Commit Graph

35 Commits

Author SHA1 Message Date
Miklos Szeredi
292f902a40 ovl: call secutiry hook in ovl_real_ioctl()
Verify LSM permissions for underlying file, since vfs_ioctl() doesn't do
it.

[Stephen Rothwell] export security_file_ioctl

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-06-03 09:45:18 +02:00
Miklos Szeredi
c853680453 ovl: fix lockdep warning for async write
Lockdep reports "WARNING: lock held when returning to user space!" due to
async write holding freeze lock over the write.  Apparently aio.c already
deals with this by lying to lockdep about the state of the lock.

Do the same here.  No need to check for S_IFREG() here since these file ops
are regular-only.

Reported-by: syzbot+9331a354f4f624a52a55@syzkaller.appspotmail.com
Fixes: 2406a307ac ("ovl: implement async IO routines")
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-03-13 15:53:06 +01:00
Miklos Szeredi
a4ac9d45c0 ovl: fix lseek overflow on 32bit
ovl_lseek() is using ssize_t to return the value from vfs_llseek().  On a
32-bit kernel ssize_t is a 32-bit signed int, which overflows above 2 GB.

Assign the return value of vfs_llseek() to loff_t to fix this.

Reported-by: Boris Gjenero <boris.gjenero@gmail.com>
Fixes: 9e46b840c7 ("ovl: support stacked SEEK_HOLE/SEEK_DATA")
Cc: <stable@vger.kernel.org> # v4.19
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-02-03 11:41:53 +01:00
Murphy Zhou
1a980b8cbf ovl: add splice file read write helper
Now overlayfs falls back to use default file splice read
and write, which is not compatiple with overlayfs, returning
EFAULT. xfstests generic/591 can reproduce part of this.

Tested this patch with xfstests auto group tests.

Signed-off-by: Murphy Zhou <jencce.kernel@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-01-24 16:28:15 +01:00
Jiufei Xue
2406a307ac ovl: implement async IO routines
A performance regression was observed since linux v4.19 with aio test using
fio with iodepth 128 on overlayfs.  The queue depth of the device was
always 1 which is unexpected.

After investigation, it was found that commit 16914e6fc7 ("ovl: add
ovl_read_iter()") and commit 2a92e07edc ("ovl: add ovl_write_iter()")
resulted in vfs_iter_{read,write} being called on underlying filesystem,
which always results in syncronous IO.

Implement async IO for stacked reading and writing.  This resolves the
performance regresion.

This is implemented by allocating a new kiocb for submitting the AIO
request on the underlying filesystem.  When the request is completed, the
new kiocb is freed and the completion callback is called on the original
iocb.

Signed-off-by: Jiufei Xue <jiufei.xue@linux.alibaba.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-01-24 09:46:46 +01:00
Amir Goldstein
b1f9d3858f ovl: use ovl_inode_lock in ovl_llseek()
In ovl_llseek() we use the overlay inode rwsem to protect against
concurrent modifications to real file f_pos, because we copy the overlay
file f_pos to/from the real file f_pos.

This caused a lockdep warning of locking order violation when the
ovl_llseek() operation was called on a lower nested overlay layer while the
upper layer fs sb_writers is held (with patch improving copy-up efficiency
for big sparse file).

Use the internal ovl_inode_lock() instead of the overlay inode rwsem in
those cases. It is meant to be used for protecting against concurrent
changes to overlay inode internal state changes.

The locking order rules are documented to explain this case.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-01-22 20:11:41 +01:00
Linus Torvalds
c884d8ac7f SPDX update for 5.2-rc6
Another round of SPDX updates for 5.2-rc6
 
 Here is what I am guessing is going to be the last "big" SPDX update for
 5.2.  It contains all of the remaining GPLv2 and GPLv2+ updates that
 were "easy" to determine by pattern matching.  The ones after this are
 going to be a bit more difficult and the people on the spdx list will be
 discussing them on a case-by-case basis now.
 
 Another 5000+ files are fixed up, so our overall totals are:
 	Files checked:            64545
 	Files with SPDX:          45529
 
 Compared to the 5.1 kernel which was:
 	Files checked:            63848
 	Files with SPDX:          22576
 This is a huge improvement.
 
 Also, we deleted another 20000 lines of boilerplate license crud, always
 nice to see in a diffstat.
 
 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 -----BEGIN PGP SIGNATURE-----
 
 iG0EABECAC0WIQT0tgzFv3jCIUoxPcsxR9QN2y37KQUCXQyQYA8cZ3JlZ0Brcm9h
 aC5jb20ACgkQMUfUDdst+ymnGQCghETUBotn1p3hTjY56VEs6dGzpHMAnRT0m+lv
 kbsjBGEJpLbMRB2krnaU
 =RMcT
 -----END PGP SIGNATURE-----

Merge tag 'spdx-5.2-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/spdx

Pull still more SPDX updates from Greg KH:
 "Another round of SPDX updates for 5.2-rc6

  Here is what I am guessing is going to be the last "big" SPDX update
  for 5.2. It contains all of the remaining GPLv2 and GPLv2+ updates
  that were "easy" to determine by pattern matching. The ones after this
  are going to be a bit more difficult and the people on the spdx list
  will be discussing them on a case-by-case basis now.

  Another 5000+ files are fixed up, so our overall totals are:
	Files checked:            64545
	Files with SPDX:          45529

  Compared to the 5.1 kernel which was:
	Files checked:            63848
	Files with SPDX:          22576

  This is a huge improvement.

  Also, we deleted another 20000 lines of boilerplate license crud,
  always nice to see in a diffstat"

* tag 'spdx-5.2-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/spdx: (65 commits)
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 507
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 506
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 505
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 504
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 503
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 502
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 501
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 499
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 498
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 497
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 496
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 495
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 491
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 490
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 489
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 488
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 487
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 486
  treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 485
  ...
2019-06-21 09:58:42 -07:00
Thomas Gleixner
d2912cb15b treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500
Based on 2 normalized pattern(s):

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license version 2 as
  published by the free software foundation

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license version 2 as
  published by the free software foundation #

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-only

has been chosen to replace the boilerplate/reference in 4122 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Enrico Weigelt <info@metux.net>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190604081206.933168790@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-06-19 17:09:55 +02:00
Amir Goldstein
941d935ac7 ovl: fix wrong flags check in FS_IOC_FS[SG]ETXATTR ioctls
The ioctl argument was parsed as the wrong type.

Fixes: b21d9c435f ("ovl: support the FS_IOC_FS[SG]ETXATTR ioctls")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2019-06-11 17:17:41 +02:00
Amir Goldstein
b21d9c435f ovl: support the FS_IOC_FS[SG]ETXATTR ioctls
They are the extended version of FS_IOC_FS[SG]ETFLAGS ioctls.
xfs_io -c "chattr <flags>" uses the new ioctls for setting flags.

This used to work in kernel pre v4.19, before stacked file ops
introduced the ovl_ioctl whitelist.

Reported-by: Dave Chinner <david@fromorbit.com>
Fixes: d1d04ef857 ("ovl: stack file ops")
Cc: <stable@vger.kernel.org> # v4.19
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2019-05-27 10:03:10 +02:00
Jiufei Xue
98487de318 ovl: check the capability before cred overridden
We found that it return success when we set IMMUTABLE_FL flag to a file in
docker even though the docker didn't have the capability
CAP_LINUX_IMMUTABLE.

The commit d1d04ef857 ("ovl: stack file ops") and dab5ca8fd9 ("ovl: add
lsattr/chattr support") implemented chattr operations on a regular overlay
file. ovl_real_ioctl() overridden the current process's subjective
credentials with ofs->creator_cred which have the capability
CAP_LINUX_IMMUTABLE so that it will return success in
vfs_ioctl()->cap_capable().

Fix this by checking the capability before cred overridden. And here we
only care about APPEND_FL and IMMUTABLE_FL, so get these information from
inode.

[SzM: move check and call to underlying fs inside inode locked region to
prevent two such calls from racing with each other]

Signed-off-by: Jiufei Xue <jiufei.xue@linux.alibaba.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2019-05-06 14:00:37 +02:00
Amir Goldstein
d989903058 ovl: do not generate duplicate fsnotify events for "fake" path
Overlayfs "fake" path is used for stacked file operations on underlying
files.  Operations on files with "fake" path must not generate fsnotify
events with path data, because those events have already been generated at
overlayfs layer and because the reported event->fd for fanotify marks on
underlying inode/filesystem will have the wrong path (the overlayfs path).

Link: https://lore.kernel.org/linux-fsdevel/20190423065024.12695-1-jencce.kernel@gmail.com/
Reported-by: Murphy Zhou <jencce.kernel@gmail.com>
Fixes: d1d04ef857 ("ovl: stack file ops")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2019-05-06 13:54:51 +02:00
Amir Goldstein
9e46b840c7 ovl: support stacked SEEK_HOLE/SEEK_DATA
Overlay file f_pos is the master copy that is preserved
through copy up and modified on read/write, but only real
fs knows how to SEEK_HOLE/SEEK_DATA and real fs may impose
limitations that are more strict than ->s_maxbytes for specific
files, so we use the real file to perform seeks.

We do not call real fs for SEEK_CUR:0 query and for SEEK_SET:0
requests.

Fixes: d1d04ef857 ("ovl: stack file ops")
Reported-by: Eddie Horng <eddiehorng.tw@gmail.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2019-05-06 13:54:51 +02:00
Amir Goldstein
3428030da0 ovl: fix missing upper fs freeze protection on copy up for ioctl
Generalize the helper ovl_open_maybe_copy_up() and use it to copy up file
with data before FS_IOC_SETFLAGS ioctl.

The FS_IOC_SETFLAGS ioctl is a bit of an odd ball in vfs, which probably
caused the confusion.  File may be open O_RDONLY, but ioctl modifies the
file.  VFS does not call mnt_want_write_file() nor lock inode mutex, but
fs-specific code for FS_IOC_SETFLAGS does.  So ovl_ioctl() calls
mnt_want_write_file() for the overlay file, and fs-specific code calls
mnt_want_write_file() for upper fs file, but there was no call for
ovl_want_write() for copy up duration which prevents overlayfs from copying
up on a frozen upper fs.

Fixes: dab5ca8fd9 ("ovl: add lsattr/chattr support")
Cc: <stable@vger.kernel.org> # v4.19
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2019-05-06 13:54:50 +02:00
Darrick J. Wong
df36583619 vfs: plumb remap flags through the vfs dedupe functions
Plumb a remap_flags argument through the vfs_dedupe_file_range_one
functions so that dedupe can take advantage of it.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
2018-10-30 10:42:03 +11:00
Darrick J. Wong
452ce65951 vfs: plumb remap flags through the vfs clone functions
Plumb a remap_flags argument through the {do,vfs}_clone_file_range
functions so that clone can take advantage of it.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
2018-10-30 10:41:56 +11:00
Darrick J. Wong
42ec3d4c02 vfs: make remap_file_range functions take and return bytes completed
Change the remap_file_range functions to take a number of bytes to
operate upon and return the number of bytes they operated on.  This is a
requirement for allowing fs implementations to return short clone/dedupe
results to the user, which will enable us to obey resource limits in a
graceful manner.

A subsequent patch will enable copy_file_range to signal to the
->clone_file_range implementation that it can handle a short length,
which will be returned in the function's return value.  For now the
short return is not implemented anywhere so the behavior won't change --
either copy_file_range manages to clone the entire range or it tries an
alternative.

Neither clone ioctl can take advantage of this, alas.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
2018-10-30 10:41:49 +11:00
Darrick J. Wong
2e5dfc99f2 vfs: combine the clone and dedupe into a single remap_file_range
Combine the clone_file_range and dedupe_file_range operations into a
single remap_file_range file operation dispatch since they're
fundamentally the same operation.  The differences between the two can
be made in the prep functions.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>
2018-10-30 10:41:21 +11:00
Amir Goldstein
a725356b66 vfs: swap names of {do,vfs}_clone_file_range()
Commit 031a072a0b ("vfs: call vfs_clone_file_range() under freeze
protection") created a wrapper do_clone_file_range() around
vfs_clone_file_range() moving the freeze protection to former, so
overlayfs could call the latter.

The more common vfs practice is to call do_xxx helpers from vfs_xxx
helpers, where freeze protecction is taken in the vfs_xxx helper, so
this anomality could be a source of confusion.

It seems that commit 8ede205541 ("ovl: add reflink/copyfile/dedup
support") may have fallen a victim to this confusion -
ovl_clone_file_range() calls the vfs_clone_file_range() helper in the
hope of getting freeze protection on upper fs, but in fact results in
overlayfs allowing to bypass upper fs freeze protection.

Swap the names of the two helpers to conform to common vfs practice
and call the correct helpers from overlayfs and nfsd.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-09-24 10:54:01 +02:00
Amir Goldstein
d9d150ae50 ovl: fix freeze protection bypass in ovl_clone_file_range()
Tested by doing clone on overlayfs while upper xfs+reflink is frozen:

  xfs_io -f /ovl/y
                             fsfreeze -f /xfs
  xfs_io> reflink /ovl/x

Before the fix xfs_io enters xfs_reflink_remap_range() and blocks
in xfs_trans_alloc(). After the fix, xfs_io blocks outside xfs code
in ovl_clone_file_range().

Fixes: 8ede205541 ("ovl: add reflink/copyfile/dedup support")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-09-24 10:54:01 +02:00
Amir Goldstein
898cc19d8a ovl: fix freeze protection bypass in ovl_write_iter()
Tested by re-writing to an open overlayfs file while upper ext4 is frozen:

  xfs_io -f /ovl/x
  xfs_io> pwrite 0 4096
                             fsfreeze -f /ext4
  xfs_io> pwrite 0 4096

  WARNING: CPU: 0 PID: 1492 at fs/ext4/ext4_jbd2.c:53 \
           ext4_journal_check_start+0x48/0x82

After the fix, the second write blocks in ovl_write_iter() and avoids
hitting WARN_ON(sb->s_writers.frozen == SB_FREEZE_COMPLETE) in
ext4_journal_check_start().

Fixes: 2a92e07edc ("ovl: add ovl_write_iter()")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-09-24 10:54:01 +02:00
Amir Goldstein
b833a36603 ovl: add ovl_fadvise()
Implement stacked fadvise to fix syscalls readahead(2) and fadvise64(2)
on an overlayfs file.

Suggested-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: d1d04ef857 ("ovl: stack file ops")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-09-03 09:43:10 +02:00
Amir Goldstein
5b910bd615 ovl: fix GPF in swapfile_activate of file from overlayfs over xfs
Since overlayfs implements stacked file operations, the underlying
filesystems are not supposed to be exposed to the overlayfs file,
whose f_inode is an overlayfs inode.

Assigning an overlayfs file to swap_file results in an attempt of xfs
code to dereference an xfs_inode struct from an ovl_inode pointer:

 CPU: 0 PID: 2462 Comm: swapon Not tainted
 4.18.0-xfstests-12721-g33e17876ea4e #3402
 RIP: 0010:xfs_find_bdev_for_inode+0x23/0x2f
 Call Trace:
  xfs_iomap_swapfile_activate+0x1f/0x43
  __se_sys_swapon+0xb1a/0xee9

Fix this by not assigning the real inode mapping to f_mapping, which
will cause swapon() to return an error (-EINVAL). Although it makes
sense not to allow setting swpafile on an overlayfs file, some users
may depend on it, so we may need to fix this up in the future.

Keeping f_mapping pointing to overlay inode mapping will cause O_DIRECT
open to fail. Fix this by installing ovl_aops with noop_direct_IO in
overlay inode mapping.

Keeping f_mapping pointing to overlay inode mapping will cause other
a_ops related operations to fail (e.g. readahead()). Those will be
fixed by follow up patches.

Suggested-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: f7c72396d0 ("ovl: add O_DIRECT support")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-08-30 17:08:35 +02:00
Vivek Goyal
935a074f48 ovl: Do not do metacopy only for ioctl modifying file attr
ovl_copy_up() by default will only do metadata only copy up (if enabled).
That means when ovl_real_ioctl() calls ovl_real_file(), it will still get
the lower file (as ovl_real_file() opens data file and not metacopy).  And
that means "chattr +i" will end up modifying lower inode.

There seem to be two ways to solve this.
A. Open metacopy file in ovl_real_ioctl() and do operations on that
B. Force full copy up when FS_IOC_SETFLAGS is called.

I am resorting to option B for now as it feels little safer option.  If
there are performance issues due to this, we can revisit it.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-07-20 09:56:17 +02:00
Vivek Goyal
8c444d2a97 ovl: Open file with data except for the case of fsync
ovl_open() should open file which contains data and not open metacopy
inode.  With the introduction of metacopy inodes, with current
implementaion we will end up opening metacopy inode as well.

But there can be certain circumstances like ovl_fsync() where we want to
allow opening a metacopy inode instead.

Hence, change ovl_open_realfile() and and add extra parameter which
specifies whether to allow opening metacopy inode or not.  If this
parameter is false, we look for data inode and open that.

This should allow covering both the cases.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-07-20 09:56:12 +02:00
Miklos Szeredi
8ede205541 ovl: add reflink/copyfile/dedup support
Since set of arguments are so similar, handle in a common helper.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-07-18 15:44:42 +02:00
Miklos Szeredi
f7c72396d0 ovl: add O_DIRECT support
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-07-18 15:44:42 +02:00
Miklos Szeredi
dab5ca8fd9 ovl: add lsattr/chattr support
Implement FS_IOC_GETFLAGS and FS_IOC_SETFLAGS.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-07-18 15:44:42 +02:00
Miklos Szeredi
aab8848cee ovl: add ovl_fallocate()
Implement stacked fallocate.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-07-18 15:44:42 +02:00
Miklos Szeredi
2f502839e8 ovl: add ovl_mmap()
Implement stacked mmap.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-07-18 15:44:42 +02:00
Miklos Szeredi
de30dfd629 ovl: add ovl_fsync()
Implement stacked fsync().

Don't sync if lower (noticed by Amir Goldstein).

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-07-18 15:44:42 +02:00
Miklos Szeredi
2a92e07edc ovl: add ovl_write_iter()
Implement stacked writes.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-07-18 15:44:41 +02:00
Miklos Szeredi
16914e6fc7 ovl: add ovl_read_iter()
Implement stacked reading.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-07-18 15:44:41 +02:00
Miklos Szeredi
2ef66b8a03 ovl: add helper to return real file
In the common case we can just use the real file cached in
file->private_data.  There are two exceptions:

1) File has been copied up since open: in this unlikely corner case just
use a throwaway real file for the operation.  If ever this becomes a
perfomance problem (very unlikely, since overlayfs has been doing most fine
without correctly handling this case at all), then we can deal with that by
updating the cached real file.

2) File's f_flags have changed since open: no need to reopen the cached
real file, we can just change the flags there as well.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-07-18 15:44:41 +02:00
Miklos Szeredi
d1d04ef857 ovl: stack file ops
Implement file operations on a regular overlay file.  The underlying file
is opened separately and cached in ->private_data.

It might be worth making an exception for such files when accounting in
nr_file to confirm to userspace expectations.  We are only adding a small
overhead (248bytes for the struct file) since the real inode and dentry are
pinned by overlayfs anyway.

This patch doesn't have any effect, since the vfs will use d_real() to find
the real underlying file to open.  The patch at the end of the series will
actually enable this functionality.

AV: make it use open_with_fake_path(), don't mess with override_creds

SzM: still need to mess with override_creds() until no fs uses
current_cred() in their open method.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-07-18 15:44:41 +02:00