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Message-ID: <20161118082605.GG18676@quack2.suse.cz>
Date: Fri, 18 Nov 2016 09:26:05 +0100
From: Jan Kara <jack@...e.cz>
To: Johannes Weiner <hannes@...xchg.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Jan Kara <jack@...e.cz>,
"Kirill A. Shutemov" <kirill@...temov.name>,
Linus Torvalds <torvalds@...ux-foundation.org>,
linux-mm@...ck.org, linux-kernel@...r.kernel.org,
kernel-team@...com
Subject: Re: [PATCH 7/9] lib: radix-tree: update callback for changing leaf
nodes
On Thu 17-11-16 14:31:34, Johannes Weiner wrote:
> Support handing __radix_tree_replace() a callback that gets invoked
> for all leaf nodes that change or get freed as a result of the slot
> replacement, to assist users tracking nodes with node->private_list.
>
> This prepares for putting page cache shadow entries into the radix
> tree root again and drastically simplifying the shadow tracking.
>
> Suggested-by: Jan Kara <jack@...e.cz>
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
Looks good. You can add:
Reviewed-by: Jan Kara <jack@...e.cz>
Honza
> ---
> fs/dax.c | 3 ++-
> include/linux/radix-tree.h | 4 +++-
> lib/radix-tree.c | 42 +++++++++++++++++++++++++++++-------------
> mm/shmem.c | 3 ++-
> 4 files changed, 36 insertions(+), 16 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 85930c2a2749..6916ed37d463 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -649,7 +649,8 @@ static void *dax_insert_mapping_entry(struct address_space *mapping,
>
> ret = __radix_tree_lookup(page_tree, index, &node, &slot);
> WARN_ON_ONCE(ret != entry);
> - __radix_tree_replace(page_tree, node, slot, new_entry);
> + __radix_tree_replace(page_tree, node, slot,
> + new_entry, NULL, NULL);
> }
> if (vmf->flags & FAULT_FLAG_WRITE)
> radix_tree_tag_set(page_tree, index, PAGECACHE_TAG_DIRTY);
> diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
> index 2d1b9b8be983..15c972ea9510 100644
> --- a/include/linux/radix-tree.h
> +++ b/include/linux/radix-tree.h
> @@ -263,9 +263,11 @@ void *__radix_tree_lookup(struct radix_tree_root *root, unsigned long index,
> struct radix_tree_node **nodep, void ***slotp);
> void *radix_tree_lookup(struct radix_tree_root *, unsigned long);
> void **radix_tree_lookup_slot(struct radix_tree_root *, unsigned long);
> +typedef void (*radix_tree_update_node_t)(struct radix_tree_node *, void *);
> void __radix_tree_replace(struct radix_tree_root *root,
> struct radix_tree_node *node,
> - void **slot, void *item);
> + void **slot, void *item,
> + radix_tree_update_node_t update_node, void *private);
> void radix_tree_replace_slot(struct radix_tree_root *root,
> void **slot, void *item);
> bool __radix_tree_delete_node(struct radix_tree_root *root,
> diff --git a/lib/radix-tree.c b/lib/radix-tree.c
> index 5d8930f3b3d8..df4ff18dd63c 100644
> --- a/lib/radix-tree.c
> +++ b/lib/radix-tree.c
> @@ -325,7 +325,6 @@ static void radix_tree_node_rcu_free(struct rcu_head *head)
> tag_clear(node, i, 0);
>
> node->slots[0] = NULL;
> - node->count = 0;
>
> kmem_cache_free(radix_tree_node_cachep, node);
> }
> @@ -542,7 +541,9 @@ static int radix_tree_extend(struct radix_tree_root *root,
> * radix_tree_shrink - shrink radix tree to minimum height
> * @root radix tree root
> */
> -static inline bool radix_tree_shrink(struct radix_tree_root *root)
> +static inline bool radix_tree_shrink(struct radix_tree_root *root,
> + radix_tree_update_node_t update_node,
> + void *private)
> {
> bool shrunk = false;
>
> @@ -597,8 +598,12 @@ static inline bool radix_tree_shrink(struct radix_tree_root *root)
> * also results in a stale slot). So tag the slot as indirect
> * to force callers to retry.
> */
> - if (!radix_tree_is_internal_node(child))
> + node->count = 0;
> + if (!radix_tree_is_internal_node(child)) {
> node->slots[0] = RADIX_TREE_RETRY;
> + if (update_node)
> + update_node(node, private);
> + }
>
> radix_tree_node_free(node);
> shrunk = true;
> @@ -608,7 +613,8 @@ static inline bool radix_tree_shrink(struct radix_tree_root *root)
> }
>
> static bool delete_node(struct radix_tree_root *root,
> - struct radix_tree_node *node)
> + struct radix_tree_node *node,
> + radix_tree_update_node_t update_node, void *private)
> {
> bool deleted = false;
>
> @@ -617,7 +623,8 @@ static bool delete_node(struct radix_tree_root *root,
>
> if (node->count) {
> if (node == entry_to_node(root->rnode))
> - deleted |= radix_tree_shrink(root);
> + deleted |= radix_tree_shrink(root, update_node,
> + private);
> return deleted;
> }
>
> @@ -880,17 +887,20 @@ static void replace_slot(struct radix_tree_root *root,
>
> /**
> * __radix_tree_replace - replace item in a slot
> - * @root: radix tree root
> - * @node: pointer to tree node
> - * @slot: pointer to slot in @node
> - * @item: new item to store in the slot.
> + * @root: radix tree root
> + * @node: pointer to tree node
> + * @slot: pointer to slot in @node
> + * @item: new item to store in the slot.
> + * @update_node: callback for changing leaf nodes
> + * @private: private data to pass to @update_node
> *
> * For use with __radix_tree_lookup(). Caller must hold tree write locked
> * across slot lookup and replacement.
> */
> void __radix_tree_replace(struct radix_tree_root *root,
> struct radix_tree_node *node,
> - void **slot, void *item)
> + void **slot, void *item,
> + radix_tree_update_node_t update_node, void *private)
> {
> /*
> * This function supports replacing exceptional entries and
> @@ -900,7 +910,13 @@ void __radix_tree_replace(struct radix_tree_root *root,
> replace_slot(root, node, slot, item,
> !node && slot != (void **)&root->rnode);
>
> - delete_node(root, node);
> + if (!node)
> + return;
> +
> + if (update_node)
> + update_node(node, private);
> +
> + delete_node(root, node, update_node, private);
> }
>
> /**
> @@ -1585,7 +1601,7 @@ unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item)
> bool __radix_tree_delete_node(struct radix_tree_root *root,
> struct radix_tree_node *node)
> {
> - return delete_node(root, node);
> + return delete_node(root, node, NULL, NULL);
> }
>
> static inline void delete_sibling_entries(struct radix_tree_node *node,
> @@ -1642,7 +1658,7 @@ void *radix_tree_delete_item(struct radix_tree_root *root,
> node_tag_clear(root, node, tag, offset);
>
> delete_sibling_entries(node, node_to_entry(slot), offset);
> - __radix_tree_replace(root, node, slot, NULL);
> + __radix_tree_replace(root, node, slot, NULL, NULL, NULL);
>
> return entry;
> }
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 7f3a08df25c9..62ac381069fc 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -311,7 +311,8 @@ static int shmem_radix_tree_replace(struct address_space *mapping,
> return -ENOENT;
> if (item != expected)
> return -ENOENT;
> - __radix_tree_replace(&mapping->page_tree, node, pslot, replacement);
> + __radix_tree_replace(&mapping->page_tree, node, pslot,
> + replacement, NULL, NULL);
> return 0;
> }
>
> --
> 2.10.2
>
--
Jan Kara <jack@...e.com>
SUSE Labs, CR
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