linux/fs
Filipe Manana 06989c799f Btrfs: fix race updating log root item during fsync
When syncing the log, the final phase of a fsync operation, we need to
either create a log root's item or update the existing item in the log
tree of log roots, and that depends on the current value of the log
root's log_transid - if it's 1 we need to create the log root item,
otherwise it must exist already and we update it. Since there is no
synchronization between updating the log_transid and checking it for
deciding whether the log root's item needs to be created or updated, we
end up with a tiny race window that results in attempts to update the
item to fail because the item was not yet created:

              CPU 1                                    CPU 2

  btrfs_sync_log()

    lock root->log_mutex

    set log root's log_transid to 1

    unlock root->log_mutex

                                               btrfs_sync_log()

                                                 lock root->log_mutex

                                                 sets log root's
                                                 log_transid to 2

                                                 unlock root->log_mutex

    update_log_root()

      sees log root's log_transid
      with a value of 2

        calls btrfs_update_root(),
        which fails with -EUCLEAN
        and causes transaction abort

Until recently the race lead to a BUG_ON at btrfs_update_root(), but after
the recent commit 7ac1e464c4 ("btrfs: Don't panic when we can't find a
root key") we just abort the current transaction.

A sample trace of the BUG_ON() on a SLE12 kernel:

  ------------[ cut here ]------------
  kernel BUG at ../fs/btrfs/root-tree.c:157!
  Oops: Exception in kernel mode, sig: 5 [#1]
  SMP NR_CPUS=2048 NUMA pSeries
  (...)
  Supported: Yes, External
  CPU: 78 PID: 76303 Comm: rtas_errd Tainted: G                 X 4.4.156-94.57-default #1
  task: c00000ffa906d010 ti: c00000ff42b08000 task.ti: c00000ff42b08000
  NIP: d000000036ae5cdc LR: d000000036ae5cd8 CTR: 0000000000000000
  REGS: c00000ff42b0b860 TRAP: 0700   Tainted: G                 X  (4.4.156-94.57-default)
  MSR: 8000000002029033 <SF,VEC,EE,ME,IR,DR,RI,LE>  CR: 22444484  XER: 20000000
  CFAR: d000000036aba66c SOFTE: 1
  GPR00: d000000036ae5cd8 c00000ff42b0bae0 d000000036bda220 0000000000000054
  GPR04: 0000000000000001 0000000000000000 c00007ffff8d37c8 0000000000000000
  GPR08: c000000000e19c00 0000000000000000 0000000000000000 3736343438312079
  GPR12: 3930373337303434 c000000007a3a800 00000000007fffff 0000000000000023
  GPR16: c00000ffa9d26028 c00000ffa9d261f8 0000000000000010 c00000ffa9d2ab28
  GPR20: c00000ff42b0bc48 0000000000000001 c00000ff9f0d9888 0000000000000001
  GPR24: c00000ffa9d26000 c00000ffa9d261e8 c00000ffa9d2a800 c00000ff9f0d9888
  GPR28: c00000ffa9d26028 c00000ffa9d2aa98 0000000000000001 c00000ffa98f5b20
  NIP [d000000036ae5cdc] btrfs_update_root+0x25c/0x4e0 [btrfs]
  LR [d000000036ae5cd8] btrfs_update_root+0x258/0x4e0 [btrfs]
  Call Trace:
  [c00000ff42b0bae0] [d000000036ae5cd8] btrfs_update_root+0x258/0x4e0 [btrfs] (unreliable)
  [c00000ff42b0bba0] [d000000036b53610] btrfs_sync_log+0x2d0/0xc60 [btrfs]
  [c00000ff42b0bce0] [d000000036b1785c] btrfs_sync_file+0x44c/0x4e0 [btrfs]
  [c00000ff42b0bd80] [c00000000032e300] vfs_fsync_range+0x70/0x120
  [c00000ff42b0bdd0] [c00000000032e44c] do_fsync+0x5c/0xb0
  [c00000ff42b0be10] [c00000000032e8dc] SyS_fdatasync+0x2c/0x40
  [c00000ff42b0be30] [c000000000009488] system_call+0x3c/0x100
  Instruction dump:
  7f43d378 4bffebb9 60000000 88d90008 3d220000 e8b90000 3b390009 e87a01f0
  e8898e08 e8f90000 4bfd48e5 60000000 <0fe00000> e95b0060 39200004 394a0ea0
  ---[ end trace 8f2dc8f919cabab8 ]---

So fix this by doing the check of log_transid and updating or creating the
log root's item while holding the root's log_mutex.

Fixes: 7237f18336 ("Btrfs: fix tree logs parallel sync")
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2019-05-28 19:26:46 +02:00
..
9p Pull request for inlusion in 5.1 2019-03-17 09:10:56 -07:00
adfs adfs: use timespec64 for time conversion 2018-08-22 10:52:51 -07:00
affs
afs afs: Fix in-progess ops to ignore server-level callback invalidation 2019-04-13 08:37:37 +01:00
autofs autofs: clear O_NONBLOCK on the pipe 2019-03-07 18:32:01 -08:00
befs
bfs bfs: extra sanity checking and static inode bitmap 2019-01-04 13:13:47 -08:00
btrfs Btrfs: fix race updating log root item during fsync 2019-05-28 19:26:46 +02:00
cachefiles fscache, cachefiles: remove redundant variable 'cache' 2018-11-30 16:00:58 +00:00
ceph ceph: fix ci->i_head_snapc leak 2019-04-23 21:37:54 +02:00
cifs cifs: fix page reference leak with readv/writev 2019-04-24 12:33:59 -05:00
coda
configfs configfs: fix registered group removal 2018-07-17 06:14:07 -07:00
cramfs Make the Cramfs code more robust against filesystem corruptions, 2018-10-30 12:46:25 -07:00
crypto fscrypt updates for v5.1 2019-03-09 10:54:24 -08:00
debugfs debugfs: fix use-after-free on symlink traversal 2019-04-01 00:31:02 -04:00
devpts fs/devpts: always delete dcache dentry-s in dput() 2019-01-24 13:38:30 -05:00
dlm socket: Rename SO_RCVTIMEO/ SO_SNDTIMEO with _OLD suffixes 2019-02-03 11:17:31 -08:00
ecryptfs crypto: clarify name of WEAK_KEY request flag 2019-01-25 18:41:52 +08:00
efivarfs efivars: Call guid_parse() against guid_t type of variable 2018-07-22 14:13:44 +02:00
efs
exportfs exportfs: do not read dentry after free 2018-11-23 09:08:17 -05:00
ext2 \n 2019-03-07 09:01:33 -08:00
ext4 Miscellaneous ext4 bug fixes for 5.1. 2019-03-24 13:41:37 -07:00
f2fs f2fs-for-5.1-rc1 2019-03-15 13:42:53 -07:00
fat fat: enable .splice_write to support splice on O_DIRECT file 2019-03-07 18:32:01 -08:00
freevxfs
fscache fscache: fix race between enablement and dropping of object 2018-11-30 15:57:31 +00:00
fuse Merge branch 'page-refs' (page ref overflow) 2019-04-14 15:09:40 -07:00
gfs2 We've only got three patches ready for this merge window: 2019-03-09 11:52:11 -08:00
hfs hfs: do not free node before using 2018-11-30 14:56:14 -08:00
hfsplus hfsplus: return file attributes on statx 2019-01-04 13:13:47 -08:00
hostfs vfs: discard ATTR_ATTR_FLAG 2018-08-17 16:20:28 -07:00
hpfs hpfs: fix spelling mistake "partion" -> "partition" 2019-03-12 09:58:03 -07:00
hugetlbfs hugetlbfs: fix memory leak for resv_map 2019-04-05 16:02:31 -10:00
isofs Update email address 2018-09-29 22:47:48 -04:00
jbd2 jbd2: jbd2_get_transaction does not need to return a value 2019-03-01 00:36:57 -05:00
jffs2 jffs2: fix use-after-free on symlink traversal 2019-04-01 00:31:02 -04:00
jfs jfs: remove redundant dquot_initialize() in jfs_evict_inode() 2018-09-20 09:28:49 -05:00
kernfs Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-03-12 14:08:19 -07:00
lockd NFS: fix mount/umount race in nlmclnt. 2019-03-18 22:39:34 -04:00
minix
nfs NFSv4.1 fix incorrect return value in copy_file_range 2019-04-11 15:23:48 -04:00
nfs_common
nfsd nfsd: wake blocked file lock waiters before sending callback 2019-04-22 15:38:41 -04:00
nilfs2 XArray: Change xa_insert to return -EBUSY 2019-02-06 13:12:15 -05:00
nls
notify fanotify: Allow copying of file handle to userspace 2019-03-19 09:29:07 +01:00
ntfs mm: convert totalram_pages and totalhigh_pages variables to atomic 2018-12-28 12:11:47 -08:00
ocfs2 ocfs2: fix inode bh swapping mixup in ocfs2_reflink_inodes_lock 2019-03-29 10:01:37 -07:00
omfs
openpromfs fs/openpromfs: Use of_node_name_eq for node name comparisons 2018-11-18 13:35:19 -08:00
orangefs Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-03-12 13:27:20 -07:00
overlayfs ovl: Do not lose security.capability xattr over metadata file copy-up 2019-02-13 11:14:46 +01:00
proc fs/proc/proc_sysctl.c: Fix a NULL pointer dereference 2019-04-26 09:18:05 -07:00
pstore pstore/ram: Avoid needless alloc during header write 2019-02-12 13:45:53 -08:00
qnx4
qnx6
quota quota: Lock s_umount in exclusive mode for Q_XQUOTA{ON,OFF} quotactls. 2018-12-18 18:29:15 +01:00
ramfs
reiserfs reiserfs: remove workaround code for GCC 3.x 2018-10-31 08:54:14 -07:00
romfs
squashfs Squashfs: Compute expected length from inode size rather than block length 2018-08-02 09:34:02 -07:00
sysfs Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-03-16 10:31:02 -07:00
sysv sysv: return 'err' instead of 0 in __sysv_write_inode 2018-11-10 08:02:40 -05:00
tracefs tracefs: Annotate tracefs_ops with __ro_after_init 2018-07-31 11:32:44 -04:00
ubifs ubifs: fix use-after-free on symlink traversal 2019-04-01 00:31:02 -04:00
udf udf: Propagate errors from udf_truncate_extents() 2019-03-18 16:30:02 +01:00
ufs fs/ufs: use ktime_get_real_seconds for sb and cg timestamps 2018-08-17 16:20:27 -07:00
xfs xfs: serialize unaligned dio writes against all other dio writes 2019-03-26 08:37:55 -07:00
aio.c aio: use kmem_cache_free() instead of kfree() 2019-04-04 20:13:59 -04:00
anon_inodes.c anon_inode_getfile(): switch to alloc_file_pseudo() 2018-07-12 10:04:27 -04:00
attr.c
bad_inode.c get rid of 'opened' argument of ->atomic_open() - part 3 2018-07-12 10:04:20 -04:00
binfmt_aout.c a.out: remove core dumping support 2019-03-05 10:00:35 -08:00
binfmt_elf_fdpic.c
binfmt_elf.c fs/binfmt_elf.c: spread const a little 2019-03-07 18:32:01 -08:00
binfmt_em86.c
binfmt_flat.c
binfmt_misc.c
binfmt_script.c exec: load_script: Do not exec truncated interpreter path 2019-02-18 16:49:36 -08:00
block_dev.c block: fix the return errno for direct IO 2019-04-11 21:22:21 -06:00
buffer.c fs: fix guard_bio_eod to check for real EOD errors 2019-02-28 13:59:41 -07:00
char_dev.c
compat_binfmt_elf.c y2038: globally rename compat_time to old_time32 2018-08-27 14:48:48 +02:00
compat_ioctl.c media updates for v4.20-rc1 2018-10-29 14:29:58 -07:00
compat.c
coredump.c signal: Distinguish between kernel_siginfo and siginfo 2018-10-03 16:47:43 +02:00
d_path.c
dax.c fs/dax: Deposit pagetable even when installing zero page 2019-03-13 13:58:46 -07:00
dcache.c fs/dcache: Track & report number of negative dentries 2019-01-30 11:02:11 -08:00
dcookies.c
direct-io.c block: allow bio_for_each_segment_all() to iterate over multi-page bvec 2019-02-15 08:40:11 -07:00
drop_caches.c fs/drop_caches.c: avoid softlockups in drop_pagecache_sb() 2019-02-01 15:46:24 -08:00
eventfd.c
eventpoll.c epoll: use rwlock in order to reduce ep_poll_callback() contention 2019-03-07 18:32:01 -08:00
exec.c exec: increase BINPRM_BUF_SIZE to 256 2019-03-07 18:32:01 -08:00
fcntl.c signal: Distinguish between kernel_siginfo and siginfo 2018-10-03 16:47:43 +02:00
fhandle.c
file_table.c fs: add fget_many() and fput_many() 2019-02-28 08:24:23 -07:00
file.c io_uring-2019-03-06 2019-03-08 14:48:40 -08:00
filesystems.c vfs: Implement a filesystem superblock creation/configuration context 2019-02-28 03:29:26 -05:00
fs_context.c vfs: Implement logging through fs_context 2019-02-28 03:29:37 -05:00
fs_parser.c fs: fs_parser: fix printk format warning 2019-03-29 10:01:38 -07:00
fs_pin.c
fs_struct.c
fs_types.c fs: common implementation of file type 2019-01-21 17:48:13 +01:00
fs-writeback.c writeback: synchronize sync(2) against cgroup writeback membership switches 2019-01-22 14:39:38 -07:00
inode.c fs/inode.c: inode_set_flags(): replace opencoded set_mask_bits() 2019-03-05 21:07:13 -08:00
internal.h vfs: Add configuration parser helpers 2019-02-28 03:28:53 -05:00
io_uring.c io_uring: remove 'state' argument from io_{read,write} path 2019-04-23 08:17:58 -06:00
ioctl.c Remove 'type' argument from access_ok() function 2019-01-03 18:57:57 -08:00
iomap.c block: add BIO_NO_PAGE_REF flag 2019-03-18 10:44:48 -06:00
Kconfig Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-03-12 14:08:19 -07:00
Kconfig.binfmt kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
libfs.c
locks.c locks: wake any locks blocked on request before deadlock check 2019-03-25 08:36:24 -04:00
Makefile Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-03-12 14:08:19 -07:00
mbcache.c
mount.h saner handling of temporary namespaces 2019-01-30 17:44:07 -05:00
mpage.c block: allow bio_for_each_segment_all() to iterate over multi-page bvec 2019-02-15 08:40:11 -07:00
namei.c Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-03-12 14:08:19 -07:00
namespace.c Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-03-12 14:08:19 -07:00
no-block.c
nsfs.c
open.c fs: stream_open - opener for stream-like files so that read and write can run simultaneously without deadlock 2019-04-06 07:01:55 -10:00
pipe.c Merge branch 'page-refs' (page ref overflow) 2019-04-14 15:09:40 -07:00
pnode.c separate copying and locking mount tree on cross-userns copies 2019-01-30 17:14:50 -05:00
pnode.h separate copying and locking mount tree on cross-userns copies 2019-01-30 17:14:50 -05:00
posix_acl.c
proc_namespace.c
read_write.c fs: stream_open - opener for stream-like files so that read and write can run simultaneously without deadlock 2019-04-06 07:01:55 -10:00
readdir.c Remove 'type' argument from access_ok() function 2019-01-03 18:57:57 -08:00
select.c y2038: syscalls: rename y2038 compat syscalls 2019-02-07 00:13:27 +01:00
seq_file.c fs/seq_file.c: simplify seq_file iteration code and interface 2018-08-17 16:20:28 -07:00
signalfd.c signal: Distinguish between kernel_siginfo and siginfo 2018-10-03 16:47:43 +02:00
splice.c There tracing fixes: 2019-04-26 11:09:55 -07:00
stack.c
stat.c fs: move generic stat response attr handling to vfs_getattr_nosec 2019-02-01 01:55:45 -05:00
statfs.c vfs: add vfs_get_fsid() helper 2019-02-07 16:38:35 +01:00
super.c vfs: Add some logging to the core users of the fs_context log 2019-02-28 03:29:38 -05:00
sync.c
timerfd.c y2038: syscalls: rename y2038 compat syscalls 2019-02-07 00:13:27 +01:00
userfaultfd.c coredump: fix race condition between mmget_not_zero()/get_task_mm() and core dumping 2019-04-19 09:46:05 -07:00
utimes.c y2038: syscalls: rename y2038 compat syscalls 2019-02-07 00:13:27 +01:00
xattr.c sysfs: Do not return POSIX ACL xattrs via listxattr 2018-09-18 07:30:48 -04:00