On 18.02.21 12:33, Stoiko Ivanov wrote: > This patch addresses an issue we recently saw on a production machine: > * after booting a ZFS pool failed to get imported (due to an empty > /etc/zfs/zpool.cache) > * pvestatd/guest-startall eventually tried to import the pool > * the pool was imported, yet the datasets of the pool remained > not mounted > > A bit of debugging showed that `zpool import <poolname>` is not > atomic, in fact it does fork+exec `mount` with appropriate parameters. > If an import ran longer than the hardcoded timeout of 15s, it could > happen that the pool got imported, but the zpool command (and its > forks) got terminated due to timing out. > > reproducing this is straight-forward by setting (drastic) bw+iops > limits on a guests' disk (which contains a zpool) - e.g.: > `qm set 100 -scsi1 wd:vm-100-disk-1,iops_rd=10,iops_rd_max=20,\ > iops_wr=15,iops_wr_max=20,mbps_rd=10,mbps_rd_max=15,mbps_wr=10,mbps_wr_max=15` > afterwards running `timeout 15 zpool import <poolname>` resulted in > that situation in the guest on my machine > > The patch changes the check in activate_storage for the ZFSPoolPlugin, > to check if the configured 'pool' (which can also be a sub-dataset) is > mounted (via `zfs get mounted <dataset>`). > > * In case this errors out we try to import the pool (and run `zfs > mount -a` if the dataset is not mounted after importing) > * In case it succeeds but reports the dataset as not mounted, > we run `zfs mount -a` > > The choice of running `zfs mount -a` has potential for regression, in > case someone manually umounts some dataset after booting the system > (but does not set the canmount option)
Why not # zfs mount <dataset> ? > > Signed-off-by: Stoiko Ivanov <[email protected]> > --- > * sending as RFC since I have the feeling that I miss quite a few > corner-cases. > * an alternative to getting the mounted property via `zfs get` might be > parsing /proc/mounts (but zfs get mounted does mostly just that +stating > files in /sys, and 2 (potentially blocking) ioctls > * could reproduce the issue with ZFS 2.0.1 and 0.8.6 - so my current guess > is the issue on the production box might be related to some other > performance regression in its disk-subsystem (maybe introduced with the > new kernel) > * huge thanks to Dominik for many suggestions (including the idea of > limiting the disk-speed via our stack instead of dm-delay :) > > PVE/Storage/ZFSPoolPlugin.pm | 25 +++++++++++++++++++++---- > 1 file changed, 21 insertions(+), 4 deletions(-) > > diff --git a/PVE/Storage/ZFSPoolPlugin.pm b/PVE/Storage/ZFSPoolPlugin.pm > index 105d802..32ad1c9 100644 > --- a/PVE/Storage/ZFSPoolPlugin.pm > +++ b/PVE/Storage/ZFSPoolPlugin.pm > @@ -525,8 +525,17 @@ sub activate_storage { > my ($class, $storeid, $scfg, $cache) = @_; > > # Note: $scfg->{pool} can include dataset <pool>/<dataset> > - my $pool = $scfg->{pool}; > - $pool =~ s!/.*$!!; > + my $dataset = $scfg->{pool}; > + my $pool = ($dataset =~ s!/.*$!!r); > + > + my $dataset_mounted = sub { > + my $mounted = eval { $class->zfs_get_properties($scfg, 'mounted', > "$dataset") }; quotes don't do anything here, just gets you a "undefined value in string ..." warning if undefined (and underlying run_command does not change behavior either). I.e., # perl -we 'use PVE::Tools qw(run_command); my $arg; run_command(["touch", "$arg"])' Use of uninitialized value $arg in string at -e line 1. touch: cannot touch '': No such file or directory command 'touch ''' failed: exit code 1 vs. # perl -we 'use PVE::Tools qw(run_command); my $arg; run_command(["touch", $arg])' Use of uninitialized value $_[1] in exec at /usr/share/perl/5.28/IPC/Open3.pm line 178. touch: cannot touch '': No such file or directory command 'touch ''' failed: exit code 1 I like to avoid using quotes in such cases to avoid suggesting that they have any use. > + if ($@) { > + warn "$@\n"; > + return undef; > + } I know this is just copied, but both should just use a simple warn "$@\n" if ($@); as the return is correctly using a defined check anyway > + return defined($mounted) && $mounted =~ m/^yes$/; > + }; > > my $pool_imported = sub { > my @param = ('-o', 'name', '-H', "$pool"); > @@ -538,13 +547,21 @@ sub activate_storage { > return defined($res) && $res =~ m/$pool/; > }; > > - if (!$pool_imported->()) { > + if (!defined($dataset_mounted->())) { don't complicated boolean, drop the defined. > + # error from zfs get mounted - pool import necessary > # import can only be done if not yet imported! > my @param = ('-d', '/dev/disk/by-id/', '-o', 'cachefile=none', "$pool"); > eval { $class->zfs_request($scfg, undef, 'zpool_import', @param) }; > if (my $err = $@) { > # just could've raced with another import, so recheck if it is > imported > - die "could not activate storage '$storeid', $@\n" if > !$pool_imported->(); > + die "could not activate storage '$storeid', $err\n" if > !$pool_imported->(); > + } > + if (!$dataset_mounted->()) { > + eval { $class->zfs_request($scfg, undef, 'mount', '-a') }; > + if (my $err = $@) { > + # just could've raced with another import, so recheck if it is > imported but you do not (re-)check anything? > + die "could not activate storage '$storeid', $err\n"; > + } > } > } > return 1; > _______________________________________________ pve-devel mailing list [email protected] https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel
