Add deleted flag in the header of chunk map file

Signed-off-by: Qi Wang <[email protected]>

storage/src/cache/state/blob_state_map.rs

@@ -164,6 +164,10 @@ where
         any.downcast_ref::<BlobStateMap<IndexedChunkMap, u32>>()
             .map(|v| v as &dyn RangeMap<I = u32>)
     }
+
+    fn is_deleted(&self) -> bool {
+        self.c.is_deleted()
+    }
 }
 
 impl RangeMap for BlobStateMap<IndexedChunkMap, u32> {

storage/src/cache/state/indexed_chunk_map.rs

@@ -30,22 +30,30 @@ const FILE_SUFFIX: &str = "chunk_map";
 /// set_ready(3), the layout should be changed to [0b00010000, 0b00000000].
 pub struct IndexedChunkMap {
     map: PersistMap,
+    filename: String,
 }
 
 impl IndexedChunkMap {
     /// Create a new instance of `IndexedChunkMap`.
     pub fn new(blob_path: &str, chunk_count: u32, persist: bool) -> Result<Self> {
         let filename = format!("{}.{}", blob_path, FILE_SUFFIX);
 
-        PersistMap::open(&filename, chunk_count, true, persist).map(|map| IndexedChunkMap { map })
+        PersistMap::open(&filename, chunk_count, true, persist)
+            .map(|map| IndexedChunkMap { map, filename })
     }
 
     /// Create a new instance of `IndexedChunkMap` from an existing chunk map file.
     pub fn open(blob_info: &BlobInfo, workdir: &str) -> Result<Self> {
         let filename = format!("{}/{}.{}", workdir, blob_info.blob_id(), FILE_SUFFIX);
 
         PersistMap::open(&filename, blob_info.chunk_count(), false, true)
-            .map(|map| IndexedChunkMap { map })
+            .map(|map| IndexedChunkMap { map, filename })
+    }
+
+    pub fn remove(self) -> Result<()> {
+        self.map.mark_deleted();
+        std::fs::remove_file(self.filename)?;
+        Ok(())
     }
 }
 
@@ -70,6 +78,10 @@ impl ChunkMap for IndexedChunkMap {
     fn as_range_map(&self) -> Option<&dyn RangeMap<I = u32>> {
         Some(self)
     }
+
+    fn is_deleted(&self) -> bool {
+        self.map.is_file_deleted()
+    }
 }
 
 impl RangeMap for IndexedChunkMap {
@@ -279,6 +291,7 @@ mod tests {
             version: 1,
             magic2: MAGIC2,
             all_ready: MAGIC_ALL_READY,
+            deleted: 0,
             reserved: [0x0u8; HEADER_RESERVED_SIZE],
         };
 
@@ -324,6 +337,7 @@ mod tests {
             version: 0,
             magic2: 0,
             all_ready: 0,
+            deleted: 0,
             reserved: [0x0u8; HEADER_RESERVED_SIZE],
         };
 

storage/src/cache/state/mod.rs

@@ -86,6 +86,11 @@ pub trait ChunkMap: Any + Send + Sync {
     fn as_range_map(&self) -> Option<&dyn RangeMap<I = u32>> {
         None
     }
+
+    /// Check whether the on-disk file is deleted.
+    fn is_deleted(&self) -> bool {
+        false
+    }
 }
 
 /// Trait to track chunk or data readiness state.

storage/src/cache/state/persist_map.rs

@@ -3,6 +3,7 @@
 //
 // SPDX-License-Identifier: Apache-2.0
 
+use std::cell::Cell;
 use std::ffi::c_void;
 use std::fs::{File, OpenOptions};
 use std::io::{Result, Write};
@@ -16,8 +17,9 @@ use crate::utils::readahead;
 pub(crate) const MAGIC1: u32 = 0x424D_4150;
 pub(crate) const MAGIC2: u32 = 0x434D_4150;
 pub(crate) const MAGIC_ALL_READY: u32 = 0x4D4D_4150;
+pub(crate) const MAGIC_DELETED: u32 = 0x4E4D_4150;
 pub(crate) const HEADER_SIZE: usize = 4096;
-pub(crate) const HEADER_RESERVED_SIZE: usize = HEADER_SIZE - 16;
+pub(crate) const HEADER_RESERVED_SIZE: usize = HEADER_SIZE - 20;
 
 /// The blob chunk map file header, 4096 bytes.
 #[repr(C)]
@@ -27,6 +29,7 @@ pub(crate) struct Header {
     pub version: u32,
     pub magic2: u32,
     pub all_ready: u32,
+    pub deleted: u32,
     pub reserved: [u8; HEADER_RESERVED_SIZE],
 }
 
@@ -46,6 +49,7 @@ pub(crate) struct PersistMap {
     pub size: usize,
     pub base: *const u8,
     pub not_ready_count: AtomicU32,
+    pub is_deleted: Cell<bool>,
 }
 
 impl PersistMap {
@@ -167,6 +171,7 @@ impl PersistMap {
             size: expected_size as usize,
             base: base as *const u8,
             not_ready_count: AtomicU32::new(not_ready_count),
+            is_deleted: Cell::new(false),
         })
     }
 
@@ -176,6 +181,7 @@ impl PersistMap {
             version: 1,
             magic2: MAGIC2,
             all_ready: 0,
+            deleted: 0,
             reserved: [0x0u8; HEADER_RESERVED_SIZE],
         };
 
@@ -268,6 +274,38 @@ impl PersistMap {
         }
     }
 
+    pub fn is_file_deleted(&self) -> bool {
+        if self.is_deleted.get() {
+            return true;
+        }
+        let base = self.base as *const c_void as *mut c_void;
+        unsafe {
+            if libc::msync(base, self.size, libc::MS_SYNC) == 0 {
+                let header = &mut *(self.base as *mut Header);
+                if header.deleted == MAGIC_DELETED {
+                    self.is_deleted.set(true);
+                    return true;
+                }
+            }
+        }
+        false
+    }
+
+    pub fn mark_deleted(&self) {
+        if self.is_file_deleted() {
+            return;
+        }
+        let base = self.base as *const c_void as *mut c_void;
+        unsafe {
+            if libc::msync(base, self.size, libc::MS_SYNC) == 0 {
+                let header = &mut *(self.base as *mut Header);
+                header.deleted = MAGIC_DELETED;
+                self.is_deleted.set(true);
+                let _ = libc::msync(base, HEADER_SIZE, libc::MS_SYNC);
+            }
+        }
+    }
+
     #[inline]
     pub fn is_range_all_ready(&self) -> bool {
         self.not_ready_count.load(Ordering::Acquire) == 0