diff options
author | Nicolas Lacasse <nlacasse@google.com> | 2019-10-16 14:29:20 -0700 |
---|---|---|
committer | gVisor bot <gvisor-bot@google.com> | 2019-10-16 15:01:23 -0700 |
commit | fd4e43600242c4929269afd529a8c1de4681e62e (patch) | |
tree | 6f7dd1ec886116cc91a646555536f8f590a70dac /pkg/sentry/fs/gofer | |
parent | bbdcf44ebbf1e001a134c9412719891f150befd6 (diff) |
Support O_SYNC and O_DSYNC flags.
When any of these flags are set, all writes will trigger a subsequent fsync
call. This behavior already existed for "write-through" mounts.
O_DIRECT is treated as an alias for O_SYNC. Better support coming soon.
PiperOrigin-RevId: 275114392
Diffstat (limited to 'pkg/sentry/fs/gofer')
-rw-r--r-- | pkg/sentry/fs/gofer/file.go | 66 |
1 files changed, 51 insertions, 15 deletions
diff --git a/pkg/sentry/fs/gofer/file.go b/pkg/sentry/fs/gofer/file.go index 9e2e412cd..7960b9c7b 100644 --- a/pkg/sentry/fs/gofer/file.go +++ b/pkg/sentry/fs/gofer/file.go @@ -214,28 +214,64 @@ func (f *fileOperations) readdirAll(ctx context.Context) (map[string]fs.DentAttr return entries, nil } +// maybeSync will call FSync on the file if either the cache policy or file +// flags require it. +func (f *fileOperations) maybeSync(ctx context.Context, file *fs.File, offset, n int64) error { + if n == 0 { + // Nothing to sync. + return nil + } + + if f.inodeOperations.session().cachePolicy.writeThrough(file.Dirent.Inode) { + // Call WriteOut directly, as some "writethrough" filesystems + // do not support sync. + return f.inodeOperations.cachingInodeOps.WriteOut(ctx, file.Dirent.Inode) + } + + flags := file.Flags() + var syncType fs.SyncType + switch { + case flags.Direct || flags.Sync: + syncType = fs.SyncAll + case flags.DSync: + syncType = fs.SyncData + default: + // No need to sync. + return nil + } + + return f.Fsync(ctx, file, offset, offset+n, syncType) +} + // Write implements fs.FileOperations.Write. func (f *fileOperations) Write(ctx context.Context, file *fs.File, src usermem.IOSequence, offset int64) (int64, error) { if fs.IsDir(file.Dirent.Inode.StableAttr) { // Not all remote file systems enforce this so this client does. return 0, syserror.EISDIR } - cp := f.inodeOperations.session().cachePolicy - if cp.useCachingInodeOps(file.Dirent.Inode) { - n, err := f.inodeOperations.cachingInodeOps.Write(ctx, src, offset) - if err != nil { - return n, err - } - if cp.writeThrough(file.Dirent.Inode) { - // Write out the file. - err = f.inodeOperations.cachingInodeOps.WriteOut(ctx, file.Dirent.Inode) - } - return n, err + + var ( + n int64 + err error + ) + // The write is handled in different ways depending on the cache policy + // and availability of a host-mappable FD. + if f.inodeOperations.session().cachePolicy.useCachingInodeOps(file.Dirent.Inode) { + n, err = f.inodeOperations.cachingInodeOps.Write(ctx, src, offset) + } else if f.inodeOperations.fileState.hostMappable != nil { + n, err = f.inodeOperations.fileState.hostMappable.Write(ctx, src, offset) + } else { + n, err = src.CopyInTo(ctx, f.handles.readWriterAt(ctx, offset)) } - if f.inodeOperations.fileState.hostMappable != nil { - return f.inodeOperations.fileState.hostMappable.Write(ctx, src, offset) + + // We may need to sync the written bytes. + if syncErr := f.maybeSync(ctx, file, offset, n); syncErr != nil { + // Sync failed. Report 0 bytes written, since none of them are + // guaranteed to have been synced. + return 0, syncErr } - return src.CopyInTo(ctx, f.handles.readWriterAt(ctx, offset)) + + return n, err } // incrementReadCounters increments the read counters for the read starting at the given time. We @@ -273,7 +309,7 @@ func (f *fileOperations) Read(ctx context.Context, file *fs.File, dst usermem.IO } // Fsync implements fs.FileOperations.Fsync. -func (f *fileOperations) Fsync(ctx context.Context, file *fs.File, start int64, end int64, syncType fs.SyncType) error { +func (f *fileOperations) Fsync(ctx context.Context, file *fs.File, start, end int64, syncType fs.SyncType) error { switch syncType { case fs.SyncAll, fs.SyncData: if err := file.Dirent.Inode.WriteOut(ctx); err != nil { |