Matthew Rosato <mjros...@linux.ibm.com> 于2023年6月3日周六 02:41写道：
>
> On 6/2/23 2:18 PM, Sam Li wrote:
> > Matthew Rosato <mjros...@linux.ibm.com> 于2023年6月1日周四 02:21写道：
> >>
> >> On 5/15/23 12:04 PM, Stefan Hajnoczi wrote:
> >>> From: Sam Li <faithilike...@gmail.com>
> >>>
> >>> Use get_sysfs_str_val() to get the string value of device
> >>> zoned model. Then get_sysfs_zoned_model() can convert it to
> >>> BlockZoneModel type of QEMU.
> >>>
> >>> Use get_sysfs_long_val() to get the long value of zoned device
> >>> information.
> >>
> >> Hi Stefan, Sam,
> >>
> >> I am having an issue on s390x using virtio-blk-{pci,ccw} backed by an NVMe
> >> partition, and I've bisected the root cause to this commit.
> >>
> >> I noticed that tests which use the partition e.g. /dev/nvme0n1p1 as a
> >> backing device would fail, but those that use the namespace e.g.
> >> /dev/nvme0n1 would still succeed. The root issue appears to be that the
> >> block device associated with the partition does not have a "max_segments"
> >> attribute, and prior to this patch hdev_get_max_segment() would return
> >> -ENOENT in this case. After this patch, however, QEMU is instead
> >> crashing. It looks like g_file_get_contents is returning 0 with a len ==
> >> 0 if the specified sysfs path does not exist. The following diff on top
> >> seems to resolve the issue for me:
> >>
> >>
> >> diff --git a/block/file-posix.c b/block/file-posix.c
> >> index 0ab158efba2..eeb0247c74e 100644
> >> --- a/block/file-posix.c
> >> +++ b/block/file-posix.c
> >> @@ -1243,7 +1243,7 @@ static int get_sysfs_str_val(struct stat *st, const
> >> char *attribute,
> >> major(st->st_rdev), minor(st->st_rdev),
> >> attribute);
> >> ret = g_file_get_contents(sysfspath, val, &len, NULL);
> >> - if (ret == -1) {
> >> + if (ret == -1 || len == 0) {
> >> return -ENOENT;
> >> }
> >>
> >
> > Hi Matthew,
> >
> > Thanks for the information. After some checking, I think the bug here
> > is that g_file_get_contens returns g_boolean value and the error case
> > will return 0 instead of -1 in my previous code. Can the following
> > line fix your issue on the s390x device?
> >
> > + if (ret == FALSE) {
> >
> > https://docs.gtk.org/glib/func.file_get_contents.html
>
> Hi Sam,
>
> Ah, good point, I didn't notice file_get_contents was meant to be a bool
> return and wondered why I was getting a return of 0 in the failing case,
> hence the check for len == 0.
>
> Anyway, yes, I verified that checking for ret == FALSE fixes the issue.
> FWIW, along the same line I also checked that this works:
>
> if (!g_file_get_contents(sysfspath, val, &len, NULL)) {
> return -ENOENT;
> }
>
> which I personally think looks cleaner and matches the other uses of
> g_file_get_contents in QEMU. Could also get rid of ret and just return 0 at
> the bottom of the function.
Indeed. I will fix this. Thanks!
Sam
