FWIW, there's a bit of abuse of struct kstat in overlayfs object
creation paths - for one thing, it ends up with a very small subset
of struct kstat (mode + rdev), for another it also needs link in
case of symlinks and ends up passing it separately.

IMO it would be better to introduce a separate object for that.

In principle, we might even lift that thing into general API and switch
 ->mkdir()/->mknod()/->symlink() to identical calling conventions.  Hell
knows, perhaps ->create() as well...
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

This removes code duplication.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

The benefit of making directories opaque on creation is that lookups can
stop short when they reach the original created directory, instead of
continue lookup the entire depth of parent directory stack.

The best case is overlay with N layers, performing lookup for first level
directory, which exists only in upper.  In that case, there will be only
one lookup instead of N.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

oe->opaque is set for

 a) whiteouts
 b) directories having the "trusted.overlay.opaque" xattr

Case b can be simplified, since setting the xattr always implies setting
oe->opaque.  Also once set, the opaque flag is never cleared.

Don't need to set opaque flag for non-directories.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Show the value of redirect_dir in /proc/mounts.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Add a module option to allow tuning the max size of absolute redirects.
Default is 256.

Size of relative redirects is naturally limited by the the underlying
filesystem's max filename length (usually 255).
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

This patch introduces a kernel config option and a module param.  Both can
be used independently to turn the default value of redirect_dir on or off.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Before introducing redirect_dir feature, the condition
!ovl_lower_positive(dentry) for a directory, implied that it is a pure
upper directory, which may be removed if empty.

Now that directory can be redirect, it is possible that upper does not
cover any lower (i.e. !ovl_lower_positive(dentry)), but the directory is a
merge (with redirected path) and maybe non empty.

Check for this case in ovl_remove_upper().

This change fixes the following test case from rename-pop-dir.py
of unionmount-testsuite:

    """Remove dir and rename old name"""
    d = ctx.non_empty_dir()
    d2 = ctx.no_dir()

    ctx.rmdir(d, err=ENOTEMPTY)
    ctx.rename(d, d2)
    ctx.rmdir(d, err=ENOENT)
    ctx.rmdir(d2, err=ENOTEMPTY)

./run --ov rename-pop-dir
/mnt/a/no_dir103: Expected error (Directory not empty) was not produced
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Current code returns EXDEV when a directory would need to be copied up to
move.  We could copy up the directory tree in this case, but there's
another, simpler solution: point to old lower directory from moved upper
directory.

This is achieved with a "trusted.overlay.redirect" xattr storing the path
relative to the root of the overlay.  After such attribute has been set,
the directory can be moved without further actions required.

This is a backward incompatible feature, old kernels won't be able to
correctly mount an overlay containing redirected directories.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

If a directory has the "trusted.overlay.redirect" xattr, it means that the
value of the xattr should be used to find the underlying directory on the
next lower layer.

The redirect may be relative or absolute.  Absolute redirects begin with a
slash.

A relative redirect means: instead of the current dentry's name use the
value of the redirect to find the directory in the next lower
layer. Relative redirects must not contain a slash.

An absolute redirect means: look up the directory relative to the root of
the overlay using the value of the redirect in the next lower layer.

Redirects work on lower layers as well.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Use a common helper for lookup of upper and lower layers.  This paves the
way for looking up directory redirects.

No functional change.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

When the upper overlayfs checks "trusted.overlay.*" xattr on the underlying
overlayfs mount, it gets -EPERM, which confuses the upper overlayfs.

Fix this by returning -EOPNOTSUPP instead of -EPERM from
ovl_own_xattr_get() and ovl_own_xattr_set().  This behavior is consistent
with the behavior of ovl_listxattr(), which filters out the private
overlayfs xattrs.

Note: nested overlays are deprecated.  But this change makes sense
regardless: these xattrs are private to the overlay and should always be
hidden.  Hence getting and setting them should indicate this.

[SzMi: Use EOPNOTSUPP instead of ENODATA and use it for both getting and
setting "trusted.overlay." xattrs.  This is a perfectly valid error code
for "we don't support this prefix", which is the case here.]
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

We already calculate f_namelen in statfs as the maximum of the name lengths
provided by the filesystems taking part in the overlay.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/overlayfs/super.c is the biggest of the overlayfs source files and it
contains various utility functions as well as the rather complicated lookup
code.  Split these parts out to separate files.

Before:

 1446 fs/overlayfs/super.c

After:

  919 fs/overlayfs/super.c
  267 fs/overlayfs/namei.c
  235 fs/overlayfs/util.c
   51 fs/overlayfs/ovl_entry.h
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

If encountering a non-directory, then stop looking at lower layers.

In this case the oe->opaque flag is not set anymore, which doesn't matter
since existence of lower file is now checked at remove/rename time.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Check if something exists on the lower layer(s) under the target or rename
to decide if directory needs to be marked "opaque".

Marking opaque is done before the rename, and on failure the marking was
undone.  Also the opaque xattr was removed if the target didn't cover
anything.

This patch changes behavior so that removal of "opaque" is not done in
either of the above cases.  This means that directory may have the opaque
flag even if it doesn't cover anything.  However this shouldn't affect the
performance or semantics of the overalay, while simplifying the code.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

d_is_dir() is safe to call on a negative dentry.  Use this fact to simplify
handling of the lower or merged directories.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

The remainging uses of __OVL_PATH_PURE can be replaced by
ovl_dentry_is_opaque().
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Currently ovl_lookup() checks existence of lower file even if there's a
non-directory on upper (which is always opaque).  This is done so that
remove can decide whether a whiteout is needed or not.

It would be better to defer this check to unlink, since most of the time
the gathered information about opaqueness will be unused.

This adds a helper ovl_lower_positive() that checks if there's anything on
the lower layer(s).

The following patches also introduce changes to how the "opaque" attribute
is updated on directories: this attribute is added when the directory is
creted or moved over a whiteout or object covering something on the lower
layer.  However following changes will allow the attribute to remain on the
directory after being moved, even if the new location doesn't cover
anything.  Because of this, we need to check lower layers even for opaque
directories, so that whiteout is only created when necessary.

This function will later be also used to decide about marking a directory
opaque, so deal with negative dentries as well.  When dealing with
negative, it's enough to check for being a whiteout

If the dentry is positive but not upper then it also obviously needs
whiteout/opaque.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

And use it instead of ovl_dentry_is_opaque() where appropriate.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Since commit 07a2daab ("ovl: Copy up underlying inode's ->i_mode to
overlay inode") sticky checking on overlay inode is performed by the vfs,
so checking against sticky on underlying inode is not needed.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

This is redundant, the vfs already performed this check (and was broken,
see commit 9409e22a ("vfs: rename: check backing inode being equal")).
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

No sense in opening special files on the underlying layers, they work just
as well if opened on the overlay.

Side effect is that it's no longer possible to connect one side of a pipe
opened on overlayfs with the other side opened on the underlying layer.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

When copying up within the same fs, try to use vfs_clone_file_range().
This is very efficient when lower and upper are on the same fs
with file reflink support. If vfs_clone_file_range() fails for any
reason, copy up falls back to the regular data copy code.

Tested correct behavior when lower and upper are on:
1. same ext4 (copy)
2. same xfs + reflink patches + mkfs.xfs (copy)
3. same xfs + reflink patches + mkfs.xfs -m reflink=1 (reflink)
4. different xfs + reflink patches + mkfs.xfs -m reflink=1 (copy)

For comparison, on my laptop, xfstest overlay/001 (copy up of large
sparse files) takes less than 1 second in the xfs reflink setup vs.
25 seconds on the rest of the setups.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

This reverts commit 03bea604.

Commit 4d0c5ba2 ("vfs: do get_write_access() on upper layer of
overlayfs") makes the writecount checks inside overlayfs superfluous, the
file is already copied up and write access acquired on the upper inode when
ovl_setattr is called with ATTR_SIZE.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

The quirk for file locks and leases no longer applies.

Add missing info about renaming directory residing on lower layer.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

With overlayfs, it is wrong to compare file_inode(inode)->i_sb
of regular files with those of non-regular files, because the
former reference the real (upper/lower) sb and the latter reference
the overlayfs sb.

Move the test for same super block after the sanity tests for
clone range of directory and non-regular file.

This change fixes xfstest generic/157, which returned EXDEV instead
of EISDIR/EINVAL in the following test cases over overlayfs:

  echo "Try to reflink a dir"
  _reflink_range $testdir1/dir1 0 $testdir1/file2 0 $blksz

  echo "Try to reflink a device"
  _reflink_range $testdir1/dev1 0 $testdir1/file2 0 $blksz
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Move sb_start_write()/sb_end_write() out of the vfs helper and up into the
ioctl handler.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

FICLONE/FICLONERANGE ioctls return -EXDEV if src and dest
files are not on the same mount point.
Practically, clone only requires that src and dest files
are on the same file system.

Move the check for same mount point to ioctl handler and keep
only the check for same super block in the vfs helper.

A following patch is going to use the vfs_clone_file_range()
helper in overlayfs to copy up between lower and upper
mount points on the same file system.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

We've checked for file_out being opened for write.  This ensures that we
already have mnt_want_write() on target.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

This reverts commit 9409e22a.

Since commit 51f7e52d ("ovl: share inode for hard link") there's no
need to call d_real_inode() to check two overlay inodes for equality.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

This reverts commit eb0a4a47.

Since commit 51f7e52d ("ovl: share inode for hard link") there's no
need to call d_real_inode() to check two overlay inodes for equality.

Side effect of this revert is that it's no longer possible to connect one
socket on overlayfs to one on the underlying layer (something which didn't
make sense anyway).
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Pull drm fixes from Dave Airlie:
 "A pretty small pull request: a couple of AMD powerxpress regression
  fixes and a power management fix, a couple of i915 fixes and one hdlcd
  fix, along with one core don't oops because of incorrect API usage fix"

* tag 'drm-fixes-for-v4.9-rc8' of git://people.freedesktop.org/~airlied/linux:
  drm/i915: drop the struct_mutex when wedged or trying to reset
  drm/i915: Don't touch NULL sg on i915_gem_object_get_pages_gtt() error
  drm: Don't call drm_for_each_crtc with a non-KMS driver
  drm/radeon: fix check for port PM availability
  drm/amdgpu: fix check for port PM availability
  drm/amd/powerplay: initialize the soft_regs offset in struct smu7_hwmgr
  drm: hdlcd: Fix cleanup order

Merge tag 'drm-intel-fixes-2016-12-01' of git://anongit.freedesktop.org/git/drm-intel into drm-fixes

2 intel fixes.

* tag 'drm-intel-fixes-2016-12-01' of git://anongit.freedesktop.org/git/drm-intel:
  drm/i915: drop the struct_mutex when wedged or trying to reset
  drm/i915: Don't touch NULL sg on i915_gem_object_get_pages_gtt() error

Merge more fixes from Andrew Morton:
 "2 fixes"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
  mm, vmscan: add cond_resched() into shrink_node_memcg()
  mm: workingset: fix NULL ptr in count_shadow_nodes

Boris Zhmurov has reported RCU stalls during the kswapd reclaim:

  INFO: rcu_sched detected stalls on CPUs/tasks:
   23-...: (22 ticks this GP) idle=92f/140000000000000/0 softirq=2638404/2638404 fqs=23
   (detected by 4, t=6389 jiffies, g=786259, c=786258, q=42115)
  Task dump for CPU 23:
  kswapd1         R  running task        0   148      2 0x00000008
  Call Trace:
    shrink_node+0xd2/0x2f0
    kswapd+0x2cb/0x6a0
    mem_cgroup_shrink_node+0x160/0x160
    kthread+0xbd/0xe0
    __switch_to+0x1fa/0x5c0
    ret_from_fork+0x1f/0x40
    kthread_create_on_node+0x180/0x180

a closer code inspection has shown that we might indeed miss all the
scheduling points in the reclaim path if no pages can be isolated from
the LRU list.  This is a pathological case but other reports from Donald
Buczek have shown that we might indeed hit such a path:

        clusterd-989   [009] .... 118023.654491: mm_vmscan_direct_reclaim_end: nr_reclaimed=193
         kswapd1-86    [001] dN.. 118023.987475: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239830 nr_taken=0 file=1
         kswapd1-86    [001] dN.. 118024.320968: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239844 nr_taken=0 file=1
         kswapd1-86    [001] dN.. 118024.654375: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239858 nr_taken=0 file=1
         kswapd1-86    [001] dN.. 118024.987036: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239872 nr_taken=0 file=1
         kswapd1-86    [001] dN.. 118025.319651: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239886 nr_taken=0 file=1
         kswapd1-86    [001] dN.. 118025.652248: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239900 nr_taken=0 file=1
         kswapd1-86    [001] dN.. 118025.984870: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4239914 nr_taken=0 file=1
  [...]
         kswapd1-86    [001] dN.. 118084.274403: mm_vmscan_lru_isolate: isolate_mode=0 classzone=0 order=0 nr_requested=32 nr_scanned=4241133 nr_taken=0 file=1

this is minute long snapshot which didn't take a single page from the
LRU.  It is not entirely clear why only 1303 pages have been scanned
during that time (maybe there was a heavy IRQ activity interfering).

In any case it looks like we can really hit long periods without
scheduling on non preemptive kernels so an explicit cond_resched() in
shrink_node_memcg which is independent on the reclaim operation is due.

Link: http://lkml.kernel.org/r/20161202095841.16648-1-mhocko@kernel.orgSigned-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: Boris Zhmurov <bb@kernelpanic.ru>
Tested-by: Boris Zhmurov <bb@kernelpanic.ru>
Reported-by: Donald Buczek <buczek@molgen.mpg.de>
Reported-by: "Christopher S. Aker" <caker@theshore.net>
Reported-by: Paul Menzel <pmenzel@molgen.mpg.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Commit 0a6b76dd ("mm: workingset: make shadow node shrinker memcg
aware") has made the workingset shadow nodes shrinker memcg aware.  The
implementation is not correct though because memcg_kmem_enabled() might
become true while we are doing a global reclaim when the sc->memcg might
be NULL which is exactly what Marek has seen:

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000400
  IP: [<ffffffff8122d520>] mem_cgroup_node_nr_lru_pages+0x20/0x40
  PGD 0
  Oops: 0000 [#1] SMP
  CPU: 0 PID: 60 Comm: kswapd0 Tainted: G           O   4.8.10-12.pvops.qubes.x86_64 #1
  task: ffff880011863b00 task.stack: ffff880011868000
  RIP: mem_cgroup_node_nr_lru_pages+0x20/0x40
  RSP: e02b:ffff88001186bc70  EFLAGS: 00010293
  RAX: 0000000000000000 RBX: ffff88001186bd20 RCX: 0000000000000002
  RDX: 000000000000000c RSI: 0000000000000000 RDI: 0000000000000000
  RBP: ffff88001186bc70 R08: 28f5c28f5c28f5c3 R09: 0000000000000000
  R10: 0000000000006c34 R11: 0000000000000333 R12: 00000000000001f6
  R13: ffffffff81c6f6a0 R14: 0000000000000000 R15: 0000000000000000
  FS:  0000000000000000(0000) GS:ffff880013c00000(0000) knlGS:ffff880013d00000
  CS:  e033 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 0000000000000400 CR3: 00000000122f2000 CR4: 0000000000042660
  Call Trace:
    count_shadow_nodes+0x9a/0xa0
    shrink_slab.part.42+0x119/0x3e0
    shrink_node+0x22c/0x320
    kswapd+0x32c/0x700
    kthread+0xd8/0xf0
    ret_from_fork+0x1f/0x40
  Code: 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 3b 35 dd eb b1 00 55 48 89 e5 73 2c 89 d2 31 c9 31 c0 4c 63 ce 48 0f a3 ca 73 13 <4a> 8b b4 cf 00 04 00 00 41 89 c8 4a 03 84 c6 80 00 00 00 83 c1
  RIP  mem_cgroup_node_nr_lru_pages+0x20/0x40
   RSP <ffff88001186bc70>
  CR2: 0000000000000400
  ---[ end trace 100494b9edbdfc4d ]---

This patch fixes the issue by checking sc->memcg rather than
memcg_kmem_enabled() which is sufficient because shrink_slab makes sure
that only memcg aware shrinkers will get non-NULL memcgs and only if
memcg_kmem_enabled is true.

Fixes: 0a6b76dd ("mm: workingset: make shadow node shrinker memcg aware")
Link: http://lkml.kernel.org/r/20161201132156.21450-1-mhocko@kernel.orgSigned-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: Marek Marczykowski-Górecki <marmarek@mimuw.edu.pl>
Tested-by: Marek Marczykowski-Górecki <marmarek@mimuw.edu.pl>
Acked-by: Vladimir Davydov <vdavydov.dev@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Balbir Singh <bsingharora@gmail.com>
Cc: <stable@vger.kernel.org>	[4.6+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>