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WIP: Pin fmap grants that are borrowed too.

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This might not be the most ideal solution, since a GiB grant can be
EBUSY blocked if a single page is used by an indefinitely-blocking
UserScheme. But, the alternatives would impose lots of additional
complexity, such as increasing the PageInfo size, adding more
refcounting arrays to grants, etc.
This commit is contained in:
4lDO2
2023-07-17 15:17:55 +02:00
parent e054a5b211
commit 2660c3e07a
3 changed files with 55 additions and 16 deletions
Download Patch File Download Diff File Expand all files Collapse all files
rmm
+1 -1
Submodule rmm updated: d9d892261e...8e22e69c94
src/context/memory.rs
+53 -14
View File
@@ -482,6 +482,20 @@ impl UserGrants {
.take_while(move |(base, info)| PageSpan::new(**base, info.page_count).intersects(span))
.map(|(base, info)| (*base, info))
}
// TODO: DEDUPLICATE CODE!
pub fn conflicts_mut(&mut self, span: PageSpan) -> impl Iterator<Item = (Page, &'_ mut GrantInfo)> + '_ {
let start = self.contains(span.base);
// If there is a grant that contains the base page, start searching at the base of that
// grant, rather than the requested base here.
let start_span = start.map(|(base, info)| PageSpan::new(base, info.page_count)).unwrap_or(span);
self
.inner
.range_mut(start_span.base..)
.take_while(move |(base, info)| PageSpan::new(**base, info.page_count).intersects(span))
.map(|(base, info)| (*base, info))
}
/// Return a free region with the specified size
// TODO: Alignment (x86_64: 4 KiB, 2 MiB, or 1 GiB).
// TODO: Support finding grant close to a requested address?
@@ -655,7 +669,7 @@ pub enum Provider {
/// Since the address space is not tracked here, all nonpresent pages must be present before
/// the fmap operation completes, unless MAP_LAZY is specified. They are tracked using
/// PageInfo, or treated as PhysBorrowed if any frame lacks a PageInfo.
FmapBorrowed { file_ref: GrantFileRef },
FmapBorrowed { file_ref: GrantFileRef, pin_refcount: usize },
}
#[derive(Debug)]
@@ -828,7 +842,7 @@ impl Grant {
page_count: span.count,
mapped: true,
flags: new_flags,
provider: Provider::FmapBorrowed { file_ref },
provider: Provider::FmapBorrowed { file_ref, pin_refcount: 0 },
}
})
}
@@ -839,7 +853,7 @@ impl Grant {
/// pages that are unmaped or moved will not be made visible to the destination address space.
pub fn borrow(
src_address_space_lock: Arc<RwLock<AddrSpace>>,
src_address_space: &AddrSpace,
src_address_space: &mut AddrSpace,
src_base: Page,
dst_base: Page,
page_count: usize,
@@ -861,7 +875,11 @@ impl Grant {
let src_span = PageSpan::new(src_base, page_count);
let mut prev_span = None;
for (src_grant_base, src_grant) in src_address_space.grants.conflicts(src_span) {
for (src_grant_base, src_grant) in src_address_space.grants.conflicts_mut(src_span) {
if let Provider::FmapBorrowed { ref mut pin_refcount, .. } = src_grant.provider {
*pin_refcount += 1;
}
let grant_span = PageSpan::new(src_grant_base, src_grant.page_count);
let prev_span = prev_span.replace(grant_span);
@@ -1030,6 +1048,20 @@ impl Grant {
#[must_use = "will not unmap itself"]
pub fn unmap(mut self, mapper: &mut PageMapper, mut flusher: impl Flusher<RmmA>) -> UnmapResult {
assert!(self.info.mapped);
assert!(!self.info.is_pinned());
if let Provider::External { ref address_space, src_base, .. } = self.info.provider {
let mut guard = address_space.write();
for (_, grant) in guard.grants.conflicts_mut(PageSpan::new(src_base, self.info.page_count)) {
match grant.provider {
Provider::FmapBorrowed { ref mut pin_refcount, .. } => *pin_refcount = pin_refcount.checked_sub(1).expect("fmap pinning code is wrong"),
_ => continue,
}
}
// TODO: Verify deadlock immunity
}
for page in self.span().pages() {
// Lazy mappings do not need to be unmapped.
@@ -1070,7 +1102,7 @@ impl Grant {
size: self.info.page_count * PAGE_SIZE,
file_desc: match provider {
Provider::Allocated { cow_file_ref } => cow_file_ref,
Provider::FmapBorrowed { file_ref } => Some(file_ref),
Provider::FmapBorrowed { file_ref, .. } => Some(file_ref),
_ => None,
}
}
@@ -1112,7 +1144,7 @@ impl Grant {
Provider::Allocated { ref cow_file_ref } => Provider::Allocated { cow_file_ref: cow_file_ref.clone() },
Provider::AllocatedShared { .. } => Provider::AllocatedShared { is_pinned_userscheme_borrow: false },
Provider::PhysBorrowed { base } => Provider::PhysBorrowed { base: base.clone() },
Provider::FmapBorrowed { ref file_ref } => Provider::FmapBorrowed { file_ref: file_ref.clone() }
Provider::FmapBorrowed { ref file_ref, .. } => Provider::FmapBorrowed { file_ref: file_ref.clone(), pin_refcount: 0 },
}
},
});
@@ -1121,7 +1153,7 @@ impl Grant {
match self.info.provider {
Provider::PhysBorrowed { ref mut base } => *base = base.next_by(middle_page_offset),
Provider::FmapBorrowed { ref mut file_ref } | Provider::Allocated { cow_file_ref: Some(ref mut file_ref) } => file_ref.base_offset += middle_page_offset * PAGE_SIZE,
Provider::FmapBorrowed { ref mut file_ref, .. } | Provider::Allocated { cow_file_ref: Some(ref mut file_ref) } => file_ref.base_offset += middle_page_offset * PAGE_SIZE,
Provider::Allocated { cow_file_ref: None } | Provider::AllocatedShared { .. } | Provider::External { .. } => (),
}
@@ -1146,10 +1178,13 @@ impl Grant {
},
Provider::PhysBorrowed { base } => Provider::PhysBorrowed { base: base.next_by(this_span.count) },
Provider::FmapBorrowed { ref file_ref } => Provider::FmapBorrowed { file_ref: GrantFileRef {
base_offset: file_ref.base_offset + this_span.count * PAGE_SIZE,
description: Arc::clone(&file_ref.description),
}},
Provider::FmapBorrowed { ref file_ref, .. } => Provider::FmapBorrowed {
file_ref: GrantFileRef {
base_offset: file_ref.base_offset + this_span.count * PAGE_SIZE,
description: Arc::clone(&file_ref.description),
},
pin_refcount: 0,
},
}
},
});
@@ -1162,7 +1197,11 @@ impl Grant {
}
impl GrantInfo {
pub fn is_pinned(&self) -> bool {
matches!(self.provider, Provider::External { is_pinned_userscheme_borrow: true, .. } | Provider::AllocatedShared { is_pinned_userscheme_borrow: true, .. })
matches!(self.provider,
Provider::External { is_pinned_userscheme_borrow: true, .. }
| Provider::AllocatedShared { is_pinned_userscheme_borrow: true, .. }
| Provider::FmapBorrowed { pin_refcount: 1.., .. }
)
}
pub fn unpin(&mut self) {
if let Provider::External { ref mut is_pinned_userscheme_borrow, .. } | Provider::AllocatedShared { ref mut is_pinned_userscheme_borrow, .. } = self.provider {
@@ -1236,7 +1275,7 @@ impl GrantInfo {
pub fn file_ref(&self) -> Option<&GrantFileRef> {
// TODO: This would be bad for PhysBorrowed head/tail buffers, but otherwise the physical
// base address could be included in offset, for PhysBorrowed.
if let Provider::FmapBorrowed { ref file_ref } | Provider::Allocated { cow_file_ref: Some(ref file_ref) } = self.provider {
if let Provider::FmapBorrowed { ref file_ref, .. } | Provider::Allocated { cow_file_ref: Some(ref file_ref) } = self.provider {
Some(file_ref)
} else {
None
@@ -1588,7 +1627,7 @@ fn correct_inner<'l>(addr_space_lock: &'l Arc<RwLock<AddrSpace>>, mut addr_space
}
// TODO: NonfatalInternalError if !MAP_LAZY and this page fault occurs.
Provider::FmapBorrowed { ref file_ref } => {
Provider::FmapBorrowed { ref file_ref, .. } => {
let file_ref = file_ref.clone();
let flags = map_flags(grant_info.flags());
drop(addr_space_guard);
src/scheme/proc.rs
+1 -1
View File
@@ -694,7 +694,7 @@ impl KernelScheme for ProcScheme {
let result_base = if consume {
AddrSpace::r#move(&mut *dst_addr_space, &mut *src_addr_space, src_span, requested_dst_base, map.flags, &mut notify_files)?
} else {
dst_addr_space.mmap(requested_dst_base, src_page_count, map.flags, &mut notify_files, |dst_page, flags, dst_mapper, flusher| Ok(Grant::borrow(Arc::clone(addrspace), &*src_addr_space, src_span.base, dst_page, src_span.count, flags, dst_mapper, flusher, true, true, false)?))?
dst_addr_space.mmap(requested_dst_base, src_page_count, map.flags, &mut notify_files, |dst_page, flags, dst_mapper, flusher| Ok(Grant::borrow(Arc::clone(addrspace), &mut *src_addr_space, src_span.base, dst_page, src_span.count, flags, dst_mapper, flusher, true, true, false)?))?
};
handle_notify_files(notify_files);