Some filesystems don't use the VFS inode hash and fake the fact they
are hashed so that all the writeback code works correctly. However,
this means the evict() path still tries to remove the inode from the
hash, meaning that the inode_hash_lock() needs to be taken
unnecessarily. Hence under certain workloads the inode_hash_lock can
be contended even if the inode is never actually hashed.

To avoid this add hlist_fake to test if the inode isn't actually
hashed to avoid taking the hash lock on inodes that have never been
hashed.  Based on Dave Chinner's

inode: add IOP_NOTHASHED to avoid inode hash lock in evict

basd on Al's suggestions.  Thanks,
Signed-off-by: NJosef Bacik <jbacik@fb.com>
Reviewed-by: NJan Kara <jack@suse.cz>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Tested-by: NDave Chinner <dchinner@redhat.com>

Dave Hansen reported the following;

	My laptop has been behaving strangely with 4.2-rc2.  Once I log
	in to my X session, I start getting all kinds of strange errors
	from applications and see this in my dmesg:

        	VFS: file-max limit 8192 reached

The problem is that the file-max is calculated before memory is fully
initialised and miscalculates how much memory the kernel is using.  This
patch recalculates file-max after deferred memory initialisation.  Note
that using memory hotplug infrastructure would not have avoided this
problem as the value is not recalculated after memory hot-add.

4.1:             files_stat.max_files = 6582781
4.2-rc2:         files_stat.max_files = 8192
4.2-rc2 patched: files_stat.max_files = 6562467

Small differences with the patch applied and 4.1 but not enough to matter.
Signed-off-by: NMel Gorman <mgorman@suse.de>
Reported-by: NDave Hansen <dave.hansen@intel.com>
Cc: Nicolai Stange <nicstange@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Alex Ng <alexng@microsoft.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

They just call file_inode and then the corresponding *_inode_file_wait
function. Just make them static inlines instead.
Signed-off-by: NJeff Layton <jeff.layton@primarydata.com>

Allow callers to pass in an inode instead of a filp.
Signed-off-by: NJeff Layton <jeff.layton@primarydata.com>
Reviewed-by: N"J. Bruce Fields" <bfields@fieldses.org>
Tested-by: N"J. Bruce Fields" <bfields@fieldses.org>

To ensure it is safe to mount proc and sysfs I need to check if
filesystems that are mounted on top of them are mounted on truly empty
directories.  Given that some directories can gain entries over time,
knowing that a directory is empty right now is insufficient.

Therefore add supporting infrastructure for permantently empty
directories that proc and sysfs can use when they create mount points
for filesystems and fs_fully_visible can use to test for permanently
empty directories to ensure that nothing will be gained by mounting a
fresh copy of proc or sysfs.

Cc: stable@vger.kernel.org
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

Comment in include/linux/security.h says that ->inode_killpriv() should
be called when setuid bit is being removed and that similar security
labels (in fact this applies only to file capabilities) should be
removed at this time as well. However we don't call ->inode_killpriv()
when we remove suid bit on truncate.

We fix the problem by calling ->inode_need_killpriv() and subsequently
->inode_killpriv() on truncate the same way as we do it on file write.

After this patch there's only one user of should_remove_suid() - ocfs2 -
and indeed it's buggy because it doesn't call ->inode_killpriv() on
write. However fixing it is difficult because of special locking
constraints.
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Provide function telling whether file_remove_privs() will do anything.
Currently we only have should_remove_suid() and that does something
slightly different.
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

file_remove_suid() is a misnomer since it removes also file capabilities
stored in xattrs and sets S_NOSEC flag. Also should_remove_suid() tells
something else than whether file_remove_suid() call is necessary which
leads to bugs.
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Turn
	d_path(&file->f_path, ...);
into
	file_path(file, ...);
Signed-off-by: NMiklos Szeredi <mszeredi@suse.cz>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Make file->f_path always point to the overlay dentry so that the path in
/proc/pid/fd is correct and to ensure that label-based LSMs have access to the
overlay as well as the underlay (path-based LSMs probably don't need it).

Using my union testsuite to set things up, before the patch I see:

	[root@andromeda union-testsuite]# bash 5</mnt/a/foo107
	[root@andromeda union-testsuite]# ls -l /proc/$$/fd/
	...
	lr-x------. 1 root root 64 Jun  5 14:38 5 -> /a/foo107
	[root@andromeda union-testsuite]# stat /mnt/a/foo107
	...
	Device: 23h/35d Inode: 13381       Links: 1
	...
	[root@andromeda union-testsuite]# stat -L /proc/$$/fd/5
	...
	Device: 23h/35d Inode: 13381       Links: 1
	...

After the patch:

	[root@andromeda union-testsuite]# bash 5</mnt/a/foo107
	[root@andromeda union-testsuite]# ls -l /proc/$$/fd/
	...
	lr-x------. 1 root root 64 Jun  5 14:22 5 -> /mnt/a/foo107
	[root@andromeda union-testsuite]# stat /mnt/a/foo107
	...
	Device: 23h/35d Inode: 40346       Links: 1
	...
	[root@andromeda union-testsuite]# stat -L /proc/$$/fd/5
	...
	Device: 23h/35d Inode: 40346       Links: 1
	...

Note the change in where /proc/$$/fd/5 points to in the ls command.  It was
pointing to /a/foo107 (which doesn't exist) and now points to /mnt/a/foo107
(which is correct).

The inode accessed, however, is the lower layer.  The union layer is on device
25h/37d and the upper layer on 24h/36d.
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

FS_CGROUP_WRITEBACK indicates whether a file_system_type supports
cgroup writeback; however, different super_blocks of the same
file_system_type may or may not support cgroup writeback depending on
filesystem options.  This patch replaces FS_CGROUP_WRITEBACK with a
per-super_block flag.

super_block->s_flags carries some internal flags in the high bits but
it's exposd to userland through uapi header and running out of space
anyway.  This patch adds a new field super_block->s_iflags to carry
kernel-internal flags.  It is currently only used by the new
SB_I_CGROUPWB flag whose concatenated and abbreviated name is for
consistency with other super_block flags.

ext2_fill_super() is updated to set SB_I_CGROUPWB.

v2: Added super_block->s_iflags instead of stealing another high bit
    from sb->s_flags as suggested by Christoph and Jan.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Jan Kara <jack@suse.cz>
Cc: linux-ext4@vger.kernel.org
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@fb.com>

Some filesystems cannot call dax_fault() directly because they have
different locking and/or allocation constraints in the page fault IO
path. To handle this, we need to follow the same model as the
generic block_page_mkwrite code, where the internals are exposed via
__block_page_mkwrite() so that filesystems can wrap the correct
locking and operations around the outside. 

This is loosely based on a patch originally from Matthew Willcox.
Unlike the original patch, it does not change ext4 code, error
returns or unwritten extent conversion handling.  It also adds a
__dax_mkwrite() wrapper for .page_mkwrite implementations to do the
right thing, too.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NJan Kara <jack@suse.cz>
Signed-off-by: NDave Chinner <david@fromorbit.com>

dax_fault() currently relies on the get_block callback to attach an
io completion callback to the mapping buffer head so that it can
run unwritten extent conversion after zeroing allocated blocks.

Instead of this hack, pass the conversion callback directly into
dax_fault() similar to the get_block callback. When the filesystem
allocates unwritten extents, it will set the buffer_unwritten()
flag, and hence the dax_fault code can call the completion function
in the contexts where it is necessary without overloading the
mapping buffer head.

Note: The changes to ext4 to use this interface are suspect at best.
In fact, the way ext4 did this end_io assignment in the first place
looks suspect because it only set a completion callback when there
wasn't already some other write() call taking place on the same
inode. The ext4 end_io code looks rather intricate and fragile with
all it's reference counting and passing to different contexts for
modification via inode private pointers that aren't protected by
locks...
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Acked-by: NJan Kara <jack@suse.cz>
Signed-off-by: NDave Chinner <david@fromorbit.com>

The mechanism for detecting whether an inode should switch its wb
(bdi_writeback) association is now in place.  This patch build the
framework for the actual switching.

This patch adds a new inode flag I_WB_SWITCHING, which has two
functions.  First, the easy one, it ensures that there's only one
switching in progress for a give inode.  Second, it's used as a
mechanism to synchronize wb stat updates.

The two stats, WB_RECLAIMABLE and WB_WRITEBACK, aren't event counters
but track the current number of dirty pages and pages under writeback
respectively.  As such, when an inode is moved from one wb to another,
the inode's portion of those stats have to be transferred together;
unfortunately, this is a bit tricky as those stat updates are percpu
operations which are performed without holding any lock in some
places.

This patch solves the problem in a similar way as memcg.  Each such
lockless stat updates are wrapped in transaction surrounded by
unlocked_inode_to_wb_begin/end().  During normal operation, they map
to rcu_read_lock/unlock(); however, if I_WB_SWITCHING is asserted,
mapping->tree_lock is grabbed across the transaction.

In turn, the switching path sets I_WB_SWITCHING and waits for a RCU
grace period to pass before actually starting to switch, which
guarantees that all stat update paths are synchronizing against
mapping->tree_lock.

This patch still doesn't implement the actual switching.

v3: Updated on top of the recent cancel_dirty_page() updates.
    unlocked_inode_to_wb_begin() now nests inside
    mem_cgroup_begin_page_stat() to match the locking order.

v2: The i_wb access transaction will be used for !stat accesses too.
    Function names and comments updated accordingly.

    s/inode_wb_stat_unlocked_{begin|end}/unlocked_inode_to_wb_{begin|end}/
    s/switch_wb/switch_wbs/
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Greg Thelen <gthelen@google.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

As concurrent write sharing of an inode is expected to be very rare
and memcg only tracks page ownership on first-use basis severely
confining the usefulness of such sharing, cgroup writeback tracks
ownership per-inode.  While the support for concurrent write sharing
of an inode is deemed unnecessary, an inode being written to by
different cgroups at different points in time is a lot more common,
and, more importantly, charging only by first-use can too readily lead
to grossly incorrect behaviors (single foreign page can lead to
gigabytes of writeback to be incorrectly attributed).

To resolve this issue, cgroup writeback detects the majority dirtier
of an inode and will transfer the ownership to it.  To avoid
unnnecessary oscillation, the detection mechanism keeps track of
history and gives out the switch verdict only if the foreign usage
pattern is stable over a certain amount of time and/or writeback
attempts.

The detection mechanism has fairly low space and computation overhead.
It adds 8 bytes to struct inode (one int and two u16's) and minimal
amount of calculation per IO.  The detection mechanism converges to
the correct answer usually in several seconds of IO time when there's
a clear majority dirtier.  Even when there isn't, it can reach an
acceptable answer fairly quickly under most circumstances.

Please see wb_detach_inode() for more details.

This patch only implements detection.  Following patches will
implement actual switching.

v2: wbc_account_io() now checks whether the wbc is associated with a
    wb before dereferencing it.  This can happen when pageout() is
    writing pages directly without going through the usual writeback
    path.  As pageout() path is single-threaded, we don't want it to
    be blocked behind a slow cgroup and ultimately want it to delegate
    actual writing to the usual writeback path.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Greg Thelen <gthelen@google.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

For the planned cgroup writeback support, on each bdi
(backing_dev_info), each memcg will be served by a separate wb
(bdi_writeback).  This patch updates bdi so that a bdi can host
multiple wbs (bdi_writebacks).

On the default hierarchy, blkcg implicitly enables memcg.  This allows
using memcg's page ownership for attributing writeback IOs, and every
memcg - blkcg combination can be served by its own wb by assigning a
dedicated wb to each memcg.  This means that there may be multiple
wb's of a bdi mapped to the same blkcg.  As congested state is per
blkcg - bdi combination, those wb's should share the same congested
state.  This is achieved by tracking congested state via
bdi_writeback_congested structs which are keyed by blkcg.

bdi->wb remains unchanged and will keep serving the root cgroup.
cgwb's (cgroup wb's) for non-root cgroups are created on-demand or
looked up while dirtying an inode according to the memcg of the page
being dirtied or current task.  Each cgwb is indexed on bdi->cgwb_tree
by its memcg id.  Once an inode is associated with its wb, it can be
retrieved using inode_to_wb().

Currently, none of the filesystems has FS_CGROUP_WRITEBACK and all
pages will keep being associated with bdi->wb.

v3: inode_attach_wb() in account_page_dirtied() moved inside
    mapping_cap_account_dirty() block where it's known to be !NULL.
    Also, an unnecessary NULL check before kfree() removed.  Both
    detected by the kbuild bot.

v2: Updated so that wb association is per inode and wb is per memcg
    rather than blkcg.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: kbuild test robot <fengguang.wu@intel.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: NJens Axboe <axboe@fb.com>

cgroup writeback requires support from both bdi and filesystem sides.
Add BDI_CAP_CGROUP_WRITEBACK and FS_CGROUP_WRITEBACK to indicate
support and enable BDI_CAP_CGROUP_WRITEBACK on block based bdi's by
default.  Also, define CONFIG_CGROUP_WRITEBACK which is enabled if
both MEMCG and BLK_CGROUP are enabled.

inode_cgwb_enabled() which determines whether a given inode's both bdi
and fs support cgroup writeback is added.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: NJens Axboe <axboe@fb.com>

Now that bdi definitions are moved to backing-dev-defs.h,
backing-dev.h can include blkdev.h and inline inode_to_bdi() without
worrying about introducing circular include dependency.  The function
gets called from hot paths and fairly trivial.

This patch makes inode_to_bdi() and sb_is_blkdev_sb() that the
function calls inline.  blockdev_superblock and noop_backing_dev_info
are EXPORT_GPL'd to allow the inline functions to be used from
modules.

While at it, make sb_is_blkdev_sb() return bool instead of int.

v2: Fixed typo in description as suggested by Jan.
Signed-off-by: NTejun Heo <tj@kernel.org>
Reviewed-by: NJens Axboe <axboe@kernel.dk>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: NJens Axboe <axboe@fb.com>

This patch exports blkdev_reread_part() for block drivers, also
introduce __blkdev_reread_part().

For some drivers, such as loop, reread of partitions can be run
from the release path, and bd_mutex may already be held prior to
calling ioctl_by_bdev(bdev, BLKRRPART, 0), so introduce
__blkdev_reread_part for use in such cases.

CC: Christoph Hellwig <hch@lst.de>
CC: Jens Axboe <axboe@kernel.dk>
CC: Tejun Heo <tj@kernel.org>
CC: Alexander Viro <viro@zeniv.linux.org.uk>
CC: Markus Pargmann <mpa@pengutronix.de>
CC: Stefan Weinhuber <wein@de.ibm.com>
CC: Stefan Haberland <stefan.haberland@de.ibm.com>
CC: Sebastian Ott <sebott@linux.vnet.ibm.com>
CC: Fabian Frederick <fabf@skynet.be>
CC: Ming Lei <ming.lei@canonical.com>
CC: David Herrmann <dh.herrmann@gmail.com>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Peter Zijlstra <peterz@infradead.org>
CC: nbd-general@lists.sourceforge.net
CC: linux-s390@vger.kernel.org
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJarod Wilson <jarod@redhat.com>
Signed-off-by: NMing Lei <ming.lei@canonical.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

pointless forward declarations, stale comments
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

touch_atime is not RCU-safe, and so cannot be called on an RCU walk.
However, in situations where RCU-walk makes a difference, the symlink
will likely to accessed much more often than it is useful to update
the atime.

So split out the test of "Does the atime actually need to be updated"
into  atime_needs_update(), and have get_link() unlazy if it finds that
it will need to do that update.
Signed-off-by: NNeilBrown <neilb@suse.de>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Fresh mounts of proc and sysfs are a very special case that works very
much like a bind mount.  Unfortunately the current structure can not
preserve the MNT_LOCK... mount flags.  Therefore refactor the logic
into a form that can be modified to preserve those lock bits.

Add a new filesystem flag FS_USERNS_VISIBLE that requires some mount
of the filesystem be fully visible in the current mount namespace,
before the filesystem may be mounted.

Move the logic for calling fs_fully_visible from proc and sysfs into
fs/namespace.c where it has greater access to mount namespace state.

Cc: stable@vger.kernel.org
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

similar to kfree_put_link()
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

only one instance looks at that argument at all; that sole
exception wants inode rather than dentry.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

its only use is getting passed to nd_jump_link(), which can obtain
it from current->nameidata
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

a) instead of storing the symlink body (via nd_set_link()) and returning
an opaque pointer later passed to ->put_link(), ->follow_link() _stores_
that opaque pointer (into void * passed by address by caller) and returns
the symlink body.  Returning ERR_PTR() on error, NULL on jump (procfs magic
symlinks) and pointer to symlink body for normal symlinks.  Stored pointer
is ignored in all cases except the last one.

Storing NULL for opaque pointer (or not storing it at all) means no call
of ->put_link().

b) the body used to be passed to ->put_link() implicitly (via nameidata).
Now only the opaque pointer is.  In the cases when we used the symlink body
to free stuff, ->follow_link() now should store it as opaque pointer in addition
to returning it.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

let "fast" symlinks store the pointer to the body into ->i_link and
use simple_follow_link for ->follow_link()
Reviewed-by: NJan Kara <jack@suse.cz>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

I_DIO_WAKEUP is never directly used, but fix it up anyway.
Signed-off-by: NEric Sandeen <sandeen@redhat.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

do_blockdev_direct_IO() increments and decrements the inode
->i_dio_count for each IO operation. It does this to protect against
truncate of a file. Block devices don't need this sort of protection.

For a capable multiqueue setup, this atomic int is the only shared
state between applications accessing the device for O_DIRECT, and it
presents a scaling wall for that. In my testing, as much as 30% of
system time is spent incrementing and decrementing this value. A mixed
read/write workload improved from ~2.5M IOPS to ~9.6M IOPS, with
better latencies too. Before:

clat percentiles (usec):
 |  1.00th=[   33],  5.00th=[   34], 10.00th=[   34], 20.00th=[   34],
 | 30.00th=[   34], 40.00th=[   34], 50.00th=[   35], 60.00th=[   35],
 | 70.00th=[   35], 80.00th=[   35], 90.00th=[   37], 95.00th=[   80],
 | 99.00th=[   98], 99.50th=[  151], 99.90th=[  155], 99.95th=[  155],
 | 99.99th=[  165]

After:

clat percentiles (usec):
 |  1.00th=[   95],  5.00th=[  108], 10.00th=[  129], 20.00th=[  149],
 | 30.00th=[  155], 40.00th=[  161], 50.00th=[  167], 60.00th=[  171],
 | 70.00th=[  177], 80.00th=[  185], 90.00th=[  201], 95.00th=[  270],
 | 99.00th=[  390], 99.50th=[  398], 99.90th=[  418], 99.95th=[  422],
 | 99.99th=[  438]

In other setups, Robert Elliott reported seeing good performance
improvements:

https://lkml.org/lkml/2015/4/3/557

The more applications accessing the device, the worse it gets.

Add a new direct-io flags, DIO_SKIP_DIO_COUNT, which tells
do_blockdev_direct_IO() that it need not worry about incrementing
or decrementing the inode i_dio_count for this caller.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Elliott, Robert (Server Storage) <elliott@hp.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NJens Axboe <axboe@fb.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Let's show locks which are associated with a file descriptor in
its fdinfo file.

Currently we don't have a reliable way to determine who holds a lock.  We
can find some information in /proc/locks, but PID which is reported there
can be wrong.  For example, a process takes a lock, then forks a child and
dies.  In this case /proc/locks contains the parent pid, which can be
reused by another process.

$ cat /proc/locks
...
6: FLOCK  ADVISORY  WRITE 324 00:13:13431 0 EOF
...

$ ps -C rpcbind
  PID TTY          TIME CMD
  332 ?        00:00:00 rpcbind

$ cat /proc/332/fdinfo/4
pos:	0
flags:	0100000
mnt_id:	22
lock:	1: FLOCK  ADVISORY  WRITE 324 00:13:13431 0 EOF

$ ls -l /proc/332/fd/4
lr-x------ 1 root root 64 Mar  5 14:43 /proc/332/fd/4 -> /run/rpcbind.lock

$ ls -l /proc/324/fd/
total 0
lrwx------ 1 root root 64 Feb 27 14:50 0 -> /dev/pts/0
lrwx------ 1 root root 64 Feb 27 14:50 1 -> /dev/pts/0
lrwx------ 1 root root 64 Feb 27 14:49 2 -> /dev/pts/0

You can see that the process with the 324 pid doesn't hold the lock.

This information is required for proper dumping and restoring file
locks.
Signed-off-by: NAndrey Vagin <avagin@openvz.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Acked-by: NJeff Layton <jlayton@poochiereds.net>
Acked-by: N"J. Bruce Fields" <bfields@fieldses.org>
Acked-by: NCyrill Gorcunov <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch removes mm->mmap_sem from mm->exe_file read side.
Also it kills dup_mm_exe_file() and moves exe_file duplication into
dup_mmap() where both mmap_sems are locked.

[akpm@linux-foundation.org: fix comment typo]
Signed-off-by: NKonstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Davidlohr Bueso <dbueso@suse.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

From: Yigal Korman <yigal@plexistor.com>

[v1]
Without this patch, c/mtime is not updated correctly when mmap'ed page is
first read from and then written to.

A new xfstest is submitted for testing this (generic/080)

[v2]
Jan Kara has pointed out that if we add the
sb_start/end_pagefault pair in the new pfn_mkwrite we
are then fixing another bug where: A user could start
writing to the page while filesystem is frozen.
Signed-off-by: NYigal Korman <yigal@plexistor.com>
Signed-off-by: NBoaz Harrosh <boaz@plexistor.com>
Reviewed-by: NJan Kara <jack@suse.cz>
Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

vfs_readdir() was replaced by iterate_dir() in commit 5c0ba4e0
("[readdir] introduce iterate_dir() and dir_context").
Signed-off-by: NZhang Zhen <zhenzhang.zhang@huawei.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

... avoiding write_iter/fcntl races.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

... returning -E... upon error and amount of data left in iter after
(possible) truncation upon success.  Note, that normal case gives
a non-zero (positive) return value, so any tests for != 0 _must_ be
updated.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Conflicts:
	fs/ext4/file.c

all remaining callers are passing 0; some just obscure that fact.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Now that no one is using rw, remove it completely.
Signed-off-by: NOmar Sandoval <osandov@osandov.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

And use iov_iter_rw() instead.
Signed-off-by: NOmar Sandoval <osandov@osandov.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Most filesystems call through to these at some point, so we'll start
here.
Signed-off-by: NOmar Sandoval <osandov@osandov.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

no remaining users
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>