Implement external journal device initialization

Added a function simplefs_parse_options in the fill super process to
obtain the external journal device and configure it using jbd2 related
functions. Additionally, journal-related functionality was added to the
write functions to record metadata "extent" information.

Also, added a "make journal" command in the Makefile, allowing users
to create an external journal device image and mount it to simplefs.

Makefile

@@ -10,6 +10,9 @@ all: $(MKFS)
 
 IMAGE ?= test.img
 IMAGESIZE ?= 200
+JOURNAL ?= journal.img
+JOURNALSIZE ?= 8
+
 # To test max files(40920) in directory, the image size should be at least 159.85 MiB
 # 40920 * 4096(block size) ~= 159.85 MiB
 
@@ -20,12 +23,18 @@ $(IMAGE): $(MKFS)
 	dd if=/dev/zero of=${IMAGE} bs=1M count=${IMAGESIZE}
 	./$< $(IMAGE)
 
+journal: $(JOURNAL)
+
+$(JOURNAL):
+	dd if=/dev/zero of=$(JOURNAL) bs=1M count=$(JOURNALSIZE)
+	mke2fs -b 4096 -O journal_dev $(JOURNAL)
+
 check: all
 	script/test.sh $(IMAGE) $(IMAGESIZE) $(MKFS)
 
 clean:
 	make -C $(KDIR) M=$(PWD) clean
 	rm -f *~ $(PWD)/*.ur-safe
-	rm -f $(MKFS) $(IMAGE)
+	rm -f $(MKFS) $(IMAGE) $(JOURNAL)
 
-.PHONY: all clean
+.PHONY: all clean journal

file.c

@@ -2,6 +2,7 @@
 
 #include <linux/buffer_head.h>
 #include <linux/fs.h>
+#include <linux/jbd2.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/mpage.h>
@@ -34,6 +35,20 @@ static int simplefs_file_get_block(struct inode *inode,
     bh_index = sb_bread(sb, ci->ei_block);
     if (!bh_index)
         return -EIO;
+
+    handle_t *handle = journal_current_handle();
+    if (!handle) {
+        brelse(bh_index);
+        return -EIO;
+    }
+
+    ret = jbd2_journal_get_write_access(handle, bh_index);
+    if (ret) {
+        brelse(bh_index);
+        pr_info("Can't get write access for bh\n");
+        return ret;
+    }
+
     index = (struct simplefs_file_ei_block *) bh_index->b_data;
 
     extent = simplefs_ext_search(index, iblock);
@@ -63,6 +78,13 @@ static int simplefs_file_get_block(struct inode *inode,
             extent ? index->extents[extent - 1].ee_block +
                          index->extents[extent - 1].ee_len
                    : 0;
+        ret = jbd2_journal_dirty_metadata(handle, bh_index);
+        if (ret) {
+            brelse(bh_index);
+            return ret;
+        }
+        mark_buffer_dirty_inode(bh_index, inode);
+
     } else {
         bno = index->extents[extent].ee_start + iblock -
               index->extents[extent].ee_block;
@@ -133,6 +155,7 @@ static int simplefs_write_begin(struct file *file,
     struct simplefs_sb_info *sbi = SIMPLEFS_SB(file->f_inode->i_sb);
     int err;
     uint32_t nr_allocs = 0;
+    handle_t *handle;
 
     /* Check if the write can be completed (enough space?) */
     if (pos + len > SIMPLEFS_MAX_FILESIZE)
@@ -146,6 +169,16 @@ static int simplefs_write_begin(struct file *file,
     if (nr_allocs > sbi->nr_free_blocks)
         return -ENOSPC;
 
+    /* handle journal starting here */
+    /*
+     * FIXME: the metadata type we should store into journal
+     * In the current situation, we only record the location of the extent
+     * and write that metadata to the journal.
+     */
+    handle = jbd2_journal_start(sbi->journal, 1);
+    if (IS_ERR(handle))
+        return PTR_ERR(handle);
+
         /* prepare the write */
 #if SIMPLEFS_AT_LEAST(5, 19, 0)
     err = block_write_begin(mapping, pos, len, pagep, simplefs_file_get_block);
@@ -174,6 +207,16 @@ static int simplefs_write_end(struct file *file,
     struct inode *inode = file->f_inode;
     struct simplefs_inode_info *ci = SIMPLEFS_INODE(inode);
     struct super_block *sb = inode->i_sb;
+
+    handle_t *handle;
+
+    /* handle journal start here */
+    handle = journal_current_handle();
+    if (!handle) {
+        pr_err("can't get journal handle\n");
+        return -EIO;
+    }
+
 #if SIMPLEFS_AT_LEAST(6, 6, 0)
     struct timespec64 cur_time;
 #endif
@@ -223,6 +266,14 @@ static int simplefs_write_end(struct file *file,
                    nr_blocks_old - inode->i_blocks);
             goto end;
         }
+
+        int retval = jbd2_journal_get_write_access(handle, bh_index);
+        if (WARN_ON(retval)) {
+            brelse(bh_index);
+            pr_info("cant get journal write access\n");
+            return retval;
+        }
+
         index = (struct simplefs_file_ei_block *) bh_index->b_data;
 
         first_ext = simplefs_ext_search(index, inode->i_blocks - 1);
@@ -238,9 +289,13 @@ static int simplefs_write_end(struct file *file,
                        index->extents[i].ee_len);
             memset(&index->extents[i], 0, sizeof(struct simplefs_extent));
         }
+        jbd2_journal_dirty_metadata(handle, bh_index);
         mark_buffer_dirty(bh_index);
         brelse(bh_index);
     }
+
+    jbd2_journal_stop(handle);
+
 end:
     return ret;
 }

simplefs.h

@@ -37,6 +37,9 @@
  * |      blocks   |  rest of the blocks
  * +---------------+
  */
+#ifdef __KERNEL__
+#include <linux/jbd2.h>
+#endif
 
 struct simplefs_inode {
     uint32_t i_mode;   /* File mode */
@@ -69,6 +72,10 @@ struct simplefs_sb_info {
     uint32_t nr_free_blocks; /* Number of free blocks */
 
 #ifdef __KERNEL__
+    journal_t *journal;
+    struct block_device *s_journal_bdev; /* v6.5 external journal device */
+    struct bdev_handle
+        *s_journal_bdev_handle;  /* v6.8 external journal device */
     unsigned long *ifree_bitmap; /* In-memory free inodes bitmap */
     unsigned long *bfree_bitmap; /* In-memory free blocks bitmap */
 #endif