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authorNicolas Lacasse <nlacasse@google.com>2019-10-16 14:29:20 -0700
committergVisor bot <gvisor-bot@google.com>2019-10-16 15:01:23 -0700
commitfd4e43600242c4929269afd529a8c1de4681e62e (patch)
tree6f7dd1ec886116cc91a646555536f8f590a70dac /pkg/sentry/fs/gofer
parentbbdcf44ebbf1e001a134c9412719891f150befd6 (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.go66
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 {