| Message ID | 20180712110314.1295-1-colin.king@canonical.com |
|---|---|
| State | New |
| Headers | show |
| Series | [COSMIC-unstable] UBUNTU: SAUCE: (noup) zfs to 0.7.9-3ubuntu4 | expand |
On Thu, Jul 12, 2018 at 12:03:14PM +0100, Colin King wrote: > From: Colin Ian King <colin.king@canonical.com> > > BugLink: http://bugs.launchpad.net/bugs/1781364 > > This is a sync of zfs 0.7.9-3ubuntu4 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@llnl.gov> > (backport from ZFS upstream commit ac09630d8b0bf6c92084a30fdaefd03fd0adbdc1) > Signed-off-by: Colin Ian King <colin.king@canonical.com> Applied to cosmic/master-next and unstable/master, thanks!
diff --git a/zfs/META b/zfs/META index 374dda5..0e2d3d2 100644 --- a/zfs/META +++ b/zfs/META @@ -2,7 +2,7 @@ Meta: 1 Name: zfs Branch: 1.0 Version: 0.7.9 -Release: 3ubuntu3 +Release: 3ubuntu4 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 2326da4..927153b 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 fc10271..5c426b0 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));