diff options
Diffstat (limited to 'pkg')
| -rw-r--r-- | pkg/sentry/fs/gofer/inode.go | 31 |
1 files changed, 30 insertions, 1 deletions
diff --git a/pkg/sentry/fs/gofer/inode.go b/pkg/sentry/fs/gofer/inode.go index 454242923..c00da5fec 100644 --- a/pkg/sentry/fs/gofer/inode.go +++ b/pkg/sentry/fs/gofer/inode.go @@ -206,7 +206,7 @@ func (i *inodeFileState) WriteFromBlocksAt(ctx context.Context, srcs safemem.Blo // SetMaskedAttributes implements fsutil.CachedFileObject.SetMaskedAttributes. func (i *inodeFileState) SetMaskedAttributes(ctx context.Context, mask fs.AttrMask, attr fs.UnstableAttr) error { - if mask.Empty() { + if i.skipSetAttr(mask) { return nil } as, ans := attr.AccessTime.Unix() @@ -237,6 +237,35 @@ func (i *inodeFileState) SetMaskedAttributes(ctx context.Context, mask fs.AttrMa }) } +// skipSetAttr checks if attribute change can be skipped. It can be skipped +// when: +// - Mask is empty +// - Mask contains only atime and/or mtime, and host FD exists +// +// Updates to atime and mtime can be skipped because cached value will be +// "close enough" to host value, given that operation went directly to host FD. +// Skipping atime updates is particularly important to reduce the number of +// operations sent to the Gofer for readonly files. +func (i *inodeFileState) skipSetAttr(mask fs.AttrMask) bool { + if mask.Empty() { + return true + } + + cpy := mask + cpy.AccessTime = false + cpy.ModificationTime = false + if !cpy.Empty() { + // More than just atime and mtime is being set. + return false + } + + i.handlesMu.RLock() + defer i.handlesMu.RUnlock() + return (i.readonly != nil && i.readonly.Host != nil) || + (i.readthrough != nil && i.readthrough.Host != nil) || + (i.writeback != nil && i.writeback.Host != nil) +} + // Sync implements fsutil.CachedFileObject.Sync. func (i *inodeFileState) Sync(ctx context.Context) error { i.handlesMu.RLock() |