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linux/fs/nilfs2
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Ryusuke Konishi 283ee1482f nilfs2: fix deadlock of segment constructor during recovery 
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 7ef3ff2fea ("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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-03-12 18:46:08 -07:00
..
alloc.c
alloc.h
bmap.c
bmap.h
btnode.c
btnode.h
btree.c nilfs2: fix potential memory overrun on inode 2015-02-28 09:57:51 -08:00
btree.h
cpfile.c
cpfile.h
dat.c
dat.h
dir.c
direct.c
direct.h
export.h
file.c mm: drop vm_ops->remap_pages and generic_file_remap_pages() stub 2015-02-10 14:30:30 -08:00
gcinode.c fs: remove mapping->backing_dev_info 2015-01-20 14:03:05 -07:00
ifile.c
ifile.h
inode.c nilfs2: fix the nilfs_iget() vs. nilfs_new_inode() races 2014-12-10 17:41:16 -08:00
ioctl.c
Kconfig
Makefile
mdt.c fs: remove mapping->backing_dev_info 2015-01-20 14:03:05 -07:00
mdt.h
namei.c nilfs2: fix the nilfs_iget() vs. nilfs_new_inode() races 2014-12-10 17:41:16 -08:00
nilfs.h nilfs2: fix deadlock of segment constructor over I_SYNC flag 2015-02-05 13:35:29 -08:00
page.c fs: remove mapping->backing_dev_info 2015-01-20 14:03:05 -07:00
page.h fs: remove mapping->backing_dev_info 2015-01-20 14:03:05 -07:00
recovery.c
segbuf.c
segbuf.h
segment.c nilfs2: fix deadlock of segment constructor during recovery 2015-03-12 18:46:08 -07:00
segment.h nilfs2: fix deadlock of segment constructor over I_SYNC flag 2015-02-05 13:35:29 -08:00
sufile.c
sufile.h
super.c fs: remove mapping->backing_dev_info 2015-01-20 14:03:05 -07:00
sysfs.c
sysfs.h
the_nilfs.c
the_nilfs.h