In order to handle idmapped mounts we will extend the vfs rename helper
to take two new arguments in follow up patches. Since this operations
already takes a bunch of arguments add a simple struct renamedata and
make the current helper use it before we extend it.
Link: https://lore.kernel.org/r/20210121131959.646623-14-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
When interacting with extended attributes the vfs verifies that the
caller is privileged over the inode with which the extended attribute is
associated. For posix access and posix default extended attributes a uid
or gid can be stored on-disk. Let the functions handle posix extended
attributes on idmapped mounts. If the inode is accessed through an
idmapped mount we need to map it according to the mount's user
namespace. Afterwards the checks are identical to non-idmapped mounts.
This has no effect for e.g. security xattrs since they don't store uids
or gids and don't perform permission checks on them like posix acls do.
Link: https://lore.kernel.org/r/20210121131959.646623-10-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: Tycho Andersen <tycho@tycho.pizza>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
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>
This will be used in next patch to be able to change uuid checks and add
uuid nullification based on ofs->config.index for a new "uuid=off" mode.
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
[S|G]ETFLAGS and FS[S|G]ETXATTR ioctls are applicable to both files and
directories, so add ioctl operations to dir as well.
We teach ovl_real_fdget() to get the realfile of directories which use
a different type of file->private_data.
Ifdef away compat ioctl implementation to conform to standard practice.
With this change, xfstest generic/079 which tests these ioctls on files
and directories passes.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Xiao Yang <yangx.jy@cn.fujitsu.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Instead of passing the xattr name down to the ovl_do_*xattr() accessor
functions, pass an enumerated value. The enum can use the same names as
the the previous #define for each xattr name.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Use the convention of calling ovl_do_foo() for operations which are overlay
specific.
This patch is a no-op, and will have significance for supporting
"user.overlay." xattr namespace.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
ovl_getattr() returns the value of an xattr in a kmalloced buffer. There
are two callers:
ovl_copy_up_meta_inode_data() (copy_up.c)
ovl_get_redirect_xattr() (util.c)
This patch just copies ovl_getxattr() to copy_up.c, the following patches
will deal with the differences in idividual callers.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
"ovl_copy_up_flags" is used in copy_up.c.
so, change it static.
Signed-off-by: youngjun <her0gyugyu@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
syzbot reported out of bounds memory access from open_by_handle_at()
with a crafted file handle that looks like this:
{ .handle_bytes = 2, .handle_type = OVL_FILEID_V1 }
handle_bytes gets rounded down to 0 and we end up calling:
ovl_check_fh_len(fh, 0) => ovl_check_fb_len(fh + 3, -3)
But fh buffer is only 2 bytes long, so accessing struct ovl_fb at
fh + 3 is illegal.
Fixes: cbe7fba8ed ("ovl: make sure that real fid is 32bit aligned in memory")
Reported-and-tested-by: syzbot+61958888b1c60361a791@syzkaller.appspotmail.com
Cc: <stable@vger.kernel.org> # v5.5
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Share inode with different whiteout files for saving inode and speeding up
delete operation.
If EMLINK is encountered when linking a shared whiteout, create a new one.
In case of any other error, disable sharing for this super block.
Note: ofs->whiteout is protected by inode lock on workdir.
Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Teach ovl_indexdir_cleanup() to remove temp directories containing
whiteouts to prepare for using index dir instead of work dir for removing
merge directories.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
So far, with xino=auto, we only enable xino if we know that all
underlying filesystem use 32bit inode numbers.
When users configure overlay with xino=auto, they already declare that
they are ready to handle 64bit inode number from overlay.
It is a very common case, that underlying filesystem uses 64bit ino,
but rarely or never uses the high inode number bits (e.g. tmpfs, xfs).
Leaving it for the users to declare high ino bits are unused with
xino=on is not a recipe for many users to enjoy the benefits of xino.
There appears to be very little reason not to enable xino when users
declare xino=auto even if we do not know how many bits underlying
filesystem uses for inode numbers.
In the worst case of xino bits overflow by real inode number, we
already fall back to the non-xino behavior - real inode number with
unique pseudo dev or to non persistent inode number and overlay st_dev
(for directories).
The only annoyance from auto enabling xino is that xino bits overflow
emits a warning to kmsg. Suppress those warnings unless users explicitly
asked for xino=on, suggesting that they expected high ino bits to be
unused by underlying filesystem.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
The current codebase makes use of the zero-length array language extension
to the C90 standard, but the preferred mechanism to declare variable-length
types such as these ones is a flexible array member[1][2], introduced in
C99:
struct foo {
int stuff;
struct boo array[];
};
By making use of the mechanism above, we will get a compiler warning in
case the flexible array does not occur last in the structure, which will
help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.
Also, notice that, dynamic memory allocations won't be affected by this
change:
"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]
This issue was found with the help of Coccinelle.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 7649773293 ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Fixes: cbe7fba8ed ("ovl: make sure that real fid is 32bit aligned in memory")
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
As with other required upper fs features, we only warn if support is
missing to avoid breaking existing sub-optimal setups.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Allow completely skipping ->revalidate() on a per-dentry basis, in case the
underlying layers used for a dentry do not themselves have ->revalidate().
E.g. negative overlay dentry has no underlying layers, hence revalidate is
unnecessary. Or if lower layer is remote but overlay dentry is pure-upper,
then can skip revalidate.
The following places need to update whether the dentry needs revalidate or
not:
- fill-super (root dentry)
- lookup
- create
- fh_to_dentry
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Move i_ino initialization to ovl_inode_init() to avoid the dance of setting
i_ino in ovl_fill_inode() sometimes on the first call and sometimes on the
seconds call.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
ovl_inode_lock() is interruptible. When inode_lock() in ovl_llseek()
was replaced with ovl_inode_lock(), we did not add a check for error.
Fix this by making ovl_inode_lock() uninterruptible and change the
existing call sites to use an _interruptible variant.
Reported-by: syzbot+66a9752fa927f745385e@syzkaller.appspotmail.com
Fixes: b1f9d3858f ("ovl: use ovl_inode_lock in ovl_llseek()")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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>
No code uses the sb returned from this helper, so make it retrun a boolean
and rename it to ovl_same_fs().
The xino mode is irrelevant when all layers are on same fs, so instead of
describing samefs with mode OVL_XINO_OFF, use a new xino_mode state, which
is 0 in the case of samefs, -1 in the case of xino=off and > 0 with xino
enabled.
Create a new helper ovl_same_dev(), to use instead of the common check for
(ovl_same_fs() || xinobits).
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Seprate on-disk encoding from in-memory and on-wire resresentation
of overlay file handle.
In-memory and on-wire we only ever pass around pointers to struct
ovl_fh, which encapsulates at offset 3 the on-disk format struct
ovl_fb. struct ovl_fb encapsulates at offset 21 the real file handle.
That makes sure that the real file handle is always 32bit aligned
in-memory when passed down to the underlying filesystem.
On-disk format remains the same and store/load are done into
correctly aligned buffer.
New nfs exported file handles are exported with aligned real fid.
Old nfs file handles are copied to an aligned buffer before being
decoded.
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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>
Overlapping overlay layers are not supported and can cause unexpected
behavior, but overlayfs does not currently check or warn about these
configurations.
User is not supposed to specify the same directory for upper and
lower dirs or for different lower layers and user is not supposed to
specify directories that are descendants of each other for overlay
layers, but that is exactly what this zysbot repro did:
https://syzkaller.appspot.com/x/repro.syz?x=12c7a94f400000
Moving layer root directories into other layers while overlayfs
is mounted could also result in unexpected behavior.
This commit places "traps" in the overlay inode hash table.
Those traps are dummy overlay inodes that are hashed by the layers
root inodes.
On mount, the hash table trap entries are used to verify that overlay
layers are not overlapping. While at it, we also verify that overlay
layers are not overlapping with directories "in-use" by other overlay
instances as upperdir/workdir.
On lookup, the trap entries are used to verify that overlay layers
root inodes have not been moved into other layers after mount.
Some examples:
$ ./run --ov --samefs -s
...
( mkdir -p base/upper/0/u base/upper/0/w base/lower lower upper mnt
mount -o bind base/lower lower
mount -o bind base/upper upper
mount -t overlay none mnt ...
-o lowerdir=lower,upperdir=upper/0/u,workdir=upper/0/w)
$ umount mnt
$ mount -t overlay none mnt ...
-o lowerdir=base,upperdir=upper/0/u,workdir=upper/0/w
[ 94.434900] overlayfs: overlapping upperdir path
mount: mount overlay on mnt failed: Too many levels of symbolic links
$ mount -t overlay none mnt ...
-o lowerdir=upper/0/u,upperdir=upper/0/u,workdir=upper/0/w
[ 151.350132] overlayfs: conflicting lowerdir path
mount: none is already mounted or mnt busy
$ mount -t overlay none mnt ...
-o lowerdir=lower:lower/a,upperdir=upper/0/u,workdir=upper/0/w
[ 201.205045] overlayfs: overlapping lowerdir path
mount: mount overlay on mnt failed: Too many levels of symbolic links
$ mount -t overlay none mnt ...
-o lowerdir=lower,upperdir=upper/0/u,workdir=upper/0/w
$ mv base/upper/0/ base/lower/
$ find mnt/0
mnt/0
mnt/0/w
find: 'mnt/0/w/work': Too many levels of symbolic links
find: 'mnt/0/u': Too many levels of symbolic links
Reported-by: syzbot+9c69c282adc4edd2b540@syzkaller.appspotmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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>
If a file has been copied up metadata only, and later data is copied up,
upper loses any security.capability xattr it has (underlying filesystem
clears it as upon file write).
From a user's point of view, this is just a file copy-up and that should
not result in losing security.capability xattr. Hence, before data copy
up, save security.capability xattr (if any) and restore it on upper after
data copy up is complete.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Fixes: 0c28887493 ("ovl: A new xattr OVL_XATTR_METACOPY for file on upper")
Cc: <stable@vger.kernel.org> # v4.19+
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
It just makes the interface strange without adding any significant value.
The only case where locked is false and return value is 0 is in
ovl_rename() when new is negative, so handle that case explicitly in
ovl_rename().
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Format has a typo: it was meant to be "%.*s", not "%*s". But at some point
callers grew nonprintable values as well, so use "%*pE" instead with a
maximized length.
Reported-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: 3a1e819b4e ("ovl: store file handle of lower inode on copy up")
Cc: <stable@vger.kernel.org> # v4.12
Right now we seem to check redirect only if upperdentry is found. But it
is possible that there is no upperdentry but later we found an index.
We need to check redirect on index as well and set it in
ovl_inode->redirect. Otherwise link code can assume that dentry does not
have redirect and place a new one which breaks things. In my testing
overlay/033 test started failing in xfstests. Following are the details.
For example do following.
$ mkdir lower upper work merged
- Make lower dir with 4 links.
$ echo "foo" > lower/l0.txt
$ ln lower/l0.txt lower/l1.txt
$ ln lower/l0.txt lower/l2.txt
$ ln lower/l0.txt lower/l3.txt
- Mount with index on and metacopy on.
$ mount -t overlay -o lowerdir=lower,upperdir=upper,workdir=work,\
index=on,metacopy=on none merged
- Link lower
$ ln merged/l0.txt merged/l4.txt
(This will metadata copy up of l0.txt and put an absolute redirect
/l0.txt)
$ echo 2 > /proc/sys/vm/drop/caches
$ ls merged/l1.txt
(Now l1.txt will be looked up. There is no upper dentry but there is
lower dentry and index will be found. We don't check for redirect on
index, hence ovl_inode->redirect will be NULL.)
- Link Upper
$ ln merged/l4.txt merged/l5.txt
(Lookup of l4.txt will use inode from l1.txt lookup which is still in
cache. It has ovl_inode->redirect NULL, hence link will put a new
redirect and replace /l0.txt with /l4.txt
- Drop caches.
echo 2 > /proc/sys/vm/drop_caches
- List l1.txt and it returns -ESTALE
$ ls merged/l0.txt
(It returns stale because, we found a metacopy of l0.txt in upper and it
has redirect l4.txt but there is no file named l4.txt in lower layer.
So lower data copy is not found and -ESTALE is returned.)
So problem here is that we did not process redirect on index. Check
redirect on index as well and then problem is fixed.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Add an ovl_inode flag OVL_CONST_INO. This flag signifies if inode number
will remain constant over copy up or not. This flag does not get updated
over copy up and remains unmodifed after setting once.
Next patch in the series will make use of this flag. It will basically
figure out if dentry is of type ORIGIN or not. And this can be derived by
this flag.
ORIGIN = (upperdentry && ovl_test_flag(OVL_CONST_INO, inode)).
Suggested-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Add an helper to retrieve real data inode associated with overlay inode.
This helper will ignore all metacopy inodes and will return only the real
inode which has data.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Right now ovl_inode stores inode pointer for lower inode. This helps with
quickly getting lower inode given overlay inode (ovl_inode_lower()).
Now with metadata only copy-up, we can have metacopy inode in middle layer
as well and inode containing data can be different from ->lower. I need to
be able to open the real file in ovl_open_realfile() and for that I need to
quickly find the lower data inode.
Hence store lower data inode also in ovl_inode. Also provide an helper
ovl_inode_lowerdata() to access this field.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
If an inode has been copied up metadata only, then we need to query the
number of blocks from lower and fill up the stat->st_blocks.
We need to be careful about races where we are doing stat on one cpu and
data copy up is taking place on other cpu. We want to return
stat->st_blocks either from lower or stable upper and not something in
between. Hence, ovl_has_upperdata() is called first to figure out whether
block reporting will take place from lower or upper.
We now support metacopy dentries in middle layer. That means number of
blocks reporting needs to come from lowest data dentry and this could be
different from lower dentry. Hence we end up making a separate
vfs_getxattr() call for metacopy dentries to get number of blocks.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Now we have the notion of data dentry and metacopy dentry.
ovl_dentry_lower() will return uppermost lower dentry, but it could be
either data or metacopy dentry. Now we support metacopy dentries in lower
layers so it is possible that lowerstack[0] is metacopy dentry while
lowerstack[1] is actual data dentry.
So add an helper which returns lowest most dentry which is supposed to be
data dentry.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
So far lower could not be a meta inode. So whenever it was time to copy up
data of a meta inode, we could copy it up from top most lower dentry.
But now lower itself can be a metacopy inode. That means data copy up
needs to take place from a data inode in metacopy inode chain. Find lower
data inode in the chain and use that for data copy up.
Introduced a helper called ovl_path_lowerdata() to find the lower data
inode chain.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This patch modifies ovl_lookup() and friends to lookup metacopy dentries.
It also allows for presence of metacopy dentries in lower layer.
During lookup, check for presence of OVL_XATTR_METACOPY and if not present,
set OVL_UPPERDATA bit in flags.
We don't support metacopy feature with nfs_export. So in nfs_export code,
we set OVL_UPPERDATA flag set unconditionally if upper inode exists.
Do not follow metacopy origin if we find a metacopy only inode and metacopy
feature is not enabled for that mount. Like redirect, this can have
security implications where an attacker could hand craft upper and try to
gain access to file on lower which it should not have to begin with.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Now we will have the capability to have upper inodes which might be only
metadata copy up and data is still on lower inode. So add a new xattr
OVL_XATTR_METACOPY to distinguish between two cases.
Presence of OVL_XATTR_METACOPY reflects that file has been copied up
metadata only and and data will be copied up later from lower origin. So
this xattr is set when a metadata copy takes place and cleared when data
copy takes place.
We also use a bit in ovl_inode->flags to cache OVL_UPPERDATA which reflects
whether ovl inode has data or not (as opposed to metadata only copy up).
If a file is copied up metadata only and later when same file is opened for
WRITE, then data copy up takes place. We copy up data, remove METACOPY
xattr and then set the UPPERDATA flag in ovl_inode->flags. While all these
operations happen with oi->lock held, read side of oi->flags can be
lockless. That is another thread on another cpu can check if UPPERDATA
flag is set or not.
So this gives us an ordering requirement w.r.t UPPERDATA flag. That is, if
another cpu sees UPPERDATA flag set, then it should be guaranteed that
effects of data copy up and remove xattr operations are also visible.
For example.
CPU1 CPU2
ovl_open() acquire(oi->lock)
ovl_open_maybe_copy_up() ovl_copy_up_data()
open_open_need_copy_up() vfs_removexattr()
ovl_already_copied_up()
ovl_dentry_needs_data_copy_up() ovl_set_flag(OVL_UPPERDATA)
ovl_test_flag(OVL_UPPERDATA) release(oi->lock)
Say CPU2 is copying up data and in the end sets UPPERDATA flag. But if
CPU1 perceives the effects of setting UPPERDATA flag but not the effects of
preceding operations (ex. upper that is not fully copied up), it will be a
problem.
Hence this patch introduces smp_wmb() on setting UPPERDATA flag operation
and smp_rmb() on UPPERDATA flag test operation.
May be some other lock or barrier is already covering it. But I am not sure
what that is and is it obvious enough that we will not break it in future.
So hence trying to be safe here and introducing barriers explicitly for
UPPERDATA flag/bit.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
There are couple of places where we need to know if file is already copied
up (in lockless manner). Right now its open coded and there are only two
conditions to check. Soon this patch series will introduce another
condition to check and Amir wants to introduce one more. So introduce a
helper instead to check this so that code is easier to read.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Right now two copy up helpers are in inode.c. Amir suggested it might be
better to move these to copy_up.c.
There will one more related function which will come in later patch.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
ovl_inode->redirect is an inode property and should be initialized in
ovl_get_inode() only when we are adding a new inode to cache. If inode is
already in cache, it is already initialized and we should not be touching
ovl_inode->redirect field.
As of now this is not a problem as redirects are used only for directories
which don't share inode. But soon I want to use redirects for regular
files also and there it can become an issue.
Hence, move ->redirect initialization in ovl_get_inode().
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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>
Copy i_size of the underlying inode to the overlay inode in ovl_copyattr().
This is in preparation for stacking I/O operations on overlay files.
This patch shouldn't have any observable effect.
Remove stale comment from ovl_setattr() [spotted by Vivek Goyal].
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
On inode creation copy certain inode flags from the underlying real inode
to the overlay inode.
This is in preparation for moving overlay functionality out of the VFS.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Copy up mtime and ctime to overlay inode after times in real object are
modified. Be careful not to dirty cachelines when not necessary.
This is in preparation for moving overlay functionality out of the VFS.
This patch shouldn't have any observable effect.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
