Problem with ioctl() is that it's a file operation, yet often used as an
inode operation (i.e. modify the inode despite the file being opened for
read-only).

mnt_want_write_file() is used by filesystems in such cases to get write
access on an arbitrary open file.

Since overlayfs lets filesystems do all file operations, including ioctl,
this can lead to mnt_want_write_file() returning OK for a lower file and
modification of that lower file.

This patch prevents modification by checking if the file is from an
overlayfs lower layer and returning EPERM in that case.

Need to introduce a mnt_want_write_file_path() variant that still does the
old thing for inode operations that can do the copy up + modification
correctly in such cases (fchown, fsetxattr, fremovexattr).

This does not address the correctness of such ioctls on overlayfs (the
correct way would be to copy up and attempt to perform ioctl on upper
file).

In theory this could be a regression. We very much hope that nobody is
relying on such a hack in any sane setup.

While this patch meddles in VFS code, it has no effect on non-overlayfs
filesystems.

Reported-by: "zhangyi (F)" <yi.zhang@huawei.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Need to treat non-regular overlayfs files the same as regular files when
checking for an atime update.

Add a d_real() flag to make it return the upper dentry for all file types.

Reported-by: "zhangyi (F)" <yi.zhang@huawei.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Add a separate flags argument (in addition to the open flags) to control
the behavior of d_real().

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

d_real() is never called with a negative dentry. So remove the
d_is_negative() check (which would never trigger anyway, since d_is_reg()
returns false for a negative dentry).

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

Impure directories are ones which contain objects with origins (i.e. those
that have been copied up). These are relevant to readdir operation only
because of the d_ino field, no other transformation is necessary. Also a
directory can become impure between two getdents(2) calls.

This patch creates a cache for impure directories. Unlike the cache for
merged directories, this one only contains entries with origin and is not
refcounted but has a its lifetime tied to that of the dentry.

Similarly to the merged cache, the impure cache is invalidated based on a
version number. This version number is incremented when an entry with
origin is added or removed from the directory.

If the cache is empty, then the impure xattr is removed from the directory.

This patch also fixes up handling of d_ino for the ".." entry if the parent
directory is merged.

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

When all layers are on the same fs, and iterating a directory which may
contain copy up entries, call vfs_getattr() on the overlay entries to make
sure that d_ino will be consistent with st_ino from stat(2).

There is an overhead of lookup per upper entry in readdir.

The overhead is minimal if the iterated entries are already in dcache. It
is also quite useful for the common case of 'ls -l' that readdir() pre
populates the dcache with the listed entries, making the following stat()
calls faster.

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

actor's return value is taken as a bool (filled/not filled) so we need to
return the error in the context.

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

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

This adds a perl script to actually parse the MAINTAINERS file, clean up
some whitespace in it, warn about errors in it, and then properly sort
the end result.

My perl-fu is atrocious, so the script has basically been created by
randomly putting various characters in a pile, mixing them around, and
then looking it the end result does anything interesting when used as a
perl script.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Prepping for scripting the MAINTAINERS file cleanup (and possible split)
showed a couple of cases where the headers for a couple of entries were
bogus.

There's a few different kinds of bogosities:

- the X-GENE SOC EDAC case was confused and split over two lines

- there were four entries for "GREYBUS PROTOCOLS DRIVERS" that were all
different things.

- the NOKIA N900 CAMERA SUPPORT" was duplicated

all of which were more obvious when you started doing associative arrays
in perl to track these things by the header (so that we can alphabetize
this thing properly, and so that we might split it up by the data too).

Cc: Joe Perches <joe@perches.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull xen fixes from Juergen Gross:
"Some fixes and cleanups for running under Xen"

* tag 'for-linus-4.13b-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
xen/balloon: don't online new memory initially
xen/x86: fix cpu hotplug
xen/grant-table: log the lack of grants
xen/x86: Don't BUG on CPU0 offlining

Pull hwmon fix from Guenter Roeck:
"Avoid buffer overruns in applesmc driver"

* tag 'hwmon-for-linus-v4.13-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/groeck/linux-staging:
hwmon: (applesmc) Avoid buffer overruns