Fix "kmem -i" and "swap" commands on Linux 6.10-rc1 and later kernels

Kernel commit 798cb7f9aec3 ("swapon(2)/swapoff(2): don't bother with
block size") removed swap_info_struct.old_block_size member at Linux
6.10-rc1.  The crash-utility has used this to determine whether a swap
is a partition or file and to determine the way to get the swap path.

Withtout the patch, the "kmem -i" and "swap" commands fail with the
following error messsage:

  crash> kmem -i
  ...
     TOTAL HUGE  13179392      50.3 GB         ----
      HUGE FREE  13179392      50.3 GB  100% of TOTAL HUGE

  swap: invalid (optional) structure member offsets: swap_info_struct_swap_device or swap_info_struct_old_block_size
        FILE: memory.c  LINE: 16032  FUNCTION: dump_swap_info()

The swap_file member of recent swap_info_struct is a pointer to a
struct file (once upon a time it was dentry), use this fact directly.

Tested-by: Li Zhijian <[email protected]>
Signed-off-by: Kazuhito Hagio <[email protected]>

defs.h

@@ -2242,6 +2242,7 @@ struct offset_table {                    /* stash of commonly-used offsets */
 	long log_caller_id;
 	long vmap_node_busy;
 	long rb_list_head;
+	long file_f_inode;
 };
 
 struct size_table {         /* stash of commonly-used sizes */

filesys.c

@@ -2038,6 +2038,7 @@ vfs_init(void)
 	MEMBER_OFFSET_INIT(file_f_dentry, "file", "f_dentry");
 	MEMBER_OFFSET_INIT(file_f_vfsmnt, "file", "f_vfsmnt");
 	MEMBER_OFFSET_INIT(file_f_count, "file", "f_count");
+	MEMBER_OFFSET_INIT(file_f_inode, "file", "f_inode");
 	MEMBER_OFFSET_INIT(path_mnt, "path", "mnt");
 	MEMBER_OFFSET_INIT(path_dentry, "path", "dentry");
 	if (INVALID_MEMBER(file_f_dentry)) {

memory.c

@@ -16075,6 +16075,8 @@ dump_swap_info(ulong swapflags, ulong *totalswap_pages, ulong *totalused_pages)
 	char buf3[BUFSIZE];
 	char buf4[BUFSIZE];
 	char buf5[BUFSIZE];
+	int swap_file_is_file =
+		STREQ(MEMBER_TYPE_NAME("swap_info_struct", "swap_file"), "file");
 
 	if (!symbol_exists("nr_swapfiles"))
 		error(FATAL, "nr_swapfiles doesn't exist in this kernel!\n");
@@ -16118,9 +16120,21 @@ dump_swap_info(ulong swapflags, ulong *totalswap_pages, ulong *totalused_pages)
 		swap_file = ULONG(vt->swap_info_struct + 
 			OFFSET(swap_info_struct_swap_file));
 
-                swap_device = INT(vt->swap_info_struct +
-                        OFFSET_OPTION(swap_info_struct_swap_device, 
-			swap_info_struct_old_block_size));
+		/* Linux 6.10 and later */
+		if (INVALID_MEMBER(swap_info_struct_swap_device) &&
+		    INVALID_MEMBER(swap_info_struct_old_block_size) &&
+		    swap_file_is_file) {
+			ulong inode;
+			ushort mode;
+			readmem(swap_file + OFFSET(file_f_inode), KVADDR, &inode,
+				sizeof(ulong), "swap_file.f_inode", FAULT_ON_ERROR);
+			readmem(inode + OFFSET(inode_i_mode), KVADDR, &mode,
+				sizeof(ushort), "inode.i_mode", FAULT_ON_ERROR);
+			swap_device = S_ISBLK(mode);
+		} else
+			swap_device = INT(vt->swap_info_struct +
+				OFFSET_OPTION(swap_info_struct_swap_device,
+				swap_info_struct_old_block_size));
 
                 pages = INT(vt->swap_info_struct +
                         OFFSET(swap_info_struct_pages));
@@ -16161,8 +16175,12 @@ dump_swap_info(ulong swapflags, ulong *totalswap_pages, ulong *totalused_pages)
                         		OFFSET(swap_info_struct_swap_vfsmnt));
 				get_pathname(swap_file, buf, BUFSIZE, 
 					1, vfsmnt);
-			} else if (VALID_MEMBER
-				(swap_info_struct_old_block_size)) {
+			} else if (VALID_MEMBER(swap_info_struct_old_block_size) ||
+				    swap_file_is_file) {
+				/*
+				 * Linux 6.10 and later kernels do not have old_block_size,
+				 * but this still should work, if swap_file is file.
+				 */
 				devname = vfsmount_devname(file_to_vfsmnt(swap_file), 
 					buf1, BUFSIZE);
 				get_pathname(file_to_dentry(swap_file), 

symbols.c

@@ -10522,6 +10522,7 @@ dump_offset_table(char *spec, ulong makestruct)
 		OFFSET(file_f_count));
         fprintf(fp, "                   file_f_path: %ld\n", 
 		OFFSET(file_f_path));
+        fprintf(fp, "                  file_f_inode: %ld\n", OFFSET(file_f_inode));
         fprintf(fp, "                      path_mnt: %ld\n", 
 		OFFSET(path_mnt));
         fprintf(fp, "                   path_dentry: %ld\n",