diff options
Diffstat (limited to 'sys-fs/zfs-kmod/files/zfs-kmod-0.6.1-fix-zfsctl_expire_snapshot-deadlock.patch')
| -rw-r--r-- | sys-fs/zfs-kmod/files/zfs-kmod-0.6.1-fix-zfsctl_expire_snapshot-deadlock.patch | 73 |
1 files changed, 73 insertions, 0 deletions
diff --git a/sys-fs/zfs-kmod/files/zfs-kmod-0.6.1-fix-zfsctl_expire_snapshot-deadlock.patch b/sys-fs/zfs-kmod/files/zfs-kmod-0.6.1-fix-zfsctl_expire_snapshot-deadlock.patch new file mode 100644 index 000000000000..7cca7d1137c8 --- /dev/null +++ b/sys-fs/zfs-kmod/files/zfs-kmod-0.6.1-fix-zfsctl_expire_snapshot-deadlock.patch @@ -0,0 +1,73 @@ +From 76351672c222f28ea1b681097a9eff58a6791555 Mon Sep 17 00:00:00 2001 +From: Brian Behlendorf <behlendorf1@llnl.gov> +Date: Thu, 11 Jul 2013 14:11:32 -0700 +Subject: [PATCH] Fix zfsctl_expire_snapshot() deadlock + +It is possible for an automounted snapshot which is expiring to +deadlock with a manual unmount of the snapshot. This can occur +because taskq_cancel_id() will block if the task is currently +executing until it completes. But it will never complete because +zfsctl_unmount_snapshot() is holding the zsb->z_ctldir_lock which +zfsctl_expire_snapshot() must acquire. + +---------------------- z_unmount/0:2153 --------------------- + mutex_lock <blocking on zsb->z_ctldir_lock> + zfsctl_unmount_snapshot + zfsctl_expire_snapshot + taskq_thread + +------------------------- zfs:10690 ------------------------- + taskq_wait_id <waiting for z_unmount to exit> + taskq_cancel_id + __zfsctl_unmount_snapshot + zfsctl_unmount_snapshot <takes zsb->z_ctldir_lock> + zfs_unmount_snap + zfs_ioc_destroy_snaps_nvl + zfsdev_ioctl + do_vfs_ioctl + +We resolve the deadlock by dropping the zsb->z_ctldir_lock before +calling __zfsctl_unmount_snapshot(). The lock is only there to +prevent concurrent modification to the zsb->z_ctldir_snaps AVL +tree. Moreover, we're careful to remove the zfs_snapentry_t from +the AVL tree before dropping the lock which ensures no other tasks +can find it. On failure it's added back to the tree. + +Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> +Signed-off-by: Chris Dunlap <cdunlap@llnl.gov> +Closes #1527 +--- + module/zfs/zfs_ctldir.c | 8 ++++++++ + 1 file changed, 8 insertions(+) + +diff --git a/module/zfs/zfs_ctldir.c b/module/zfs/zfs_ctldir.c +index 4fa530b..168f853 100644 +--- a/module/zfs/zfs_ctldir.c ++++ b/module/zfs/zfs_ctldir.c +@@ -732,7 +732,11 @@ struct inode * + sep = avl_find(&zsb->z_ctldir_snaps, &search, NULL); + if (sep) { + avl_remove(&zsb->z_ctldir_snaps, sep); ++ mutex_exit(&zsb->z_ctldir_lock); ++ + error = __zfsctl_unmount_snapshot(sep, flags); ++ ++ mutex_enter(&zsb->z_ctldir_lock); + if (error == EBUSY) + avl_add(&zsb->z_ctldir_snaps, sep); + else +@@ -767,7 +771,11 @@ struct inode * + while (sep != NULL) { + next = AVL_NEXT(&zsb->z_ctldir_snaps, sep); + avl_remove(&zsb->z_ctldir_snaps, sep); ++ mutex_exit(&zsb->z_ctldir_lock); ++ + error = __zfsctl_unmount_snapshot(sep, flags); ++ ++ mutex_enter(&zsb->z_ctldir_lock); + if (error == EBUSY) { + avl_add(&zsb->z_ctldir_snaps, sep); + (*count)++; +-- +1.8.1.6 + |