Use FD limit and file size limit from host

FD limit and file size limit is read from the host, instead
of using hard-coded defaults, given that they effect the sandbox
process. Also limit the direct cache to use no more than half
if the available FDs.

PiperOrigin-RevId: 244050323
Change-Id: I787ad0fdf07c49d589e51aebfeae477324fe26e6

1 files changed, 12 insertions, 0 deletions

diff --git a/pkg/sentry/fs/context.go b/pkg/sentry/fs/context.go
index c0e6075e4..4869428a8 100644
--- a/pkg/sentry/fs/context.go
+++ b/pkg/sentry/fs/context.go
@@ -26,6 +26,9 @@ type contextID int
 const (
 	// CtxRoot is a Context.Value key for a Dirent.
 	CtxRoot contextID = iota
+
+	// CtxDirentCacheLimiter is a Context.Value key for DirentCacheLimiter.
+	CtxDirentCacheLimiter
 )
 
 // ContextCanAccessFile determines whether `file` can be accessed in the requested way
@@ -100,3 +103,12 @@ func RootFromContext(ctx context.Context) *Dirent {
 	}
 	return nil
 }
+
+// DirentCacheLimiterFromContext returns the DirentCacheLimiter used by ctx, or
+// nil if ctx does not have a dirent cache limiter.
+func DirentCacheLimiterFromContext(ctx context.Context) *DirentCacheLimiter {
+	if v := ctx.Value(CtxDirentCacheLimiter); v != nil {
+		return v.(*DirentCacheLimiter)
+	}
+	return nil
+}