fix: FullyContiguous Memory Region Size Bug (#3175)

Signed-off-by: Olga Andreeva <oandreeva@nvidia.com>

lib/llm/src/block_manager/block/data/local.rs

@@ -124,7 +124,15 @@ impl<S: Storage> BlockDataViews<S> for LocalBlockData<S> {
         if self.is_fully_contiguous() {
             let mr = self.layout.memory_region(self.block_idx, 0, 0)?;
             let offset = mr.addr();
-            let size = mr.size() * self.num_layers();
+            let size = mr.size()
+                .checked_mul(self.num_layers())
+                .and_then(|intermediate| intermediate.checked_mul(self.num_outer_dims()))
+                .ok_or_else(|| {
+                    BlockError::InvalidState(format!(
+                        "Block size calculation overflow: region_size={} * layers={} * outer_dims={}",
+                        mr.size(), self.num_layers(), self.num_outer_dims()
+                    ))
+                })?;
             let storage_type = mr.storage_type();
             unsafe { view::BlockView::new(self, offset, size, storage_type) }
         } else {
@@ -138,7 +146,15 @@ impl<S: Storage> BlockDataViews<S> for LocalBlockData<S> {
         if self.is_fully_contiguous() {
             let mr = self.layout.memory_region(self.block_idx, 0, 0)?;
             let offset = mr.addr();
-            let size = mr.size() * self.num_layers();
+            let size = mr.size()
+                .checked_mul(self.num_layers())
+                .and_then(|intermediate| intermediate.checked_mul(self.num_outer_dims()))
+                .ok_or_else(|| {
+                    BlockError::InvalidState(format!(
+                        "Block size calculation overflow: region_size={} * layers={} * outer_dims={}",
+                        mr.size(), self.num_layers(), self.num_outer_dims()
+                    ))
+                })?;
             let storage_type = mr.storage_type();
             unsafe { view::BlockViewMut::new(self, offset, size, storage_type) }
         } else {

lib/llm/src/block_manager/layout.rs

@@ -325,7 +325,7 @@ impl FullyContiguousConfig {
         let outer_dim_stride_in_bytes =
             config.page_size * config.inner_dim * config.dtype_width_bytes;
         let layer_stride_in_bytes = outer_dim_stride_in_bytes * config.outer_dim;
-        let memory_region_size = layer_stride_in_bytes;
+        let memory_region_size = outer_dim_stride_in_bytes;
         let natural_block_stride = config.num_layers * layer_stride_in_bytes;
 
         let block_stride_in_bytes = if alignment > 1 {

lib/llm/src/block_manager/layout/utils.rs

 // SPDX-FileCopyrightText: Copyright (c) 2024-2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
 // SPDX-License-Identifier: Apache-2.0
 
-use crate::block_manager::layout::{BlockLayoutConfig, LayoutError};
+use crate::block_manager::layout::{BlockLayoutConfig, GenericBlockLayout, LayoutError};
 use crate::block_manager::storage::Storage;
 
 use validator::ValidationError;
 
+/// Verification result for a memory region
+#[derive(Debug, Clone)]
+#[allow(dead_code)]
+pub struct RegionVerificationResult {
+    /// Block index that was verified
+    pub block_idx: usize,
+    /// Layer index that was verified
+    pub layer_idx: usize,
+    /// Outer dimension index that was verified
+    pub outer_idx: usize,
+    /// Expected memory address for this region
+    pub expected_addr: usize,
+    /// Actual memory address for this region
+    pub actual_addr: usize,
+    /// Expected size in bytes for this region
+    pub expected_size: usize,
+    /// Actual size in bytes for this region
+    pub actual_size: usize,
+    /// Whether the addresses match
+    pub addr_matches: bool,
+    /// Whether the sizes match
+    pub size_matches: bool,
+}
+
+/// Layout verification statistics
+#[derive(Debug, Clone, Default)]
+#[allow(dead_code)]
+pub struct LayoutVerificationStats {
+    /// Total number of memory regions verified
+    pub total_regions: usize,
+    /// Number of regions with address mismatches
+    pub addr_mismatches: usize,
+    /// Number of regions with size mismatches
+    pub size_mismatches: usize,
+    /// Number of regions that passed all verifications
+    pub successful_verifications: usize,
+}
+
+#[derive(Debug)]
+#[allow(dead_code)]
+pub struct WorkerLayoutVerifier {
+    stats: LayoutVerificationStats,
+}
+
+#[allow(dead_code)]
+impl WorkerLayoutVerifier {
+    // Constructor: Start with clean slate
+    pub fn new() -> Self {
+        Self {
+            stats: LayoutVerificationStats::default(),
+        }
+    }
+
+    pub fn verify_layout_consistency<L: GenericBlockLayout>(
+        &mut self,
+        layout: &L,
+    ) -> Result<Vec<RegionVerificationResult>, LayoutError> {
+        // This is the main orchestrator method.
+        // It systematically checks every memory region in
+        // the layout to ensure consistency.
+
+        self.stats = LayoutVerificationStats::default();
+        let mut results = Vec::new();
+
+        // Iterate over all blocks, layers, and outer dimensions
+        for block_idx in 0..layout.num_blocks() {
+            for layer_idx in 0..layout.num_layers() {
+                for outer_idx in 0..layout.outer_dim() {
+                    let result =
+                        self.verify_memory_region(layout, block_idx, layer_idx, outer_idx)?;
+                    self.update_stats(&result);
+                    results.push(result);
+                }
+            }
+        }
+
+        Ok(results)
+    }
+
+    pub fn verify_memory_region<L: GenericBlockLayout>(
+        &mut self,
+        layout: &L,
+        block_idx: usize,
+        layer_idx: usize,
+        outer_idx: usize,
+    ) -> Result<RegionVerificationResult, LayoutError> {
+        let memory_region = layout.memory_region(block_idx, layer_idx, outer_idx)?;
+
+        let config = layout.config();
+        let expected_size = config.page_size * config.inner_dim * config.dtype_width_bytes;
+
+        let expected_addr = memory_region.addr();
+
+        Ok(RegionVerificationResult {
+            block_idx,
+            layer_idx,
+            outer_idx,
+            expected_addr,
+            actual_addr: memory_region.addr(),
+            expected_size,
+            actual_size: memory_region.size(),
+            addr_matches: expected_addr == memory_region.addr(),
+            size_matches: expected_size == memory_region.size(),
+        })
+    }
+
+    fn update_stats(&mut self, result: &RegionVerificationResult) {
+        self.stats.total_regions += 1;
+        if !result.addr_matches {
+            self.stats.addr_mismatches += 1;
+        }
+        if !result.size_matches {
+            self.stats.size_mismatches += 1;
+        }
+        if result.addr_matches && result.size_matches {
+            self.stats.successful_verifications += 1;
+        }
+    }
+
+    pub fn has_critical_mismatches(&self) -> bool {
+        self.stats.size_mismatches > 0
+    }
+}
+
 /// Validation function for Option<usize> to check if it's Some(power_of_2).
 pub fn validate_power_of_2(alignment: usize) -> Result<(), ValidationError> {
     if !alignment.is_power_of_two() {
@@ -87,3 +211,90 @@ pub fn validate_indices<C: BlockLayoutConfig>(
 
     Ok(())
 }
+
+#[cfg(test)]
+mod worker_verification_tests {
+    use super::*;
+    use crate::block_manager::LayoutConfig;
+    use crate::block_manager::layout::{FullyContiguous, LayerSeparate};
+    use crate::block_manager::storage::tests::{NullDeviceAllocator, NullDeviceStorage};
+
+    // Test constants (same as layout.rs tests)
+    const NUM_BLOCKS: usize = 7;
+    const NUM_LAYERS: usize = 5;
+    const OUTER_DIM: usize = 2;
+    const PAGE_SIZE: usize = 4;
+    const INNER_DIM: usize = 13;
+    const DTYPE_WIDTH_BYTES: usize = 4;
+
+    fn create_test_config() -> LayoutConfig {
+        LayoutConfig {
+            num_blocks: NUM_BLOCKS,
+            num_layers: NUM_LAYERS,
+            outer_dim: OUTER_DIM,
+            page_size: PAGE_SIZE,
+            inner_dim: INNER_DIM,
+            alignment: 1,
+            dtype_width_bytes: DTYPE_WIDTH_BYTES,
+        }
+    }
+
+    fn create_fully_contiguous_layout() -> Result<FullyContiguous<NullDeviceStorage>, LayoutError> {
+        let config = create_test_config();
+        FullyContiguous::allocate(config, &NullDeviceAllocator)
+    }
+
+    fn create_layer_separate_layout() -> Result<LayerSeparate<NullDeviceStorage>, LayoutError> {
+        let config = create_test_config();
+        LayerSeparate::allocate(config, &NullDeviceAllocator, true) // outer_contiguous = true
+    }
+
+    #[test]
+    fn test_verify_initialisation() {
+        let verifier = WorkerLayoutVerifier::new();
+
+        assert_eq!(verifier.stats.total_regions, 0);
+        assert_eq!(verifier.stats.addr_mismatches, 0);
+        assert_eq!(verifier.stats.size_mismatches, 0);
+        assert_eq!(verifier.stats.successful_verifications, 0);
+
+        assert!(!verifier.has_critical_mismatches());
+    }
+
+    #[test]
+    fn test_layer_separate_verification() {
+        let layout = create_layer_separate_layout().expect("Failed to create LayerSeparate layout");
+        let mut verifier = WorkerLayoutVerifier::new();
+        let results = verifier
+            .verify_layout_consistency(&layout)
+            .expect("Failed to verify layout");
+
+        assert_eq!(results.len(), NUM_BLOCKS * NUM_LAYERS * OUTER_DIM);
+        assert!(
+            !verifier.has_critical_mismatches(),
+            "Expected no critical mismatches but got: total={}, size_mismatches={}, successful={}",
+            verifier.stats.total_regions,
+            verifier.stats.size_mismatches,
+            verifier.stats.successful_verifications
+        );
+    }
+
+    #[test]
+    fn test_fully_contiguous_verification() {
+        let layout =
+            create_fully_contiguous_layout().expect("Failed to create FullyContiguous layout");
+        let mut verifier = WorkerLayoutVerifier::new();
+        let results = verifier
+            .verify_layout_consistency(&layout)
+            .expect("Failed to verify layout");
+        assert_eq!(results.len(), NUM_BLOCKS * NUM_LAYERS * OUTER_DIM);
+
+        assert!(
+            !verifier.has_critical_mismatches(),
+            "Expected no critical mismatches but got: total={}, size_mismatches={}, successful={}",
+            verifier.stats.total_regions,
+            verifier.stats.size_mismatches,
+            verifier.stats.successful_verifications
+        );
+    }
+}