linux_dsm_epyc7002/Documentation
Sargun Dhillon 8ccf963c62 ovl: implement volatile-specific fsync error behaviour
commit 335d3fc57941e5c6164c69d439aec1cb7a800876 upstream.

Overlayfs's volatile option allows the user to bypass all forced sync calls
to the upperdir filesystem. This comes at the cost of safety. We can never
ensure that the user's data is intact, but we can make a best effort to
expose whether or not the data is likely to be in a bad state.

The best way to handle this in the time being is that if an overlayfs's
upperdir experiences an error after a volatile mount occurs, that error
will be returned on fsync, fdatasync, sync, and syncfs. This is
contradictory to the traditional behaviour of VFS which fails the call
once, and only raises an error if a subsequent fsync error has occurred,
and been raised by the filesystem.

One awkward aspect of the patch is that we have to manually set the
superblock's errseq_t after the sync_fs callback as opposed to just
returning an error from syncfs. This is because the call chain looks
something like this:

sys_syncfs ->
	sync_filesystem ->
		__sync_filesystem ->
			/* The return value is ignored here
			sb->s_op->sync_fs(sb)
			_sync_blockdev
		/* Where the VFS fetches the error to raise to userspace */
		errseq_check_and_advance

Because of this we call errseq_set every time the sync_fs callback occurs.
Due to the nature of this seen / unseen dichotomy, if the upperdir is an
inconsistent state at the initial mount time, overlayfs will refuse to
mount, as overlayfs cannot get a snapshot of the upperdir's errseq that
will increment on error until the user calls syncfs.

Signed-off-by: Sargun Dhillon <sargun@sargun.me>
Suggested-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Fixes: c86243b090 ("ovl: provide a mount option "volatile"")
Cc: stable@vger.kernel.org
Reviewed-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-02-10 09:29:16 +01:00
..
ABI driver core: Fix device link device name collision 2021-01-27 11:55:18 +01:00
accounting
admin-guide x86/xen: Add xen_no_vector_callback option to test PCI INTX delivery 2021-01-27 11:55:01 +01:00
arm documentation: arm: sunxi: add Allwinner H6 documents 2020-10-28 11:19:24 -06:00
arm64 arm64: Add workaround for Arm Cortex-A77 erratum 1508412 2020-10-29 12:56:01 +00:00
block block-5.10-2020-10-24 2020-10-24 12:46:42 -07:00
bpf bpf: Migrate from patchwork.ozlabs.org to patchwork.kernel.org. 2020-10-11 22:05:47 +02:00
cdrom
core-api dma-mapping: document dma_{alloc,free}_pages 2020-10-23 12:07:46 +02:00
cpu-freq
crypto
dev-tools linux-kselftest-kunit-fixes-5.10-rc5 2020-11-18 11:57:55 -08:00
devicetree dt-bindings: net: renesas,etheravb: RZ/G2H needs tx-internal-delay-ps 2021-01-23 16:04:03 +01:00
doc-guide docs: kerneldoc.py: add support for kerneldoc -nosymbol 2020-10-15 07:49:38 +02:00
driver-api media: vidtv.rst: add kernel-doc markups 2020-11-26 08:05:24 +01:00
fault-injection A handful of late-arriving documentation fixes. 2020-10-23 17:13:53 -07:00
fb drm fixes (round two) for 5.10-rc1 2020-10-23 13:56:34 -07:00
features s390 updates for the 5.10 merge window 2020-10-16 12:36:38 -07:00
filesystems ovl: implement volatile-specific fsync error behaviour 2021-02-10 09:29:16 +01:00
firmware_class
firmware-guide Documentation: ACPI: fix spelling mistakes 2020-11-10 18:48:56 +01:00
fpga
gpu fbcon: Disable accelerated scrolling 2021-01-06 14:56:51 +01:00
hid
hwmon docs: hwmon: mp2975.rst: address some html build warnings 2020-10-28 11:26:10 -06:00
i2c Documentation: i2c: add testunit docs to index 2020-10-05 22:57:45 +02:00
ia64
ide
iio
infiniband
input
isdn
kbuild kbuild: remove unused OBJSIZE 2020-11-02 11:31:00 +09:00
kernel-hacking
leds docs: leds: index.rst: add a missing file 2020-11-02 13:45:37 +01:00
litmus-tests
livepatch
locking Documentation: seqlock: s/LOCKTYPE/LOCKNAME/g 2020-12-30 11:54:11 +01:00
m68k
maintainer
mhi
mips dt: Remove booting-without-of.rst 2020-10-13 13:33:16 -05:00
misc-devices Documentation: remove mic/index from misc-devices/index.rst 2020-11-04 11:38:32 +01:00
netlabel
networking Documentation: netdev-FAQ: suggest how to post co-dependent series 2020-11-24 20:45:22 -08:00
nios2
nvdimm
openrisc
parisc
PCI Documentation: better locations for sysfs-pci, sysfs-tagging 2020-10-09 09:33:23 -06:00
pcmcia
power PCI/PM: Rename pci_dev.d3_delay to d3hot_delay 2020-09-29 14:21:50 -05:00
powerpc docs updates for v5.10-rc1 2020-10-16 15:02:21 -07:00
process net: switch to the kernel.org patchwork instance 2020-11-11 17:12:00 -08:00
RCU Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu 2020-10-09 08:21:56 +02:00
riscv
s390
scheduler
scsi SPDX patches for 5.10-rc1 2020-10-14 16:19:42 -07:00
security
sh dt: Remove booting-without-of.rst 2020-10-13 13:33:16 -05:00
sound ALSA: doc: Fix reference to mixart.rst 2021-01-19 18:27:17 +01:00
sparc
sphinx A small number of fixes, plus a build tweak to respect the desire for 2020-11-03 09:57:30 -08:00
sphinx-static
spi
staging
target
timers
trace docs updates for v5.10-rc1 2020-10-16 15:02:21 -07:00
translations net: switch to the kernel.org patchwork instance 2020-11-11 17:12:00 -08:00
usb
userspace-api docs: userspace-api: add iommu.rst to the index file 2020-10-28 11:26:10 -06:00
virt KVM: Documentation: Fix spec for KVM_CAP_ENABLE_CAP_VM 2021-02-03 23:28:43 +01:00
vm A handful of late-arriving documentation fixes. 2020-10-23 17:13:53 -07:00
w1 docs: w1: w1_therm: Fix broken xref, mistakes, clarify text 2020-10-08 09:47:15 +02:00
watchdog
x86 x86/CPU/AMD: Save AMD NodeId as cpu_die_id 2020-12-30 11:54:29 +01:00
xtensa xtensa: fix TLBTEMP area placement 2020-11-16 02:13:15 -08:00
.gitignore
asm-annotations.rst x86/entry: Emit a symbol for register restoring thunk 2021-02-03 23:28:40 +01:00
atomic_bitops.txt
atomic_t.txt
Changes
CodingStyle
conf.py This pull contains a series of warning fixes from Mauro; once applied, the 2020-11-03 13:14:14 -08:00
COPYING-logo
docutils.conf
dontdiff
index.rst
Kconfig docs: Kconfig/Makefile: add a check for broken ABI files 2020-10-30 13:08:07 +01:00
logo.gif
Makefile A small number of fixes, plus a build tweak to respect the desire for 2020-11-03 09:57:30 -08:00
memory-barriers.txt
SubmittingPatches
watch_queue.rst