sys_util: add FileAllocate trait

This trait provides a generic interface for allocating space on the
filesystem within a given file.  It is equivalent to the fallocate(2)
system call with the default mode (mode = 0).

BUG=chromium:858815
TEST=cargo build --features=composite-disk

Change-Id: I2f4e8aceb4878790e8dec2e3d539071915efd205
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2015828
Reviewed-by: Dylan Reid <dgreid@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Commit-Queue: Daniel Verkamp <dverkamp@chromium.org>

1 files changed, 24 insertions, 1 deletions

diff --git a/disk/src/composite.rs b/disk/src/composite.rs
index c3cca00..cd048c1 100644
--- a/disk/src/composite.rs
+++ b/disk/src/composite.rs
@@ -13,7 +13,9 @@ use crate::{create_disk_file, DiskFile, DiskGetLen, ImageType};
 use data_model::VolatileSlice;
 use protos::cdisk_spec;
 use remain::sorted;
-use sys_util::{AsRawFds, FileReadWriteAtVolatile, FileSetLen, FileSync, PunchHole, WriteZeroesAt};
+use sys_util::{
+    AsRawFds, FileAllocate, FileReadWriteAtVolatile, FileSetLen, FileSync, PunchHole, WriteZeroesAt,
+};
 
 #[sorted]
 #[derive(Debug)]
@@ -292,6 +294,27 @@ impl PunchHole for CompositeDiskFile {
     }
 }
 
+impl FileAllocate for CompositeDiskFile {
+    fn allocate(&mut self, offset: u64, length: u64) -> io::Result<()> {
+        let range = offset..(offset + length);
+        let disks = self.disks_in_range(&range);
+        for disk in disks {
+            let intersection = range_intersection(&range, &disk.range());
+            if intersection.start >= intersection.end {
+                continue;
+            }
+            let result = disk.file.allocate(
+                intersection.start - disk.offset,
+                intersection.end - intersection.start,
+            );
+            if result.is_err() {
+                return result;
+            }
+        }
+        Ok(())
+    }
+}
+
 impl WriteZeroesAt for CompositeDiskFile {
     fn write_zeroes_at(&mut self, offset: u64, length: usize) -> io::Result<usize> {
         let cursor_location = offset;