* Mike Rapoport <rppt@xxxxxxxxxx> [220202 12:11]: > Hi Liam, > > On Wed, Feb 02, 2022 at 02:41:56AM +0000, Liam Howlett wrote: > > From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx> > > > > The maple tree is an RCU-safe range based B-tree designed to use modern > > processor cache efficiently. There are a number of places in the kernel > > that a non-overlapping range-based tree would be beneficial, especially > > one with a simple interface. The first user that is covered in this > > patch set is the vm_area_struct, where three data structures are > > replaced by the maple tree: the augmented rbtree, the vma cache, and the > > linked list of VMAs in the mm_struct. The long term goal is to reduce > > or remove the mmap_sem contention. > > > > The tree has a branching factor of 10 for non-leaf nodes and 16 for leaf > > nodes. With the increased branching factor, it is significantly shorter than > > the rbtree so it has fewer cache misses. The removal of the linked list > > between subsequent entries also reduces the cache misses and the need to pull > > in the previous and next VMA during many tree alterations. > > > > Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> > > Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> > > --- > > Documentation/core-api/index.rst | 1 + > > Documentation/core-api/maple_tree.rst | 196 + > > MAINTAINERS | 12 + > > include/linux/maple_tree.h | 673 ++ > > include/trace/events/maple_tree.h | 123 + > > lib/Kconfig.debug | 9 + > > lib/Makefile | 3 +- > > lib/maple_tree.c | 6943 +++++++++++++++++ > > tools/testing/radix-tree/.gitignore | 2 + > > tools/testing/radix-tree/Makefile | 13 +- > > tools/testing/radix-tree/generated/autoconf.h | 1 + > > tools/testing/radix-tree/linux/maple_tree.h | 7 + > > tools/testing/radix-tree/maple.c | 59 + > > .../radix-tree/trace/events/maple_tree.h | 3 + > > 14 files changed, 8042 insertions(+), 3 deletions(-) > > create mode 100644 Documentation/core-api/maple_tree.rst > > create mode 100644 include/linux/maple_tree.h > > create mode 100644 include/trace/events/maple_tree.h > > create mode 100644 lib/maple_tree.c > > create mode 100644 tools/testing/radix-tree/linux/maple_tree.h > > create mode 100644 tools/testing/radix-tree/maple.c > > create mode 100644 tools/testing/radix-tree/trace/events/maple_tree.h > > > > diff --git a/Documentation/core-api/index.rst b/Documentation/core-api/index.rst > > index 5de2c7a4b1b3..c669e0abcfd6 100644 > > --- a/Documentation/core-api/index.rst > > +++ b/Documentation/core-api/index.rst > > @@ -34,6 +34,7 @@ Library functionality that is used throughout the kernel. > > kref > > assoc_array > > xarray > > + maple_tree > > idr > > circular-buffers > > rbtree > > diff --git a/Documentation/core-api/maple_tree.rst b/Documentation/core-api/maple_tree.rst > > new file mode 100644 > > index 000000000000..06c54230d985 > > --- /dev/null > > +++ b/Documentation/core-api/maple_tree.rst > > @@ -0,0 +1,196 @@ > > +.. SPDX-License-Identifier: GPL-2.0+ > > + > > + > > +========== > > +Maple Tree > > +========== > > + > > +:Author: Liam R. Howlett > > + > > +Overview > > +======== > > + > > +The Maple Tree is a B-Tree data type which is optimized for storing > > +non-overlapping ranges, including ranges of size 1. The tree was designed to > > +be simple to use and does not require a user written search method. It > > +supports iterating over a range of entries and going to the previous or next in > > entry ^ Thanks > > > +a cache-efficient manner. The tree can also be put into an RCU-safe mode of > > +operation which allows reading and writing concurrently. Writers must > > +synchronize on a lock, which can be the default spinlock, or the user can set > > +the lock to an external lock of a different type. > > + > > +The Maple Tree maintains a small memory footprint and was designed to use > > +modern processor cache efficiently. The most important user of the Maple Tree > > +is the virtual memory area. > > For me it sounds like VMA *is* the maple tree user. Maybe > > The most important usage of the Maple Tree is tracking of the virtual > memory areas. > Thanks, I can see that now. I'm not a fan of either of the ways this is written but yours is more clear. > > + > > +The Maple Tree can store between 0 and ``ULONG_MAX``. The Maple Tree reserves > > ^ values Thanks > > > +values with the bottom two bits set to '10' which are below 4096 (ie 2, 6, 10 > > +.. 4094) for internal use. If the entries may use reserved entries then the > > +users can convert the entries using xa_mk_value() and convert them back by > > Maybe > > If an entry needs to use a reserved value then the user can convert the > value using ... I'll make a change here to see if i can clarify. > > > +calling xa_to_value(). The reserved values can be used by the advanced API, > > +but are blocked by the normal API. > > I'd add a sentence about existence of "normal" and "advanced" API to the > first two paragraphs. I agree, that would be good. I'll also create :ref: to them and such as you suggest later. > > > + > > +The Maple Tree can also be configured to support searching for a gap of a given > > +size (or larger). The tree must be initialized as an allocation tree to > > +support this feature. > > I afraid it's not clear at this point what "an allocation tree" means. I > think the first sentence alone would be enough for the overview section. Okay, I will drop the last part. > > > + > > +Pre-allocating of nodes is also supported using the advanced API. This is > > +useful for users who must guarantee a successful store operation within a given > > +code segment when allocating cannot be done. Allocations of nodes are > > +relatively small at 256 bytes. > > I doubt the size here will get timely updates when the node size will > change in the code, maybe use "around" or "roughly" to be future proof? :) Good plan. > > > + > > +Normal API > > +========== > > + > > +Start by initialising a maple tree, either with DEFINE_MTREE() for statically > > +allocated maple trees or mt_init() for dynamically allocated ones. A > > +freshly-initialised maple tree contains a ``NULL`` pointer for the range 0 - > > +``ULONG_MAX``. There are currently two types of maple trees supported: the > > +allocation tree and the regular tree. The regular tree has a higher branching > > +factor for internal nodes. The allocation tree has a lower branching factor > > +but allows the user to search for a gap of a given size or larger from either 0 > > +upwards or ``ULONG_MAX`` down. An allocation tree can be used by passing in > > +the ``MAPLE_ALLOC_RANGE`` flag when initialising the tree. > > + > > +You can then set entries using mtree_store() or mtree_store_range(). > > +mtree_store will overwrite any entry with the new entry and return the previous > > ^ Did you intentionally drop brackets here? I did not. I will fix that. > > > +entry stored at that index. mtree_store_range works in the same way but only > > +returns the first entry that is overwritten. mtree_load() is used to retrieve > > kernel-doc of these functions says that they return 0 or errno. What did I > miss? I will update the documentation to match the return types of the function/kernel-doc. > > > +the entry stored at a given index. You can use mtree_erase() to erase an > > +entire range by only knowing one value within that range, or mtree_store() call > > +with an entry of NULL may be used to partially erase a range. > > + > > +If you want to only store a new entry to a range (or index) if that range is > > +currently ``NULL``, you can use mtree_insert_range() or mtree_insert() which > > +return -EEXIST if the range is not empty. > > + > > +You can search for an entry from an index upwards by using mt_find(). > > + > > +You can walk each entry within a range by calling mt_for_each(). You must > > +provide a temporary variable to store a cursor. If you want to walk each > > +element of the tree then 0 and ``ULONG_MAX`` may be used as the range. If the > > Why 0 and ULONG_MAX have different markup? I will change 0 to ``0`` where necessary, thanks. > > > +caller is going to hold the lock for the duration of the walk then it is worth > > Do you refer to the maple tree internal lock or any lock here? > > > +looking at the mas_for_each() API in the Advanced API section. > > Maybe make "Advanced API" a hyperlink. > > > + > > +Sometimes it is necessary to ensure the next call to store to a maple tree does > > +not allocate memory, please see the advanced API for this use case. > > + > > +Finally, you can remove all entries from a maple tree by calling > > +mtree_destroy(). If the maple tree entries are pointers, you may wish to free > > +the entries first. > > + > > +Allocating Nodes > > +---------------- > > + > > +When using the normal API, the allocations are handled by the internal > > +tree code. > > Since this is a part of "Normal API" description the "When using normal > API" seems redundant. I was trying to avoid people who need special allocations from disregarding the tree when they see that with a quick scan. I will add a link to the advanced api allocating of nodes instead. > > > + > > +Locking > > +------- > > + > > +When using the Normal API, you do not have to worry about locking. > > Ditto We support using an external lock and so people who see it's handled internally in the normal API may just stop reading and go look for another data structure. I will add an advanced locking section and link it here instead. > > > +The Maple Tree uses RCU and an internal spinlock to synchronise access: > > + > > +Takes RCU read lock: > > + * mtree_load() > > + * mt_find() > > + * mt_for_each() > > + * mt_next() > > + * mt_prev() > > + > > +Takes ma_lock internally: > > + * mtree_store() > > + * mtree_store_range() > > + * mtree_insert() > > + * mtree_insert_range() > > + * mtree_erase() > > + * mtree_destroy() > > + * mt_set_in_rcu() > > + * mt_clear_in_rcu() > > + > > +If you want to take advantage of the lock to protect the data structures > > I believe this is about the internal lock, it would be nice to spell this > out. Thanks. > > > +that you are storing in the Maple Tree, you can call mtree_lock() before > > +calling mtree_load(), then take a reference count on the object you have > > +found before calling mtree_unlock(). This will prevent stores from > > +removing the object from the tree between looking up the object and > > +incrementing the refcount. You can also use RCU to avoid dereferencing > > +freed memory, but an explanation of that is beyond the scope of this > > +document. > > + > > +Advanced API > > +============ > > + > > +The advanced API offers more flexibility and better performance at the > > +cost of an interface which can be harder to use and has fewer safeguards. > > +You must take care of your own locking while using the advanced API. > > +You can use the ma_lock, RCU or an external lock for protection. > > +You can mix advanced and normal operations on the same array, as long > > +as the locking is compatible. The normal API is implemented in terms > > +of the advanced API. > > + > > +The advanced API is based around the ma_state, this is where the 'mas' > > +prefix originates. The ma_state struct keeps track of tree operations to make > > +life easier for both internal and external tree users. > > + > > +Initialising the maple tree is the same as in the normal API. Please see > > +above. > > + > > +The maple state keeps track of the range start and end in mas->index and > > +mas->last, respectively. > > + > > +mas_walk() will walk the tree to the location of index and set the index > > +and last according to the range for the entry. > > ^ fields? or maybe even mas->index and mas->last? Yes, I will use mas->index/mas->last here. > > + > > +You can set entries using mas_store(). mas_store() will overwrite any entry > > +with the new entry and return the first existing entry that is overwritten. > > +The range is passed in as members of the maple state: index and last. > > + > > +You can use mas_erase() to erase an entire range by setting index and > > +last of the maple state to the desired range to erase. This will erase > > +the first range that is found in that range, set the maple state index > > +and last as the range that was erased and return the entry that existed > > +at that location. > > + > > +You can walk each entry within a range by using mas_for_each(). If you want to > > +walk each element of the tree then 0 and ``ULONG_MAX`` may be used as the > > +range. If the lock needs to be periodically dropped, see the locking section > > +mas_pause(). > > + > > +Using a maple state allows mas_next() and mas_prev() to function as if the > > +tree was a linked list. With such a high branching factor the amortized > > +performance penalty is outweighed by cache optimization. mas_next() will > > +return the next entry which occurs after the entry at index. mas_prev() > > +will return the previous entry which occurs before the entry at index. > > + > > +mas_find() will find the first entry which exists at or above index on > > +the first call, and the next entry from every subsequent calls. > > + > > +mas_find_rev() will find the fist entry which exists at or below the last on > > +the first call, and the previous entry from every subsequent calls. > > + > > +If the user needs to yield the lock during an operation, then the maple state > > +must be paused using mas_pause(). > > + > > +There are a few extra interfaces provided when using an allocation tree. > > +If you wish to search for a gap within a range, then mas_empty_area() > > +or mas_empty_area_rev() can be used. mas_empty_area searches for a > > ^ brackets? > Thanks > > +gap starting at the lowest index given up to the maximum of the range. > > +mas_empty_area_rev searches for a gap starting at the highest index > > ^ and here? Thanks > > > +given and continues downward to the lower bound of the range. > > + > > +Allocating Nodes > > +---------------- > > + > > +Allocations are usually handled internally to the tree, however if allocations > > +need to occur before a write occurs then calling mas_entry_count() will > > +allocate the worst-case number of needed nodes to insert the provided number of > > +ranges. This also causes the tree to enter mass insertion mode. Once > > +insertions are complete calling mas_destroy() on the maple state will free the > > +unused allocations. > > + > > +Functions and structures > > +======================== > > + > > +.. kernel-doc:: include/linux/maple_tree.h > > +.. kernel-doc:: lib/maple_tree.c > > + > > diff --git a/MAINTAINERS b/MAINTAINERS > > index f41088418aae..a35478a3dee3 100644 > > --- a/MAINTAINERS > > +++ b/MAINTAINERS > > @@ -11415,6 +11415,18 @@ L: linux-man@xxxxxxxxxxxxxxx > > S: Maintained > > W: http://www.kernel.org/doc/man-pages > > > > +MAPLE TREE > > +M: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> > > +L: linux-mm@xxxxxxxxx > > +S: Supported > > +F: Documentation/core-api/maple_tree.rst > > +F: include/linux/maple_tree.h > > +F: include/trace/events/maple_tree.h > > +F: lib/maple_tree.c > > +F: lib/test_maple_tree.c > > +F: tools/testing/_adix-tree/linux/maple_tree.h > > +F: tools/testing/radix-tree/maple.c > > + > > MARDUK (CREATOR CI40) DEVICE TREE SUPPORT > > M: Rahul Bedarkar <rahulbedarkar89@xxxxxxxxx> > > L: linux-mips@xxxxxxxxxxxxxxx > > diff --git a/include/linux/maple_tree.h b/include/linux/maple_tree.h > > new file mode 100644 > > index 000000000000..14ddeaa8f3e7 > > --- /dev/null > > +++ b/include/linux/maple_tree.h > > @@ -0,0 +1,673 @@ > > +/* SPDX-License-Identifier: GPL-2.0+ */ > > +#ifndef _LINUX_MAPLE_TREE_H > > +#define _LINUX_MAPLE_TREE_H > > +/* > > + * Maple Tree - An RCU-safe adaptive tree for storing ranges > > + * Copyright (c) 2018 Oracle > > 2018 - 2022? Wait, what happened in 2019-2022? Did I miss anything? > > > + * Authors: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> > > + * Matthew Wilcox <willy@xxxxxxxxxxxxx> > > + */ > > + > > +#include <linux/kernel.h> > > +#include <linux/rcupdate.h> > > +#include <linux/spinlock.h> > > +/* #define CONFIG_MAPLE_RCU_DISABLED */ > > +/* #define CONFIG_DEBUG_MAPLE_TREE_VERBOSE */ > > + > > +/* > > + * Allocated nodes are mutable until they have been inserted into the tree, > > + * at which time they cannot change their type until they have been removed > > + * from the tree and an RCU grace period has passed. > > + * > > + * Removed nodes have their ->parent set to point to themselves. RCU readers > > + * check ->parent before relying on the value that they loaded from the > > + * slots array. This lets us reuse the slots array for the RCU head. > > + * > > + * Nodes in the tree point to their parent unless bit 0 is set. > > There are a lots of comments describing the maple tree internals here and > below. Did yaou consider adding a section "Implementation details" or > something like that to the maple_tree.rst and linking these comments there > with DOC: and some glue text? I did. I actually had it in there but moved it into the code in an effort to avoid the documentation from being a developer doc. I'd like it to be a user document. I also did not want the implementation details to be too far away from the code to avoid it being missed when the code changes. > > > + */ > > +#if defined(CONFIG_64BIT) || defined(BUILD_VDSO32_64) > > +/* 64bit sizes */ > > +#define MAPLE_NODE_SLOTS 31 /* 256 bytes including ->parent */ > > +#define MAPLE_RANGE64_SLOTS 16 /* 256 bytes */ > > +#define MAPLE_ARANGE64_SLOTS 10 /* 240 bytes */ > > +#define MAPLE_ARANGE64_META_MAX 15 /* Out of range for metadata */ > > +#define MAPLE_ALLOC_SLOTS (MAPLE_NODE_SLOTS - 1) > > +#else > > +/* 32bit sizes */ > > +#define MAPLE_NODE_SLOTS 63 /* 256 bytes including ->parent */ > > +#define MAPLE_RANGE64_SLOTS 32 /* 256 bytes */ > > +#define MAPLE_ARANGE64_SLOTS 21 /* 240 bytes */ > > +#define MAPLE_ARANGE64_META_MAX 22 /* Out of range for metadata */ > > +#define MAPLE_ALLOC_SLOTS (MAPLE_NODE_SLOTS - 2) > > +#endif /* defined(CONFIG_64BIT) || defined(BUILD_VDSO32_64) */ > > + > > +#define MAPLE_NODE_MASK 255UL > > ... > > > +/** > > + * DOC: Maple tree flags > > I don't see this referenced in the Documentation/ changes It is referenced incorrectly, thanks. > > > + * > > + * * MT_FLAGS_ALLOC_RANGE - Track gaps in this tree > > + * * MT_FLAGS_USE_RCU - Operate in RCU mode > > + * * MT_FLAGS_HEIGHT_OFFSET - The position of the tree height in the flags > > + * * MT_FLAGS_HEIGHT_MASK - The mask for the maple tree height value > > + * * MT_FLAGS_LOCK_MASK - How the mt_lock is used > > + * * MT_FLAGS_LOCK_IRQ - Acquired irq-safe > > + * * MT_FLAGS_LOCK_BH - Acquired bh-safe > > + * * MT_FLAGS_LOCK_EXTERN - mt_lock is not used > > + * > > + * MAPLE_HEIGHT_MAX The largest height that can be stored > > + */ > > +#define MT_FLAGS_ALLOC_RANGE 0x01 > > +#define MT_FLAGS_USE_RCU 0x02 > > +#define MT_FLAGS_HEIGHT_OFFSET 0x02 > > +#define MT_FLAGS_HEIGHT_MASK 0x7C > > Is extra alignment here intentional? No, I will fix it. > > > +#define MT_FLAGS_LOCK_MASK 0x300 > > +#define MT_FLAGS_LOCK_IRQ 0x100 > > +#define MT_FLAGS_LOCK_BH 0x200 > > +#define MT_FLAGS_LOCK_EXTERN 0x300 > > ... > > > +/* > > + * More complicated stores can cause two nodes to become one or tree and > > ^ three? Yes, perhaps I typed my accent here :) > > > + * potentially alter the height of the tree. Either half of the tree may need > > + * to be rebalanced against the other. The ma_topiary struct is used to track > > + * which nodes have been 'cut' from the tree so that the change can be done > > + * safely at a later date. This is done to support RCU. > > + */ > > +struct ma_topiary { > > + struct maple_enode *head; > > + struct maple_enode *tail; > > + struct maple_tree *mtree; > > +}; > > ... > > > +/* Advanced API */ > > + > > +/* > > + * The maple state is defined in the struct ma_state and is used to keep track > > + * of information during operations, and even between operations when using the > > + * advanced API. > > + * > > + * If state->node has bit 0 set then it references a tree location which is not > > + * a node (eg the root). If bit 1 is set, the rest of the bits are a negative > > + * errno. Bit 2 (the 'unallocated slots' bit) is clear. Bits 3-6 indicate the > > + * node type. > > + * > > + * state->alloc either has a request number of nodes or an allocated node. If > > + * stat->alloc has a requested number of nodes, the first bit will be set (0x1) > > + * and the remaining bits are the value. If state->alloc is a node, then the > > + * node will be of type maple_alloc. maple_alloc has MAPLE_NODE_SLOTS - 1 for > > + * storing more allocated nodes, a total, and the node_count in this node. > > + * total is the number of nodes allocated. node_count is the number of > > Maybe merge "total is the number of nodes allocated" with "a total": > > ... allocated nodes, total number of nodes allocated, and the node_count... That would probably read better. Thanks. > > > + * allocated nodes in this node. The scaling beyond MAPLE_NODE_SLOTS - 1 is > > + * handled by storing further nodes into state->alloc->slot[0]'s node. Nodes > > + * are taken from state->alloc by removing a node from the state->alloc node > > + * until state->alloc->node_count is 1, when state->alloc is returned and the > > + * state->alloc->slot[0] is promoted to state->alloc. Nodes are pushed onto > > + * state->alloc by putting the current state->alloc into the pushed node's > > + * slot[0]. > > + * > > + * The state also contains the implied min/max of the state->node, the depth of > > + * this search, and the offset. The implied min/max are either from the parent > > + * node or are 0-oo for the root node. The depth is incremented or decremented > > + * every time a node is walked down or up. The offset is the slot/pivot of > > + * interest in the node - either for reading or writing. > > + * > > + * When returning a value the maple state index and last respectively contain > > + * the start and end of the range for the entry. Ranges are inclusive in the > > + * Maple Tree. > > + */ > > +struct ma_state { > > + struct maple_tree *tree; /* The tree we're operating in */ > > + unsigned long index; /* The index we're operating on - range start */ > > + unsigned long last; /* The last index we're operating on - range end */ > > + struct maple_enode *node; /* The node containing this entry */ > > + unsigned long min; /* The minimum index of this node - implied pivot min */ > > + unsigned long max; /* The maximum index of this node - implied pivot max */ > > + struct maple_alloc *alloc; /* Allocated nodes for this operation */ > > + unsigned char depth; /* depth of tree descent during write */ > > + unsigned char offset; > > + unsigned char mas_flags; > > +}; > > ... > > > +/** > > + * mt_for_each - Searches for an entry starting at index until max. > > Isn't it an iterator? Yes, thanks. Not sure how that happened. > > > + * @tree: The Maple Tree > > + * @entry: The current entry > > + * @index: The index to update to track the location in the tree > > + * @max: The maximum limit for @index > > + * > > + * Note: Will not return the zero entry. > > + */ > > +#define mt_for_each(tree, entry, index, max) \ > > + for (entry = mt_find(tree, &index, max); \ > > + entry; entry = mt_find_after(tree, &index, max)) > > + > > + > > ... > > > diff --git a/lib/maple_tree.c b/lib/maple_tree.c > > new file mode 100644 > > index 000000000000..6a57745319ba > > --- /dev/null > > +++ b/lib/maple_tree.c > > @@ -0,0 +1,6943 @@ > > +// SPDX-License-Identifier: GPL-2.0+ > > +/* > > + * Maple Tree implementation > > + * Copyright (c) 2018 Oracle Corporation > > + * Authors: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> > > + * Matthew Wilcox <willy@xxxxxxxxxxxxx> > > + */ > > + > > +/* > > + * Interesting implementation details of the Maple Tree > > DOC:? Sure. > > > + * > > + * Each node type has a number of slots for entries and a number of slots for > > + * pivots. In the case of dense nodes, the pivots are implied by the position > > + * and are simply the slot index + the minimum of the node. > > + * > > + * In regular B-Tree terms, pivots are called keys. The term pivot is used to > > + * indicate that the tree is specifying ranges, Pivots may appear in the > > + * subtree with an entry attached to the value where as keys are unique to a > > + * specific position of a B-tree. Pivot values are inclusive of the slot with > > + * the same index. > > + * > > + * > > + * The following illustrates the layout of a range64 nodes slots and pivots. > > + * > > + * > > + * Slots -> | 0 | 1 | 2 | ... | 12 | 13 | 14 | 15 | > > + * ┬ ┬ ┬ ┬ ┬ ┬ ┬ ┬ ┬ > > + * │ │ │ │ │ │ │ │ └─ Implied maximum > > + * │ │ │ │ │ │ │ └─ Pivot 14 > > + * │ │ │ │ │ │ └─ Pivot 13 > > + * │ │ │ │ │ └─ Pivot 12 > > + * │ │ │ │ └─ Pivot 11 > > + * │ │ │ └─ Pivot 2 > > + * │ │ └─ Pivot 1 > > + * │ └─ Pivot 0 > > + * └─ Implied minimum > > + * > > + * Slot contents: > > + * Internal (non-leaf) nodes contain pointers to other nodes. > > + * Leaf nodes contain entries. > > + * > > + * The location of interest is often referred to as an offset. All offsets have > > + * a slot, but the last offset has an implied pivot from the node above (or > > + * UINT_MAX for the root node. > > + * > > + * Ranges complicate certain write activities. When modifying any of > > + * the B-tree variants, it is known that one entry will either be added or > > + * deleted. When modifying the Maple Tree, one store operation may overwrite > > + * the entire data set, or one half of the tree, or the middle half of the tree. > > + * > > + */ > > ... > > > +/* Interface */ > > + > > +/** > > + * mas_store() - Store an @entry. > > + * @mas: The maple state. > > + * @entry: The entry to store. > > + * > > + * The @mas->index and @mas->last is used to set the range for the @entry. > > + * Note: The @mas should have pre-allocated entries to ensure there is memory to > > + * store the entry. Please see mas_expected_entries()/mas_destroy() for more details. > > Return: ? I will add it. > > > + */ > > +void *mas_store(struct ma_state *mas, void *entry) > > +{ > > + MA_WR_STATE(wr_mas, mas, entry); > > + > > + trace_ma_write(__func__, mas, 0, entry); > > +#ifdef CONFIG_DEBUG_MAPLE_TREE > > + if (mas->index > mas->last) > > + printk("Error %lu > %lu %p\n", mas->index, mas->last, entry); > > + MT_BUG_ON(mas->tree, mas->index > mas->last); > > + if (mas->index > mas->last) { > > + mas_set_err(mas, -EINVAL); > > + return NULL; > > + } > > + > > +#endif > > + > > +/* > > + * Storing is the same operation as insert with the added caveat that it can > > + * overwrite entries. Although this seems simple enough, one may want to > > + * examine what happens if a single store operation was to overwrite multiple > > + * entries within a self-balancing B-Tree. > > + */ > > + mas_wr_store_setup(&wr_mas); > > + mas_wr_store_entry(&wr_mas); > > + return wr_mas.content; > > +} > > ... > > > +/** > > + * mt_next() - get the next value in the maple tree > > + * @mt: The maple tree > > + * @index: The start index > > + * @max: The maximum index to check > > + * > > + * Returns: The entry at @index or higher, or %NULL if nothing is found. > > Please s/Returns/Return/ I've fixed this before too. Thanks for catching it. > > > + */ > > +void *mt_next(struct maple_tree *mt, unsigned long index, unsigned long max) > > +{ > > + void *entry = NULL; > > + MA_STATE(mas, mt, index, index); > > + > > + rcu_read_lock(); > > + entry = mas_next(&mas, max); > > + rcu_read_unlock(); > > + return entry; > > +} > > +EXPORT_SYMBOL_GPL(mt_next); > > ... > > > +/* > > kernel-doc? Thanks > > > + * mas_find: If mas->node == MAS_START, find the first > > + * non-NULL entry >= mas->index. > > + * Otherwise, find the first non-NULL entry > mas->index > > although this might render not nicely in html... I will spell it out and check the generated html. > > > + * @mas: The maple state > > + * @max: The maximum value to check. > > + * > > + * Must hold rcu_read_lock or the write lock. > > + * If an entry exists, last and index are updated accordingly. > > + * May set @mas->node to MAS_NONE. > > + * > > + * Return: The entry or %NULL. > > + */ > > +void *mas_find(struct ma_state *mas, unsigned long max) > > +{ > > + if (unlikely(mas_is_paused(mas))) { > > + if (unlikely(mas->last == ULONG_MAX)) { > > + mas->node = MAS_NONE; > > + return NULL; > > + } > > + mas->node = MAS_START; > > + mas->index = ++mas->last; > > + } > > + > > + if (unlikely(mas_is_start(mas))) { > > + /* First run or continue */ > > + void *entry; > > + > > + if (mas->index > max) > > + return NULL; > > + > > + entry = mas_walk(mas); > > + if (entry) > > + return entry; > > + } > > + > > + if (unlikely(!mas_searchable(mas))) > > + return NULL; > > + > > + /* Retries on dead nodes handled by mas_next_entry */ > > + return mas_next_entry(mas, max); > > +} > > + > > +/** > > + * mas_find: If mas->node == MAS_START, find the first > > mas_find_rev Thanks. > > > + * non-NULL entry <= mas->last. > > + * Otherwise, find the first non-NULL entry < mas->index > > So does this look Ok in html? ;-) I'll check and fix this. > > > + * @mas: The maple state > > + * @min: The minimum value to check. > > + * > > + * Must hold rcu_read_lock or the write lock. > > + * If an entry exists, last and index are updated accordingly. > > + * May set @mas->node to MAS_NONE. > > + * > > + * Return: The entry or %NULL. > > + */void *mas_find_rev(struct ma_state *mas, unsigned long min) > > +{ > > + if (unlikely(mas_is_paused(mas))) { > > + if (unlikely(mas->last == ULONG_MAX)) { > > + mas->node = MAS_NONE; > > + return NULL; > > + } > > + mas->node = MAS_START; > > + mas->last = --mas->index; > > + } > > + > > + if (unlikely(mas_is_start(mas))) { > > + /* First run or continue */ > > + void *entry; > > + > > + if (mas->index < min) > > + return NULL; > > + > > + entry = mas_walk(mas); > > + if (entry) > > + return entry; > > + } > > + > > + if (unlikely(!mas_searchable(mas))) > > + return NULL; > > + > > + /* Retries on dead nodes handled by mas_next_entry */ > > + return mas_prev_entry(mas, min); > > +} > > +EXPORT_SYMBOL_GPL(mas_find); > > + > > +/** > > + * mas_erase() - Find the range in which index resides and erase the entire > > + * range. > > + * @mas: The maple state > > + * > > + * Must hold the write lock. > > + * Searches for @mas->index, sets @mas->index and @mas->last to the range and > > + * erases that range. > > + * > > + * Return: the entry that was erased, @mas->index and @mas->last are updated. > > the entry that was erased or %NULL? Thanks, yes. > > > + */ > > +void *mas_erase(struct ma_state *mas) > > +{ > > + void *entry; > > + MA_WR_STATE(wr_mas, mas, NULL); > > + > > + if (mas_is_none(mas) || mas_is_paused(mas)) > > + mas->node = MAS_START; > > + > > + /* Retry unnecessary when holding the write lock. */ > > + entry = mas_state_walk(mas); > > + if (!entry) > > + return NULL; > > + > > +write_retry: > > + /* Must reset to ensure spanning writes of last slot are detected */ > > + mas_reset(mas); > > + mas_wr_store_setup(&wr_mas); > > + mas_wr_store_entry(&wr_mas); > > + if (mas_nomem(mas, GFP_KERNEL)) > > + goto write_retry; > > + > > + return entry; > > +} > > +EXPORT_SYMBOL_GPL(mas_erase); > > + > > +/* > > kernel-doc? There are no external users so I wasn't going to, but it won't hurt. I mean, it could be used as a widget to allocate nodes if someone is brave. > > > + * mas_nomem() - * Check if there was an error allocating and do the allocation > > ^ not needed. > > + * if necessary If there are allocations, then free them. > > ^ period? > > > + * @mas: The maple state > > + * @gfp: The GFP_FALGS to use for allocations > > Return:? Thanks, it totally does too :) > > > + */ > > +bool mas_nomem(struct ma_state *mas, gfp_t gfp) > > + __must_hold(mas->tree->lock) > > +{ > > + if (likely(mas->node != MA_ERROR(-ENOMEM))) { > > + mas_destroy(mas); > > + return false; > > + } > > + > > + if (gfpflags_allow_blocking(gfp) && !mt_external_lock(mas->tree)) { > > + mtree_unlock(mas->tree); > > + mas_alloc_nodes(mas, gfp); > > + mtree_lock(mas->tree); > > + } else { > > + mas_alloc_nodes(mas, gfp); > > + } > > + > > + if (!mas_allocated(mas)) > > + return false; > > + > > + mas->node = MAS_START; > > + return true; > > +} > > + > > +void __init maple_tree_init(void) > > +{ > > + maple_node_cache = kmem_cache_create("maple_node", > > + sizeof(struct maple_node), sizeof(struct maple_node), > > + SLAB_PANIC, NULL); > > +} > > + > > +/** > > + * mtree_load() - Load a value stored in a maple tree > > + * @mt: The maple tree > > + * @index: The index to load > > + * > > + * Return: the entry of %NULL > > ^ or? Thanks. > > + */ > > +void *mtree_load(struct maple_tree *mt, unsigned long index) > > +{ > > + MA_STATE(mas, mt, index, index); > > + void *entry; > > + > > + trace_ma_read(__func__, &mas); > > + rcu_read_lock(); > > +retry: > > + entry = mas_start(&mas); > > + if (unlikely(mas_is_none(&mas))) > > + goto unlock; > > + > > + if (unlikely(mas_is_ptr(&mas))) { > > + if (index) > > + entry = NULL; > > + > > + goto unlock; > > + } > > + > > + entry = mtree_lookup_walk(&mas); > > + if (!entry && unlikely(mas_is_start(&mas))) > > + goto retry; > > +unlock: > > + rcu_read_unlock(); > > + if (xa_is_zero(entry)) > > + return NULL; > > + > > + return entry; > > +} > > +EXPORT_SYMBOL(mtree_load); > > -- > Sincerely yours, > Mike.
