f2fs: show the list of donation files

This patch introduces a proc entry to show the currently enrolled donation
files.

- "File path" indicates a file.
- "Status"
 a. "Donated" means the file is registed in the donation list by
    fadvise(offset, length, POSIX_FADV_NOREUSE)
 b. "Evicted" means the donated pages were reclaimed.
- "Offset (kb)" and "Length (kb) show the registered donation range.
- "Cached pages (kb)" shows the amount of cached pages in the inode page cache.

For example,

 # of files  : 2
 File path                                              Status Donation offset (kb)   Donation size (kb)  File cached size (kb)
---
 /local/test2                                          Donated                    0              1048576                2097152
 /local/test                                           Evicted                    0              1048576                1048576

Reviewed-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>

Author: Jaegeuk Kim

fs/f2fs/sysfs.c

@@ -1769,6 +1769,68 @@ static int __maybe_unused disk_map_seq_show(struct seq_file *seq,
 	return 0;
 }
 
+static int __maybe_unused donation_list_seq_show(struct seq_file *seq,
+						void *offset)
+{
+	struct super_block *sb = seq->private;
+	struct f2fs_sb_info *sbi = F2FS_SB(sb);
+	struct inode *inode;
+	struct f2fs_inode_info *fi;
+	struct dentry *dentry;
+	char *buf, *path;
+	int i;
+
+	buf = f2fs_getname(sbi);
+	if (!buf)
+		return 0;
+
+	seq_printf(seq, "Donation List\n");
+	seq_printf(seq, " # of files  : %u\n", sbi->donate_files);
+	seq_printf(seq, " %-50s %10s %20s %20s %22s\n",
+			"File path", "Status", "Donation offset (kb)",
+			"Donation size (kb)", "File cached size (kb)");
+	seq_printf(seq, "---\n");
+
+	for (i = 0; i < sbi->donate_files; i++) {
+		spin_lock(&sbi->inode_lock[DONATE_INODE]);
+		if (list_empty(&sbi->inode_list[DONATE_INODE])) {
+			spin_unlock(&sbi->inode_lock[DONATE_INODE]);
+			break;
+		}
+		fi = list_first_entry(&sbi->inode_list[DONATE_INODE],
+					struct f2fs_inode_info, gdonate_list);
+		list_move_tail(&fi->gdonate_list, &sbi->inode_list[DONATE_INODE]);
+		inode = igrab(&fi->vfs_inode);
+		spin_unlock(&sbi->inode_lock[DONATE_INODE]);
+
+		if (!inode)
+			continue;
+
+		inode_lock_shared(inode);
+
+		dentry = d_find_alias(inode);
+		if (!dentry) {
+			path = NULL;
+		} else {
+			path = dentry_path_raw(dentry, buf, PATH_MAX);
+			if (IS_ERR(path))
+				goto next;
+		}
+		seq_printf(seq, " %-50s %10s %20llu %20llu %22llu\n",
+				path ? path : "<unlinked>",
+				is_inode_flag_set(inode, FI_DONATE_FINISHED) ?
+				"Evicted" : "Donated",
+				(loff_t)fi->donate_start << (PAGE_SHIFT - 10),
+				(loff_t)(fi->donate_end + 1) << (PAGE_SHIFT - 10),
+				(loff_t)inode->i_mapping->nrpages << (PAGE_SHIFT - 10));
+next:
+		inode_unlock_shared(inode);
+		iput(inode);
+	}
+	f2fs_putname(buf);
+	return 0;
+}
+
 #ifdef CONFIG_F2FS_FAULT_INJECTION
 static int __maybe_unused inject_stats_seq_show(struct seq_file *seq,
 						void *offset)
@@ -1878,6 +1940,8 @@ int f2fs_register_sysfs(struct f2fs_sb_info *sbi)
 				discard_plist_seq_show, sb);
 	proc_create_single_data("disk_map", 0444, sbi->s_proc,
 				disk_map_seq_show, sb);
+	proc_create_single_data("donation_list", 0444, sbi->s_proc,
+				donation_list_seq_show, sb);
 #ifdef CONFIG_F2FS_FAULT_INJECTION
 	proc_create_single_data("inject_stats", 0444, sbi->s_proc,
 				inject_stats_seq_show, sb);