Fix mount point selection to return longest match instead of first match

src/dmvfs.c

@@ -336,17 +336,38 @@ static mount_point_t* get_mount_point_for_path(const char* path)
         return NULL;
     }
 
+    mount_point_t* best_match = NULL;
+    size_t best_match_length = 0;
+
     for(int i = 0; i < g_max_mount_points; i++)
     {
-        if(g_mount_points[i].mount_point != NULL &&
-           strncmp(path, g_mount_points[i].mount_point, strlen(g_mount_points[i].mount_point)) == 0)
+        if(g_mount_points[i].mount_point != NULL)
         {
-            return &g_mount_points[i];
+            size_t mount_point_length = strlen(g_mount_points[i].mount_point);
+            // Check if path starts with mount point and either:
+            // - The mount point is the root "/" (special case - matches all paths)
+            // - The mount point is exactly the path (path[mount_point_length] == '\0')
+            // - The next character is a path separator (path[mount_point_length] == '/')
+            // This ensures we match at path boundaries only
+            bool is_root_mount = (mount_point_length == 1 && g_mount_points[i].mount_point[0] == '/');
+            bool is_boundary_match = (path[mount_point_length] == '/' || path[mount_point_length] == '\0');
+
+            if(strncmp(path, g_mount_points[i].mount_point, mount_point_length) == 0 &&
+               (is_root_mount || is_boundary_match) &&
+               mount_point_length > best_match_length)
+            {
+                best_match = &g_mount_points[i];
+                best_match_length = mount_point_length;
+            }
         }
     }
 
-    DMOD_LOG_WARN("No mount point found for path '%s'\n", path);
-    return NULL;
+    if(best_match == NULL)
+    {
+        DMOD_LOG_WARN("No mount point found for path '%s'\n", path);
+    }
+
+    return best_match;
 }
 
 /**

tests/CMakeLists.txt

@@ -36,4 +36,10 @@ include_directories(${PROJECT_SOURCE_DIR})
 target_link_libraries(${PROJECT_NAME} dmod dmvfs dmlist)
 
 target_link_options(${PROJECT_NAME} PRIVATE -L ${DMOD_DIR}/scripts)
-target_link_options(${PROJECT_NAME} PRIVATE -T ${CMAKE_CURRENT_SOURCE_DIR}/main.ld)
+target_link_options(${PROJECT_NAME} PRIVATE -T ${CMAKE_CURRENT_SOURCE_DIR}/main.ld)
+
+# Add mount point selection test
+add_executable(mount_point_test test_mount_point_selection.c)
+target_link_libraries(mount_point_test dmod dmvfs)
+target_link_options(mount_point_test PRIVATE -L ${DMOD_DIR}/scripts)
+target_link_options(mount_point_test PRIVATE -T ${CMAKE_CURRENT_SOURCE_DIR}/main.ld)

tests/test_mount_point_selection.c

@@ -0,0 +1,239 @@
+/*
+ * Test program to verify correct mount point selection
+ * Tests the fix for: get_mount_point_for_path should return the longest matching mount point
+ */
+
+#define DMOD_ENABLE_REGISTRATION
+#include <stdio.h>
+#include <string.h>
+#include <stdbool.h>
+#include "dmod.h"
+#include "dmvfs.h"
+
+static int test_passed = 0;
+static int test_failed = 0;
+
+#define TEST_PASS(msg) do { \
+    printf("✓ PASS: %s\n", msg); \
+    test_passed++; \
+} while(0)
+
+#define TEST_FAIL(msg) do { \
+    printf("✗ FAIL: %s\n", msg); \
+    test_failed++; \
+} while(0)
+
+int main(int argc, char *argv[])
+{
+    if (argc < 3) {
+        printf("Usage: %s <fs1_module.dmf> <fs2_module.dmf>\n", argv[0]);
+        printf("This test requires two filesystem modules to test mount point selection.\n");
+        return -1;
+    }
+
+    const char* fs1_path = argv[1];
+    const char* fs2_path = argv[2];
+
+    printf("========================================\n");
+    printf("  Mount Point Selection Test\n");
+    printf("========================================\n\n");
+
+    // Load first filesystem module
+    Dmod_Context_t* context1 = Dmod_LoadFile(fs1_path);
+    if (context1 == NULL) {
+        printf("✗ Cannot load module: %s\n", fs1_path);
+        return -1;
+    }
+
+    if (!Dmod_Enable(context1, false, NULL)) {
+        printf("✗ Cannot enable module: %s\n", fs1_path);
+        Dmod_Unload(context1, false);
+        return -1;
+    }
+
+    // Load second filesystem module
+    Dmod_Context_t* context2 = Dmod_LoadFile(fs2_path);
+    if (context2 == NULL) {
+        printf("✗ Cannot load module: %s\n", fs2_path);
+        Dmod_Unload(context1, false);
+        return -1;
+    }
+
+    if (!Dmod_Enable(context2, false, NULL)) {
+        printf("✗ Cannot enable module: %s\n", fs2_path);
+        Dmod_Unload(context2, false);
+        Dmod_Unload(context1, false);
+        return -1;
+    }
+
+    const char* fs1_name = Dmod_GetName(context1);
+    const char* fs2_name = Dmod_GetName(context2);
+
+    printf("Loaded filesystems:\n");
+    printf("  FS1: %s\n", fs1_name);
+    printf("  FS2: %s\n", fs2_name);
+    printf("\n");
+
+    // Initialize DMVFS
+    if (!dmvfs_init(16, 32)) {
+        printf("✗ Cannot initialize DMVFS\n");
+        return -1;
+    }
+
+    printf("Test scenario: Mount FS1 at '/' and FS2 at '/configs'\n");
+    printf("Expected behavior: Paths under '/configs' should use FS2, not FS1\n\n");
+
+    // Mount first filesystem at root
+    if (!dmvfs_mount_fs(fs1_name, "/", NULL)) {
+        printf("✗ Cannot mount %s at /\n", fs1_name);
+        dmvfs_deinit();
+        return -1;
+    }
+    printf("✓ Mounted %s at /\n", fs1_name);
+
+    // Mount second filesystem at /configs
+    if (!dmvfs_mount_fs(fs2_name, "/configs", NULL)) {
+        printf("✗ Cannot mount %s at /configs\n", fs2_name);
+        dmvfs_unmount_fs("/");
+        dmvfs_deinit();
+        return -1;
+    }
+    printf("✓ Mounted %s at /configs\n\n", fs2_name);
+
+    printf("Running tests...\n\n");
+
+    // Test 1: Create file at /test.txt (should use FS1)
+    printf("Test 1: Create /test.txt (should use %s at /)\n", fs1_name);
+    void* fp1 = NULL;
+    int ret = dmvfs_fopen(&fp1, "/test.txt", DMFSI_O_CREAT | DMFSI_O_WRONLY, 0, 0);
+    if (ret == DMFSI_OK && fp1 != NULL) {
+        const char* data = "Root filesystem";
+        size_t written = 0;
+        dmvfs_fwrite(fp1, data, strlen(data), &written);
+        dmvfs_fclose(fp1);
+        TEST_PASS("Created file at root mount point");
+    } else {
+        TEST_FAIL("Cannot create file at root mount point");
+    }
+
+    // Test 2: Create file at /configs/app.conf (should use FS2, not FS1)
+    printf("Test 2: Create /configs/app.conf (should use %s at /configs)\n", fs2_name);
+    void* fp2 = NULL;
+    ret = dmvfs_fopen(&fp2, "/configs/app.conf", DMFSI_O_CREAT | DMFSI_O_WRONLY, 0, 0);
+    if (ret == DMFSI_OK && fp2 != NULL) {
+        const char* data = "Config filesystem";
+        size_t written = 0;
+        dmvfs_fwrite(fp2, data, strlen(data), &written);
+        dmvfs_fclose(fp2);
+        TEST_PASS("Created file at /configs mount point");
+    } else {
+        TEST_FAIL("Cannot create file at /configs mount point");
+    }
+
+    // Test 3: Read back the files to verify they're in different filesystems
+    printf("Test 3: Verify files can be read back\n");
+
+    // Read /test.txt
+    ret = dmvfs_fopen(&fp1, "/test.txt", DMFSI_O_RDONLY, 0, 0);
+    if (ret == DMFSI_OK && fp1 != NULL) {
+        char buffer[64] = {0};
+        size_t read_bytes = 0;
+        dmvfs_fread(fp1, buffer, sizeof(buffer), &read_bytes);
+        dmvfs_fclose(fp1);
+        if (strcmp(buffer, "Root filesystem") == 0) {
+            TEST_PASS("Read /test.txt successfully");
+        } else {
+            TEST_FAIL("Content mismatch in /test.txt");
+        }
+    } else {
+        TEST_FAIL("Cannot read /test.txt");
+    }
+
+    // Read /configs/app.conf
+    ret = dmvfs_fopen(&fp2, "/configs/app.conf", DMFSI_O_RDONLY, 0, 0);
+    if (ret == DMFSI_OK && fp2 != NULL) {
+        char buffer[64] = {0};
+        size_t read_bytes = 0;
+        dmvfs_fread(fp2, buffer, sizeof(buffer), &read_bytes);
+        dmvfs_fclose(fp2);
+        if (strcmp(buffer, "Config filesystem") == 0) {
+            TEST_PASS("Read /configs/app.conf successfully");
+        } else {
+            TEST_FAIL("Content mismatch in /configs/app.conf");
+        }
+    } else {
+        TEST_FAIL("Cannot read /configs/app.conf");
+    }
+
+    // Test 4: List files in both mount points
+    printf("Test 4: Directory listing verification\n");
+
+    // List root
+    void* dp = NULL;
+    ret = dmvfs_opendir(&dp, "/");
+    if (ret == DMFSI_OK && dp != NULL) {
+        printf("  Files in /:\n");
+        dmfsi_dir_entry_t entry;
+        bool found_test_txt = false;
+        while (dmvfs_readdir(dp, &entry) == DMFSI_OK) {
+            printf("    - %s\n", entry.name);
+            if (strcmp(entry.name, "test.txt") == 0) {
+                found_test_txt = true;
+            }
+        }
+        dmvfs_closedir(dp);
+        if (found_test_txt) {
+            TEST_PASS("Found test.txt in root directory");
+        } else {
+            TEST_FAIL("test.txt not found in root directory");
+        }
+    } else {
+        TEST_FAIL("Cannot list root directory");
+    }
+
+    // List /configs
+    ret = dmvfs_opendir(&dp, "/configs");
+    if (ret == DMFSI_OK && dp != NULL) {
+        printf("  Files in /configs:\n");
+        dmfsi_dir_entry_t entry;
+        bool found_app_conf = false;
+        while (dmvfs_readdir(dp, &entry) == DMFSI_OK) {
+            printf("    - %s\n", entry.name);
+            if (strcmp(entry.name, "app.conf") == 0) {
+                found_app_conf = true;
+            }
+        }
+        dmvfs_closedir(dp);
+        if (found_app_conf) {
+            TEST_PASS("Found app.conf in /configs directory");
+        } else {
+            TEST_FAIL("app.conf not found in /configs directory");
+        }
+    } else {
+        TEST_FAIL("Cannot list /configs directory");
+    }
+
+    // Cleanup
+    printf("\nCleaning up...\n");
+    dmvfs_unmount_fs("/configs");
+    dmvfs_unmount_fs("/");
+    dmvfs_deinit();
+
+    // Print summary
+    printf("\n========================================\n");
+    printf("  Test Summary\n");
+    printf("========================================\n");
+    printf("Total tests: %d\n", test_passed + test_failed);
+    printf("Passed:      %d\n", test_passed);
+    printf("Failed:      %d\n", test_failed);
+    printf("========================================\n");
+
+    if (test_failed == 0) {
+        printf("\n✓ ALL TESTS PASSED\n");
+        printf("The fix correctly selects the longest matching mount point!\n\n");
+        return 0;
+    } else {
+        printf("\n✗ SOME TESTS FAILED\n\n");
+        return 1;
+    }
+}