android/android_kernel_samsung_sm8650
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

UPSTREAM: maple_tree: reorder replacement of nodes to avoid live lock

Browse Source 
Replacing nodes may cause a live lock-up if CPU resources are saturated by
write operations on the tree by continuously retrying on dead nodes.  To
avoid the continuous retry scenario, ensure the new node is inserted into
the tree prior to marking the old data as dead.  This will define a window
where old and new data is swapped.

When reusing lower level nodes, ensure the parent pointer is updated after
the parent is marked dead.  This ensures that the child is still reachable
from the top of the tree, but walking up to a dead node will result in a
single retry that will start a fresh walk from the top down through the
new node.

Link: https://lkml.kernel.org/r/20230804165951.2661157-3-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

(cherry picked from commit 72bcf4aa86ece2b49fbdc7fe83d3a05c7ebcfc97)
Bug: 305159730
Signed-off-by: Hyesoo Yu <hyesoo.yu@samsung.com>
Change-Id: Ib052ccf4a73dfe68a0662185226891d59f98b51a
This commit is contained in:
Liam R. Howlett 2023-08-04 12:59:47 -04:00 committed by Suren Baghdasaryan
parent 545cc51b9f
commit d2e45cee2d
1 changed files with 46 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

56
lib/maple_tree.c
View File

@ -1786,6 +1786,36 @@ static inline void mas_replace(struct ma_state *mas, bool advanced)
}
}
/*
* mas_replace_node() - Replace a node by putting it in the tree, marking it
* dead, and freeing it.
* the parent encoding to locate the maple node in the tree.
* @mas - the ma_state with @mas->node pointing to the new node.
* @old_enode - The old maple encoded node.
*/
static inline void mas_replace_node(struct ma_state *mas,
struct maple_enode *old_enode)
__must_hold(mas->tree->ma_lock)
{
if (mte_is_root(mas->node)) {
mas_mn(mas)->parent = ma_parent_ptr(
((unsigned long)mas->tree | MA_ROOT_PARENT));
rcu_assign_pointer(mas->tree->ma_root, mte_mk_root(mas->node));
mas_set_height(mas);
} else {
unsigned char offset = 0;
void __rcu **slots = NULL;
offset = mte_parent_slot(mas->node);
slots = ma_slots(mte_parent(mas->node),
mas_parent_enum(mas, mas->node));
rcu_assign_pointer(slots[offset], mas->node);
}
mte_set_node_dead(old_enode);
mas_free(mas, old_enode);
}
/*
* mas_new_child() - Find the new child of a node.
* @mas: the maple state
@ -3229,7 +3259,7 @@ static inline void mas_destroy_rebalance(struct ma_state *mas, unsigned char end
{
enum maple_type mt = mte_node_type(mas->node);
struct maple_node reuse, *newnode, *parent, *new_left, *left, *node;
struct maple_enode *eparent;
struct maple_enode *eparent, *old_eparent;
unsigned char offset, tmp, split = mt_slots[mt] / 2;
void __rcu **l_slots, **slots;
unsigned long *l_pivs, *pivs, gap;
@ -3271,7 +3301,7 @@ static inline void mas_destroy_rebalance(struct ma_state *mas, unsigned char end
l_mas.max = l_pivs[split];
mas->min = l_mas.max + 1;
eparent = mt_mk_node(mte_parent(l_mas.node),
old_eparent = mt_mk_node(mte_parent(l_mas.node),
mas_parent_enum(&l_mas, l_mas.node));
tmp += end;
if (!in_rcu) {
@ -3287,7 +3317,7 @@ static inline void mas_destroy_rebalance(struct ma_state *mas, unsigned char end
memcpy(node, newnode, sizeof(struct maple_node));
ma_set_meta(node, mt, 0, tmp - 1);
mte_set_pivot(eparent, mte_parent_slot(l_mas.node),
mte_set_pivot(old_eparent, mte_parent_slot(l_mas.node),
l_pivs[split]);
/* Remove data from l_pivs. */
@ -3295,6 +3325,7 @@ static inline void mas_destroy_rebalance(struct ma_state *mas, unsigned char end
memset(l_pivs + tmp, 0, sizeof(unsigned long) * (max_p - tmp));
memset(l_slots + tmp, 0, sizeof(void *) * (max_s - tmp));
ma_set_meta(left, mt, 0, split);
eparent = old_eparent;
goto done;
}
@ -3319,7 +3350,7 @@ static inline void mas_destroy_rebalance(struct ma_state *mas, unsigned char end
parent = mas_pop_node(mas);
slots = ma_slots(parent, mt);
pivs = ma_pivots(parent, mt);
memcpy(parent, mte_to_node(eparent), sizeof(struct maple_node));
memcpy(parent, mte_to_node(old_eparent), sizeof(struct maple_node));
rcu_assign_pointer(slots[offset], mas->node);
rcu_assign_pointer(slots[offset - 1], l_mas.node);
pivs[offset - 1] = l_mas.max;
@ -3331,8 +3362,10 @@ static inline void mas_destroy_rebalance(struct ma_state *mas, unsigned char end
mte_set_gap(eparent, mte_parent_slot(l_mas.node), gap);
mas_ascend(mas);
if (in_rcu)
mas_replace(mas, false);
if (in_rcu) {
mas_replace_node(mas, old_eparent);
mas_adopt_children(mas, mas->node);
}
mas_update_gap(mas);
}
@ -3650,11 +3683,13 @@ static inline int mas_commit_b_node(struct ma_wr_state *wr_mas,
struct maple_big_node *b_node, unsigned char end)
{
struct maple_node *node;
struct maple_enode *old_enode;
unsigned char b_end = b_node->b_end;
enum maple_type b_type = b_node->type;
old_enode = wr_mas->mas->node;
if ((b_end < mt_min_slots[b_type]) &&
(!mte_is_root(wr_mas->mas->node)) &&
(!mte_is_root(old_enode)) &&
(mas_mt_height(wr_mas->mas) > 1))
return mas_rebalance(wr_mas->mas, b_node);
@ -3672,7 +3707,7 @@ static inline int mas_commit_b_node(struct ma_wr_state *wr_mas,
node->parent = mas_mn(wr_mas->mas)->parent;
wr_mas->mas->node = mt_mk_node(node, b_type);
mab_mas_cp(b_node, 0, b_end, wr_mas->mas, false);
mas_replace(wr_mas->mas, false);
mas_replace_node(wr_mas->mas, old_enode);
reuse_node:
mas_update_gap(wr_mas->mas);
return 1;
@ -4218,9 +4253,10 @@ static inline bool mas_wr_node_store(struct ma_wr_state *wr_mas)
done:
mas_leaf_set_meta(mas, newnode, dst_pivots, maple_leaf_64, new_end);
if (in_rcu) {
mte_set_node_dead(mas->node);
struct maple_enode *old_enode = mas->node;
mas->node = mt_mk_node(newnode, wr_mas->type);
mas_replace(mas, false);
mas_replace_node(mas, old_enode);
} else {
memcpy(wr_mas->node, newnode, sizeof(struct maple_node));
}