fix: amplify io is too large to hold in fuse buffer (#1311)

backport the logic of master commit c8a39c8

* fix: amplify io is too large to hold in fuse buffer

Fuse request buffer is fixed by `FUSE_KERN_BUF_SIZE * pagesize() + FUSE_HEADER_ SIZE`. When amplify io is larger than it, FuseDevWriter suffers from smaller buffer. As a result, invalid data error is returned.

Reproduction:
    run nydusd with 3MB amplify_io
    error from random io:
        reply error header OutHeader { len: 16, error: -5, unique: 108 }, error Custom { kind: InvalidData, error: "data out of range, available 1052656 requested 1250066" }

Details:
    size of fuse buffer = 1052656 + 16 (size of inner header) = 256(page number) * 4096(page size) + 4096(fuse header)
    let amplify_io = min(user_specified, fuseWriter.available_bytes())

Resolution:
    This pr is not best implements, but independent of modification to [fuse-backend-rs]("https://github.com/cloud-hypervisor/fuse-backend-rs").
    In future, evalucation of amplify_io will be replaced with [ZeroCopyWriter.available_bytes()]("cloud-hypervisor/fuse-backend-rs#135").

Signed-off-by: 泰友 <[email protected]>

* feat: e2e for amplify io larger than fuse buffer

Signed-off-by: 泰友 <[email protected]>

---------

Signed-off-by: 泰友 <[email protected]>
Co-authored-by: 泰友 <[email protected]>
Signed-off-by: Peng Tao <[email protected]>

rafs/src/fs.rs

@@ -54,6 +54,10 @@ pub type Handle = u64;
 pub const RAFS_DEFAULT_ATTR_TIMEOUT: u64 = 1 << 32;
 /// Rafs default entry timeout value.
 pub const RAFS_DEFAULT_ENTRY_TIMEOUT: u64 = RAFS_DEFAULT_ATTR_TIMEOUT;
+/// FUSE_KERN_BUF_SIZE * pagesize() + FUSE_HEADER_ SIZE
+/// Use a const as stable v2.1 does not complie with latset fuse-backend-rs that
+/// exports a writer's available buffer size.
+pub const RAFS_MAX_AMPLIFIED_IO: usize = 1052656;
 
 fn default_threads_count() -> usize {
     8
@@ -765,18 +769,19 @@ impl FileSystem for Rafs {
         debug_assert!(!descs.is_empty() && !descs[0].bi_vec.is_empty());
 
         // Try to amplify user io for Rafs v5, to improve performance.
-        if self.sb.meta.is_v5() && size < self.amplify_io {
+        let amplify_io = cmp::min(self.amplify_io as usize, RAFS_MAX_AMPLIFIED_IO) as u32;
+        if self.sb.meta.is_v5() && size < amplify_io {
             let all_chunks_ready = self.device.all_chunks_ready(&descs);
             if !all_chunks_ready {
-                let chunk_size = self.metadata().chunk_size as u64;
-                let next_chunk_base = (offset + (size as u64) + chunk_size) & !chunk_size;
-                let window_base = std::cmp::min(next_chunk_base, inode_size);
-                let actual_size = window_base - (offset & !chunk_size);
-                if actual_size < self.amplify_io as u64 {
-                    let window_size = self.amplify_io as u64 - actual_size;
+                let chunk_mask = self.metadata().chunk_size as u64 - 1;
+                let next_chunk_base = (offset + (size as u64) + chunk_mask) & !chunk_mask;
+                let window_base = cmp::min(next_chunk_base, inode_size);
+                let actual_size = window_base - (offset & !chunk_mask);
+                if actual_size < amplify_io as u64 {
+                    let window_size = amplify_io as u64 - actual_size;
                     self.sb.amplify_io(
                         &self.device,
-                        self.amplify_io,
+                        amplify_io,
                         &mut descs,
                         &inode,
                         window_base,