With inodes index enabled, an overlay inode nlink counts the union of upper
and non-covered lower hardlinks. During the lifetime of a non-pure upper
inode, the following nlink modifying operations can happen:

1. Lower hardlink copy up
2. Upper hardlink created, unlinked or renamed over
3. Lower hardlink whiteout or renamed over

For the first, copy up case, the union nlink does not change, whether the
operation succeeds or fails, but the upper inode nlink may change.
Therefore, before copy up, we store the union nlink value relative to the
lower inode nlink in the index inode xattr trusted.overlay.nlink.

For the second, upper hardlink case, the union nlink should be incremented
or decremented IFF the operation succeeds, aligned with nlink change of the
upper inode. Therefore, before link/unlink/rename, we store the union nlink
value relative to the upper inode nlink in the index inode.

For the last, lower cover up case, we simplify things by preceding the
whiteout or cover up with copy up. This makes sure that there is an index
upper inode where the nlink xattr can be stored before the copied up upper
entry is unlink.

Return the overlay inode nlinks for indexed upper inodes on stat(2).
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Implement a copy up method for non-dir objects using index dir to
prevent breaking lower hardlinks on copy up.

This method requires that the inodes index dir feature was enabled and
that all underlying fs support file handle encoding/decoding.

On the first lower hardlink copy up, upper file is created in index dir,
named after the hex representation of the lower origin inode file handle.
On the second lower hardlink copy up, upper file is found in index dir,
by the same lower handle key.
On either case, the upper indexed inode is then linked to the copy up
upper path.

The index entry remains linked for future lower hardlink copy up and for
lower to upper inode map, that is needed for exporting overlayfs to NFS.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Move ovl_copy_up_start()/ovl_copy_up_end() out so that it's used for both
tempfile and workdir copy ups.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Split up and rearrange copy up functions to make them better readable.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

For rename, we need to ensure that an upper alias exists for hard links
before attempting the operation.  Introduce a flag in ovl_entry to track
the state of the upper alias.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

This cleans up functions with too many arguments.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

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

Factor out helper for copying lower inode data and metadata to temp
upper inode, that is common to copy up using O_TMPFILE and workdir.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

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

On copy up of regular file using an O_TMPFILE, lock upper dir only
before linking the tempfile in place.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

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

Bad index entries are entries whose name does not match the
origin file handle stored in trusted.overlay.origin xattr.
Bad index entries could be a result of a system power off in
the middle of copy up.

Stale index entries are entries whose origin file handle is
stale. Stale index entries could be a result of copying layers
or removing lower entries while the overlay is not mounted.
The case of copying layers should be detected earlier by the
verification of upper root dir origin and index dir origin.

Both bad and stale index entries are detected and removed
on mount.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

When inodes index feature is enabled, lookup in indexdir for the index
entry of lower real inode or copy up origin inode. The index entry name
is the hex representation of the lower inode file handle.

If the index dentry in negative, then either no lower aliases have been
copied up yet, or aliases have been copied up in older kernels and are
not indexed.

If the index dentry for a copy up origin inode is positive, but points
to an inode different than the upper inode, then either the upper inode
has been copied up and not indexed or it was indexed, but since then
index dir was cleared. Either way, that index cannot be used to indentify
the overlay inode.

If a positive dentry that matches the upper inode was found, then it is
safe to use the copy up origin st_ino for upper hardlinks, because all
indexed upper hardlinks are represented by the same overlay inode as the
copy up origin.

Set the INDEX type flag on an indexed upper dentry. A non-upper dentry
may also have a positive index from copy up of another lower hardlink.
This situation will be handled by following patches.

Index lookup is going to be used to prevent breaking hardlinks on copy up.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

An index dir contains persistent hardlinks to files in upper dir.
Therefore, we must never mount an existing index dir with a differnt
upper dir.

Store the upper root dir file handle in index dir inode when index
dir is created and verify the file handle before using an existing
index dir on mount.

Add an 'is_upper' flag to the overlay file handle encoding and set it
when encoding the upper root file handle. This is not critical for index
dir verification, but it is good practice towards a standard overlayfs
file handle format for NFS export.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

When inodes index feature is enabled, verify that the file handle stored
in upper root dir matches the lower root dir or fail to mount.

If upper root dir has no stored file handle, encode and store the lower
root dir file handle in overlay.origin xattr.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Create the index dir on mount. The index dir will contain hardlinks to
upper inodes, named after the hex representation of their origin lower
inodes.

The index dir is going to be used to prevent breaking lower hardlinks
on copy up and to implement overlayfs NFS export.

Because the feature is not fully backward compat, enabling the feature
is opt-in by config/module/mount option.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Pass in the subdir name to create and specify if subdir is persistent
or if it should be cleaned up on every mount.

Move fallback to readonly mount on failure to create dir and print of error
message into the helper.

This function is going to be used for creating the persistent 'index' dir
under workbasedir.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

For the case of all layers not on the same fs, try to decode the copy up
origin file handle on any of the lower layers.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Bad things can happen if several concurrent overlay mounts try to
use the same upperdir/workdir path.

Try to get the 'inuse' advisory lock on upperdir and workdir.
Fail mount if another overlay mount instance or another user
holds the 'inuse' lock on these directories.

Note that this provides no protection for concurrent overlay
mount that use overlapping (i.e. descendant) upper/work dirs.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Added an i_state flag I_INUSE and helpers to set/clear/test the bit.

The 'inuse' lock is an 'advisory' inode lock, that can be used to extend
exclusive create protection beyond parent->i_mutex lock among cooperating
users.

This is going to be used by overlayfs to get exclusive ownership on upper
and work dirs among overlayfs mounts.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

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

Use the new ovl_inode mutex to synchonize concurrent copy up
instead of the super block copy up workqueue.

Moving the synchronization object from the overlay dentry to
the overlay inode is needed for synchonizing concurrent copy up
of lower hardlinks to the same upper inode.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

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

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

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

When checking for consistency in directory operations (unlink, rename,
etc.) match inodes not dentries.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

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

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

We need some more space to store overlay inode data in memory,
so allocate overlay inodes from a slab of struct ovl_inode.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

This patch fixes an overlay inode nlink leak in the case where
ovl_rename() renames over a non-dir.

This is not so critical, because overlay inode doesn't rely on
nlink dropping to zero for inode deletion.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

UUID/GUID updates:

 - introduce the new uuid_t/guid_t types that are going to replace
   the somewhat confusing uuid_be/uuid_le types and make the terminology
   fit the various specs, as well as the userspace libuuid library.
   (me, based on a previous version from Amir)
 - consolidated generic uuid/guid helper functions lifted from XFS
   and libnvdimm (Amir and me)
 - conversions to the new types and helpers (Amir, Andy and me)

When copying up a file that has multiple hard links we need to break any
association with the origin file.  This makes copy-up be essentially an
atomic replace.

The new file has nothing to do with the old one (except having the same
data and metadata initially), so don't set the overlay.origin attribute.

We can relax this in the future when we are able to index upper object by
origin.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: 3a1e819b ("ovl: store file handle of lower inode on copy up")

Nothing prevents mischief on upper layer while we are busy copying up the
data.

Move the lookup right before the looked up dentry is actually used.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: 01ad3eb8 ("ovl: concurrent copy up of regular files")
Cc: <stable@vger.kernel.org> # v4.11

Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

Pull x86 fix from Thomas Gleixner:
 "A single fix to unbreak the vdso32 build for 64bit kernels caused by
  excess #includes in the mshyperv header"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/mshyperv: Remove excess #includes from mshyperv.h

Pull timer fixes from Thomas Gleixner:
 "A few fixes for timekeeping and timers:

   - Plug a subtle race due to a missing READ_ONCE() in the timekeeping
     code where reloading of a pointer results in an inconsistent
     callback argument being supplied to the clocksource->read function.

   - Correct the CLOCK_MONOTONIC_RAW sub-nanosecond accounting in the
     time keeping core code, to prevent a possible discontuity.

   - Apply a similar fix to the arm64 vdso clock_gettime()
     implementation

   - Add missing includes to clocksource drivers, which relied on
     indirect includes which fails in certain configs.

   - Use the proper iomem pointer for read/iounmap in a probe function"

* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  arm64/vdso: Fix nsec handling for CLOCK_MONOTONIC_RAW
  time: Fix CLOCK_MONOTONIC_RAW sub-nanosecond accounting
  time: Fix clock->read(clock) race around clocksource changes
  clocksource: Explicitly include linux/clocksource.h when needed
  clocksource/drivers/arm_arch_timer: Fix read and iounmap of incorrect variable

Pull perf fixes from Thomas Gleixner:
 "Three fixlets for perf:

   - Return the proper error code if aux buffers for a event are not
     supported.

   - Calculate the probe offset for inlined functions correctly

   - Update the Skylake DTLB load/store miss event so it can count 1G
     TLB entries as well"

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf probe: Fix probe definition for inlined functions
  perf/x86/intel: Add 1G DTLB load/store miss support for SKL
  perf/aux: Correct return code of rb_alloc_aux() if !has_aux(ev)

Pull irq fix from Thomas Gleixner:
 "A single fix for the MIPS GIC to prevent ftrace recursion"

* 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  irqchip/mips-gic: Mark count and compare accessors notrace

Pull input fixes from Dmitry Torokhov:

 - a quirk to i8042 to ignore timeout bit on Lifebook AH544

 - a fixup to Synaptics RMI function 54 that was breaking some Dells

 - a fix for memory leak in soc_button_array driver

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input:
  Input: synaptics-rmi4 - only read the F54 query registers which are used
  Input: i8042 - add Fujitsu Lifebook AH544 to notimeout list
  Input: soc_button_array - fix leaking the ACPI button descriptor buffer