15 Aug, 2016
1 commit
-
The manpage for quotactl says that the Q_XGETQSTAT command is
"useful in finding out how much space is spent to store quota
information," but the current implementation does not report this
info if the inode is allocated, but its quota type is not enabled.This is a change from the earlier XFS implementation, which
reported information about allocated quota inodes even if their
quota type was not currently active.Change quota_getstate() and quota_getstatev() to copy out the inode
information if the filesystem has provided it, even if the quota
type for that inode is not currently active.Signed-off-by: Eric Sandeen
Reviewed-by: Bill O'Donnell
Signed-off-by: Jan Kara
30 Jul, 2016
1 commit
-
Pull userns vfs updates from Eric Biederman:
"This tree contains some very long awaited work on generalizing the
user namespace support for mounting filesystems to include filesystems
with a backing store. The real world target is fuse but the goal is
to update the vfs to allow any filesystem to be supported. This
patchset is based on a lot of code review and testing to approach that
goal.While looking at what is needed to support the fuse filesystem it
became clear that there were things like xattrs for security modules
that needed special treatment. That the resolution of those concerns
would not be fuse specific. That sorting out these general issues
made most sense at the generic level, where the right people could be
drawn into the conversation, and the issues could be solved for
everyone.At a high level what this patchset does a couple of simple things:
- Add a user namespace owner (s_user_ns) to struct super_block.
- Teach the vfs to handle filesystem uids and gids not mapping into
to kuids and kgids and being reported as INVALID_UID and
INVALID_GID in vfs data structures.By assigning a user namespace owner filesystems that are mounted with
only user namespace privilege can be detected. This allows security
modules and the like to know which mounts may not be trusted. This
also allows the set of uids and gids that are communicated to the
filesystem to be capped at the set of kuids and kgids that are in the
owning user namespace of the filesystem.One of the crazier corner casees this handles is the case of inodes
whose i_uid or i_gid are not mapped into the vfs. Most of the code
simply doesn't care but it is easy to confuse the inode writeback path
so no operation that could cause an inode write-back is permitted for
such inodes (aka only reads are allowed).This set of changes starts out by cleaning up the code paths involved
in user namespace permirted mounts. Then when things are clean enough
adds code that cleanly sets s_user_ns. Then additional restrictions
are added that are possible now that the filesystem superblock
contains owner information.These changes should not affect anyone in practice, but there are some
parts of these restrictions that are changes in behavior.- Andy's restriction on suid executables that does not honor the
suid bit when the path is from another mount namespace (think
/proc/[pid]/fd/) or when the filesystem was mounted by a less
privileged user.- The replacement of the user namespace implicit setting of MNT_NODEV
with implicitly setting SB_I_NODEV on the filesystem superblock
instead.Using SB_I_NODEV is a stronger form that happens to make this state
user invisible. The user visibility can be managed but it caused
problems when it was introduced from applications reasonably
expecting mount flags to be what they were set to.There is a little bit of work remaining before it is safe to support
mounting filesystems with backing store in user namespaces, beyond
what is in this set of changes.- Verifying the mounter has permission to read/write the block device
during mount.- Teaching the integrity modules IMA and EVM to handle filesystems
mounted with only user namespace root and to reduce trust in their
security xattrs accordingly.- Capturing the mounters credentials and using that for permission
checks in d_automount and the like. (Given that overlayfs already
does this, and we need the work in d_automount it make sense to
generalize this case).Furthermore there are a few changes that are on the wishlist:
- Get all filesystems supporting posix acls using the generic posix
acls so that posix_acl_fix_xattr_from_user and
posix_acl_fix_xattr_to_user may be removed. [Maintainability]- Reducing the permission checks in places such as remount to allow
the superblock owner to perform them.- Allowing the superblock owner to chown files with unmapped uids and
gids to something that is mapped so the files may be treated
normally.I am not considering even obvious relaxations of permission checks
until it is clear there are no more corner cases that need to be
locked down and handled generically.Many thanks to Seth Forshee who kept this code alive, and putting up
with me rewriting substantial portions of what he did to handle more
corner cases, and for his diligent testing and reviewing of my
changes"* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (30 commits)
fs: Call d_automount with the filesystems creds
fs: Update i_[ug]id_(read|write) to translate relative to s_user_ns
evm: Translate user/group ids relative to s_user_ns when computing HMAC
dquot: For now explicitly don't support filesystems outside of init_user_ns
quota: Handle quota data stored in s_user_ns in quota_setxquota
quota: Ensure qids map to the filesystem
vfs: Don't create inodes with a uid or gid unknown to the vfs
vfs: Don't modify inodes with a uid or gid unknown to the vfs
cred: Reject inodes with invalid ids in set_create_file_as()
fs: Check for invalid i_uid in may_follow_link()
vfs: Verify acls are valid within superblock's s_user_ns.
userns: Handle -1 in k[ug]id_has_mapping when !CONFIG_USER_NS
fs: Refuse uid/gid changes which don't map into s_user_ns
selinux: Add support for unprivileged mounts from user namespaces
Smack: Handle labels consistently in untrusted mounts
Smack: Add support for unprivileged mounts from user namespaces
fs: Treat foreign mounts as nosuid
fs: Limit file caps to the user namespace of the super block
userns: Remove the now unnecessary FS_USERNS_DEV_MOUNT flag
userns: Remove implicit MNT_NODEV fragility.
...
06 Jul, 2016
3 commits
-
Mostly supporting filesystems outside of init_user_ns is
s/&init_usre_ns/dquot->dq_sb->s_user_ns/. An actual need for
supporting quotas on filesystems outside of s_user_ns is quite a ways
away and to be done responsibily needs an audit on what can happen
with hostile quota files. Until that audit is complete don't attempt
to support quota files on filesystems outside of s_user_ns.Cc: Jan Kara
Acked-by: Seth Forshee
Signed-off-by: "Eric W. Biederman" -
In Q_XSETQLIMIT use sb->s_user_ns to detect when we are dealing with
the filesystems notion of id 0.Cc: Jan Kara
Acked-by: Seth Forshee
Inspired-by: Seth Forshee
Signed-off-by: "Eric W. Biederman" -
Introduce the helper qid_has_mapping and use it to ensure that the
quota system only considers qids that map to the filesystems
s_user_ns.In practice for quota supporting filesystems today this is the exact
same check as qid_valid. As only 0xffffffff aka (qid_t)-1 does not
map into init_user_ns.Replace the qid_valid calls with qid_has_mapping as values come in
from userspace. This is harmless today and it prepares the quota
system to work on filesystems with quotas but mounted by unprivileged
users.Call qid_has_mapping from dqget. This ensures the passed in qid has a
prepresentation on the underlying filesystem. Previously this was
unnecessary as filesystesm never had qids that could not map. With
the introduction of filesystems outside of s_user_ns this will not
remain true.All of this ensures the quota code never has to deal with qids that
don't map to the underlying filesystem.Cc: Jan Kara
Acked-by: Seth Forshee
Signed-off-by: "Eric W. Biederman"
20 Jun, 2016
1 commit
-
The quota subsystem has two formats, the old v1 format using architecture
specific time_t values on the on-disk format, while the v2 format
(introduced in Linux 2.5.16 and 2.4.22) uses fixed 64-bit little-endian.While there is no future for the v1 format beyond y2038, the v2 format
is almost there on 32-bit architectures, as both the user interface
and the on-disk format use 64-bit timestamps, just not the time_t
inbetween.This changes the internal representation to use time64_t, which will
end up doing the right thing everywhere for v2 format.Signed-off-by: Arnd Bergmann
Signed-off-by: Jan Kara
27 Apr, 2016
1 commit
-
Signed-off-by: Nicolas Dichtel
Acked-by: Jan Kara
Signed-off-by: David S. Miller
29 Mar, 2016
1 commit
-
Currently we oopsed when Q_GETNEXTQUOTA got called when quota was
disabled. Properly check whether quota is enabled for the filesystem
before calling into quota format handler.Reported-by: Ted Tso
Signed-off-by: Jan Kara
22 Mar, 2016
2 commits
-
Pull UDF and quota updates from Jan Kara:
"This contains a rewrite of UDF handling of filename encoding to fix
remaining overflow issues from Andrew Gabbasov and quota changes to
support new Q_[X]GETNEXTQUOTA quotactl for VFS quota formats"* 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs:
quota: Fix possible GPF due to uninitialised pointers
ext4: Make Q_GETNEXTQUOTA work for quota in hidden inodes
quota: Forbid Q_GETQUOTA and Q_GETNEXTQUOTA for frozen filesystem
quota: Fix possible races during quota loading
ocfs2: Implement get_next_id()
quota_v2: Implement get_next_id() for V2 quota format
quota: Add support for ->get_nextdqblk() for VFS quota
udf: Merge linux specific translation into CS0 conversion function
udf: Remove struct ustr as non-needed intermediate storage
udf: Use separate buffer for copying split names
udf: Adjust UDF_NAME_LEN to better reflect actual restrictions
udf: Join functions for UTF8 and NLS conversions
udf: Parameterize output length in udf_put_filename
quota: Allow Q_GETQUOTA for frozen filesystem
quota: Fixup comments about return value of Q_[X]GETNEXTQUOTA -
Pull xfs updates from Dave Chinner:
"There's quite a lot in this request, and there's some cross-over with
ext4, dax and quota code due to the nature of the changes being made.As for the rest of the XFS changes, there are lots of little things
all over the place, which add up to a lot of changes in the end.The major changes are that we've reduced the size of the struct
xfs_inode by ~100 bytes (gives an inode cache footprint reduction of
>10%), the writepage code now only does a single set of mapping tree
lockups so uses less CPU, delayed allocation reservations won't
overrun under random write loads anymore, and we added compile time
verification for on-disk structure sizes so we find out when a commit
or platform/compiler change breaks the on disk structure as early as
possible.Change summary:
- error propagation for direct IO failures fixes for both XFS and
ext4
- new quota interfaces and XFS implementation for iterating all the
quota IDs in the filesystem
- locking fixes for real-time device extent allocation
- reduction of duplicate information in the xfs and vfs inode, saving
roughly 100 bytes of memory per cached inode.
- buffer flag cleanup
- rework of the writepage code to use the generic write clustering
mechanisms
- several fixes for inode flag based DAX enablement
- rework of remount option parsing
- compile time verification of on-disk format structure sizes
- delayed allocation reservation overrun fixes
- lots of little error handling fixes
- small memory leak fixes
- enable xfsaild freezing again"* tag 'xfs-for-linus-4.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/dgc/linux-xfs: (66 commits)
xfs: always set rvalp in xfs_dir2_node_trim_free
xfs: ensure committed is initialized in xfs_trans_roll
xfs: borrow indirect blocks from freed extent when available
xfs: refactor delalloc indlen reservation split into helper
xfs: update freeblocks counter after extent deletion
xfs: debug mode forced buffered write failure
xfs: remove impossible condition
xfs: check sizes of XFS on-disk structures at compile time
xfs: ioends require logically contiguous file offsets
xfs: use named array initializers for log item dumping
xfs: fix computation of inode btree maxlevels
xfs: reinitialise per-AG structures if geometry changes during recovery
xfs: remove xfs_trans_get_block_res
xfs: fix up inode32/64 (re)mount handling
xfs: fix format specifier , should be %llx and not %llu
xfs: sanitize remount options
xfs: convert mount option parsing to tokens
xfs: fix two memory leaks in xfs_attr_list.c error paths
xfs: XFS_DIFLAG2_DAX limited by PAGE_SIZE
xfs: dynamically switch modes when XFS_DIFLAG2_DAX is set/cleared
...
14 Mar, 2016
1 commit
-
Signed-off-by: Al Viro
03 Mar, 2016
1 commit
-
When dqget() in __dquot_initialize() fails e.g. due to IO error,
__dquot_initialize() will pass an array of uninitialized pointers to
dqput_all() and thus can lead to deference of random data. Fix the
problem by properly initializing the array.CC: stable@vger.kernel.org
Signed-off-by: Nikolay Borisov
Signed-off-by: Jan Kara
18 Feb, 2016
2 commits
-
Commit 7955118eafc4 (quota: Allow Q_GETQUOTA for frozen filesystem)
allowed Q_GETQUOTA call for frozen filesystem. It makes sense on the
first look but zero-day testing has shown that with this change ext4
warns about starting a transaction for frozen filesystem. This happens
because ext4_acquire_dquot() prepares for allocating space for new quota
structure. Although it would be possible to implement Q_GETQUOTA for
ext4 without allocating space for non-existent structures, the matter
further complicates because OCFS2 needs to update on-disk structure use
count when a new cluster node loads quota information from disk. So just
revert the change and forbid Q_GETQUOTA together with Q_GETNEXTQUOTA for
frozen filesystem. Add comment to quotactl_cmd_write() to save us from
repeating this excercise in a few years when I forget again.Signed-off-by: Jan Kara
-
When loading new quota structure from disk, there is a possibility caller
of dqget() will see uninitialized data due to CPU reordering loads or
stores - loads from dquot can be reordered before test of DQ_ACTIVE_B
bit or setting of this bit could be reordered before filling of the
structure. Fix the issue by adding proper memory barriers.Signed-off-by: Jan Kara
09 Feb, 2016
4 commits
-
Implement functions to get id of next existing quota structure in quota
file for quota tree based formats and thus for V2 quota format.Signed-off-by: Jan Kara
-
Add infrastructure for supporting get_nextdqblk() callback for VFS
quotas. Translate the operation into a callback to appropriate
filesystem and consequently to quota format callback.Signed-off-by: Jan Kara
-
quota_cmd_write() forgot to list Q_GETQUOTA among commands allowed for
frozen filesystem. Thus Q_GETQUOTA quotactl would unnecessarily block
on frozen filesystems. Fix the issue by properly listing Q_GETQUOTA.Signed-off-by: Jan Kara
-
We actually return ENOENT, not ESRCH, when there is no structure with
higher ID from ->get_nextdqblk. Fixup comments.Signed-off-by: Jan Kara
08 Feb, 2016
3 commits
-
Q_GETNEXTQUOTA is exactly like Q_GETQUOTA, except that it
will return quota information for the id equal to or greater
than the id requested. In other words, if the requested id has
no quota, the command will return quota information for the
next higher id which does have a quota set. If no higher id
has an active quota, -ESRCH is returned.This allows filesystems to do efficient iteration in kernelspace,
much like extN filesystems do in userspace when asked to report
all active quotas.This does require a new data structure for userspace, as the
current structure does not include an ID for the returned quota
information.Today, Ext4 with a hidden quota inode requires getpwent-style
iterations, and for systems which have i.e. LDAP backends,
this can be very slow, or even impossible if iteration is not
allowed in the configuration.Signed-off-by: Eric Sandeen
Reviewed-by: Jan Kara
Signed-off-by: Dave Chinner -
Q_XGETNEXTQUOTA is exactly like Q_XGETQUOTA, except that it
will return quota information for the id equal to or greater
than the id requested. In other words, if the requested id has
no quota, the command will return quota information for the
next higher id which does have a quota set. If no higher id
has an active quota, -ESRCH is returned.This allows filesystems to do efficient iteration in kernelspace,
much like extN filesystems do in userspace when asked to report
all active quotas.The patch adds a d_id field to struct qc_dqblk so that we can
pass back the id of the quota which was found, and return it
to userspace.Today, filesystems such as XFS require getpwent-style iterations,
and for systems which have i.e. LDAP backends, this can be very
slow, or even impossible if iteration is not allowed in the
configuration.Signed-off-by: Eric Sandeen
Reviewed-by: Jan Kara
Signed-off-by: Dave Chinner -
The cmd argument to quota_quotaon() via Q_QUOTAON quotactl
is not used, so remove it.Signed-off-by: Eric Sandeen
Reviewed-by: Jan Kara
Signed-off-by: Dave Chinner
23 Jan, 2016
1 commit
-
parallel to mutex_{lock,unlock,trylock,is_locked,lock_nested},
inode_foo(inode) being mutex_foo(&inode->i_mutex).Please, use those for access to ->i_mutex; over the coming cycle
->i_mutex will become rwsem, with ->lookup() done with it held
only shared.Signed-off-by: Al Viro
04 Jan, 2016
1 commit
-
The qtree_fmt_operations structures are never modified, so declare them as
const.Done with the help of Coccinelle.
Signed-off-by: Julia Lawall
Signed-off-by: Jan Kara
14 Dec, 2015
2 commits
-
The Kconfig currently controlling compilation of this code is:
config QUOTA
bool "Quota support"...meaning that it currently is not being built as a module by anyone.
Lets remove the couple traces of modularity so that when reading the
driver there is no doubt it is builtin-only.Since module_init translates to device_initcall in the non-modular
case, the init ordering gets bumped to one level earlier when we
use the more appropriate fs_initcall here. However we've made similar
changes before without any fallout and none is expected here either.We don't delete module.h because the code in turn tries to load other
modules as appropriate and so it still needs that header.Cc: Jan Kara
Cc: Alexander Viro
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Paul Gortmaker
Signed-off-by: Jan Kara -
The Kconfig currently controlling compilation of this code is:
config QUOTA_NETLINK_INTERFACE
bool "Report quota messages through netlink interface"...meaning that it currently is not being built as a module by anyone.
Lets remove the couple traces of modularity so that when reading the
driver there is no doubt it is builtin-only.Since module_init translates to device_initcall in the non-modular
case, the init ordering gets bumped to one level earlier when we
use the more appropriate fs_initcall here. However we've made similar
changes before without any fallout and none is expected here either.Cc: Jan Kara
Signed-off-by: Paul Gortmaker
Signed-off-by: Jan Kara
06 Sep, 2015
1 commit
-
Pull vfs updates from Al Viro:
"In this one:- d_move fixes (Eric Biederman)
- UFS fixes (me; locking is mostly sane now, a bunch of bugs in error
handling ought to be fixed)- switch of sb_writers to percpu rwsem (Oleg Nesterov)
- superblock scalability (Josef Bacik and Dave Chinner)
- swapon(2) race fix (Hugh Dickins)"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (65 commits)
vfs: Test for and handle paths that are unreachable from their mnt_root
dcache: Reduce the scope of i_lock in d_splice_alias
dcache: Handle escaped paths in prepend_path
mm: fix potential data race in SyS_swapon
inode: don't softlockup when evicting inodes
inode: rename i_wb_list to i_io_list
sync: serialise per-superblock sync operations
inode: convert inode_sb_list_lock to per-sb
inode: add hlist_fake to avoid the inode hash lock in evict
writeback: plug writeback at a high level
change sb_writers to use percpu_rw_semaphore
shift percpu_counter_destroy() into destroy_super_work()
percpu-rwsem: kill CONFIG_PERCPU_RWSEM
percpu-rwsem: introduce percpu_rwsem_release() and percpu_rwsem_acquire()
percpu-rwsem: introduce percpu_down_read_trylock()
document rwsem_release() in sb_wait_write()
fix the broken lockdep logic in __sb_start_write()
introduce __sb_writers_{acquired,release}() helpers
ufs_inode_get{frag,block}(): get rid of 'phys' argument
ufs_getfrag_block(): tidy up a bit
...
18 Aug, 2015
1 commit
-
The process of reducing contention on per-superblock inode lists
starts with moving the locking to match the per-superblock inode
list. This takes the global lock out of the picture and reduces the
contention problems to within a single filesystem. This doesn't get
rid of contention as the locks still have global CPU scope, but it
does isolate operations on different superblocks form each other.Signed-off-by: Dave Chinner
Signed-off-by: Josef Bacik
Reviewed-by: Jan Kara
Reviewed-by: Christoph Hellwig
Tested-by: Dave Chinner
11 Aug, 2015
1 commit
-
We know "ret" is zero here so we can remove this condition.
Signed-off-by: Dan Carpenter
Signed-off-by: Jan Kara
24 Jul, 2015
1 commit
-
Currently when some error happened in ->acquire_dquot(), dqget() just
returned NULL. That was indistinguishable from a case when e.g. someone
run quotaoff and so was generally silently ignored. However
->acquire_dquot() can fail because of ENOSPC or EIO in which case user
should better know. So propagate error up from ->acquire_dquot properly.Signed-off-by: Jan Kara
27 Apr, 2015
1 commit
-
Pull fourth vfs update from Al Viro:
"d_inode() annotations from David Howells (sat in for-next since before
the beginning of merge window) + four assorted fixes"* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
RCU pathwalk breakage when running into a symlink overmounting something
fix I_DIO_WAKEUP definition
direct-io: only inc/dec inode->i_dio_count for file systems
fs/9p: fix readdir()
VFS: assorted d_backing_inode() annotations
VFS: fs/inode.c helpers: d_inode() annotations
VFS: fs/cachefiles: d_backing_inode() annotations
VFS: fs library helpers: d_inode() annotations
VFS: assorted weird filesystems: d_inode() annotations
VFS: normal filesystems (and lustre): d_inode() annotations
VFS: security/: d_inode() annotations
VFS: security/: d_backing_inode() annotations
VFS: net/: d_inode() annotations
VFS: net/unix: d_backing_inode() annotations
VFS: kernel/: d_inode() annotations
VFS: audit: d_backing_inode() annotations
VFS: Fix up some ->d_inode accesses in the chelsio driver
VFS: Cachefiles should perform fs modifications on the top layer only
VFS: AF_UNIX sockets should call mknod on the top layer only
16 Apr, 2015
1 commit
-
library helpers called by filesystem drivers on their own inodes
Signed-off-by: David Howells
Signed-off-by: Al Viro
19 Mar, 2015
1 commit
-
This patch adds support for a new quota type PRJQUOTA for project quota
enforcement. Also a new method get_projid() is added into dquot_operations
structure.Signed-off-by: Li Xi
Signed-off-by: Dmitry Monakhov
Reviewed-by: Jan Kara
Signed-off-by: Jan Kara
16 Mar, 2015
1 commit
04 Mar, 2015
7 commits
-
Currently quota format that supports 64-bit usage sets maximum quota
limit as 2^64-1. However quota core code uses signed numbers to track
usage and even limits themselves are stored in long long. Checking of
maximum allowable limits worked by luck until commit 14bf61ffe6ac
(quota: Switch ->get_dqblk() and ->set_dqblk() to use bytes as space
units) because variable we compared with was unsigned. After that commit
the type we compared against changed to signed and thus checks for
maximum limits with the newest VFS quota format started to refuse any
non-negative value. Later the problem was inadvertedly fixed by commit
b10a08194c2b (quota: Store maximum space limit in bytes) because we
started to compare against unsigned type as well.Fix possible future problems of this kind by setting maximum limits to
2^63-1 to avoid overflow issues.Reported-by: Carlos Carvalho
Signed-off-by: Jan Kara -
Root level in quota tree must be already allocated otherwise this block
could be used for something else.Signed-off-by: Konstantin Khlebnikov
Signed-off-by: Jan Kara -
Remove redundant calls of i_dquot(), keep pointer in local variable.
add/remove: 0/0 grow/shrink: 3/7 up/down: 40/-278 (-238)
function old new delta
__dquot_free_space 734 750 +16
__dquot_alloc_space 484 500 +16
dquot_free_inode 324 332 +8
dquot_drop 82 69 -13
vfs_load_quota_inode 1357 1341 -16
dquot_reclaim_space_nodirty 348 316 -32
dquot_disable 1980 1944 -36
dquot_claim_space_nodirty 354 314 -40
__dquot_drop 125 83 -42
__dquot_initialize 522 423 -99Signed-off-by: Konstantin Khlebnikov
Signed-off-by: Jan Kara -
Setting timers or warning counts for id 0 via Q_XSETQLIM is used to
actually set time limits and warning limits for all users. Hook up
->set_info to this so that VFS quota time limits get set the same
way as XFS ones.When doing this Q_XSETQLIM for XFS is effectively split into two
independent transactions - one for setting timers and warning limits and
one for setting space and inode limits. Although this is inefficient, it
is rare enough that it does not matter.Reviewed-by: Christoph Hellwig
Signed-off-by: Jan Kara -
Change ->set_info to take new qc_info structure which contains all the
necessary information both for XFS and VFS. Convert Q_SETINFO handler
to use this structure.Signed-off-by: Jan Kara
-
These callbacks are now unused. Remove them.
Reviewed-by: Christoph Hellwig
Signed-off-by: Jan Kara -
Add appropriate conversion functions so that filesystems supporting
->get_state() method can be queried using Q_GETXSTATE and Q_GETXSTATV
calls.Reviewed-by: Christoph Hellwig
Signed-off-by: Jan Kara
