From: Matthew Wilcox <mawil...@microsoft.com>
This is the first user of the radix tree I've converted which was
storing numbers rather than pointers. I'm fairly pleased with how
well it came out. There's less boiler-plate involved than there was
with the radix tree, so that's a win. It does use the advanced API,
and I think that's a signal that there needs to be a separate API for
using the XArray for only integers.
Signed-off-by: Matthew Wilcox <mawil...@microsoft.com>
---
drivers/md/raid5-cache.c | 119 ++++++++++++++++-------------------------------
1 file changed, 40 insertions(+), 79 deletions(-)
diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index 39f31f07ffe9..2c8ad0ed9b48 100644
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -158,9 +158,8 @@ struct r5l_log {
/* to disable write back during in degraded mode */
struct work_struct disable_writeback_work;
- /* to for chunk_aligned_read in writeback mode, details below */
- spinlock_t tree_lock;
- struct radix_tree_root big_stripe_tree;
+ /* for chunk_aligned_read in writeback mode, details below */
+ struct xarray big_stripe;
};
/*
@@ -170,9 +169,8 @@ struct r5l_log {
* chunk contains 64 4kB-page, so this chunk contain 64 stripes). For
* chunk_aligned_read, these stripes are grouped into one "big_stripe".
* For each big_stripe, we count how many stripes of this big_stripe
- * are in the write back cache. These data are tracked in a radix tree
- * (big_stripe_tree). We use radix_tree item pointer as the counter.
- * r5c_tree_index() is used to calculate keys for the radix tree.
+ * are in the write back cache. This counter is tracked in an xarray
+ * (big_stripe). r5c_index() is used to calculate the index.
*
* chunk_aligned_read() calls r5c_big_stripe_cached() to look up
* big_stripe of each chunk in the tree. If this big_stripe is in the
@@ -180,9 +178,9 @@ struct r5l_log {
* rcu_read_lock().
*
* It is necessary to remember whether a stripe is counted in
- * big_stripe_tree. Instead of adding new flag, we reuses existing flags:
+ * big_stripe. Instead of adding new flag, we reuses existing flags:
* STRIPE_R5C_PARTIAL_STRIPE and STRIPE_R5C_FULL_STRIPE. If either of these
- * two flags are set, the stripe is counted in big_stripe_tree. This
+ * two flags are set, the stripe is counted in big_stripe. This
* requires moving set_bit(STRIPE_R5C_PARTIAL_STRIPE) to
* r5c_try_caching_write(); and moving clear_bit of
* STRIPE_R5C_PARTIAL_STRIPE and STRIPE_R5C_FULL_STRIPE to
@@ -190,23 +188,13 @@ struct r5l_log {
*/
/*
- * radix tree requests lowest 2 bits of data pointer to be 2b'00.
- * So it is necessary to left shift the counter by 2 bits before using it
- * as data pointer of the tree.
- */
-#define R5C_RADIX_COUNT_SHIFT 2
-
-/*
- * calculate key for big_stripe_tree
+ * calculate key for big_stripe
*
* sect: align_bi->bi_iter.bi_sector or sh->sector
*/
-static inline sector_t r5c_tree_index(struct r5conf *conf,
- sector_t sect)
+static inline sector_t r5c_index(struct r5conf *conf, sector_t sect)
{
- sector_t offset;
-
- offset = sector_div(sect, conf->chunk_sectors);
+ sector_div(sect, conf->chunk_sectors);
return sect;
}
@@ -2646,10 +2634,6 @@ int r5c_try_caching_write(struct r5conf *conf,
int i;
struct r5dev *dev;
int to_cache = 0;
- void **pslot;
- sector_t tree_index;
- int ret;
- uintptr_t refcount;
BUG_ON(!r5c_is_writeback(log));
@@ -2697,39 +2681,29 @@ int r5c_try_caching_write(struct r5conf *conf,
}
}
- /* if the stripe is not counted in big_stripe_tree, add it now */
+ /* if the stripe is not counted in big_stripe, add it now */
if (!test_bit(STRIPE_R5C_PARTIAL_STRIPE, &sh->state) &&
!test_bit(STRIPE_R5C_FULL_STRIPE, &sh->state)) {
- tree_index = r5c_tree_index(conf, sh->sector);
- spin_lock(&log->tree_lock);
- pslot = radix_tree_lookup_slot(&log->big_stripe_tree,
- tree_index);
- if (pslot) {
- refcount = (uintptr_t)radix_tree_deref_slot_protected(
- pslot, &log->tree_lock) >>
- R5C_RADIX_COUNT_SHIFT;
- radix_tree_replace_slot(
- &log->big_stripe_tree, pslot,
- (void *)((refcount + 1) <<
R5C_RADIX_COUNT_SHIFT));
- } else {
- /*
- * this radix_tree_insert can fail safely, so no
- * need to call radix_tree_preload()
- */
- ret = radix_tree_insert(
- &log->big_stripe_tree, tree_index,
- (void *)(1 << R5C_RADIX_COUNT_SHIFT));
- if (ret) {
- spin_unlock(&log->tree_lock);
- r5c_make_stripe_write_out(sh);
- return -EAGAIN;
- }
+ XA_STATE(xas, &log->big_stripe, r5c_index(conf, sh->sector));
+ void *entry;
+
+ /* Caller would rather handle failures than supply GFP flags */
+ xas_lock(&xas);
+ entry = xas_create(&xas);
+ if (entry)
+ entry = xa_mk_value(xa_to_value(entry) + 1);
+ else
+ entry = xa_mk_value(1);
+ xas_store(&xas, entry);
+ xas_unlock(&xas);
+ if (xas_error(&xas)) {
+ r5c_make_stripe_write_out(sh);
+ return -EAGAIN;
}
- spin_unlock(&log->tree_lock);
/*
* set STRIPE_R5C_PARTIAL_STRIPE, this shows the stripe is
- * counted in the radix tree
+ * counted in big_stripe
*/
set_bit(STRIPE_R5C_PARTIAL_STRIPE, &sh->state);
atomic_inc(&conf->r5c_cached_partial_stripes);
@@ -2812,9 +2786,6 @@ void r5c_finish_stripe_write_out(struct r5conf *conf,
struct r5l_log *log = conf->log;
int i;
int do_wakeup = 0;
- sector_t tree_index;
- void **pslot;
- uintptr_t refcount;
if (!log || !test_bit(R5_InJournal, &sh->dev[sh->pd_idx].flags))
return;
@@ -2852,24 +2823,21 @@ void r5c_finish_stripe_write_out(struct r5conf *conf,
atomic_dec(&log->stripe_in_journal_count);
r5c_update_log_state(log);
- /* stop counting this stripe in big_stripe_tree */
+ /* stop counting this stripe in big_stripe */
if (test_bit(STRIPE_R5C_PARTIAL_STRIPE, &sh->state) ||
test_bit(STRIPE_R5C_FULL_STRIPE, &sh->state)) {
- tree_index = r5c_tree_index(conf, sh->sector);
- spin_lock(&log->tree_lock);
- pslot = radix_tree_lookup_slot(&log->big_stripe_tree,
- tree_index);
- BUG_ON(pslot == NULL);
- refcount = (uintptr_t)radix_tree_deref_slot_protected(
- pslot, &log->tree_lock) >>
- R5C_RADIX_COUNT_SHIFT;
- if (refcount == 1)
- radix_tree_delete(&log->big_stripe_tree, tree_index);
+ XA_STATE(xas, &log->big_stripe, r5c_index(conf, sh->sector));
+ void *entry;
+
+ xas_lock(&xas);
+ entry = xas_load(&xas);
+ BUG_ON(!entry);
+ if (entry == xa_mk_value(1))
+ entry = NULL;
else
- radix_tree_replace_slot(
- &log->big_stripe_tree, pslot,
- (void *)((refcount - 1) <<
R5C_RADIX_COUNT_SHIFT));
- spin_unlock(&log->tree_lock);
+ entry = xa_mk_value(xa_to_value(entry) - 1);
+ xas_store(&xas, entry);
+ xas_unlock(&xas);
}
if (test_and_clear_bit(STRIPE_R5C_PARTIAL_STRIPE, &sh->state)) {
@@ -2949,16 +2917,10 @@ int r5c_cache_data(struct r5l_log *log, struct
stripe_head *sh)
bool r5c_big_stripe_cached(struct r5conf *conf, sector_t sect)
{
struct r5l_log *log = conf->log;
- sector_t tree_index;
- void *slot;
if (!log)
return false;
-
- WARN_ON_ONCE(!rcu_read_lock_held());
- tree_index = r5c_tree_index(conf, sect);
- slot = radix_tree_lookup(&log->big_stripe_tree, tree_index);
- return slot != NULL;
+ return xa_load(&log->big_stripe, r5c_index(conf, sect)) != NULL;
}
static int r5l_load_log(struct r5l_log *log)
@@ -3112,8 +3074,7 @@ int r5l_init_log(struct r5conf *conf, struct md_rdev
*rdev)
if (!log->meta_pool)
goto out_mempool;
- spin_lock_init(&log->tree_lock);
- INIT_RADIX_TREE(&log->big_stripe_tree, GFP_NOWAIT | __GFP_NOWARN);
+ xa_init(&log->big_stripe);
log->reclaim_thread = md_register_thread(r5l_reclaim_thread,
log->rdev->mddev, "reclaim");
--
2.15.1
