APPLIED: [PATCH][SRU][BIONIC] UBUNTU: SAUCE: (noup) zfs to 0.7.5-1ubuntu16.3

[Kleber Souza]

On 07/12/18 15:41, 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 0.7.5-1ubuntu16.3 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>
> ---
>  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 2110eef1b19d..c0a1e936665d 100644
> --- a/zfs/META
> +++ b/zfs/META
> @@ -2,7 +2,7 @@ Meta:         1
>  Name:         zfs
>  Branch:       1.0
>  Version:      0.7.5
> -Release:      1ubuntu15
> +Release:      1ubuntu16.3
>  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 2326da422183..927153b25af9 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 848bb3c10627..6292e2c2e2df 100644
> --- a/zfs/module/zfs/zpl_super.c
> +++ b/zfs/module/zfs/zpl_super.c
> @@ -271,8 +271,17 @@ zpl_mount_impl(struct file_system_type *fs_type, int flags, zfs_mnt_t *zm)
>  	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));
>  
> 

Applied to bionic/master-next branch.

Thanks,
Kleber