[PATCH v2 2/4] usertools: add option to change mount point owner

[Dmitry Kozlyuk <dkozlyuk@nvidia.com>]

Per mount(8), the previous owner and mode of the mount point
become invisible as long as this filesystem remains mounted.
Because dpdk-hugepages.py must be run as root,
the new owner would be root.
This is undesirable if the hugepage directory is being set up
by the administrator for an unprivileged user.
HugeTLB filesystem has options to set the mount point owner.
Add --owner/-o option to apply this option when mounting.
The benefit of performing this in dpdk-hugepages.py
is that the user does not need to care about this detail
of mount command operation.

Signed-off-by: Dmitry Kozlyuk <dkozlyuk@nvidia.com>
---
 usertools/dpdk-hugepages.py | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/usertools/dpdk-hugepages.py b/usertools/dpdk-hugepages.py
index 8bab086a2f..5120518bcb 100755
--- a/usertools/dpdk-hugepages.py
+++ b/usertools/dpdk-hugepages.py
@@ -170,7 +170,7 @@ def get_mountpoints():
     return mounted
 
 
-def mount_huge(pagesize, mountpoint):
+def mount_huge(pagesize, mountpoint, owner):
     '''Mount the huge TLB file system'''
     if mountpoint in get_mountpoints():
         print(mountpoint, "already mounted")
@@ -178,6 +178,9 @@ def mount_huge(pagesize, mountpoint):
     cmd = "mount -t hugetlbfs"
     if pagesize:
         cmd += ' -o pagesize={}'.format(pagesize * 1024)
+    if owner:
+        uid, gid = owner.split(':', maxsplit=1)
+        cmd += ' -o uid={},gid={}'.format(uid, gid)
     cmd += ' nodev ' + mountpoint
     os.system(cmd)
 
@@ -234,6 +237,11 @@ def main():
         metavar='DIR',
         default=HUGE_MOUNT,
         help='mount point')
+    parser.add_argument(
+        '--owner',
+        '-o',
+        metavar='USER:GROUP',
+        help='change the mounted directory owner')
     parser.add_argument(
         '--node', '-n', help='select numa node to reserve pages on')
     parser.add_argument(
@@ -279,7 +287,7 @@ def main():
         reserve_pages(
             int(reserve_kb / pagesize_kb), pagesize_kb, node=args.node)
     if args.mount:
-        mount_huge(pagesize_kb, args.directory)
+        mount_huge(pagesize_kb, args.directory, args.owner)
     if args.show:
         show_pages()
         print()
-- 
2.25.1