From 7a96e03148d8dd382e56d993455eab9300949e52 Mon Sep 17 00:00:00 2001
From: Zach Brown <zab@versity.com>
Date: Fri, 21 Jan 2022 16:00:06 -0800
Subject: [PATCH] Add get_allocated_inos ioctl

Add an ioctl that can give some indication of inodes that have inode
items.   We're exposing this for tests that verify the handling of open
unlinked inodes.

Signed-off-by: Zach Brown <zab@versity.com>
---
 kmod/src/ioctl.c | 80 ++++++++++++++++++++++++++++++++++++++++++++++++
 kmod/src/ioctl.h | 39 +++++++++++++++++++++++
 2 files changed, 119 insertions(+)

diff --git a/kmod/src/ioctl.c b/kmod/src/ioctl.c
index 014527ec..d30a5021 100644
--- a/kmod/src/ioctl.c
+++ b/kmod/src/ioctl.c
@@ -1320,6 +1320,84 @@ out:
 	return ret ?: count;
 }
 
+static long scoutfs_ioc_get_allocated_inos(struct file *file, unsigned long arg)
+{
+	struct super_block *sb = file_inode(file)->i_sb;
+	struct scoutfs_ioctl_get_allocated_inos __user *ugai = (void __user *)arg;
+	struct scoutfs_ioctl_get_allocated_inos gai;
+	struct scoutfs_lock *lock = NULL;
+	struct scoutfs_key key;
+	struct scoutfs_key end;
+	u64 __user *uinos;
+	u64 bytes;
+	u64 ino;
+	int nr;
+	int ret;
+
+	if (!(file->f_mode & FMODE_READ)) {
+		ret = -EBADF;
+		goto out;
+	}
+
+	if (!capable(CAP_SYS_ADMIN)) {
+		ret = -EPERM;
+		goto out;
+	}
+
+	if (copy_from_user(&gai, ugai, sizeof(gai))) {
+		ret = -EFAULT;
+		goto out;
+	}
+
+	if ((gai.inos_ptr & (sizeof(__u64) - 1)) || (gai.inos_bytes < sizeof(__u64))) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	scoutfs_inode_init_key(&key, gai.start_ino);
+	scoutfs_inode_init_key(&end, gai.start_ino | SCOUTFS_LOCK_INODE_GROUP_MASK);
+	uinos = (void __user *)gai.inos_ptr;
+	bytes = gai.inos_bytes;
+	nr = 0;
+
+	ret = scoutfs_lock_ino(sb, SCOUTFS_LOCK_READ, 0, gai.start_ino, &lock);
+	if (ret < 0)
+		goto out;
+
+	while (bytes >= sizeof(*uinos)) {
+
+		ret = scoutfs_item_next(sb, &key, &end, NULL, 0, lock);
+		if (ret < 0) {
+			if (ret == -ENOENT)
+				ret = 0;
+			break;
+		}
+
+		if (key.sk_zone != SCOUTFS_FS_ZONE) {
+			ret = 0;
+			break;
+		}
+
+		/* all fs items are owned by allocated inodes, and _first is always ino */
+		ino = le64_to_cpu(key._sk_first);
+		if (put_user(ino, uinos)) {
+			ret = -EFAULT;
+			break;
+		}
+
+		uinos++;
+		bytes -= sizeof(*uinos);
+		if (++nr == INT_MAX)
+			break;
+
+		scoutfs_inode_init_key(&key, ino + 1);
+	}
+
+	scoutfs_unlock(sb, lock, SCOUTFS_LOCK_READ);
+out:
+	return ret ?: nr;
+}
+
 long scoutfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
 	switch (cmd) {
@@ -1353,6 +1431,8 @@ long scoutfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 		return scoutfs_ioc_resize_devices(file, arg);
 	case SCOUTFS_IOC_READ_XATTR_TOTALS:
 		return scoutfs_ioc_read_xattr_totals(file, arg);
+	case SCOUTFS_IOC_GET_ALLOCATED_INOS:
+		return scoutfs_ioc_get_allocated_inos(file, arg);
 	}
 
 	return -ENOTTY;
diff --git a/kmod/src/ioctl.h b/kmod/src/ioctl.h
index 24cd9a46..459ee7fb 100644
--- a/kmod/src/ioctl.h
+++ b/kmod/src/ioctl.h
@@ -520,4 +520,43 @@ struct scoutfs_ioctl_xattr_total {
 #define SCOUTFS_IOC_READ_XATTR_TOTALS \
 	_IOW(SCOUTFS_IOCTL_MAGIC, 15, struct scoutfs_ioctl_read_xattr_totals)
 
+/*
+ * This fills the caller's inos array with inode numbers that are in use
+ * after the start ino, within an internal inode group.
+ *
+ * This only makes a promise about the state of the inode numbers within
+ * the first and last numbers returned by one call.  At one time, all of
+ * those inodes were still allocated.   They could have changed before
+ * the call returned.   And any numbers outside of the first and last
+ * (or single) are undefined.
+ *
+ * This doesn't iterate over all allocated inodes, it only probes a
+ * single group that the start inode is within.   This interface was
+ * first introduced to support tests that needed to find out about a
+ * specific inode, while having some other similarly niche uses.   It is
+ * unsuitable for a consistent iteration over all the inode numbers in
+ * use.
+ *
+ * This test of inode items doesn't serialize with the inode lifetime
+ * mechanism.   It only tells you the numbers of inodes that were once
+ * active in the system and haven't yet been fully deleted.  The inode
+ * numbers returned could have been in the process of being deleted and
+ * were already unreachable even before the call started.
+ *
+ * @start_ino: the first inode number that could be returned
+ * @inos_ptr: pointer to an aligned array of 64bit inode numbers
+ * @inos_bytes: the number of bytes available in the inos_ptr array
+ *
+ * Returns errors or the count of inode numbers returned, quite possibly
+ * including 0.
+ */
+struct scoutfs_ioctl_get_allocated_inos {
+	__u64 start_ino;
+	__u64 inos_ptr;
+	__u64 inos_bytes;
+};
+
+#define SCOUTFS_IOC_GET_ALLOCATED_INOS \
+	_IOW(SCOUTFS_IOCTL_MAGIC, 16, struct scoutfs_ioctl_get_allocated_inos)
+
 #endif