path: root/fs
diff options
authorRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>2015-03-12 16:26:00 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-03-26 15:00:59 +0100
commitf37b5d42b6d1e5da217c40b1cd3efa1df79eebd0 (patch)
tree43cb4a47aaa591e4c3fee93d458b8631931ced59 /fs
parentb94eb12be1054306bcb349ab45ce655e0b76f544 (diff)
nilfs2: fix deadlock of segment constructor during recovery
commit 283ee1482f349d6c0c09dfb725db5880afc56813 upstream. According to a report from Yuxuan Shui, nilfs2 in kernel 3.19 got stuck during recovery at mount time. The code path that caused the deadlock was as follows: nilfs_fill_super() load_nilfs() nilfs_salvage_orphan_logs() * Do roll-forwarding, attach segment constructor for recovery, and kick it. nilfs_segctor_thread() nilfs_segctor_thread_construct() * A lock is held with nilfs_transaction_lock() nilfs_segctor_do_construct() nilfs_segctor_drop_written_files() iput() iput_final() write_inode_now() writeback_single_inode() __writeback_single_inode() do_writepages() nilfs_writepage() nilfs_construct_dsync_segment() nilfs_transaction_lock() --> deadlock This can happen if commit 7ef3ff2fea8b ("nilfs2: fix deadlock of segment constructor over I_SYNC flag") is applied and roll-forward recovery was performed at mount time. The roll-forward recovery can happen if datasync write is done and the file system crashes immediately after that. For instance, we can reproduce the issue with the following steps: < nilfs2 is mounted on /nilfs (device: /dev/sdb1) > # dd if=/dev/zero of=/nilfs/test bs=4k count=1 && sync # dd if=/dev/zero of=/nilfs/test conv=notrunc oflag=dsync bs=4k count=1 && reboot -nfh < the system will immediately reboot > # mount -t nilfs2 /dev/sdb1 /nilfs The deadlock occurs because iput() can run segment constructor through writeback_single_inode() if MS_ACTIVE flag is not set on sb->s_flags. The above commit changed segment constructor so that it calls iput() asynchronously for inodes with i_nlink == 0, but that change was imperfect. This fixes the another deadlock by deferring iput() in segment constructor even for the case that mount is not finished, that is, for the case that MS_ACTIVE flag is not set. Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> Reported-by: Yuxuan Shui <yshuiv7@gmail.com> Tested-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs')
1 files changed, 4 insertions, 3 deletions
diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
index b3c95c1a4700..99294a286e66 100644
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -1906,6 +1906,7 @@ static void nilfs_segctor_drop_written_files(struct nilfs_sc_info *sci,
struct the_nilfs *nilfs)
struct nilfs_inode_info *ii, *n;
+ int during_mount = !(sci->sc_super->s_flags & MS_ACTIVE);
int defer_iput = false;
@@ -1918,10 +1919,10 @@ static void nilfs_segctor_drop_written_files(struct nilfs_sc_info *sci,
ii->i_bh = NULL;
- if (!ii->vfs_inode.i_nlink) {
+ if (!ii->vfs_inode.i_nlink || during_mount) {
- * Defer calling iput() to avoid a deadlock
- * over I_SYNC flag for inodes with i_nlink == 0
+ * Defer calling iput() to avoid deadlocks if
+ * i_nlink == 0 or mount is not yet finished.
list_add_tail(&ii->i_dirty, &sci->sc_iput_queue);
defer_iput = true;