From 492229d0176c1af2ab4ea4cf91bf211e940b5b12 Mon Sep 17 00:00:00 2001 From: Jamie Liu Date: Tue, 4 Feb 2020 11:28:36 -0800 Subject: 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 --- pkg/safemem/seq_unsafe.go | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) (limited to 'pkg/safemem') 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 +} -- cgit v1.2.3 From a690b5762480ae80ef4264402fcfa8d84b57339a Mon Sep 17 00:00:00 2001 From: Jamie Liu Date: Wed, 4 Mar 2020 14:29:11 -0800 Subject: Ensure that safemem.BlockSeqOf(safemem.Block{}) produces an empty BlockSeq. PiperOrigin-RevId: 298941855 --- pkg/safemem/seq_test.go | 21 +++++++++++++++++++++ pkg/safemem/seq_unsafe.go | 3 +++ 2 files changed, 24 insertions(+) (limited to 'pkg/safemem') diff --git a/pkg/safemem/seq_test.go b/pkg/safemem/seq_test.go index eba4bb535..de34005e9 100644 --- a/pkg/safemem/seq_test.go +++ b/pkg/safemem/seq_test.go @@ -20,6 +20,27 @@ import ( "testing" ) +func TestBlockSeqOfEmptyBlock(t *testing.T) { + bs := BlockSeqOf(Block{}) + if !bs.IsEmpty() { + t.Errorf("BlockSeqOf(Block{}).IsEmpty(): got false, wanted true; BlockSeq is %v", bs) + } +} + +func TestBlockSeqOfNonemptyBlock(t *testing.T) { + b := BlockFromSafeSlice(make([]byte, 1)) + bs := BlockSeqOf(b) + if bs.IsEmpty() { + t.Fatalf("BlockSeqOf(non-empty Block).IsEmpty(): got true, wanted false; BlockSeq is %v", bs) + } + if head := bs.Head(); head != b { + t.Fatalf("BlockSeqOf(non-empty Block).Head(): got %v, wanted %v", head, b) + } + if tail := bs.Tail(); !tail.IsEmpty() { + t.Fatalf("BlockSeqOf(non-empty Block).Tail().IsEmpty(): got false, wanted true: tail is %v", tail) + } +} + type blockSeqTest struct { desc string diff --git a/pkg/safemem/seq_unsafe.go b/pkg/safemem/seq_unsafe.go index dcdfc9600..f5f0574f8 100644 --- a/pkg/safemem/seq_unsafe.go +++ b/pkg/safemem/seq_unsafe.go @@ -56,6 +56,9 @@ type BlockSeq struct { // BlockSeqOf returns a BlockSeq representing the single Block b. func BlockSeqOf(b Block) BlockSeq { + if b.length == 0 { + return BlockSeq{} + } bs := BlockSeq{ data: b.start, length: -1, -- cgit v1.2.3