Chapter 4 - I/O scheduling

chp4/blocks.c

@@ -0,0 +1,87 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/ioctl.h>
+#include <linux/fs.h>
+
+/* get_block - for the file associated with the given fd, returns
+ * the physical block mapping to logical_block
+ */
+int get_block(int fd, int logical_block);
+
+/* get_nr_blocks - returns the number of logical blocks
+ * consumed by the file associated with fd
+ */
+int get_nr_blocks(int fd);
+
+/* print_blocks - for each logical block consumed by the file
+ * associated with fd, prints to standard out the tuple
+ * "(logical block, physical block)"
+ */
+void print_blocks(int fd);
+
+int main(int argc, char *argv[]) {
+    if (argc < 2) {
+        fprintf(stderr, "usage: %s <file>\n", argv[0]);
+        return 1;
+    }
+
+    int fd = open(argv[1], O_RDONLY);
+    if (fd < 0) {
+        perror("open");
+        return 1;
+    }
+
+    print_blocks(fd);
+    return 0;
+}
+
+int get_block(int fd, int logical_block) {
+    int ret = ioctl(fd, FIBMAP, &logical_block);
+    if (ret < 0) {
+        perror("ioctl");
+        return -1;
+    }
+    return logical_block;
+}
+
+int get_nr_blocks(int fd) {
+    struct stat buf;
+    int ret = fstat(fd, &buf);
+    if (ret < 0) {
+        perror("fstat");
+        return -1;
+    }
+    return buf.st_blocks;
+}
+
+void print_blocks(int fd) {
+    int nr_blocks = get_nr_blocks(fd);
+    if (nr_blocks < 0) {
+        fprintf(stderr, "get_nr_blocks failed!\n");
+        return;
+    }
+
+    if (nr_blocks == 0) {
+        printf("no allocated blocks\n");
+        return;
+    } else if (nr_blocks == 1) {
+        printf("1 block\n");
+    } else {
+        printf("%d blocks\n\n", nr_blocks);
+    }
+
+    for (int i = 0; i < nr_blocks; i++) {
+        int phys_block = get_block(fd, i);
+        if (phys_block < 0) {
+            fprintf(stderr, "get_block failed!\n");
+            return;
+        }
+        if (!phys_block) continue;
+
+        printf("(%u, %u) ", i, phys_block);
+    }
+    putchar('\n');
+}

chp4/inode.c

@@ -0,0 +1,39 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+/* get_inode - returns the inode of the file associated
+ * with the given file descriptor, or -1 on failure.
+ */
+int get_inode(int fd);
+
+int main(int argc, char *argv[]) {
+    if (argc < 2) {
+        fprintf(stderr, "usage: %s <file>\n", argv[0]);
+        return 1;
+    }
+
+    int fd = open(argv[1], O_RDONLY);
+    if (fd < 0) {
+        perror("open");
+        return 1;
+    }
+
+    int inode = get_inode(fd);
+    printf("%d\n", inode);
+    
+    return 0;
+}
+
+int get_inode(int fd) {
+    struct stat buf;
+
+    int ret = fstat(fd, &buf);
+    if (ret < 0) {
+        perror("fstat");
+        return -1;
+    }
+    return buf.st_ino;
+}