu_read_unlock();
> - return NULL;
> + pag = xa_find(&mp->m_perags, &index, ULONG_MAX, ici_tag_to_mark(tag));
> + if (pag) {
> + trace_xfs_perag_grab_next_tag(pag, _RET_IP_);
> + if (!atomic_inc_not_zero(&pag->pag_active_ref))
> + pag = NULL;
> }
> - trace_xfs_perag_grab_next_tag(pag, _RET_IP_);
> - if (!atomic_inc_not_zero(&pag->pag_active_ref))
> - pag = NULL;
> rcu_read_unlock();
> return pag;
> }
> @@ -1038,7 +1038,7 @@ xfs_reclaim_inodes(
> if (xfs_want_reclaim_sick(mp))
> icw.icw_flags |= XFS_ICWALK_FLAG_RECLAIM_SICK;
>
> - while (radix_tree_tagged(&mp->m_perag_tree, XFS_ICI_RECLAIM_TAG)) {
> + while (xa_marked(&mp->m_perags, XFS_PERAG_RECLAIM_MARK)) {
> xfs_ail_push_all_sync(mp->m_ail);
> xfs_icwalk(mp, XFS_ICWALK_RECLAIM, &icw);
> }
> diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
> index d0567dfbc0368d..dce2d832e1e6d1 100644
> --- a/fs/xfs/xfs_mount.h
> +++ b/fs/xfs/xfs_mount.h
> @@ -208,8 +208,7 @@ typedef struct xfs_mount {
> */
> atomic64_t m_allocbt_blks;
>
> - struct radix_tree_root m_perag_tree; /* per-ag accounting info */
> - spinlock_t m_perag_lock; /* lock for m_perag_tree */
> + struct xarray m_perags; /* per-ag accounting info */
> uint64_t m_resblks; /* total reserved blocks */
> uint64_t m_resblks_avail;/* available reserved blocks */
> uint64_t m_resblks_save; /* reserved blks @ remount,ro */
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index 27e9f749c4c7fc..c41b543f2e9121 100644
> --- a/fs/xfs/xfs_super.c
> +++ b/fs/xfs/xfs_super.c
> @@ -2009,8 +2009,7 @@ static int xfs_init_fs_context(
> return -ENOMEM;
>
> spin_lock_init(&mp->m_sb_lock);
> - INIT_RADIX_TREE(&mp->m_perag_tree, GFP_ATOMIC);
> - spin_lock_init(&mp->m_perag_lock);
> + xa_init(&mp->m_perags);
> mutex_init(&mp->m_growlock);
> INIT_WORK(&mp->m_flush_inodes_work, xfs_flush_inodes_worker);
> INIT_DELAYED_WORK(&mp->m_reclaim_work, xfs_reclaim_worker);
> --
> 2.43.0
>
>