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From: Andreas Hindborg <a.hindborg@kernel.org>
To: "Boqun Feng" <boqun.feng@gmail.com>,
	"Jens Axboe" <axboe@kernel.dk>, "Miguel Ojeda" <ojeda@kernel.org>,
	"Gary Guo" <gary@garyguo.net>,
	"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
	"Benno Lossin" <lossin@kernel.org>,
	"Alice Ryhl" <aliceryhl@google.com>,
	"Trevor Gross" <tmgross@umich.edu>,
	"Danilo Krummrich" <dakr@kernel.org>,
	"FUJITA Tomonori" <fujita.tomonori@gmail.com>,
	"Frederic Weisbecker" <frederic@kernel.org>,
	"Lyude Paul" <lyude@redhat.com>,
	"Thomas Gleixner" <tglx@kernel.org>,
	"Anna-Maria Behnsen" <anna-maria@linutronix.de>,
	"John Stultz" <jstultz@google.com>,
	"Stephen Boyd" <sboyd@kernel.org>,
	"Lorenzo Stoakes" <lorenzo.stoakes@oracle.com>,
	"Liam R. Howlett" <Liam.Howlett@oracle.com>
Cc: linux-block@vger.kernel.org, rust-for-linux@vger.kernel.org,
	 linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	 Andreas Hindborg <a.hindborg@kernel.org>
Subject: [PATCH 13/79] block: rnull: add memory backing
Date: Mon, 16 Feb 2026 00:35:00 +0100	[thread overview]
Message-ID: <20260216-rnull-v6-19-rc5-send-v1-13-de9a7af4b469@kernel.org> (raw)
In-Reply-To: <20260216-rnull-v6-19-rc5-send-v1-0-de9a7af4b469@kernel.org>

Add memory backing to the rust null block driver. This implementation will
always allocate a page on write, even though a page backing the written
sector is already allocated, in which case the page will be released again.
A later patch will fix this inefficiency.

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 drivers/block/rnull/configfs.rs |  37 +++++++++++-
 drivers/block/rnull/rnull.rs    | 125 ++++++++++++++++++++++++++++++++++------
 2 files changed, 144 insertions(+), 18 deletions(-)

diff --git a/drivers/block/rnull/configfs.rs b/drivers/block/rnull/configfs.rs
index 7952f41f42bfd..b5dc30c5d3e20 100644
--- a/drivers/block/rnull/configfs.rs
+++ b/drivers/block/rnull/configfs.rs
@@ -59,7 +59,7 @@ impl AttributeOperations<0> for Config {
 
     fn show(_this: &Config, page: &mut [u8; PAGE_SIZE]) -> Result<usize> {
         let mut writer = kernel::str::Formatter::new(page);
-        writer.write_str("blocksize,size,rotational,irqmode,completion_nsec\n")?;
+        writer.write_str("blocksize,size,rotational,irqmode,completion_nsec,memory_backed\n")?;
         Ok(writer.bytes_written())
     }
 }
@@ -83,6 +83,7 @@ fn make_group(
                 size: 3,
                 irqmode: 4,
                 completion_nsec: 5,
+                memory_backed: 6,
             ],
         };
 
@@ -100,6 +101,7 @@ fn make_group(
                     irq_mode: IRQMode::None,
                     completion_time: time::Delta::ZERO,
                     name: name.try_into()?,
+                    memory_backed: false,
                 }),
             }),
             core::iter::empty(),
@@ -154,6 +156,7 @@ struct DeviceConfigInner {
     irq_mode: IRQMode,
     completion_time: time::Delta,
     disk: Option<GenDisk<NullBlkDevice>>,
+    memory_backed: bool,
 }
 
 #[vtable]
@@ -184,6 +187,7 @@ fn store(this: &DeviceConfig, page: &[u8]) -> Result {
                 guard.capacity_mib,
                 guard.irq_mode,
                 guard.completion_time,
+                guard.memory_backed,
             )?);
             guard.powered = true;
         } else if guard.powered && !power_op {
@@ -209,3 +213,34 @@ fn from_str(s: &str) -> Result<Self> {
         value.try_into()
     }
 }
+
+#[vtable]
+impl configfs::AttributeOperations<6> for DeviceConfig {
+    type Data = DeviceConfig;
+
+    fn show(this: &DeviceConfig, page: &mut [u8; PAGE_SIZE]) -> Result<usize> {
+        let mut writer = kernel::str::Formatter::new(page);
+
+        if this.data.lock().memory_backed {
+            writer.write_fmt(fmt!("1\n"))?;
+        } else {
+            writer.write_fmt(fmt!("0\n"))?;
+        }
+
+        Ok(writer.bytes_written())
+    }
+
+    fn store(this: &DeviceConfig, page: &[u8]) -> Result {
+        if this.data.lock().powered {
+            return Err(EBUSY);
+        }
+
+        this.data.lock().memory_backed = core::str::from_utf8(page)?
+            .trim()
+            .parse::<u8>()
+            .map_err(|_| kernel::error::code::EINVAL)?
+            != 0;
+
+        Ok(())
+    }
+}
diff --git a/drivers/block/rnull/rnull.rs b/drivers/block/rnull/rnull.rs
index 33c1144550a0e..a1156a368c467 100644
--- a/drivers/block/rnull/rnull.rs
+++ b/drivers/block/rnull/rnull.rs
@@ -6,8 +6,10 @@
 
 use configfs::IRQMode;
 use kernel::{
+    bindings,
     block::{
         self,
+        bio::Segment,
         mq::{
             self,
             gen_disk::{
@@ -19,15 +21,12 @@
         },
     },
     error::Result,
-    new_mutex,
+    new_mutex, new_xarray,
+    page::SafePage,
     pr_info,
     prelude::*,
     str::CString,
-    sync::{
-        aref::ARef,
-        Arc,
-        Mutex, //
-    },
+    sync::{aref::ARef, Arc, Mutex},
     time::{
         hrtimer::{
             HrTimerCallback,
@@ -40,7 +39,8 @@
     types::{
         OwnableRefCounted,
         Owned, //
-    }, //
+    },
+    xarray::XArray,
 };
 use pin_init::PinInit;
 
@@ -76,6 +76,10 @@
             default: 10_000,
             description:  "Time in ns to complete a request in hardware. Default: 10,000ns",
         },
+        memory_backed: u8 {
+            default: 0,
+            description: "Create a memory-backed block device. 0-false, 1-true. Default: 0",
+        },
     },
 }
 
@@ -105,6 +109,7 @@ fn init(_module: &'static ThisModule) -> impl PinInit<Self, Error> {
                     *module_parameters::gb.value() * 1024,
                     (*module_parameters::irqmode.value()).try_into()?,
                     Delta::from_nanos(completion_time),
+                    *module_parameters::memory_backed.value() != 0,
                 )?;
                 disks.push(disk, GFP_KERNEL)?;
             }
@@ -129,17 +134,23 @@ fn new(
         capacity_mib: u64,
         irq_mode: IRQMode,
         completion_time: Delta,
+        memory_backed: bool,
     ) -> Result<GenDisk<Self>> {
-        let tagset = Arc::pin_init(
-            TagSet::new(1, 256, 1, mq::tag_set::Flags::default()),
-            GFP_KERNEL,
-        )?;
+        let flags = if memory_backed {
+            mq::tag_set::Flag::Blocking.into()
+        } else {
+            mq::tag_set::Flags::default()
+        };
+
+        let tagset = Arc::pin_init(TagSet::new(1, 256, 1, flags), GFP_KERNEL)?;
 
-        let queue_data = Box::new(
-            QueueData {
+        let queue_data = Box::pin_init(
+            pin_init!(QueueData {
+                tree <- new_xarray!(kernel::xarray::AllocKind::Alloc),
                 irq_mode,
                 completion_time,
-            },
+                memory_backed,
+            }),
             GFP_KERNEL,
         )?;
 
@@ -150,11 +161,72 @@ fn new(
             .rotational(rotational)
             .build(fmt!("{}", name.to_str()?), tagset, queue_data)
     }
+
+    #[inline(always)]
+    fn write(tree: &Tree, mut sector: usize, mut segment: Segment<'_>) -> Result {
+        while !segment.is_empty() {
+            let page = SafePage::alloc_page(GFP_NOIO)?;
+            let mut tree = tree.lock();
+
+            let page_idx = sector >> block::PAGE_SECTORS_SHIFT;
+
+            let page = if let Some(page) = tree.get_mut(page_idx) {
+                page
+            } else {
+                tree.store(page_idx, page, GFP_NOIO)?;
+                tree.get_mut(page_idx).unwrap()
+            };
+
+            let page_offset = (sector & block::SECTOR_MASK as usize) << block::SECTOR_SHIFT;
+            sector += segment.copy_to_page(page, page_offset) >> block::SECTOR_SHIFT;
+        }
+        Ok(())
+    }
+
+    #[inline(always)]
+    fn read(tree: &Tree, mut sector: usize, mut segment: Segment<'_>) -> Result {
+        let tree = tree.lock();
+
+        while !segment.is_empty() {
+            let idx = sector >> block::PAGE_SECTORS_SHIFT;
+
+            if let Some(page) = tree.get(idx) {
+                let page_offset = (sector & block::SECTOR_MASK as usize) << block::SECTOR_SHIFT;
+                sector += segment.copy_from_page(page, page_offset) >> block::SECTOR_SHIFT;
+            } else {
+                sector += segment.zero_page() >> block::SECTOR_SHIFT;
+            }
+        }
+
+        Ok(())
+    }
+
+    #[inline(never)]
+    fn transfer(
+        command: bindings::req_op,
+        tree: &Tree,
+        sector: usize,
+        segment: Segment<'_>,
+    ) -> Result {
+        match command {
+            bindings::req_op_REQ_OP_WRITE => Self::write(tree, sector, segment)?,
+            bindings::req_op_REQ_OP_READ => Self::read(tree, sector, segment)?,
+            _ => (),
+        }
+        Ok(())
+    }
 }
 
+type TreeNode = Owned<SafePage>;
+type Tree = XArray<TreeNode>;
+
+#[pin_data]
 struct QueueData {
+    #[pin]
+    tree: Tree,
     irq_mode: IRQMode,
     completion_time: Delta,
+    memory_backed: bool,
 }
 
 #[pin_data]
@@ -184,7 +256,7 @@ impl HasHrTimer<Self> for Pdu {
 
 #[vtable]
 impl Operations for NullBlkDevice {
-    type QueueData = KBox<QueueData>;
+    type QueueData = Pin<KBox<QueueData>>;
     type RequestData = Pdu;
 
     fn new_request_data() -> impl PinInit<Self::RequestData> {
@@ -194,7 +266,26 @@ fn new_request_data() -> impl PinInit<Self::RequestData> {
     }
 
     #[inline(always)]
-    fn queue_rq(queue_data: &QueueData, rq: Owned<mq::Request<Self>>, _is_last: bool) -> Result {
+    fn queue_rq(
+        queue_data: Pin<&QueueData>,
+        mut rq: Owned<mq::Request<Self>>,
+        _is_last: bool,
+    ) -> Result {
+        if queue_data.memory_backed {
+            let tree = &queue_data.tree;
+            let command = rq.command();
+            let mut sector = rq.sector();
+
+            for bio in rq.bio_iter_mut() {
+                let segment_iter = bio.segment_iter();
+                for segment in segment_iter {
+                    let length = segment.len();
+                    Self::transfer(command, tree, sector, segment)?;
+                    sector += length as usize >> block::SECTOR_SHIFT;
+                }
+            }
+        }
+
         match queue_data.irq_mode {
             IRQMode::None => rq.end_ok(),
             IRQMode::Soft => mq::Request::complete(rq.into()),
@@ -207,7 +298,7 @@ fn queue_rq(queue_data: &QueueData, rq: Owned<mq::Request<Self>>, _is_last: bool
         Ok(())
     }
 
-    fn commit_rqs(_queue_data: &QueueData) {}
+    fn commit_rqs(_queue_data: Pin<&QueueData>) {}
 
     fn complete(rq: ARef<mq::Request<Self>>) {
         OwnableRefCounted::try_from_shared(rq)

-- 
2.51.2




  parent reply	other threads:[~2026-02-16  4:15 UTC|newest]

Thread overview: 82+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-02-15 23:34 [PATCH 00/79] block: rnull: complete the rust null block driver Andreas Hindborg
2026-02-15 23:34 ` [PATCH 01/79] block: rnull: adopt new formatting guidelines Andreas Hindborg
2026-02-15 23:34 ` [PATCH 02/79] block: rnull: add module parameters Andreas Hindborg
2026-02-15 23:34 ` [PATCH 03/79] block: rnull: add macros to define configfs attributes Andreas Hindborg
2026-02-15 23:34 ` [PATCH 04/79] block: rust: fix generation of bindings to `BLK_STS_.*` Andreas Hindborg
2026-02-15 23:34 ` [PATCH 05/79] block: rust: change `queue_rq` request type to `Owned` Andreas Hindborg
2026-02-15 23:34 ` [PATCH 06/79] block: rust: add `Request` private data support Andreas Hindborg
2026-02-15 23:34 ` [PATCH 07/79] block: rust: allow `hrtimer::Timer` in `RequestData` Andreas Hindborg
2026-02-15 23:34 ` [PATCH 08/79] block: rnull: add timer completion mode Andreas Hindborg
2026-02-15 23:34 ` [PATCH 09/79] block: rust: introduce `kernel::block::bio` module Andreas Hindborg
2026-02-15 23:34 ` [PATCH 10/79] block: rust: add `command` getter to `Request` Andreas Hindborg
2026-02-15 23:34 ` [PATCH 11/79] block: rust: mq: use GFP_KERNEL from prelude Andreas Hindborg
2026-02-15 23:34 ` [PATCH 12/79] block: rust: add `TagSet` flags Andreas Hindborg
2026-02-15 23:35 ` Andreas Hindborg [this message]
2026-02-15 23:35 ` [PATCH 14/79] block: rnull: add submit queue count config option Andreas Hindborg
2026-02-15 23:35 ` [PATCH 15/79] block: rnull: add `use_per_node_hctx` " Andreas Hindborg
2026-02-15 23:35 ` [PATCH 16/79] block: rust: allow specifying home node when constructing `TagSet` Andreas Hindborg
2026-02-15 23:35 ` [PATCH 17/79] block: rnull: allow specifying the home numa node Andreas Hindborg
2026-02-15 23:35 ` [PATCH 18/79] block: rust: add Request::sectors() method Andreas Hindborg
2026-02-15 23:35 ` [PATCH 19/79] block: rust: mq: add max_hw_discard_sectors support to GenDiskBuilder Andreas Hindborg
2026-02-15 23:35 ` [PATCH 20/79] block: rnull: add discard support Andreas Hindborg
2026-02-15 23:35 ` [PATCH 21/79] block: rust: add `NoDefaultScheduler` flag for `TagSet` Andreas Hindborg
2026-02-15 23:35 ` [PATCH 22/79] block: rnull: add no_sched module parameter and configfs attribute Andreas Hindborg
2026-02-15 23:35 ` [PATCH 23/79] block: rust: change sector type from usize to u64 Andreas Hindborg
2026-02-15 23:35 ` [PATCH 24/79] block: rust: add `BadBlocks` for bad block tracking Andreas Hindborg
2026-02-15 23:35 ` [PATCH 25/79] block: rust: mq: add Request::end() method for custom status codes Andreas Hindborg
2026-02-15 23:35 ` [PATCH 26/79] block: rnull: add badblocks support Andreas Hindborg
2026-02-15 23:35 ` [PATCH 27/79] block: rnull: add badblocks_once support Andreas Hindborg
2026-02-15 23:35 ` [PATCH 28/79] block: rnull: add partial I/O support for bad blocks Andreas Hindborg
2026-02-15 23:35 ` [PATCH 29/79] block: rust: add `TagSet` private data support Andreas Hindborg
2026-02-15 23:35 ` [PATCH 30/79] block: rust: add `hctx` " Andreas Hindborg
2026-02-15 23:35 ` [PATCH 31/79] block: rnull: add volatile cache emulation Andreas Hindborg
2026-02-15 23:35 ` [PATCH 32/79] block: rust: implement `Sync` for `GenDisk` Andreas Hindborg
2026-02-15 23:35 ` [PATCH 33/79] block: rust: add a back reference feature to `GenDisk` Andreas Hindborg
2026-02-15 23:35 ` [PATCH 34/79] block: rust: introduce an idle type state for `Request` Andreas Hindborg
2026-02-15 23:35 ` [PATCH 35/79] block: rust: add a request queue abstraction Andreas Hindborg
2026-02-15 23:35 ` [PATCH 36/79] block: rust: add a method to get the request queue for a request Andreas Hindborg
2026-02-15 23:35 ` [PATCH 37/79] block: rust: introduce `kernel::block::error` Andreas Hindborg
2026-02-15 23:35 ` [PATCH 38/79] block: rust: require `queue_rq` to return a `BlkResult` Andreas Hindborg
2026-02-15 23:35 ` [PATCH 39/79] block: rust: add `GenDisk::queue_data` Andreas Hindborg
2026-02-15 23:35 ` [PATCH 40/79] block: rnull: add bandwidth limiting Andreas Hindborg
2026-02-15 23:35 ` [PATCH 41/79] block: rnull: add blocking queue mode Andreas Hindborg
2026-02-15 23:35 ` [PATCH 42/79] block: rnull: add shared tags Andreas Hindborg
2026-02-15 23:35 ` [PATCH 43/79] block: rnull: add queue depth config option Andreas Hindborg
2026-02-15 23:35 ` [PATCH 44/79] block: rust: add an abstraction for `bindings::req_op` Andreas Hindborg
2026-02-15 23:35 ` [PATCH 45/79] block: rust: add a method to set the target sector of a request Andreas Hindborg
2026-02-15 23:35 ` [PATCH 46/79] block: rust: move gendisk vtable construction to separate function Andreas Hindborg
2026-02-15 23:35 ` [PATCH 47/79] block: rust: add zoned block device support Andreas Hindborg
2026-02-15 23:35 ` [PATCH 48/79] block: rnull: add zoned storage support Andreas Hindborg
2026-02-15 23:35 ` [PATCH 49/79] block: rust: add `map_queues` support Andreas Hindborg
2026-02-15 23:35 ` [PATCH 50/79] block: rust: add an abstraction for `struct blk_mq_queue_map` Andreas Hindborg
2026-02-15 23:35 ` [PATCH 51/79] block: rust: add polled completion support Andreas Hindborg
2026-02-15 23:35 ` [PATCH 52/79] block: rust: add accessors to `TagSet` Andreas Hindborg
2026-02-15 23:35 ` [PATCH 53/79] block: rnull: add polled completion support Andreas Hindborg
2026-02-15 23:35 ` [PATCH 54/79] block: rnull: add REQ_OP_FLUSH support Andreas Hindborg
2026-02-15 23:35 ` [PATCH 55/79] block: rust: add request flags abstraction Andreas Hindborg
2026-02-15 23:35 ` [PATCH 56/79] block: rust: add abstraction for block queue feature flags Andreas Hindborg
2026-02-15 23:35 ` [PATCH 57/79] block: rust: allow setting write cache and FUA flags for `GenDisk` Andreas Hindborg
2026-02-15 23:35 ` [PATCH 58/79] block: rust: add `Segment::copy_to_page_limit` Andreas Hindborg
2026-02-15 23:35 ` [PATCH 59/79] block: rnull: add fua support Andreas Hindborg
2026-02-15 23:35 ` [PATCH 60/79] block: fix arg type in `blk_mq_update_nr_hw_queues` Andreas Hindborg
2026-02-15 23:35 ` [PATCH 61/79] block: rust: add `GenDisk::tag_set` Andreas Hindborg
2026-02-15 23:35 ` [PATCH 62/79] block: rust: add `TagSet::update_hw_queue_count` Andreas Hindborg
2026-02-16 23:59   ` Ken Kurematsu
2026-02-17  9:54     ` Andreas Hindborg
2026-02-15 23:35 ` [PATCH 63/79] block: rnull: add an option to change the number of hardware queues Andreas Hindborg
2026-02-15 23:35 ` [PATCH 64/79] block: rust: add an abstraction for `struct rq_list` Andreas Hindborg
2026-02-15 23:35 ` [PATCH 65/79] block: rust: add `queue_rqs` vtable hook Andreas Hindborg
2026-02-15 23:35 ` [PATCH 66/79] block: rnull: support queue_rqs Andreas Hindborg
2026-02-15 23:35 ` [PATCH 67/79] block: rust: remove the `is_poll` parameter from `queue_rq` Andreas Hindborg
2026-02-15 23:35 ` [PATCH 68/79] block: rust: add a debug assert for refcounts Andreas Hindborg
2026-02-15 23:35 ` [PATCH 69/79] block: rust: add `TagSet::tag_to_rq` Andreas Hindborg
2026-02-15 23:35 ` [PATCH 70/79] block: rust: add `Request::queue_index` Andreas Hindborg
2026-02-15 23:35 ` [PATCH 71/79] block: rust: add `Request::requeue` Andreas Hindborg
2026-02-15 23:35 ` [PATCH 72/79] block: rust: add `request_timeout` hook Andreas Hindborg
2026-02-15 23:36 ` [PATCH 73/79] block: rnull: add fault injection support Andreas Hindborg
2026-02-15 23:36 ` [PATCH 74/79] block: rust: add max_sectors option to `GenDiskBuilder` Andreas Hindborg
2026-02-15 23:36 ` [PATCH 75/79] block: rnull: allow configuration of the maximum IO size Andreas Hindborg
2026-02-15 23:36 ` [PATCH 76/79] block: rust: add `virt_boundary_mask` option to `GenDiskBuilder` Andreas Hindborg
2026-02-15 23:36 ` [PATCH 77/79] block: rnull: add `virt_boundary` option Andreas Hindborg
2026-02-15 23:36 ` [PATCH 78/79] block: rnull: add `shared_tag_bitmap` config option Andreas Hindborg
2026-02-15 23:36 ` [PATCH 79/79] block: rnull: add zone offline and readonly configfs files Andreas Hindborg

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