[pve-devel] [RFC PATCH common] sysfstools: file_write: properly catch errors

[pve-devel] [RFC PATCH common] sysfstools: file_write: properly catch errors

[Dominik Csapak]

since `print` is doing buffered IO, we don't always get an error there,
even if the underlying write does not work.

To properly catch that, do an unbuffered `syswrite` which circumvents
all buffers and writes directly to the file handle.

We aren't actually interested in the specific error here, but only if
the write was successful or not.

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
---

Note: this is heavily used when doing PCI passthrough, and it seems we
did not catch as many errors as we thought. Maybe we should introduce an
'noerr' parameter and pass that on all current code paths, since i fear
that there are many situations where the sysfs write had failed but it
still works because we ignored it and qemu/the kernel do the right thing
anyway.

 src/PVE/SysFSTools.pm | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/PVE/SysFSTools.pm b/src/PVE/SysFSTools.pm
index 57f0ac8..8eb9f2e 100644
--- a/src/PVE/SysFSTools.pm
+++ b/src/PVE/SysFSTools.pm
@@ -198,7 +198,7 @@ sub file_write {
     my $fh = IO::File->new($filename, "w");
     return undef if !$fh;
 
-    my $res = print $fh $buf;
+    my $res = defined(syswrite($fh, $buf)) ? 1 : 0;
 
     $fh->close();
 
-- 
2.39.2



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