diff options
Diffstat (limited to 'upstream-ac09630-Fix-zpl_mount-deadlock.patch')
| -rw-r--r-- | upstream-ac09630-Fix-zpl_mount-deadlock.patch | 89 |
1 files changed, 89 insertions, 0 deletions
diff --git a/upstream-ac09630-Fix-zpl_mount-deadlock.patch b/upstream-ac09630-Fix-zpl_mount-deadlock.patch new file mode 100644 index 000000000000..082964ca5641 --- /dev/null +++ b/upstream-ac09630-Fix-zpl_mount-deadlock.patch @@ -0,0 +1,89 @@ +From ac09630d8b0bf6c92084a30fdaefd03fd0adbdc1 Mon Sep 17 00:00:00 2001 +From: Brian Behlendorf <behlendorf1@llnl.gov> +Date: Wed, 11 Jul 2018 15:49:10 -0700 +Subject: [PATCH] Fix zpl_mount() deadlock + +Commit 93b43af10 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 + +Reviewed by: Alek Pinchuk <apinchuk@datto.com> +Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> +Closes #7598 +Closes #7659 +Closes #7691 +Closes #7693 +--- + include/sys/zfs_vfsops.h | 1 + + module/zfs/zpl_super.c | 11 ++++++++++- + 2 files changed, 11 insertions(+), 1 deletion(-) + +diff --git a/include/sys/zfs_vfsops.h b/include/sys/zfs_vfsops.h +index febfdff97f2..31c9c6d7f74 100644 +--- a/include/sys/zfs_vfsops.h ++++ b/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/module/zfs/zpl_super.c b/module/zfs/zpl_super.c +index fc10271b787..5c426b0a9fb 100644 +--- a/module/zfs/zpl_super.c ++++ b/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)); + |