From b428fd02e627fc151527f0f26cbff9b05f6240e0 Mon Sep 17 00:00:00 2001 From: Nicolas Lacasse Date: Mon, 22 Mar 2021 11:42:41 -0700 Subject: Avoid calling sync on each write in writethrough mode. PiperOrigin-RevId: 364370595 --- pkg/sentry/fs/gofer/file.go | 27 ++++++++++++++------------- 1 file changed, 14 insertions(+), 13 deletions(-) (limited to 'pkg/sentry/fs/gofer/file.go') diff --git a/pkg/sentry/fs/gofer/file.go b/pkg/sentry/fs/gofer/file.go index 06d450ba6..8f5a87120 100644 --- a/pkg/sentry/fs/gofer/file.go +++ b/pkg/sentry/fs/gofer/file.go @@ -204,20 +204,8 @@ 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. +// maybeSync will call FSync on the file if the 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 { @@ -254,6 +242,19 @@ func (f *fileOperations) Write(ctx context.Context, file *fs.File, src usermem.I n, err = src.CopyInTo(ctx, f.handles.readWriterAt(ctx, offset)) } + if n == 0 { + // Nothing written. We are done. + return 0, err + } + + // Write the dirty pages and attributes if cache policy tells us to. + if f.inodeOperations.session().cachePolicy.writeThrough(file.Dirent.Inode) { + if werr := f.inodeOperations.cachingInodeOps.WriteDirtyPagesAndAttrs(ctx, file.Dirent.Inode); werr != nil { + // Report no bytes written since the write faild. + return 0, werr + } + } + // 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 -- cgit v1.2.3