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authorJamie Liu <jamieliu@google.com>2020-02-04 11:28:36 -0800
committergVisor bot <gvisor-bot@google.com>2020-02-04 11:29:22 -0800
commit492229d0176c1af2ab4ea4cf91bf211e940b5b12 (patch)
tree9e59729aa6c2773a635704fea4ebb66651d2ae6a /pkg/safemem
parentd7cd484091543827678f1548b8e5668a7a86e13f (diff)
VFS2 gofer client
Updates #1198 Opening host pipes (by spinning in fdpipe) and host sockets is not yet complete, and will be done in a future CL. Major differences from VFS1 gofer client (sentry/fs/gofer), with varying levels of backportability: - "Cache policies" are replaced by InteropMode, which control the behavior of timestamps in addition to caching. Under InteropModeExclusive (analogous to cacheAll) and InteropModeWritethrough (analogous to cacheAllWritethrough), client timestamps are *not* written back to the server (it is not possible in 9P or Linux for clients to set ctime, so writing back client-authoritative timestamps results in incoherence between atime/mtime and ctime). Under InteropModeShared (analogous to cacheRemoteRevalidating), client timestamps are not used at all (remote filesystem clocks are authoritative). cacheNone is translated to InteropModeShared + new option filesystemOptions.specialRegularFiles. - Under InteropModeShared, "unstable attribute" reloading for permission checks, lookup, and revalidation are fused, which is feasible in VFS2 since gofer.filesystem controls path resolution. This results in a ~33% reduction in RPCs for filesystem operations compared to cacheRemoteRevalidating. For example, consider stat("/foo/bar/baz") where "/foo/bar/baz" fails revalidation, resulting in the instantiation of a new dentry: VFS1 RPCs: getattr("/") // fs.MountNamespace.FindLink() => fs.Inode.CheckPermission() => gofer.inodeOperations.check() => gofer.inodeOperations.UnstableAttr() walkgetattr("/", "foo") = fid1 // fs.Dirent.walk() => gofer.session.Revalidate() => gofer.cachePolicy.Revalidate() clunk(fid1) getattr("/foo") // CheckPermission walkgetattr("/foo", "bar") = fid2 // Revalidate clunk(fid2) getattr("/foo/bar") // CheckPermission walkgetattr("/foo/bar", "baz") = fid3 // Revalidate clunk(fid3) walkgetattr("/foo/bar", "baz") = fid4 // fs.Dirent.walk() => gofer.inodeOperations.Lookup getattr("/foo/bar/baz") // linux.stat() => gofer.inodeOperations.UnstableAttr() VFS2 RPCs: getattr("/") // gofer.filesystem.walkExistingLocked() walkgetattr("/", "foo") = fid1 // gofer.filesystem.stepExistingLocked() clunk(fid1) // No getattr: walkgetattr already updated metadata for permission check walkgetattr("/foo", "bar") = fid2 clunk(fid2) walkgetattr("/foo/bar", "baz") = fid3 // No clunk: fid3 used for new gofer.dentry // No getattr: walkgetattr already updated metadata for stat() - gofer.filesystem.unlinkAt() does not require instantiation of a dentry that represents the file to be deleted. Updates #898. - gofer.regularFileFD.OnClose() skips Tflushf for regular files under InteropModeExclusive, as it's nonsensical to request a remote file flush without flushing locally-buffered writes to that remote file first. - Symlink targets are cached when InteropModeShared is not in effect. - p9.QID.Path (which is already required to be unique for each file within a server, and is accordingly already synthesized from device/inode numbers in all known gofers) is used as-is for inode numbers, rather than being mapped along with attr.RDev in the client to yet another synthetic inode number. - Relevant parts of fsutil.CachingInodeOperations are inlined directly into gofer package code. This avoids having to duplicate part of its functionality in fsutil.HostMappable. PiperOrigin-RevId: 293190213
Diffstat (limited to 'pkg/safemem')
-rw-r--r--pkg/safemem/seq_unsafe.go17
1 files changed, 17 insertions, 0 deletions
diff --git a/pkg/safemem/seq_unsafe.go b/pkg/safemem/seq_unsafe.go
index 354a95dde..dcdfc9600 100644
--- a/pkg/safemem/seq_unsafe.go
+++ b/pkg/safemem/seq_unsafe.go
@@ -18,6 +18,7 @@ import (
"bytes"
"fmt"
"reflect"
+ "syscall"
"unsafe"
)
@@ -297,3 +298,19 @@ func ZeroSeq(dsts BlockSeq) (uint64, error) {
}
return done, nil
}
+
+// IovecsFromBlockSeq returns a []syscall.Iovec representing seq.
+func IovecsFromBlockSeq(bs BlockSeq) []syscall.Iovec {
+ iovs := make([]syscall.Iovec, 0, bs.NumBlocks())
+ for ; !bs.IsEmpty(); bs = bs.Tail() {
+ b := bs.Head()
+ iovs = append(iovs, syscall.Iovec{
+ Base: &b.ToSlice()[0],
+ Len: uint64(b.Len()),
+ })
+ // We don't need to care about b.NeedSafecopy(), because the host
+ // kernel will handle such address ranges just fine (by returning
+ // EFAULT).
+ }
+ return iovs
+}