From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Create a new ireq flag (for single bulkstats) that enables userspace to
ask us for a special inode number instead of interpreting @ino as a
literal inode number. This enables us to query the root inode easily.
The reason for adding the ability to query specifically the root
directory inode is that certain programs (xfsdump and xfsrestore) want
to confirm when they've been pointed to the root directory. The
userspace code assumes the root directory is always the first result
from calling bulkstat with lastino == 0, but this isn't true if the
(initial btree roots + initial AGFL + inode alignment padding) is itself
long enough to be allocated to new inodes if all of those blocks should
happen to be free at the same time. Rather than make userspace guess
at internal filesystem state, we provide a direct query.
Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Reviewed-by: Allison Collins <allison.henderson@xxxxxxxxxx>
---
v2: elaborate on why we are adding this new ireq flag
---
fs/xfs/libxfs/xfs_fs.h | 11 ++++++++++-
fs/xfs/xfs_ioctl.c | 10 ++++++++++
2 files changed, 20 insertions(+), 1 deletion(-)
diff --git a/fs/xfs/libxfs/xfs_fs.h b/fs/xfs/libxfs/xfs_fs.h
index 77c06850ac52..1489bce07d66 100644
--- a/fs/xfs/libxfs/xfs_fs.h
+++ b/fs/xfs/libxfs/xfs_fs.h
@@ -482,7 +482,16 @@ struct xfs_ireq {
uint64_t reserved[2]; /* must be zero */
};
-#define XFS_IREQ_FLAGS_ALL (0)
+/*
+ * The @ino value is a special value, not a literal inode number. See the
+ * XFS_IREQ_SPECIAL_* values below.
+ */
+#define XFS_IREQ_SPECIAL (1 << 0)
+
+#define XFS_IREQ_FLAGS_ALL (XFS_IREQ_SPECIAL)
+
+/* Operate on the root directory inode. */
+#define XFS_IREQ_SPECIAL_ROOT (1)
/*
* ioctl structures for v5 bulkstat and inumbers requests
diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index ba9a99b7860f..11ccfc5611bf 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -952,6 +952,16 @@ xfs_ireq_setup(
memchr_inv(hdr->reserved, 0, sizeof(hdr->reserved)))
return -EINVAL;
+ if (hdr->flags & XFS_IREQ_SPECIAL) {
+ switch (hdr->ino) {
+ case XFS_IREQ_SPECIAL_ROOT:
+ hdr->ino = mp->m_sb.sb_rootino;
+ break;
+ default:
+ return -EINVAL;
+ }
+ }
+
if (XFS_INO_TO_AGNO(mp, hdr->ino) >= mp->m_sb.sb_agcount)
return -EINVAL;
