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An opaque directory cannot have xwhiteouts, so instead of marking an
xwhiteouts directory with a new xattr, overload overlay.opaque xattr
for marking both opaque dir ('y') and xwhiteouts dir ('x').
This is more efficient as the overlay.opaque xattr is checked during
lookup of directory anyway.
This also prevents unnecessary checking the xattr when reading a
directory without xwhiteouts, i.e. most of the time.
Note that the xwhiteouts marker is not checked on the upper layer and
on the last layer in lowerstack, where xwhiteouts are not expected.
Fixes: bc8df7a3dc03 ("ovl: Add an alternative type of whiteout")
Cc: <stable@vger.kernel.org> # v6.7
Reviewed-by: Alexander Larsson <alexl@redhat.com>
Tested-by: Alexander Larsson <alexl@redhat.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
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Fix some indentation issues and fix missing newlines in quoted text
by converting quoted text to code blocks.
Reported-by: Christian Brauner <brauner@kernel.org>
Suggested-by: Bagas Sanjaya <bagasdotme@gmail.com>
Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
Reviewed-by: Akira Yokosawa <akiyks@gmail.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
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Use the feature names "metacopy" and "index" consistently throughout
the document.
Covert the numbered list of features "redirect_dir", "index", "xino"
to section headings, so that those features could be referenced in the
document by their name.
Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
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Add new mount options lowerdir+ and datadir+ that can be used to add
layers to lower layers stack one by one.
Unlike the legacy lowerdir mount option, special characters (i.e. colons
and cammas) are not unescaped with these new mount options.
The new mount options can be repeated to compose a large stack of lower
layers, but they may not be mixed with the lagacy lowerdir mount option,
because for displaying lower layers in mountinfo, we do not want to mix
escaped with unescaped lower layers path syntax.
Similar to data-only layer rules with the lowerdir mount option, the
datadir+ option must follow at least one lowerdir+ option and the
lowerdir+ option must not follow the datadir+ option.
If the legacy lowerdir mount option follows lowerdir+ and datadir+
mount options, it overrides them. Sepcifically, calling:
fsconfig(FSCONFIG_SET_STRING, "lowerdir", "", 0);
can be used to reset previously setup lower layers.
Suggested-by: Miklos Szeredi <miklos@szeredi.hu>
Link: https://lore.kernel.org/r/CAJfpegt7VC94KkRtb1dfHG8+4OzwPBLYqhtc8=QFUxpFJE+=RQ@mail.gmail.com/
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
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Signed-off-by: Alexander Larsson <alexl@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
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Before commit b36a5780cb44 ("ovl: modify layer parameter parsing"),
spaces and commas in lowerdir mount option value used to be escaped using
seq_show_option().
In current upstream, when lowerdir value has a space, it is not escaped
in /proc/mounts, e.g.:
none /mnt overlay rw,relatime,lowerdir=l l,upperdir=u,workdir=w 0 0
which results in broken output of the mount utility:
none on /mnt type overlay (rw,relatime,lowerdir=l)
Store the original lowerdir mount options before unescaping and show
them using the same escaping used for seq_show_option() in addition to
escaping the colon separator character.
Fixes: b36a5780cb44 ("ovl: modify layer parameter parsing")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
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Pull documentation updates from Jonathan Corbet:
"Documentation work keeps chugging along; this includes:
- Work from Carlos Bilbao to integrate rustdoc output into the
generated HTML documentation. This took some work to figure out how
to do it without slowing the docs build and without creating people
who don't have Rust installed, but Carlos got there
- Move the loongarch and mips architecture documentation under
Documentation/arch/
- Some more maintainer documentation from Jakub
... plus the usual assortment of updates, translations, and fixes"
* tag 'docs-6.6' of git://git.lwn.net/linux: (56 commits)
Docu: genericirq.rst: fix irq-example
input: docs: pxrc: remove reference to phoenix-sim
Documentation: serial-console: Fix literal block marker
docs/mm: remove references to hmm_mirror ops and clean typos
docs/zh_CN: correct regi_chg(),regi_add() to region_chg(),region_add()
Documentation: Fix typos
Documentation/ABI: Fix typos
scripts: kernel-doc: fix macro handling in enums
scripts: kernel-doc: parse DEFINE_DMA_UNMAP_[ADDR|LEN]
Documentation: riscv: Update boot image header since EFI stub is supported
Documentation: riscv: Add early boot document
Documentation: arm: Add bootargs to the table of added DT parameters
docs: kernel-parameters: Refer to the correct bitmap function
doc: update params of memhp_default_state=
docs: Add book to process/kernel-docs.rst
docs: sparse: fix invalid link addresses
docs: vfs: clean up after the iterate() removal
docs: Add a section on surveys to the researcher guidelines
docs: move mips under arch
docs: move loongarch under arch
...
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Fix typos in Documentation.
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/20230814212822.193684-4-helgaas@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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Add a new mount option uuid=auto, which is the default.
If a persistent UUID xattr is found it is used.
Otherwise, an existing ovelrayfs with copied up subdirs in upper dir
that was never mounted with uuid=on retains the null UUID.
A new overlayfs with no copied up subdirs, generates the persistent UUID
on first mount.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
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With uuid=on, store a persistent uuid in xattr on the upper dir to
give the overlayfs instance a persistent identifier.
This also makes f_fsid persistent and more reliable for reporting
fid info in fanotify events.
uuid=on is not supported on non-upper overlayfs or with upper fs
that does not support xattrs.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
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The legacy behavior of ovl_statfs() reports the f_fsid filled by
underlying upper fs. This fsid is not unique among overlayfs instances
on the same upper fs.
With mount option uuid=on, generate a non-persistent uuid per overlayfs
instance and use it as the seed for f_fsid, similar to tmpfs.
This is useful for reporting fanotify events with fid info from different
instances of overlayfs over the same upper fs.
The old behavior of null uuid and upper fs fsid is retained with the
mount option uuid=null, which is the default.
The mount option uuid=off that disables uuid checks in underlying layers
also retains the legacy behavior.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
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This adds the scaffolding (docs, config, mount options) for supporting
the new digest field in the metacopy xattr. This contains a fs-verity
digest that need to match the fs-verity digest of the lowerdata
file. The mount option "verity" specifies how this xattr is handled.
If you enable verity ("verity=on") all existing xattrs are validated
before use, and during metacopy we generate verity xattr in the upper
metacopy file (if the source file has verity enabled). This means
later accesses can guarantee that the same data is used.
Additionally you can use "verity=require". In this mode all metacopy
files must have a valid verity xattr. For this to work metadata
copy-up must be able to create a verity xattr (so that later accesses
are validated). Therefore, in this mode, if the lower data file
doesn't have fs-verity enabled we fall back to a full copy rather than
a metacopy.
Actual implementation follows in a separate commit.
Signed-off-by: Alexander Larsson <alexl@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Acked-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
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Do all the logic to set the mode during mount options parsing and
do not keep the option string around.
Use a constant_table to translate from enum redirect mode to string
in preperation for new mount api option parsing.
The mount option "off" is translated to either "follow" or "nofollow",
depending on the "redirect_always_follow" build/module config, so
in effect, there are only three possible redirect modes.
This results in a minor change to the string that is displayed
in show_options() - when redirect_dir is enabled by default and the user
mounts with the option "redirect_dir=off", instead of displaying the mode
"redirect_dir=off" in show_options(), the displayed mode will be either
"redirect_dir=follow" or "redirect_dir=nofollow", depending on the value
of "redirect_always_follow" build/module config.
The displayed mode reflects the effective mode, so mounting overlayfs
again with the dispalyed redirect_dir option will result with the same
effective and displayed mode.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
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Introduce the format lowerdir=lower1:lower2::lowerdata1::lowerdata2
where the lower layers on the right of the :: separators are not merged
into the overlayfs merge dirs.
Data-only lower layers are only allowed at the bottom of the stack.
The files in those layers are only meant to be accessible via absolute
redirect from metacopy files in lower layers. Following changes will
implement lookup in the data layers.
This feature was requested for composefs ostree use case, where the
lower data layer should only be accessiable via absolute redirects
from metacopy inodes.
The lower data layers are not required to a have a unique uuid or any
uuid at all, because they are never used to compose the overlayfs inode
st_ino/st_dev.
Reviewed-by: Alexander Larsson <alexl@redhat.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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Delete duplicate words of "the".
Signed-off-by: Deming Wang <wangdeming@inspur.com>
Link: https://lore.kernel.org/r/20220624014605.2007-1-wangdeming@inspur.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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It is possible that a directory tree is shared between multiple overlay
instances as a lower layer. In this case when one instance executes a file
residing on the lower layer, the other instance denies a truncate(2) call
on this file.
This only happens for truncate(2) and not for open(2) with the O_TRUNC
flag.
Fix this interference and inconsistency by removing the preliminary
i_writecount check before copy-up.
This means that unlike on normal filesystems truncate(argv[0]) will now
succeed. If this ever causes a regression in a real world use case this
needs to be revisited.
One way to fix this properly would be to keep a correct i_writecount in the
overlay inode, but that is difficult due to memory mapping code only
dealing with the real file/inode.
Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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Commit a888db310195 ("ovl: fix regression with re-formatted lower
squashfs") attempted to fix a regression with existing setups that
use a practice that we are trying to discourage.
The discourage part was described this way in the commit message:
"To avoid the reported regression while still allowing the new features
with single lower squashfs, do not allow decoding origin with lower null
uuid unless user opted-in to one of the new features that require
following the lower inode of non-dir upper (index, xino, metacopy)."
The three mentioned features are disabled by default in Kconfig, so
it was assumed that if they are enabled, the user opted-in for them.
Apparently, distros started to configure CONFIG_OVERLAY_FS_XINO_AUTO=y
some time ago, so users upgrading their kernels can still be affected
by said regression even though they never opted-in for any new feature.
To fix this, treat "xino=on" as "user opted-in", but not "xino=auto".
Since we are changing the behavior of "xino=auto" to no longer follow
to lower origin with null uuid, take this one step further and disable
xino in that corner case. To be consistent, disable xino also in cases
of lower fs without file handle support and upper fs without xattr
support.
Update documentation w.r.t the new "xino=auto" behavior and fix the out
dated bits of documentation regarding "xino" and regarding offline
modifications to lower layers.
Link: https://lore.kernel.org/linux-unionfs/b36a429d7c563730c28d763d4d57a6fc30508a4f.1615216996.git.kevin@kevinlocke.name/
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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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: c86243b090bc ("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>
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Optionally allow using "user.overlay." namespace instead of
"trusted.overlay."
This is necessary for overlayfs to be able to be mounted in an unprivileged
namepsace.
Make the option explicit, since it makes the filesystem format be
incompatible.
Disable redirect_dir and metacopy options, because these would allow
privilege escalation through direct manipulation of the
"user.overlay.redirect" or "user.overlay.metacopy" xattrs.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
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Some overlayfs optional features are incompatible with offline changes to
the lower tree and may result in -EXDEV, -EIO, or other errors. Such
modification is not supported and the error behavior is intentionally not
specified.
Update the "Changes to underlying filesystems" section to note this
restriction. Move the paragraph describing the offline behavior below the
online behavior so it is adjacent to the following 3 paragraphs describing
the NFS export offline modification behavior.
Link: https://lore.kernel.org/linux-unionfs/20200708142353.GA103536@redhat.com/
Link: https://lore.kernel.org/linux-unionfs/CAOQ4uxi23Zsmfb4rCed1n=On0NNA5KZD74jjjeyz+et32sk-gg@mail.gmail.com/
Link: https://lore.kernel.org/linux-unionfs/20200817135651.GA637139@redhat.com/
Link: https://lore.kernel.org/linux-unionfs/20200709153616.GE150543@redhat.com/
Link: https://lore.kernel.org/linux-unionfs/20200812135529.GA122370@kevinolos/
Signed-off-by: Kevin Locke <kevin@kevinlocke.name>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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Documentation says "The lower filesystem can be any filesystem supported by
Linux". However, this is not the case, as Linux supports vfat and vfat
doesn't work as a lower filesystem
Reported-by: nerdopolis <bluescreen_avenger@verizon.net>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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This replaces uuid with null in overlayfs file handles and thus relaxes
uuid checks for overlay index feature. It is only possible in case there is
only one filesystem for all the work/upper/lower directories and bare file
handles from this backing filesystem are unique. In other case when we have
multiple filesystems lets just fallback to "uuid=on" which is and
equivalent of how it worked before with all uuid checks.
This is needed when overlayfs is/was mounted in a container with index
enabled (e.g.: to be able to resolve inotify watch file handles on it to
paths in CRIU), and this container is copied and started alongside with the
original one. This way the "copy" container can't have the same uuid on the
superblock and mounting the overlayfs from it later would fail.
That is an example of the problem on top of loop+ext4:
dd if=/dev/zero of=loopbackfile.img bs=100M count=10
losetup -fP loopbackfile.img
losetup -a
#/dev/loop0: [64768]:35 (/loop-test/loopbackfile.img)
mkfs.ext4 loopbackfile.img
mkdir loop-mp
mount -o loop /dev/loop0 loop-mp
mkdir loop-mp/{lower,upper,work,merged}
mount -t overlay overlay -oindex=on,lowerdir=loop-mp/lower,\
upperdir=loop-mp/upper,workdir=loop-mp/work loop-mp/merged
umount loop-mp/merged
umount loop-mp
e2fsck -f /dev/loop0
tune2fs -U random /dev/loop0
mount -o loop /dev/loop0 loop-mp
mount -t overlay overlay -oindex=on,lowerdir=loop-mp/lower,\
upperdir=loop-mp/upper,workdir=loop-mp/work loop-mp/merged
#mount: /loop-test/loop-mp/merged:
#mount(2) system call failed: Stale file handle.
If you just change the uuid of the backing filesystem, overlay is not
mounting any more. In Virtuozzo we copy container disks (ploops) when
create the copy of container and we require fs uuid to be unique for a new
container.
Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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Container folks are complaining that dnf/yum issues too many sync while
installing packages and this slows down the image build. Build requirement
is such that they don't care if a node goes down while build was still
going on. In that case, they will simply throw away unfinished layer and
start new build. So they don't care about syncing intermediate state to the
disk and hence don't want to pay the price associated with sync.
So they are asking for mount options where they can disable sync on overlay
mount point.
They primarily seem to have two use cases.
- For building images, they will mount overlay with nosync and then sync
upper layer after unmounting overlay and reuse upper as lower for next
layer.
- For running containers, they don't seem to care about syncing upper layer
because if node goes down, they will simply throw away upper layer and
create a fresh one.
So this patch provides a mount option "volatile" which disables all forms
of sync. Now it is caller's responsibility to throw away upper if system
crashes or shuts down and start fresh.
With "volatile", I am seeing roughly 20% speed up in my VM where I am just
installing emacs in an image. Installation time drops from 31 seconds to 25
seconds when nosync option is used. This is for the case of building on top
of an image where all packages are already cached. That way I take out the
network operations latency out of the measurement.
Giuseppe is also looking to cut down on number of iops done on the disk. He
is complaining that often in cloud their VMs are throttled if they cross
the limit. This option can help them where they reduce number of iops (by
cutting down on frequent sync and writebacks).
Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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Pull documentation updates from Jonathan Corbet:
"It's been a busy cycle for documentation - hopefully the busiest for a
while to come. Changes include:
- Some new Chinese translations
- Progress on the battle against double words words and non-HTTPS
URLs
- Some block-mq documentation
- More RST conversions from Mauro. At this point, that task is
essentially complete, so we shouldn't see this kind of churn again
for a while. Unless we decide to switch to asciidoc or
something...:)
- Lots of typo fixes, warning fixes, and more"
* tag 'docs-5.9' of git://git.lwn.net/linux: (195 commits)
scripts/kernel-doc: optionally treat warnings as errors
docs: ia64: correct typo
mailmap: add entry for <alobakin@marvell.com>
doc/zh_CN: add cpu-load Chinese version
Documentation/admin-guide: tainted-kernels: fix spelling mistake
MAINTAINERS: adjust kprobes.rst entry to new location
devices.txt: document rfkill allocation
PCI: correct flag name
docs: filesystems: vfs: correct flag name
docs: filesystems: vfs: correct sync_mode flag names
docs: path-lookup: markup fixes for emphasis
docs: path-lookup: more markup fixes
docs: path-lookup: fix HTML entity mojibake
CREDITS: Replace HTTP links with HTTPS ones
docs: process: Add an example for creating a fixes tag
doc/zh_CN: add Chinese translation prefer section
doc/zh_CN: add clearing-warn-once Chinese version
doc/zh_CN: add admin-guide index
doc:it_IT: process: coding-style.rst: Correct __maybe_unused compiler label
futex: MAINTAINERS: Re-add selftests directory
...
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Without upperdir mount option, there is no index dir and the dependency
checks nfs_export => index for mount options parsing are incorrect.
Allow the combination nfs_export=on,index=off with no upperdir and move
the check for dependency redirect_dir=nofollow for non-upper mount case
to mount options parsing.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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Drop the doubled word "the".
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: linux-unionfs@vger.kernel.org
Link: https://lore.kernel.org/r/20200703214325.31036-8-rdunlap@infradead.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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Similar to the way that a conflict between metacopy=on,redirect_dir=off is
resolved, also resolve conflicts between nfs_export=on,index=off and
nfs_export=on,metacopy=on.
An explicit mount option wins over a default config value. Both explicit
mount options result in an error.
Without this change the xfstests group overlay/exportfs are skipped if
metacopy is enabled by default.
Reported-by: Chengguang Xu <cgxu519@mykernel.net>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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Summarize the inode properties of different configurations in a table.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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Add missing piece of documentation regarding how permissions are checked in
overlayfs.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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Fix only the obvious problems
[SzM: add SPDX license line]
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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It is already formatted as RST.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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