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Eryu Guan 79f41e0f8a xfs: truncate pagecache before writeback in xfs_setattr_size() 
[ Upstream commit 350976ae21 ]

On truncate down, if new size is not block size aligned, we zero the
rest of block to avoid exposing stale data to user, and
iomap_truncate_page() skips zeroing if the range is already in
unwritten state or a hole. Then we writeback from on-disk i_size to
the new size if this range hasn't been written to disk yet, and
truncate page cache beyond new EOF and set in-core i_size.

The problem is that we could write data between di_size and newsize
before removing the page cache beyond newsize, as the extents may
still be in unwritten state right after a buffer write. As such, the
page of data that newsize lies in has not been zeroed by page cache
invalidation before it is written, and xfs_do_writepage() hasn't
triggered it's "zero data beyond EOF" case because we haven't
updated in-core i_size yet. Then a subsequent mmap read could see
non-zeros past EOF.

I occasionally see this in fsx runs in fstests generic/112, a
simplified fsx operation sequence is like (assuming 4k block size
xfs):

  fallocate 0x0 0x1000 0x0 keep_size
  write 0x0 0x1000 0x0
  truncate 0x0 0x800 0x1000
  punch_hole 0x0 0x800 0x800
  mapread 0x0 0x800 0x800

where fallocate allocates unwritten extent but doesn't update
i_size, buffer write populates the page cache and extent is still
unwritten, truncate skips zeroing page past new EOF and writes the
page to disk, punch_hole invalidates the page cache, at last mapread
reads the block back and sees non-zero beyond EOF.

Fix it by moving truncate_setsize() to before writeback so the page
cache invalidation zeros the partial page at the new EOF. This also
triggers "zero data beyond EOF" in xfs_do_writepage() at writeback
time, because newsize has been set and page straddles the newsize.

Also fixed the wrong 'end' param of filemap_write_and_wait_range()
call while we're at it, the 'end' is inclusive and should be
'newsize - 1'.

Suggested-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>
Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2017-12-20 10:10:26 +01:00
arch powerpc/pseries/vio: Dispose of virq mapping on vdevice unregister 2017-12-20 10:10:25 +01:00
block badblocks: fix wrong return value in badblocks_set if badblocks are disabled 2017-12-20 10:10:26 +01:00
certs License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
crypto crypto: af_alg - fix NULL pointer dereference in 2017-12-20 10:10:17 +01:00
Documentation dt-bindings: usb: fix reg-property port-number range 2017-12-14 09:53:09 +01:00
drivers iommu/amd: Limit the IOVA page range to the specified addresses 2017-12-20 10:10:26 +01:00
firmware License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
fs xfs: truncate pagecache before writeback in xfs_setattr_size() 2017-12-20 10:10:26 +01:00
include mm, oom_reaper: fix memory corruption 2017-12-20 10:10:18 +01:00
init License cleanup: add SPDX license identifiers to some files 2017-11-02 10:04:46 -07:00
ipc License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
kernel PM / s2idle: Clear the events_check_enabled flag 2017-12-20 10:10:23 +01:00
lib dynamic-debug-howto: fix optional/omitted ending line number to be LARGE instead of 0 2017-12-14 09:53:08 +01:00
mm mm, oom_reaper: fix memory corruption 2017-12-20 10:10:18 +01:00
net netfilter: ipvs: Fix inappropriate output of procfs 2017-12-20 10:10:25 +01:00
samples License cleanup: add SPDX license identifiers to some files 2017-11-02 10:04:46 -07:00
scripts kbuild: rpm-pkg: fix jobserver unavailable warning 2017-12-14 09:53:13 +01:00
security apparmor: fix leak of null profile name if profile allocation fails 2017-12-14 09:53:06 +01:00
sound ASoC: Intel: Skylake: Fix uuid_module memory leak in failure case 2017-12-20 10:10:24 +01:00
tools usbip: prevent vhci_hcd driver from leaking a socket pointer address 2017-12-20 10:10:19 +01:00
usr initramfs: fix initramfs rebuilds w/ compression after disabling 2017-11-03 07:39:19 -07:00
virt KVM: arm/arm64: vgic-its: Preserve the revious read from the pending table 2017-12-17 15:07:59 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: Add support to generate LLVM assembly files 2017-04-25 08:13:52 +09:00
.mailmap .mailmap: Add Maciej W. Rozycki's Imagination e-mail address 2017-11-10 12:16:15 -08:00
COPYING [PATCH] update FSF address in COPYING 2005-09-10 10:06:29 -07:00
CREDITS MAINTAINERS: update TPM driver infrastructure changes 2017-11-09 17:58:40 -08:00
Kbuild License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
MAINTAINERS Merge branch 'akpm' (patches from Andrew) 2017-11-09 18:26:51 -08:00
Makefile Linux 4.14.7 2017-12-17 15:08:14 +01:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

README 

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.