Add synchronization for closing blobs to keep them in stable state in…

… case of future disk faults (#85)

* Add sync of blob on closing and either add sync for indices during transition to another state

* Fix 'Bad descriptor' issue

src/blob/core.rs

@@ -71,6 +71,7 @@ impl Blob {
     }
 
     pub(crate) async fn dump(&mut self) -> Result<usize> {
+        self.file.fsyncdata().await?;
         self.index
             .dump()
             .await

src/blob/file.rs

@@ -1,4 +1,4 @@
-use std::{io::Write, os::unix::prelude::FileExt};
+use std::os::unix::prelude::FileExt;
 
 use super::prelude::*;
 
@@ -166,11 +166,10 @@ impl File {
 
     pub(crate) async fn fsyncdata(&self) -> IOResult<()> {
         if let Some(ref ioring) = self.ioring {
-            let compl = ioring.fdatasync(&*self.no_lock_fd);
+            let compl = ioring.fsync(&*self.no_lock_fd);
             compl.await
         } else {
-            let file = self.no_lock_fd.clone();
-            Self::blocking_call(move || file.as_ref().flush()).await
+            self.write_fd.read().await.sync_all().await
         }
     }
 

src/blob/index/simple.rs

@@ -209,6 +209,7 @@ impl Simple {
             .with_context(|| format!("file open failed {:?}", self.name.to_path()))?;
         let size = file.write_append(&buf).await?;
         self.apply_written_byte(&file).await?;
+        file.fsyncdata().await?;
         self.inner = State::OnDisk(file);
         self.mem = None;
         Ok(size)

src/storage/core.rs

@@ -727,14 +727,9 @@ impl Safe {
         Ok(Box::pin(async move {
             let mut blobs = blobs.write().await;
             blobs.push(*old_active);
-            // FIXME: seems, like in case of disk error indices won't dump on disk and we won't
-            // know about it (the state will be okay, they will be InMemory, but there won't be any
-            // further task to dump them)
-            // Possible solution: in case of disk issues during the next write in new active blob
-            // we will receive error AND after solving it in some time we can start another job
-            // (seems like we should add one more method to public API for that)
-            // which will start dump tasks for all blobs from old_blobs array (or for the last one;
-            // seems that it's either okay; in case of OnDisk state dump works very fast)
+            // Notice: if dump of blob or indices fails, it's likely a problem with disk appeared, so
+            // all descriptors of the storage become invalid and unusable
+            // Possible solution: recreate instance of storage, when disk will be available
             if let Err(e) = blobs.last_mut().unwrap().dump().await {
                 error!("Error dumping blob: {}", e);
             }