// SPDX-License-Identifier: GPL-2.0 // Copyright (C) 2025 Google LLC. use kernel::{    page::PAGE_SIZE,    prelude::*,    rbtree::{RBTree, RBTreeNode, RBTreeNodeReservation},    seq_file::SeqFile,    seq_print,    task::Pid,}; use crate::range_alloc::{DescriptorState, FreedRange, Range}; /// Keeps track of allocations in a process' mmap.////// Each process has an mmap where the data for incoming transactions will be placed. This struct/// keeps track of allocations made in the mmap. For each allocation, we store a descriptor that/// has metadata related to the allocation. We also keep track of available free space.pub(super) struct TreeRangeAllocator<T> {    /// This collection contains descriptors for *both* ranges containing an allocation, *and* free    /// ranges between allocations. The free ranges get merged, so there are never two free ranges    /// next to each other.    tree: RBTree<usize, Descriptor<T>>,    /// Contains an entry for every free range in `self.tree`. This tree sorts the ranges by size,    /// letting us look up the smallest range whose size is at least some lower bound.    free_tree: RBTree<FreeKey, ()>,    size: usize,    free_oneway_space: usize,} impl<T> TreeRangeAllocator<T> {    pub(crate) fn from_array(        size: usize,        ranges: &mut KVec<Range<T>>,        alloc: &mut FromArrayAllocs<T>,    ) -> Self {        let mut tree = TreeRangeAllocator {            tree: RBTree::new(),            free_tree: RBTree::new(),            size,            free_oneway_space: size / 2,        };         let mut free_offset = 0;        for range in ranges.drain_all() {            let free_size = range.offset - free_offset;            if free_size > 0 {                let free_node = alloc.free_tree.pop().unwrap();                tree.free_tree                    .insert(free_node.into_node((free_size, free_offset), ()));                let tree_node = alloc.tree.pop().unwrap();                tree.tree.insert(                    tree_node.into_node(free_offset, Descriptor::new(free_offset, free_size)),                );            }            free_offset = range.endpoint();             if range.state.is_oneway() {                tree.free_oneway_space = tree.free_oneway_space.saturating_sub(range.size);            }             let free_res = alloc.free_tree.pop().unwrap();            let tree_node = alloc.tree.pop().unwrap();            let mut desc = Descriptor::new(range.offset, range.size);            desc.state = Some((range.state, free_res));            tree.tree.insert(tree_node.into_node(range.offset, desc));        }         // After the last range, we may need a free range.        if free_offset < size {            let free_size = size - free_offset;            let free_node = alloc.free_tree.pop().unwrap();            tree.free_tree                .insert(free_node.into_node((free_size, free_offset), ()));            let tree_node = alloc.tree.pop().unwrap();            tree.tree                .insert(tree_node.into_node(free_offset, Descriptor::new(free_offset, free_size)));        }         tree    }     pub(crate) fn is_empty(&self) -> bool {        let mut tree_iter = self.tree.values();        // There's always at least one range, because index zero is either the start of a free or        // allocated range.        let first_value = tree_iter.next().unwrap();        if tree_iter.next().is_some() {            // There are never two free ranges next to each other, so if there is more than one            // descriptor, then at least one of them must hold an allocated range.            return false;        }        // There is only one descriptor. Return true if it is for a free range.        first_value.state.is_none()    }     pub(crate) fn total_size(&self) -> usize {        self.size    }     pub(crate) fn free_oneway_space(&self) -> usize {        self.free_oneway_space    }     pub(crate) fn count_buffers(&self) -> usize {        self.tree            .values()            .filter(|desc| desc.state.is_some())            .count()    }     pub(crate) fn debug_print(&self, m: &SeqFile) -> Result<()> {        for desc in self.tree.values() {            let state = match &desc.state {                Some(state) => &state.0,                None => continue,            };            seq_print!(                m,                "  buffer: {} size {} pid {}",                desc.offset,                desc.size,                state.pid(),            );            if state.is_oneway() {                seq_print!(m, " oneway");            }            match state {                DescriptorState::Reserved(_res) => {                    seq_print!(m, " reserved\n");                }                DescriptorState::Allocated(_alloc) => {                    seq_print!(m, " allocated\n");                }            }        }        Ok(())    }     fn find_best_match(&mut self, size: usize) -> Option<&mut Descriptor<T>> {        let free_cursor = self.free_tree.cursor_lower_bound(&(size, 0))?;        let ((_, offset), ()) = free_cursor.current();        self.tree.get_mut(offset)    }     /// Try to reserve a new buffer, using the provided allocation if necessary.    pub(crate) fn reserve_new(        &mut self,        debug_id: usize,        size: usize,        is_oneway: bool,        pid: Pid,        alloc: ReserveNewTreeAlloc<T>,    ) -> Result<(usize, bool)> {        // Compute new value of free_oneway_space, which is set only on success.        let new_oneway_space = if is_oneway {            match self.free_oneway_space.checked_sub(size) {                Some(new_oneway_space) => new_oneway_space,                None => return Err(ENOSPC),            }        } else {            self.free_oneway_space        };         // Start detecting spammers once we have less than 20%        // of async space left (which is less than 10% of total        // buffer size).        //        // (This will short-circut, so `low_oneway_space` is        // only called when necessary.)        let oneway_spam_detected =            is_oneway && new_oneway_space < self.size / 10 && self.low_oneway_space(pid);         let (found_size, found_off, tree_node, free_tree_node) = match self.find_best_match(size) {            None => {                pr_warn!("ENOSPC from range_alloc.reserve_new - size: {}", size);                return Err(ENOSPC);            }            Some(desc) => {                let found_size = desc.size;                let found_offset = desc.offset;                 // In case we need to break up the descriptor                let new_desc = Descriptor::new(found_offset + size, found_size - size);                let (tree_node, free_tree_node, desc_node_res) = alloc.initialize(new_desc);                 desc.state = Some((                    DescriptorState::new(is_oneway, debug_id, pid),                    desc_node_res,                ));                desc.size = size;                 (found_size, found_offset, tree_node, free_tree_node)            }        };        self.free_oneway_space = new_oneway_space;        self.free_tree.remove(&(found_size, found_off));         if found_size != size {            self.tree.insert(tree_node);            self.free_tree.insert(free_tree_node);        }         Ok((found_off, oneway_spam_detected))    }     pub(crate) fn reservation_abort(&mut self, offset: usize) -> Result<FreedRange> {        let mut cursor = self.tree.cursor_lower_bound(&offset).ok_or_else(|| {            pr_warn!(                "EINVAL from range_alloc.reservation_abort - offset: {}",                offset            );            EINVAL        })?;         let (_, desc) = cursor.current_mut();         if desc.offset != offset {            pr_warn!(                "EINVAL from range_alloc.reservation_abort - offset: {}",                offset            );            return Err(EINVAL);        }         let (reservation, free_node_res) = desc.try_change_state(|state| match state {            Some((DescriptorState::Reserved(reservation), free_node_res)) => {                (None, Ok((reservation, free_node_res)))            }            None => {                pr_warn!(                    "EINVAL from range_alloc.reservation_abort - offset: {}",                    offset                );                (None, Err(EINVAL))            }            allocated => {                pr_warn!(                    "EPERM from range_alloc.reservation_abort - offset: {}",                    offset                );                (allocated, Err(EPERM))            }        })?;         let mut size = desc.size;        let mut offset = desc.offset;        let free_oneway_space_add = if reservation.is_oneway { size } else { 0 };         self.free_oneway_space += free_oneway_space_add;         let mut freed_range = FreedRange::interior_pages(offset, size);        // Compute how large the next free region needs to be to include one more page in        // the newly freed range.        let add_next_page_needed = match (offset + size) % PAGE_SIZE {            0 => usize::MAX,            unalign => PAGE_SIZE - unalign,        };        // Compute how large the previous free region needs to be to include one more page        // in the newly freed range.        let add_prev_page_needed = match offset % PAGE_SIZE {            0 => usize::MAX,            unalign => unalign,        };         // Merge next into current if next is free        let remove_next = match cursor.peek_next() {            Some((_, next)) if next.state.is_none() => {                if next.size >= add_next_page_needed {                    freed_range.end_page_idx += 1;                }                self.free_tree.remove(&(next.size, next.offset));                size += next.size;                true            }            _ => false,        };         if remove_next {            let (_, desc) = cursor.current_mut();            desc.size = size;            cursor.remove_next();        }         // Merge current into prev if prev is free        match cursor.peek_prev_mut() {            Some((_, prev)) if prev.state.is_none() => {                if prev.size >= add_prev_page_needed {                    freed_range.start_page_idx -= 1;                }                // merge previous with current, remove current                self.free_tree.remove(&(prev.size, prev.offset));                offset = prev.offset;                size += prev.size;                prev.size = size;                cursor.remove_current();            }            _ => {}        };         self.free_tree            .insert(free_node_res.into_node((size, offset), ()));         Ok(freed_range)    }     pub(crate) fn reservation_commit(&mut self, offset: usize, data: &mut Option<T>) -> Result {        let desc = self.tree.get_mut(&offset).ok_or(ENOENT)?;         desc.try_change_state(|state| match state {            Some((DescriptorState::Reserved(reservation), free_node_res)) => (                Some((                    DescriptorState::Allocated(reservation.allocate(data.take())),                    free_node_res,                )),                Ok(()),            ),            other => (other, Err(ENOENT)),        })    }     /// Takes an entry at the given offset from [`DescriptorState::Allocated`] to    /// [`DescriptorState::Reserved`].    ///    /// Returns the size of the existing entry and the data associated with it.    pub(crate) fn reserve_existing(&mut self, offset: usize) -> Result<(usize, usize, Option<T>)> {        let desc = self.tree.get_mut(&offset).ok_or_else(|| {            pr_warn!(                "ENOENT from range_alloc.reserve_existing - offset: {}",                offset            );            ENOENT        })?;         let (debug_id, data) = desc.try_change_state(|state| match state {            Some((DescriptorState::Allocated(allocation), free_node_res)) => {                let (reservation, data) = allocation.deallocate();                let debug_id = reservation.debug_id;                (                    Some((DescriptorState::Reserved(reservation), free_node_res)),                    Ok((debug_id, data)),                )            }            other => {                pr_warn!(                    "ENOENT from range_alloc.reserve_existing - offset: {}",                    offset                );                (other, Err(ENOENT))            }        })?;         Ok((desc.size, debug_id, data))    }     /// Call the provided callback at every allocated region.    ///    /// This destroys the range allocator. Used only during shutdown.    pub(crate) fn take_for_each<F: Fn(usize, usize, usize, Option<T>)>(&mut self, callback: F) {        for (_, desc) in self.tree.iter_mut() {            if let Some((DescriptorState::Allocated(allocation), _)) = &mut desc.state {                callback(                    desc.offset,                    desc.size,                    allocation.debug_id(),                    allocation.take(),                );            }        }    }     /// Find the amount and size of buffers allocated by the current caller.    ///    /// The idea is that once we cross the threshold, whoever is responsible    /// for the low async space is likely to try to send another async transaction,    /// and at some point we'll catch them in the act.  This is more efficient    /// than keeping a map per pid.    fn low_oneway_space(&self, calling_pid: Pid) -> bool {        let mut total_alloc_size = 0;        let mut num_buffers = 0;        for (_, desc) in self.tree.iter() {            if let Some((state, _)) = &desc.state {                if state.is_oneway() && state.pid() == calling_pid {                    total_alloc_size += desc.size;                    num_buffers += 1;                }            }        }         // Warn if this pid has more than 50 transactions, or more than 50% of        // async space (which is 25% of total buffer size). Oneway spam is only        // detected when the threshold is exceeded.        num_buffers > 50 || total_alloc_size > self.size / 4    }} type TreeDescriptorState<T> = (DescriptorState<T>, FreeNodeRes);struct Descriptor<T> {    size: usize,    offset: usize,    state: Option<TreeDescriptorState<T>>,} impl<T> Descriptor<T> {    fn new(offset: usize, size: usize) -> Self {        Self {            size,            offset,            state: None,        }    }     fn try_change_state<F, Data>(&mut self, f: F) -> Result<Data>    where        F: FnOnce(Option<TreeDescriptorState<T>>) -> (Option<TreeDescriptorState<T>>, Result<Data>),    {        let (new_state, result) = f(self.state.take());        self.state = new_state;        result    }} // (Descriptor.size, Descriptor.offset)type FreeKey = (usize, usize);type FreeNodeRes = RBTreeNodeReservation<FreeKey, ()>; /// An allocation for use by `reserve_new`.pub(crate) struct ReserveNewTreeAlloc<T> {    tree_node_res: RBTreeNodeReservation<usize, Descriptor<T>>,    free_tree_node_res: FreeNodeRes,    desc_node_res: FreeNodeRes,} impl<T> ReserveNewTreeAlloc<T> {    pub(crate) fn try_new() -> Result<Self> {        let tree_node_res = RBTreeNodeReservation::new(GFP_KERNEL)?;        let free_tree_node_res = RBTreeNodeReservation::new(GFP_KERNEL)?;        let desc_node_res = RBTreeNodeReservation::new(GFP_KERNEL)?;        Ok(Self {            tree_node_res,            free_tree_node_res,            desc_node_res,        })    }     fn initialize(        self,        desc: Descriptor<T>,    ) -> (        RBTreeNode<usize, Descriptor<T>>,        RBTreeNode<FreeKey, ()>,        FreeNodeRes,    ) {        let size = desc.size;        let offset = desc.offset;        (            self.tree_node_res.into_node(offset, desc),            self.free_tree_node_res.into_node((size, offset), ()),            self.desc_node_res,        )    }} /// An allocation for creating a tree from an `ArrayRangeAllocator`.pub(crate) struct FromArrayAllocs<T> {    tree: KVec<RBTreeNodeReservation<usize, Descriptor<T>>>,    free_tree: KVec<RBTreeNodeReservation<FreeKey, ()>>,} impl<T> FromArrayAllocs<T> {    pub(crate) fn try_new(len: usize) -> Result<Self> {        let num_descriptors = 2 * len + 1;         let mut tree = KVec::with_capacity(num_descriptors, GFP_KERNEL)?;        for _ in 0..num_descriptors {            tree.push(RBTreeNodeReservation::new(GFP_KERNEL)?, GFP_KERNEL)?;        }         let mut free_tree = KVec::with_capacity(num_descriptors, GFP_KERNEL)?;        for _ in 0..num_descriptors {            free_tree.push(RBTreeNodeReservation::new(GFP_KERNEL)?, GFP_KERNEL)?;        }         Ok(Self { tree, free_tree })    }}