[pve-devel] [PATCH common] add fsfreeze helper:

[Stoiko Ivanov]

fsfreeze_mountpoint issues the same ioctl's as fsfreeze(8) on the provided
directory (the $thaw parameter deciding between '--freeze' and '--unfreeze')

This is used for container backups on RBD, where snapshots on containers, which
are heavy on IO, are not mountable readonly, because the ext4 is not consistent

Needed to fix #2991 and #2528.

The ioctl numbers were found via strace -X verbose (and compared with the
kernel source).

Signed-off-by: Stoiko Ivanov <s.ivanov at proxmox.com>
---
 src/PVE/Tools.pm | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/src/PVE/Tools.pm b/src/PVE/Tools.pm
index 4b445ea..c61fc49 100644
--- a/src/PVE/Tools.pm
+++ b/src/PVE/Tools.pm
@@ -100,6 +100,9 @@ use constant {O_PATH    => 0x00200000,
 use constant {AT_EMPTY_PATH => 0x1000,
               AT_FDCWD => -100};
 
+use constant {FIFREEZE => 0xc0045877,
+              FITHAW   => 0xc0045878};
+
 sub run_with_timeout {
     my ($timeout, $code, @param) = @_;
 
@@ -1442,6 +1445,21 @@ sub sync_mountpoint {
     die "syncfs '$path' failed - $syncfs_err\n" if defined $syncfs_err;
 }
 
+sub fsfreeze_mountpoint {
+    my ($path, $thaw) = @_;
+
+    my $op = $thaw ? 'thaw' : 'freeze';
+    my $ioctl = $thaw ? FITHAW : FIFREEZE;
+
+    sysopen my $fd, $path, O_RDONLY|O_CLOEXEC or die "failed to open $path: $!\n";
+    my $ioctl_err;
+    if (!ioctl($fd, $ioctl, 0)) {
+	$ioctl_err = "$!";
+    }
+    close($fd);
+    die "fs$op '$path' failed - $ioctl_err\n" if defined $ioctl_err;
+}
+
 # support sending multi-part mail messages with a text and or a HTML part
 # mailto may be a single email string or an array of receivers
 sub sendmail {
-- 
2.20.1