ACK: [PATCH][SRU][XENIAL] UBUNTU: SAUCE: (noup) zfs to 0.6.5.6-0ubuntu25
Kleber Souza
kleber.souza at canonical.com
Thu Jul 26 16:42:46 UTC 2018
On 07/12/18 17:48, Colin King wrote:
> From: Colin Ian King <colin.king at canonical.com>
>
> BugLink: http://bugs.launchpad.net/bugs/1781364
>
> This is a sync of zfs 0.6.5.6-0ubuntu25 that fixes a mount/umount deadlock
> for upstream ZFS commit ac09630d8b0b ("Fix zpl_mount() deadlock")
>
> ZFS commit 93b43af inadvertently introduced the following scenario which
> can result in a deadlock. This issue was most easily reproduced by
> LXD containers using a ZFS storage backend but should be reproducible
> under any workload which is frequently mounting and unmounting.
>
> -- THREAD A --
> spa_sync()
> spa_sync_upgrades()
> rrw_enter(&dp->dp_config_rwlock, RW_WRITER, FTAG); <- Waiting on B
>
> -- THREAD B --
> mount_fs()
> zpl_mount()
> zpl_mount_impl()
> dmu_objset_hold()
> dmu_objset_hold_flags()
> dsl_pool_hold()
> dsl_pool_config_enter()
> rrw_enter(&dp->dp_config_rwlock, RW_READER, tag);
> sget()
> sget_userns()
> grab_super()
> down_write(&s->s_umount); <- Waiting on C
>
> -- THREAD C --
> cleanup_mnt()
> deactivate_super()
> down_write(&s->s_umount);
> deactivate_locked_super()
> zpl_kill_sb()
> kill_anon_super()
> generic_shutdown_super()
> sync_filesystem()
> zpl_sync_fs()
> zfs_sync()
> zil_commit()
> txg_wait_synced() <- Waiting on A
>
> Signed-off-by: Brian Behlendorf <behlendorf1 at llnl.gov>
> (backport from ZFS upstream commit ac09630d8b0bf6c92084a30fdaefd03fd0adbdc1)
> Signed-off-by: Colin Ian King <colin.king at canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>
> ---
> zfs/META | 2 +-
> zfs/include/sys/zfs_vfsops.h | 1 +
> zfs/module/zfs/zpl_super.c | 11 ++++++++++-
> 3 files changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/zfs/META b/zfs/META
> index 6837592..f34a9d6 100644
> --- a/zfs/META
> +++ b/zfs/META
> @@ -2,7 +2,7 @@ Meta: 1
> Name: zfs
> Branch: 1.0
> Version: 0.6.5.6
> -Release: 0ubuntu24
> +Release: 0ubuntu25
> Release-Tags: relext
> License: CDDL
> Author: OpenZFS on Linux
> diff --git a/zfs/include/sys/zfs_vfsops.h b/zfs/include/sys/zfs_vfsops.h
> index efaefda..49eefba 100644
> --- a/zfs/include/sys/zfs_vfsops.h
> +++ b/zfs/include/sys/zfs_vfsops.h
> @@ -32,6 +32,7 @@
> #include <sys/zil.h>
> #include <sys/sa.h>
> #include <sys/rrwlock.h>
> +#include <sys/dsl_dataset.h>
> #include <sys/zfs_ioctl.h>
>
> #ifdef __cplusplus
> diff --git a/zfs/module/zfs/zpl_super.c b/zfs/module/zfs/zpl_super.c
> index f75a0d8..fc467ae 100644
> --- a/zfs/module/zfs/zpl_super.c
> +++ b/zfs/module/zfs/zpl_super.c
> @@ -467,8 +467,17 @@ zpl_mount_impl(struct file_system_type *fs_type, int flags, zfs_mntopts_t *zmo)
> if (err)
> return (ERR_PTR(-err));
>
> + /*
> + * The dsl pool lock must be released prior to calling sget().
> + * It is possible sget() may block on the lock in grab_super()
> + * while deactivate_super() holds that same lock and waits for
> + * a txg sync. If the dsl_pool lock is held over over sget()
> + * this can prevent the pool sync and cause a deadlock.
> + */
> + dsl_pool_rele(dmu_objset_pool(os), FTAG);
> s = zpl_sget(fs_type, zpl_test_super, set_anon_super, flags, os);
> - dmu_objset_rele(os, FTAG);
> + dsl_dataset_rele(dmu_objset_ds(os), FTAG);
> +
> if (IS_ERR(s))
> return (ERR_CAST(s));
>
>
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