Add a new REQ_PRIO to let requests preempt others in the cfq I/O schedule,
and lave REQ_META purely for marking requests as metadata in blktrace.
All existing callers of REQ_META except for XFS are updated to also
set REQ_PRIO for now.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Namhyung Kim <namhyung@gmail.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Replace all occurnanced of the undocumented READ_META with READ | REQ_META
and remove the unused WRITE_META define.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Commit ae54870a1d ("ext3: Fix lock inversion in ext3_symlink()")
recalculated the number of credits needed for a long symlink, in the
process of splitting it into two transactions. However, the first
credit calculation under-counted because if selinux is enabled, credits
are needed to create the selinux xattr as well.
Overrunning the reservation will result in an OOPS in
journal_dirty_metadata() due to this assert:
J_ASSERT_JH(jh, handle->h_buffer_credits > 0);
Fix this by increasing the reservation size.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs-2.6:
jbd: change the field "b_cow_tid" of struct journal_head from type unsigned to tid_t
ext3.txt: update the links in the section "useful links" to the latest ones
ext3: Fix data corruption in inodes with journalled data
ext2: check xattr name_len before acquiring xattr_sem in ext2_xattr_get
ext3: Fix compilation with -DDX_DEBUG
quota: Remove unused declaration
jbd: Use WRITE_SYNC in journal checkpoint.
jbd: Fix oops in journal_remove_journal_head()
ext3: Return -EINVAL when start is beyond the end of fs in ext3_trim_fs()
ext3/ioctl.c: silence sparse warnings about different address spaces
ext3/ext4 Documentation: remove bh/nobh since it has been deprecated
ext3: Improve truncate error handling
ext3: use proper little-endian bitops
ext2: include fs.h into ext2_fs.h
ext3: Fix oops in ext3_try_to_allocate_with_rsv()
jbd: fix a bug of leaking jh->b_jcount
jbd: remove dependency on __GFP_NOFAIL
ext3: Convert ext3 to new truncate calling convention
jbd: Add fixed tracepoints
ext3: Add fixed tracepoints
Resolve conflicts in fs/ext3/fsync.c due to fsync locking push-down and
new fixed tracepoints.
Replace the ->check_acl method with a ->get_acl method that simply reads an
ACL from disk after having a cache miss. This means we can replace the ACL
checking boilerplate code with a single implementation in namei.c.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
new helper: posix_acl_create(&acl, gfp, mode_p). Replaces acl with
modified clone, on failure releases acl and replaces with NULL.
Returns 0 or -ve on error. All callers of posix_acl_create_masq()
switched.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
new helper: posix_acl_chmod(&acl, gfp, mode). Replaces acl with modified
clone or with NULL if that has failed; returns 0 or -ve on error. All
callers of posix_acl_chmod_masq() switched to that - they'd been doing
exactly the same thing.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This moves logic for checking the cached ACL values from low-level
filesystems into generic code. The end result is a streamlined ACL
check that doesn't need to load the inode->i_op->check_acl pointer at
all for the common cached case.
The filesystems also don't need to check for a non-blocking RCU walk
case in their acl_check() functions, because that is all handled at a
VFS layer.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
When journalling data for an inode (either because it is a symlink or
because the filesystem is mounted in data=journal mode), ext3_evict_inode()
can discard unwritten data by calling truncate_inode_pages(). This is
because we don't mark the buffer / page dirty when journalling data but only
add the buffer to the running transaction and thus mm does not know there
are still unwritten data.
Fix the problem by carefully tracking transaction containing inode's data,
committing this transaction, and writing uncheckpointed buffers when inode
should be reaped.
Signed-off-by: Jan Kara <jack@suse.cz>
Btrfs needs to be able to control how filemap_write_and_wait_range() is called
in fsync to make it less of a painful operation, so push down taking i_mutex and
the calling of filemap_write_and_wait() down into the ->fsync() handlers. Some
file systems can drop taking the i_mutex altogether it seems, like ext3 and
ocfs2. For correctness sake I just pushed everything down in all cases to make
sure that we keep the current behavior the same for everybody, and then each
individual fs maintainer can make up their mind about what to do from there.
Thanks,
Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This patch turns on barriers by default for ext3. mount -o barrier=0
will turn them off. Based on a patch from Chris Mason in the SuSE tree.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Eric Sandeen <sandeen@redhat.com>
Acked-by: Jan Kara <jack@suse.cz>
Acked-by: Jeff Mahoney <jeffm@suse.com>
Acked-by: Ted Ts'o <tytso@mit.edu>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Simple filesystems always pass inode->i_sb_bdev as the block device
argument, and never need a end_io handler. Let's simply things for
them and for my grepping activity by dropping these arguments. The
only thing not falling into that scheme is ext4, which passes and
end_io handler without needing special flags (yet), but given how
messy the direct I/O code there is use of __blockdev_direct_IO
in one instead of two out of three cases isn't going to make a large
difference anyway.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Let filesystems handle waiting for direct I/O requests themselves instead
of doing it beforehand. This means filesystem-specific locks to prevent
new dio referenes from appearing can be held. This is important to allow
generalizing i_dio_count to non-DIO_LOCKING filesystems.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Compilation of ext3/namei.c brought up an error and warning messages
when compiled with -DDX_DEBUG.
Signed-off-by: Bernd Schubert<bernd.schubert@itwm.fraunhofer.de>
Signed-off-by: Jan Kara <jack@suse.cz>
We should return -EINVAL when the FITRIM parameters are not sane, but
currently we are exiting silently if start is beyond the end of the
file system. This commit fixes this so we return -EINVAL as other file
systems do.
Signed-off-by: Lukas Czerner <lczerner@redhat.com>
CC: Jan Kara <jack@suse.cz>
Signed-off-by: Jan Kara <jack@suse.cz>
The 'from' argument for copy_from_user and the 'to' argument for
copy_to_user should both be tagged as __user address space.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Signed-off-by: Jan Kara <jack@suse.cz>
New truncate calling convention allows us to handle errors from
ext3_block_truncate_page(). So reorganize the code so that
ext3_block_truncate_page() is called before we change inode size.
This also removes unnecessary block zeroing from error recovery after failed
buffered writes (zeroing isn't needed because we could have never written
non-zero data to disk). We have to be careful and keep zeroing in direct IO
write error recovery because there we might have already overwritten end of the
last file block.
Signed-off-by: Jan Kara <jack@suse.cz>
Block allocation is called from two places: ext3_get_blocks_handle() and
ext3_xattr_block_set(). These two callers are not necessarily synchronized
because xattr code holds only xattr_sem and i_mutex, and
ext3_get_blocks_handle() may hold only truncate_mutex when called from
writepage() path. Block reservation code does not expect two concurrent
allocations to happen to the same inode and thus assertions can be triggered
or reservation structure corruption can occur.
Fix the problem by taking truncate_mutex in xattr code to serialize
allocations.
CC: Sage Weil <sage@newdream.net>
CC: stable@kernel.org
Reported-by: Fyodor Ustinov <ufm@ufm.su>
Signed-off-by: Jan Kara <jack@suse.cz>
Mostly trivial conversion. We fix a bug that IS_IMMUTABLE and IS_APPEND files
could not be truncated during failed writes as we change the code. In fact the
test is not needed at all because both IS_IMMUTABLE and IS_APPEND is tested in
upper layers in do_sys_[f]truncate(), may_write(), etc.
Signed-off-by: Jan Kara <jack@suse.cz>
This commit adds fixed tracepoints to the ext3 code. It is based on ext4
tracepoints, however due to the differences of both file systems, there
are some tracepoints missing (those for delaloc and for multi-block
allocator) and there are some ext3 specific as well (for reservation
windows).
Here is a list:
ext3_free_inode
ext3_request_inode
ext3_allocate_inode
ext3_evict_inode
ext3_drop_inode
ext3_mark_inode_dirty
ext3_write_begin
ext3_ordered_write_end
ext3_writeback_write_end
ext3_journalled_write_end
ext3_ordered_writepage
ext3_writeback_writepage
ext3_journalled_writepage
ext3_readpage
ext3_releasepage
ext3_invalidatepage
ext3_discard_blocks
ext3_request_blocks
ext3_allocate_blocks
ext3_free_blocks
ext3_sync_file_enter
ext3_sync_file_exit
ext3_sync_fs
ext3_rsv_window_add
ext3_discard_reservation
ext3_alloc_new_reservation
ext3_reserved
ext3_forget
ext3_read_block_bitmap
ext3_direct_IO_enter
ext3_direct_IO_exit
ext3_unlink_enter
ext3_unlink_exit
ext3_truncate_enter
ext3_truncate_exit
ext3_get_blocks_enter
ext3_get_blocks_exit
ext3_load_inode
Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Jan Kara <jack@suse.cz>
Tell the filesystem if we just updated timestamp (I_DIRTY_SYNC) or
anything else, so that the filesystem can track internally if it
needs to push out a transaction for fdatasync or not.
This is just the prototype change with no user for it yet. I plan
to push large XFS changes for the next merge window, and getting
this trivial infrastructure in this window would help a lot to avoid
tree interdependencies.
Also remove incorrect comments that ->dirty_inode can't block. That
has been changed a long time ago, and many implementations rely on it.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/djm/tmem:
xen: cleancache shim to Xen Transcendent Memory
ocfs2: add cleancache support
ext4: add cleancache support
btrfs: add cleancache support
ext3: add cleancache support
mm/fs: add hooks to support cleancache
mm: cleancache core ops functions and config
fs: add field to superblock to support cleancache
mm/fs: cleancache documentation
Fix up trivial conflict in fs/btrfs/extent_io.c due to includes
This fifth patch of eight in this cleancache series "opts-in"
cleancache for ext3. Filesystems must explicitly enable
cleancache by calling cleancache_init_fs anytime an instance
of the filesystem is mounted. For ext3, all other cleancache
hooks are in the VFS layer including the matching cleancache_flush_fs
hook which must be called on unmount.
Details and a FAQ can be found in Documentation/vm/cleancache.txt
[v6-v8: no changes]
[v5: jeremy@goop.org: simplify init hook and any future fs init changes]
Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Reviewed-by: Jeremy Fitzhardinge <jeremy@goop.org>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Andreas Dilger <adilger@sun.com>
Cc: Ted Ts'o <tytso@mit.edu>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Rik Van Riel <riel@redhat.com>
Cc: Jan Beulich <JBeulich@novell.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <joel.becker@oracle.com>
Cc: Nitin Gupta <ngupta@vflare.org>
When make_indexed_dir() fails (e.g. because of ENOSPC) after it has allocated
block for index tree root, we did not properly mark all changed buffers dirty.
This lead to only some of these buffers being written out and thus effectively
corrupting the directory.
Fix the issue by marking all changed data dirty even in the error failure case.
CC: stable@kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
ext3_symlink() cannot call __page_symlink() with transaction open.
__page_symlink() calls ext3_write_begin() which gets page lock which ranks
above transaction start (thus lock ordering is violated) and and also
ext3_write_begin() waits for a transaction commit when we run out of space
which never happens if we hold transaction open.
Fix the problem by stopping a transaction before calling __page_symlink()
(we have to be careful and put inode to orphan list so that it gets deleted
in case of crash) and starting another one after __page_symlink() returns
for addition of symlink into a directory.
Signed-off-by: Jan Kara <jack@suse.cz>
* 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs-2.6:
quota: Don't write quota info in dquot_commit()
ext3: Fix writepage credits computation for ordered mode
* 'for-2.6.39/core' of git://git.kernel.dk/linux-2.6-block: (65 commits)
Documentation/iostats.txt: bit-size reference etc.
cfq-iosched: removing unnecessary think time checking
cfq-iosched: Don't clear queue stats when preempt.
blk-throttle: Reset group slice when limits are changed
blk-cgroup: Only give unaccounted_time under debug
cfq-iosched: Don't set active queue in preempt
block: fix non-atomic access to genhd inflight structures
block: attempt to merge with existing requests on plug flush
block: NULL dereference on error path in __blkdev_get()
cfq-iosched: Don't update group weights when on service tree
fs: assign sb->s_bdi to default_backing_dev_info if the bdi is going away
block: Require subsystems to explicitly allocate bio_set integrity mempool
jbd2: finish conversion from WRITE_SYNC_PLUG to WRITE_SYNC and explicit plugging
jbd: finish conversion from WRITE_SYNC_PLUG to WRITE_SYNC and explicit plugging
fs: make fsync_buffers_list() plug
mm: make generic_writepages() use plugging
blk-cgroup: Add unaccounted time to timeslice_used.
block: fixup plugging stubs for !CONFIG_BLOCK
block: remove obsolete comments for blkdev_issue_zeroout.
blktrace: Use rq->cmd_flags directly in blk_add_trace_rq.
...
Fix up conflicts in fs/{aio.c,super.c}
Original computation forgets to count writes of indirect block themselves
(it only counts with blocks necessary for their allocation) in ordered mode.
Acked-by: Amir Goldstein <amir73il@users.sf.net>
Signed-off-by:Yongqiang Yang <xiaoqiangnk@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
And give it a kernel-doc comment.
[akpm@linux-foundation.org: btrfs changed in linux-next]
Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Daniel Lezcano <daniel.lezcano@free.fr>
Acked-by: David Howells <dhowells@redhat.com>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs-2.6:
ext3: Always set dx_node's fake_dirent explicitly.
ext3: Fix an overflow in ext3_trim_fs.
jbd: Remove one to many n's in a word.
ext3: skip orphan cleanup on rocompat fs
ext2: Fix link count corruption under heavy link+rename load
ext3: speed up group trim with the right free block count.
ext3: Adjust trim start with first_data_block.
quota: return -ENOMEM when memory allocation fails
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/security-testing-2.6: (33 commits)
AppArmor: kill unused macros in lsm.c
AppArmor: cleanup generated files correctly
KEYS: Add an iovec version of KEYCTL_INSTANTIATE
KEYS: Add a new keyctl op to reject a key with a specified error code
KEYS: Add a key type op to permit the key description to be vetted
KEYS: Add an RCU payload dereference macro
AppArmor: Cleanup make file to remove cruft and make it easier to read
SELinux: implement the new sb_remount LSM hook
LSM: Pass -o remount options to the LSM
SELinux: Compute SID for the newly created socket
SELinux: Socket retains creator role and MLS attribute
SELinux: Auto-generate security_is_socket_class
TOMOYO: Fix memory leak upon file open.
Revert "selinux: simplify ioctl checking"
selinux: drop unused packet flow permissions
selinux: Fix packet forwarding checks on postrouting
selinux: Fix wrong checks for selinux_policycap_netpeer
selinux: Fix check for xfrm selinux context algorithm
ima: remove unnecessary call to ima_must_measure
IMA: remove IMA imbalance checking
...
File system UUID is made available to application
via /proc/<pid>/mountinfo
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Now that VFS check for inode->i_nlink == 0 and returns proper
error, remove similar check from file system
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Code has been converted over to the new explicit on-stack plugging,
and delay users have been converted to use the new API for that.
So lets kill off the old plugging along with aops->sync_page().
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
(crossport of 1f7bebb9e9
by Andreas Schlick <schlick@lavabit.com>)
When ext3_dx_add_entry() has to split an index node, it has to ensure that
name_len of dx_node's fake_dirent is also zero, because otherwise e2fsck
won't recognise it as an intermediate htree node and consider the htree to
be corrupted.
CC: stable@kernel.org
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
In a bs=4096 volume, if we call FITRIM with the following parameter as
fstrim_range(start = 102400, len = 134144000, minlen = 10240), with the
following code:
if (len >= EXT3_BLOCKS_PER_GROUP(sb))
len -= (EXT3_BLOCKS_PER_GROUP(sb) - first_block);
else
last_block = first_block + len;
So if len < EXT3_BLOCKS_PER_GROUP while first_block + len >
EXT3_BLOCKS_PER_GROUP, last_block will be set to an overflow value
which exceeds EXT3_BLOCKS_PER_GROUP.
This patch fixes it and adjusts len and last_block accordingly.
Cc: Lukas Czerner <lczerner@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Orphan cleanup is currently executed even if the file system has some
number of unknown ROCOMPAT features, which deletes inodes and frees
blocks, which could be very bad for some RO_COMPAT features.
This patch skips the orphan cleanup if it contains readonly compatible
features not known by this ext3 implementation, which would prevent
the fs from being mounted (or remounted) readwrite.
Signed-off-by: Amir Goldstein <amir73il@users.sf.net>
Signed-off-by: Jan Kara <jack@suse.cz>
When we trim some free blocks in a group of ext3, we should
calculate the free blocks properly and check whether there are
enough freed blocks left for us to trim. Current solution will
only calculate free spaces if they are large for a trim which
is wrong.
Let us see a small example:
a group has 1.5M free which are 300k, 300k, 300k, 300k, 300k.
And minblocks is 1M. With current solution, we have to iterate
the whole group since these 300k will never be subtracted from
1.5M. But actually we should exit after we find the first 2
free spaces since the left 3 chunks only sum up to 900K if we
subtract the first 600K although they can't be trimed.
Cc: Jan Kara <jack@suse.cz>
Cc: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: Jan Kara <jack@suse.cz>
As we have make the consense in the e-mail[1], the trim start should
be added with first_data_block. So this patch fulfill it and remove
the check for start < first_data_block.
[1] http://www.spinics.net/lists/linux-ext4/msg22737.html
Cc: Jan Kara <jack@suse.cz>
Cc: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: Jan Kara <jack@suse.cz>
SELinux would like to implement a new labeling behavior of newly created
inodes. We currently label new inodes based on the parent and the creating
process. This new behavior would also take into account the name of the
new object when deciding the new label. This is not the (supposed) full path,
just the last component of the path.
This is very useful because creating /etc/shadow is different than creating
/etc/passwd but the kernel hooks are unable to differentiate these
operations. We currently require that userspace realize it is doing some
difficult operation like that and than userspace jumps through SELinux hoops
to get things set up correctly. This patch does not implement new
behavior, that is obviously contained in a seperate SELinux patch, but it
does pass the needed name down to the correct LSM hook. If no such name
exists it is fine to pass NULL.
Signed-off-by: Eric Paris <eparis@redhat.com>
* 'for-2.6.38/core' of git://git.kernel.dk/linux-2.6-block: (43 commits)
block: ensure that completion error gets properly traced
blktrace: add missing probe argument to block_bio_complete
block cfq: don't use atomic_t for cfq_group
block cfq: don't use atomic_t for cfq_queue
block: trace event block fix unassigned field
block: add internal hd part table references
block: fix accounting bug on cross partition merges
kref: add kref_test_and_get
bio-integrity: mark kintegrityd_wq highpri and CPU intensive
block: make kblockd_workqueue smarter
Revert "sd: implement sd_check_events()"
block: Clean up exit_io_context() source code.
Fix compile warnings due to missing removal of a 'ret' variable
fs/block: type signature of major_to_index(int) to major_to_index(unsigned)
block: convert !IS_ERR(p) && p to !IS_ERR_NOR_NULL(p)
cfq-iosched: don't check cfqg in choose_service_tree()
fs/splice: Pull buf->ops->confirm() from splice_from_pipe actors
cdrom: export cdrom_check_events()
sd: implement sd_check_events()
sr: implement sr_check_events()
...
As Al Viro pointed out path resolution during Q_QUOTAON calls to quotactl
is prone to deadlocks. We hold s_umount semaphore for reading during the
path resolution and resolution itself may need to acquire the semaphore
for writing when e. g. autofs mountpoint is passed.
Solve the problem by performing the resolution before we get hold of the
superblock (and thus s_umount semaphore). The whole thing is complicated
by the fact that some filesystems (OCFS2) ignore the path argument. So to
distinguish between filesystem which want the path and which do not we
introduce new .quota_on_meta callback which does not get the path. OCFS2
then uses this callback instead of old .quota_on.
CC: Al Viro <viro@ZenIV.linux.org.uk>
CC: Christoph Hellwig <hch@lst.de>
CC: Ted Ts'o <tytso@mit.edu>
CC: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Christoph Hellwig