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The fdnotifier package provides an API to a thread that continually epolls
arbitrary host FDs. The set of events polled for each host FD is (intended to
be) all events for which a waiter.Entry has expressed interest, as returned by
waiter.Queue.Events() for the waiter.Queue registered to the given host FD.
When the set of events changes (due to a change in the set of registered
waiter.Entries), the mutator must call fdnotifier.UpdateFD() to recalculate the
new event set and propagate it to the epoll FD.
PiperOrigin-RevId: 319924719
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Calling sync on a readonly file flushes metadata that
may have been modified, like last access time.
Updates #1198
PiperOrigin-RevId: 319888290
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Reserve the MSB from ino for synthetic dentries to prevent
conflict with regular dentries. Log warning in case MSB is
set for regular dentries.
Updates #1487
PiperOrigin-RevId: 319869858
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We do not support RWF_SYNC/RWF_DSYNC and probably shouldn't silently accept
them, since the user may incorrectly believe that we are synchronizing I/O.
Remove the pwritev2 test verifying that we support these flags.
gvisor.dev/issue/2601 is the tracking bug for deciding which RWF_.* flags
we need and supporting them.
Updates #2923, #2601.
PiperOrigin-RevId: 319351286
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We were not invalidating mappings when the file size changed in shared mode.
Enabled the syscall test for vfs2.
Updates #2923
PiperOrigin-RevId: 319346569
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Some Open:TruncateXxx syscall tests were failing because the file size was
not being updated when the file was opened with O_TRUNC.
Fixes Truncate tests in test/syscalls:open_test_runsc_ptrace_vfs2.
Updates #2923
PiperOrigin-RevId: 319340127
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Currently, we always perform a full-file sync which could be extremely
expensive for some applications. Although vfs1 did not fully support
sync_file_range, there were some optimizations that allowed us skip some
unnecessary write-outs.
Updates #2923, #1897.
PiperOrigin-RevId: 319324213
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PiperOrigin-RevId: 319283715
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Updates #2923.
PiperOrigin-RevId: 318648128
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Also, while we're here, make sure that gofer inotify events are generated when
files are created in remote revalidating mode.
Updates #1479.
PiperOrigin-RevId: 318536354
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Events were only skipped on parent directories after their children were
unlinked; events on the unlinked file itself need to be skipped as well.
As a result, all Watches.Notify() calls need to know whether the dentry where
the call came from was unlinked.
Updates #1479.
PiperOrigin-RevId: 317979476
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Because there is no inode structure stored in the sandbox, inotify watches
must be held on the dentry. This would be an issue in the presence of hard
links, where multiple dentries would need to share the same set of watches,
but in VFS2, we do not support the internal creation of hard links on gofer
fs. As a result, we make the assumption that every dentry corresponds to a
unique inode.
Furthermore, dentries can be cached and then evicted, even if the underlying
file has not be deleted. We must prevent this from occurring if there are any
watches that would be lost. Note that if the dentry was deleted or invalidated
(d.vfsd.IsDead()), we should still destroy it along with its watches.
Additionally, when a dentry’s last watch is removed, we cache it if it also
has zero references. This way, the dentry can eventually be evicted from
memory if it is no longer needed. This is accomplished with a new dentry
method, OnZeroWatches(), which is called by Inotify.RmWatch and
Inotify.Release. Note that it must be called after all inotify locks are
released to avoid violating lock order. Stress tests are added to make sure
that inotify operations don't deadlock with gofer.OnZeroWatches.
Updates #1479.
PiperOrigin-RevId: 317958034
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Updates #2923.
PiperOrigin-RevId: 317700049
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Correct behavior when given zero size arguments and trying to set user.* xattrs
on files other than regular files or directories.
Updates #2923.
PiperOrigin-RevId: 317590409
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Check for unsupported flags, and silently support RWF_HIPRI by doing nothing.
From pkg/abi/linux/file.go: "gVisor does not implement the RWF_HIPRI feature,
but the flag is accepted as a valid flag argument for preadv2/pwritev2."
Updates #2923.
PiperOrigin-RevId: 317330631
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Updates #2923.
PiperOrigin-RevId: 317314460
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Updates #2923.
PiperOrigin-RevId: 317298186
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Always check if a synthetic file already exists at a location before creating a
file there, and do not try to delete synthetic gofer files from the remote fs.
This fixes runsc_ptrace socket tests that create/unlink synthetic, named socket
files.
Updates #2923.
PiperOrigin-RevId: 317293648
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Updates #1035, #1199
PiperOrigin-RevId: 317028108
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- Change FileDescriptionImpl Lock/UnlockPOSIX signature to
take {start,length,whence}, so the correct offset can be
calculated in the implementations.
- Create PosixLocker interface to make it possible to share
the same locking code from different implementations.
Closes #1480
PiperOrigin-RevId: 316910286
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PiperOrigin-RevId: 316627764
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Major differences from existing overlay filesystems:
- Linux allows lower layers in an overlay to require revalidation, but not the
upper layer. VFS1 allows the upper layer in an overlay to require
revalidation, but not the lower layer. VFS2 does not allow any layers to
require revalidation. (Now that vfs.MkdirOptions.ForSyntheticMountpoint
exists, no uses of overlay in VFS1 are believed to require upper layer
revalidation; in particular, the requirement that the upper layer support the
creation of "trusted." extended attributes for whiteouts effectively required
the upper filesystem to be tmpfs in most cases.)
- Like VFS1, but unlike Linux, VFS2 overlay does not attempt to make mutations
of the upper layer atomic using a working directory and features like
RENAME_WHITEOUT. (This may change in the future, since not having a working
directory makes error recovery for some operations, e.g. rmdir, particularly
painful.)
- Like Linux, but unlike VFS1, VFS2 represents whiteouts using character
devices with rdev == 0; the equivalent of the whiteout attribute on
directories is xattr trusted.overlay.opaque = "y"; and there is no equivalent
to the whiteout attribute on non-directories since non-directories are never
merged with lower layers.
- Device and inode numbers work as follows:
- In Linux, modulo the xino feature and a special case for when all layers
are the same filesystem:
- Directories use the overlay filesystem's device number and an
ephemeral inode number assigned by the overlay.
- Non-directories that have been copied up use the device and inode
number assigned by the upper filesystem.
- Non-directories that have not been copied up use a per-(overlay,
layer)-pair device number and the inode number assigned by the lower
filesystem.
- In VFS1, device and inode numbers always come from the lower layer unless
"whited out"; this has the adverse effect of requiring interaction with
the lower filesystem even for non-directory files that exist on the upper
layer.
- In VFS2, device and inode numbers are assigned as in Linux, except that
xino and the samefs special case are not supported.
- Like Linux, but unlike VFS1, VFS2 does not attempt to maintain memory mapping
coherence across copy-up. (This may have to change in the future, as users
may be dependent on this property.)
- Like Linux, but unlike VFS1, VFS2 uses the overlayfs mounter's credentials
when interacting with the overlay's layers, rather than the caller's.
- Like Linux, but unlike VFS1, VFS2 permits multiple lower layers in an
overlay.
- Like Linux, but unlike VFS1, VFS2's overlay filesystem is
application-mountable.
Updates #1199
PiperOrigin-RevId: 316019067
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LockFD is the generic implementation that can be embedded in
FileDescriptionImpl implementations. Unique lock ID is
maintained in vfs.FileDescription and is created on demand.
Updates #1480
PiperOrigin-RevId: 315604825
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This is mostly syscall plumbing, VFS2 already implements the internals of
mounts. In addition to the syscall defintions, the following mount-related
mechanisms are updated:
- Implement MS_NOATIME for VFS2, but only for tmpfs and goferfs. The other VFS2
filesystems don't implement node-level timestamps yet.
- Implement the 'mode', 'uid' and 'gid' mount options for VFS2's tmpfs.
- Plumb mount namespace ownership, which is necessary for checking appropriate
capabilities during mount(2).
Updates #1035
PiperOrigin-RevId: 315035352
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gofer.filesystem.createAndOpenChildLocked() doesn't need to take a reference on
the new dentry since vfs.FileDescription.Init() will do so.
PiperOrigin-RevId: 314242127
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Using tee instead of read to detect when a O_RDONLY|O_NONBLOCK pipe FD has a
writer circumvents the problem of what to do with the byte read from the pipe,
avoiding much of the complexity of the fdpipe package.
PiperOrigin-RevId: 314216146
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Limited to tmpfs. Inotify support in other filesystem implementations to
follow.
Updates #1479
PiperOrigin-RevId: 313828648
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Support in other filesystem impls is still needed. Unlike in Linux and vfs1, we
need to plumb inotify down to each filesystem implementation in order to keep
track of links/inode structures properly.
IN_EXCL_UNLINK still needs to be implemented, as well as a few inotify hooks
that are not present in either vfs1 or vfs2. Those will be addressed in
subsequent changes.
Updates #1479.
PiperOrigin-RevId: 313781995
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PiperOrigin-RevId: 313332542
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In VFS1, both fs/host and fs/gofer used the same utils for host file mappings.
Refactor parts of fsimpl/gofer to create similar utils to share with
fsimpl/host (memory accounting code moved to fsutil, page rounding arithmetic
moved to usermem).
Updates #1476.
PiperOrigin-RevId: 312345090
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PiperOrigin-RevId: 311657502
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Linux 4.18 and later make reads and writes coherent between pre-copy-up and
post-copy-up FDs representing the same file on an overlay filesystem. However,
memory mappings remain incoherent:
- Documentation/filesystems/overlayfs.rst, "Non-standard behavior": "If a file
residing on a lower layer is opened for read-only and then memory mapped with
MAP_SHARED, then subsequent changes to the file are not reflected in the
memory mapping."
- fs/overlay/file.c:ovl_mmap() passes through to the underlying FD without any
management of coherence in the overlay.
- Experimentally on Linux 5.2:
```
$ cat mmap_cat_page.c
#include <err.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <sys/mman.h>
#include <unistd.h>
int main(int argc, char **argv) {
if (argc < 2) {
errx(1, "syntax: %s [FILE]", argv[0]);
}
const int fd = open(argv[1], O_RDONLY);
if (fd < 0) {
err(1, "open(%s)", argv[1]);
}
const size_t page_size = sysconf(_SC_PAGE_SIZE);
void* page = mmap(NULL, page_size, PROT_READ, MAP_SHARED, fd, 0);
if (page == MAP_FAILED) {
err(1, "mmap");
}
for (;;) {
write(1, page, strnlen(page, page_size));
if (getc(stdin) == EOF) {
break;
}
}
return 0;
}
$ gcc -O2 -o mmap_cat_page mmap_cat_page.c
$ mkdir lowerdir upperdir workdir overlaydir
$ echo old > lowerdir/file
$ sudo mount -t overlay -o "lowerdir=lowerdir,upperdir=upperdir,workdir=workdir" none overlaydir
$ ./mmap_cat_page overlaydir/file
old
^Z
[1]+ Stopped ./mmap_cat_page overlaydir/file
$ echo new > overlaydir/file
$ cat overlaydir/file
new
$ fg
./mmap_cat_page overlaydir/file
old
```
Therefore, while the VFS1 gofer client's behavior of reopening read FDs is only
necessary pre-4.18, replacing existing memory mappings (in both sentry and
application address spaces) with mappings of the new FD is required regardless
of kernel version, and this latter behavior is common to both VFS1 and VFS2.
Re-document accordingly, and change the runsc flag to enabled by default.
New test:
- Before this CL: https://source.cloud.google.com/results/invocations/5b222d2c-e918-4bae-afc4-407f5bac509b
- After this CL: https://source.cloud.google.com/results/invocations/f28c747e-d89c-4d8c-a461-602b33e71aab
PiperOrigin-RevId: 311361267
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PiperOrigin-RevId: 311046755
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PiperOrigin-RevId: 311014995
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Updates #1197, #1198, #1672
PiperOrigin-RevId: 310432006
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PiperOrigin-RevId: 309966538
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p9.NoUID/GID (== uint32(-1) == auth.NoID) is not a valid auth.KUID/KGID; in
particular, using it for file ownership causes capabilities to be ineffective
since file capabilities require that the file's KUID and KGID are mapped into
the capability holder's user namespace [1], and auth.NoID is not mapped into
any user namespace. Map p9.NoUID/GID to a different, valid KUID/KGID; in the
unlikely case that an application actually using the overflow KUID/KGID
attempts an operation that is consequently permitted by client permission
checks, the remote operation will still fail with EPERM.
Since this changes the VFS2 gofer client to no longer ignore the invalid IDs
entirely, this CL both permits and requires that we change synthetic mount point
creation to use root credentials.
[1] See fs.Inode.CheckCapability or vfs.GenericCheckPermissions.
PiperOrigin-RevId: 309856455
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All three follow the same pattern:
1. Refactor VFS1 sockets into socketOpsCommon, so that most of the methods can
be shared with VFS2.
2. Create a FileDescriptionImpl with the corresponding socket operations,
rewriting the few that cannot be shared with VFS1.
3. Set up a VFS2 socket provider that creates a socket by setting up a dentry
in the global Kernel.socketMount and connecting it with a new
FileDescription.
This mostly completes the work for porting sockets to VFS2, and many syscall
tests can be enabled as a result.
There are several networking-related syscall tests that are still not passing:
1. net gofer tests
2. socketpair gofer tests
2. sendfile tests (splice is not implemented in VFS2 yet)
Updates #1478, #1484, #1485
PiperOrigin-RevId: 309457331
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PiperOrigin-RevId: 309317605
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Named pipes and sockets can be represented in two ways in gofer fs:
1. As a file on the remote filesystem. In this case, all file operations are
passed through 9p.
2. As a synthetic file that is internal to the sandbox. In this case, the
dentry stores an endpoint or VFSPipe for sockets and pipes respectively,
which replaces interactions with the remote fs through the gofer.
In gofer.filesystem.MknodAt, we attempt to call mknod(2) through 9p,
and if it fails, fall back to the synthetic version.
Updates #1200.
PiperOrigin-RevId: 308828161
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This change includes:
- Modifications to loader_test.go to get TestCreateMountNamespace to
pass with VFS2.
- Changes necessary to get TestHelloWorld in image tests to pass with
VFS2. This means runsc can run the hello-world container with docker
on VSF2.
Note: Containers that use sockets will not run with these changes.
See "//test/image/...". Any tests here with sockets currently fail
(which is all of them but HelloWorld).
PiperOrigin-RevId: 308363072
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PiperOrigin-RevId: 308143529
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Also fix returning EOF when 0 bytes are read.
PiperOrigin-RevId: 308089875
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Even though BoundEndpointAt is not yet implemented for gofer fs, allow path
resolution errors to be returned so that we can jump to tmpfs, where it is
implemented.
Updates #1476.
PiperOrigin-RevId: 307718335
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This change:
- Drastically simplifies the synchronization model: filesystem structure is
both implementation-defined and implementation-synchronized.
- Allows implementations of vfs.DentryImpl to use implementation-specific
dentry types, reducing casts during path traversal.
- Doesn't require dentries representing non-directory files to waste space on a
map of children.
- Allows dentry revalidation and mount lookup to be correctly ordered (fixed
FIXME in fsimpl/gofer/filesystem.go).
- Removes the need to have two separate maps in gofer.dentry
(dentry.vfsd.children and dentry.negativeChildren) for positive and negative
lookups respectively.
//pkg/sentry/fsimpl/tmpfs/benchmark_test.go:
name old time/op new time/op delta
VFS2TmpfsStat/1-112 172ns ± 4% 165ns ± 3% -4.08% (p=0.002 n=9+9)
VFS2TmpfsStat/2-112 199ns ± 3% 195ns ±10% ~ (p=0.132 n=8+9)
VFS2TmpfsStat/3-112 230ns ± 2% 216ns ± 2% -6.15% (p=0.000 n=8+8)
VFS2TmpfsStat/8-112 390ns ± 2% 358ns ± 4% -8.33% (p=0.000 n=9+8)
VFS2TmpfsStat/64-112 2.20µs ± 3% 2.01µs ± 3% -8.48% (p=0.000 n=10+8)
VFS2TmpfsStat/100-112 3.42µs ± 9% 3.08µs ± 2% -9.82% (p=0.000 n=9+8)
VFS2TmpfsMountStat/1-112 278ns ± 1% 286ns ±15% ~ (p=0.712 n=8+10)
VFS2TmpfsMountStat/2-112 311ns ± 4% 298ns ± 2% -4.27% (p=0.000 n=9+8)
VFS2TmpfsMountStat/3-112 339ns ± 3% 330ns ± 9% ~ (p=0.070 n=8+9)
VFS2TmpfsMountStat/8-112 503ns ± 3% 466ns ± 3% -7.38% (p=0.000 n=8+8)
VFS2TmpfsMountStat/64-112 2.53µs ±16% 2.17µs ± 7% -14.19% (p=0.000 n=10+9)
VFS2TmpfsMountStat/100-112 3.60µs ± 4% 3.30µs ± 8% -8.33% (p=0.001 n=8+9)
Updates #1035
PiperOrigin-RevId: 307655892
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As in VFS1, we only support the user.* namespace. Plumbing is added to tmpfs
and goferfs.
Note that because of the slightly different order of checks between VFS2 and
Linux, one of the xattr tests needs to be relaxed slightly.
Fixes #2363.
PiperOrigin-RevId: 305985121
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The sentry doesn't allow execve, but it's a good defense
in-depth measure.
PiperOrigin-RevId: 305958737
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Required directory checks were being skipped when there was
no child cached. Now the code always loads the child file
before unlinking it.
Updates #1198
PiperOrigin-RevId: 305382323
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gofer operations accumulate dentries touched in a slice to call
checkCachingLocked on them when the operation is over. In case
the same dentry is touched multiple times during the operation,
checkCachingLocked, and consequently destroyLocked, may be called
more than once for the same dentry.
Updates #1198
PiperOrigin-RevId: 305276819
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NAME_MAX should be enforced per filesystem implementation
because other file systems may not have the same restriction.
Gofer filesystem now keeps a reference to the kernel clock to
avoid lookup in the Context on file access to update atime.
Update access, modification, and status change times in tmpfs.
Updates #1197, #1198.
PiperOrigin-RevId: 304527148
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