nilfs2: localize highmem mapping for checkpoint finalization within cpfile

Move the checkpoint finalization routine to the cpfile side, and make the
page mapping local and temporary.  And use kmap_local instead of kmap to
access the checkpoint entry page when finalizing a checkpoint.

In this conversion, some of the information on the checkpoint entry being
rewritten is passed through the arguments of the newly added method
nilfs_cpfile_finalize_checkpoint().

Link: https://lkml.kernel.org/r/20240122140202.6950-13-konishi.ryusuke@gmail.com
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/nilfs2/cpfile.c

@@ -363,6 +363,80 @@ void nilfs_cpfile_put_checkpoint(struct inode *cpfile, __u64 cno,
 	brelse(bh);
 }
 
+/**
+ * nilfs_cpfile_finalize_checkpoint - fill in a checkpoint entry in cpfile
+ * @cpfile: checkpoint file inode
+ * @cno:    checkpoint number
+ * @root:   nilfs root object
+ * @blkinc: number of blocks added by this checkpoint
+ * @ctime:  checkpoint creation time
+ * @minor:  minor checkpoint flag
+ *
+ * This function completes the checkpoint entry numbered by @cno in the
+ * cpfile with the data given by the arguments @root, @blkinc, @ctime, and
+ * @minor.
+ *
+ * Return: 0 on success, or the following negative error code on failure.
+ * * %-ENOMEM	- Insufficient memory available.
+ * * %-EIO	- I/O error (including metadata corruption).
+ */
+int nilfs_cpfile_finalize_checkpoint(struct inode *cpfile, __u64 cno,
+				     struct nilfs_root *root, __u64 blkinc,
+				     time64_t ctime, bool minor)
+{
+	struct buffer_head *cp_bh;
+	struct nilfs_checkpoint *cp;
+	void *kaddr;
+	int ret;
+
+	if (WARN_ON_ONCE(cno < 1))
+		return -EIO;
+
+	down_write(&NILFS_MDT(cpfile)->mi_sem);
+	ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &cp_bh);
+	if (unlikely(ret < 0)) {
+		if (ret == -ENOENT)
+			goto error;
+		goto out_sem;
+	}
+
+	kaddr = kmap_local_page(cp_bh->b_page);
+	cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
+	if (unlikely(nilfs_checkpoint_invalid(cp))) {
+		kunmap_local(kaddr);
+		brelse(cp_bh);
+		goto error;
+	}
+
+	cp->cp_snapshot_list.ssl_next = 0;
+	cp->cp_snapshot_list.ssl_prev = 0;
+	cp->cp_inodes_count = cpu_to_le64(atomic64_read(&root->inodes_count));
+	cp->cp_blocks_count = cpu_to_le64(atomic64_read(&root->blocks_count));
+	cp->cp_nblk_inc = cpu_to_le64(blkinc);
+	cp->cp_create = cpu_to_le64(ctime);
+	cp->cp_cno = cpu_to_le64(cno);
+
+	if (minor)
+		nilfs_checkpoint_set_minor(cp);
+	else
+		nilfs_checkpoint_clear_minor(cp);
+
+	nilfs_write_inode_common(root->ifile, &cp->cp_ifile_inode);
+	nilfs_bmap_write(NILFS_I(root->ifile)->i_bmap, &cp->cp_ifile_inode);
+
+	kunmap_local(kaddr);
+	brelse(cp_bh);
+out_sem:
+	up_write(&NILFS_MDT(cpfile)->mi_sem);
+	return ret;
+
+error:
+	nilfs_error(cpfile->i_sb,
+		    "checkpoint finalization failed due to metadata corruption.");
+	ret = -EIO;
+	goto out_sem;
+}
+
 /**
  * nilfs_cpfile_delete_checkpoints - delete checkpoints
  * @cpfile: inode of checkpoint file

fs/nilfs2/cpfile.h

@@ -21,6 +21,9 @@ int nilfs_cpfile_get_checkpoint(struct inode *, __u64, int,
 				struct buffer_head **);
 int nilfs_cpfile_create_checkpoint(struct inode *cpfile, __u64 cno);
 void nilfs_cpfile_put_checkpoint(struct inode *, __u64, struct buffer_head *);
+int nilfs_cpfile_finalize_checkpoint(struct inode *cpfile, __u64 cno,
+				     struct nilfs_root *root, __u64 blkinc,
+				     time64_t ctime, bool minor);
 int nilfs_cpfile_delete_checkpoints(struct inode *, __u64, __u64);
 int nilfs_cpfile_delete_checkpoint(struct inode *, __u64);
 int nilfs_cpfile_change_cpmode(struct inode *, __u64, int);

fs/nilfs2/segment.c

@@ -880,51 +880,6 @@ static void nilfs_segctor_clear_metadata_dirty(struct nilfs_sc_info *sci)
 	nilfs_mdt_clear_dirty(nilfs->ns_dat);
 }
 
-static int nilfs_segctor_fill_in_checkpoint(struct nilfs_sc_info *sci)
-{
-	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
-	struct buffer_head *bh_cp;
-	struct nilfs_checkpoint *raw_cp;
-	struct inode *ifile;
-	int err;
-
-	err = nilfs_cpfile_get_checkpoint(nilfs->ns_cpfile, nilfs->ns_cno, 0,
-					  &raw_cp, &bh_cp);
-	if (unlikely(err)) {
-		if (err == -EINVAL || err == -ENOENT) {
-			nilfs_error(sci->sc_super,
-				    "checkpoint finalization failed due to metadata corruption.");
-			err = -EIO;
-		}
-		goto failed_ibh;
-	}
-	raw_cp->cp_snapshot_list.ssl_next = 0;
-	raw_cp->cp_snapshot_list.ssl_prev = 0;
-	raw_cp->cp_inodes_count =
-		cpu_to_le64(atomic64_read(&sci->sc_root->inodes_count));
-	raw_cp->cp_blocks_count =
-		cpu_to_le64(atomic64_read(&sci->sc_root->blocks_count));
-	raw_cp->cp_nblk_inc =
-		cpu_to_le64(sci->sc_nblk_inc + sci->sc_nblk_this_inc);
-	raw_cp->cp_create = cpu_to_le64(sci->sc_seg_ctime);
-	raw_cp->cp_cno = cpu_to_le64(nilfs->ns_cno);
-
-	if (test_bit(NILFS_SC_HAVE_DELTA, &sci->sc_flags))
-		nilfs_checkpoint_clear_minor(raw_cp);
-	else
-		nilfs_checkpoint_set_minor(raw_cp);
-
-	ifile = sci->sc_root->ifile;
-	nilfs_write_inode_common(ifile, &raw_cp->cp_ifile_inode);
-	nilfs_bmap_write(NILFS_I(ifile)->i_bmap, &raw_cp->cp_ifile_inode);
-
-	nilfs_cpfile_put_checkpoint(nilfs->ns_cpfile, nilfs->ns_cno, bh_cp);
-	return 0;
-
- failed_ibh:
-	return err;
-}
-
 static void nilfs_fill_in_file_bmap(struct inode *ifile,
 				    struct nilfs_inode_info *ii)
 
@@ -2105,7 +2060,11 @@ static int nilfs_segctor_do_construct(struct nilfs_sc_info *sci, int mode)
 
 		if (mode == SC_LSEG_SR &&
 		    nilfs_sc_cstage_get(sci) >= NILFS_ST_CPFILE) {
-			err = nilfs_segctor_fill_in_checkpoint(sci);
+			err = nilfs_cpfile_finalize_checkpoint(
+				nilfs->ns_cpfile, nilfs->ns_cno, sci->sc_root,
+				sci->sc_nblk_inc + sci->sc_nblk_this_inc,
+				sci->sc_seg_ctime,
+				!test_bit(NILFS_SC_HAVE_DELTA, &sci->sc_flags));
 			if (unlikely(err))
 				goto failed_to_write;