22//!
33//! This provides a very crude, read-only in-mem virtual file system for the WASM guests.
44//!
5- //! The data gets [ populated via a TAR container](VfsState::populate_from_tar) .
5+ //! The data gets populated via a TAR container.
66//!
77//! While this implementation has rather limited functionality, it is sufficient to get a Python guest interpreter
88//! running.
@@ -11,7 +11,10 @@ use std::{
1111 collections:: HashMap ,
1212 hash:: Hash ,
1313 io:: { Cursor , Read } ,
14- sync:: { Arc , RwLock , Weak } ,
14+ sync:: {
15+ Arc , RwLock , Weak ,
16+ atomic:: { AtomicU64 , Ordering } ,
17+ } ,
1518} ;
1619
1720use rand:: Rng ;
@@ -58,7 +61,7 @@ enum VfsNodeKind {
5861 /// A directory containing child nodes.
5962Directory {
6063 /// Child nodes indexed by name.
61- children : HashMap < String , SharedVfsNode > ,
64+ children : HashMap < Box < str > , SharedVfsNode > ,
6265 } ,
6366}
6467
@@ -188,6 +191,125 @@ impl VfsNode {
188191 }
189192}
190193
194+ /// Tracked allocation of some resource.
195+ #[ derive( Debug ) ]
196+ struct Allocation {
197+ /// Current amount of allocation.
198+ n : AtomicU64 ,
199+
200+ /// Name of the resource.
201+ name : & ' static str ,
202+
203+ /// Allocation limit.
204+ limit : u64 ,
205+ }
206+
207+ impl Allocation {
208+ /// Create new allocation tracker for given resource.
209+ fn new ( name : & ' static str , limit : u64 ) -> Self {
210+ Self {
211+ n : AtomicU64 :: new ( 0 ) ,
212+ name,
213+ limit,
214+ }
215+ }
216+
217+ /// Increase allocation by given amount.
218+ fn inc ( & self , n : u64 ) -> Result < ( ) , FailedAllocation > {
219+ self . n
220+ . fetch_update ( Ordering :: SeqCst , Ordering :: SeqCst , |old| {
221+ let new = old. checked_add ( n) ?;
222+ ( new <= self . limit ) . then_some ( new)
223+ } )
224+ . map ( |_| ( ) )
225+ . map_err ( |current| FailedAllocation {
226+ name : self . name ,
227+ limit : self . limit ,
228+ current,
229+ requested : n,
230+ } )
231+ }
232+ }
233+
234+ /// Failed allocation error.
235+ #[ derive( Debug ) ]
236+ struct FailedAllocation {
237+ /// Name of the allocation type/resource.
238+ name : & ' static str ,
239+
240+ /// Allocation limit.
241+ limit : u64 ,
242+
243+ /// Current allocation size.
244+ current : u64 ,
245+
246+ /// Requested/additional allocation.
247+ requested : u64 ,
248+ }
249+
250+ impl std:: fmt:: Display for FailedAllocation {
251+ fn fmt ( & self , f : & mut std:: fmt:: Formatter < ' _ > ) -> std:: fmt:: Result {
252+ let Self {
253+ name,
254+ limit,
255+ current,
256+ requested,
257+ } = self ;
258+
259+ write ! (
260+ f,
261+ "{name} limit reached: limit<={limit} current=={current} requested+={requested}"
262+ )
263+ }
264+ }
265+
266+ impl From < FailedAllocation > for std:: io:: Error {
267+ fn from ( e : FailedAllocation ) -> Self {
268+ Self :: new ( std:: io:: ErrorKind :: QuotaExceeded , e. to_string ( ) )
269+ }
270+ }
271+
272+ /// Limits for virtual filesystems.
273+ #[ derive( Debug , Clone ) ]
274+ #[ expect( missing_copy_implementations, reason = "allow later extensions" ) ]
275+ pub struct VfsLimits {
276+ /// Maximum number of inodes.
277+ pub inodes : u64 ,
278+
279+ /// Maximum number of bytes in size.
280+ pub bytes : u64 ,
281+ }
282+
283+ impl Default for VfsLimits {
284+ fn default ( ) -> Self {
285+ Self {
286+ inodes : 10_000 ,
287+ // 100MB
288+ bytes : 100 * 1024 * 1024 ,
289+ }
290+ }
291+ }
292+
293+ /// Current virtual filesystem allocation.
294+ #[ derive( Debug ) ]
295+ struct VfsAllocation {
296+ /// Number of inodes.
297+ inodes : Allocation ,
298+
299+ /// Number of bytes.
300+ bytes : Allocation ,
301+ }
302+
303+ impl VfsAllocation {
304+ /// Create new empty allocation tracker.
305+ fn new ( limits : & VfsLimits ) -> Self {
306+ Self {
307+ inodes : Allocation :: new ( "inodes" , limits. inodes ) ,
308+ bytes : Allocation :: new ( "bytes" , limits. bytes ) ,
309+ }
310+ }
311+ }
312+
191313/// State for the virtual filesystem.
192314#[ derive( Debug ) ]
193315pub ( crate ) struct VfsState {
@@ -196,11 +318,14 @@ pub(crate) struct VfsState {
196318
197319 /// Hash key for metadata hashes.
198320metadata_hash_key : [ u8 ; 16 ] ,
321+
322+ /// Current allocation.
323+ allocation : VfsAllocation ,
199324}
200325
201326impl VfsState {
202327 /// Create a new empty VFS.
203- pub ( crate ) fn new ( ) -> Self {
328+ pub ( crate ) fn new ( limits : & VfsLimits ) -> Self {
204329 Self {
205330 root : Arc :: new ( RwLock :: new ( VfsNode {
206331 kind : VfsNodeKind :: Directory {
@@ -209,6 +334,7 @@ impl VfsState {
209334 parent : None ,
210335 } ) ) ,
211336 metadata_hash_key : rand:: rng ( ) . random ( ) ,
337+ allocation : VfsAllocation :: new ( limits) ,
212338 }
213339 }
214340
@@ -228,6 +354,8 @@ impl VfsState {
228354 tar:: EntryType :: Regular => {
229355 let mut content = Vec :: new ( ) ;
230356 entry. read_to_end ( & mut content) ?;
357+ content. shrink_to_fit ( ) ;
358+ self . allocation . bytes . inc ( content. capacity ( ) as u64 ) ?;
231359 VfsNodeKind :: File { content }
232360 }
233361 other => {
@@ -252,6 +380,17 @@ impl VfsState {
252380 VfsNode :: resolve_path ( Arc :: clone ( & self . root ) , Arc :: clone ( & self . root ) , path_str)
253381 . map_err ( |e| std:: io:: Error :: new ( std:: io:: ErrorKind :: InvalidData , e) ) ?;
254382
383+ let child = Arc :: new ( RwLock :: new ( VfsNode {
384+ kind,
385+ parent : Some ( Arc :: downgrade ( & node) ) ,
386+ } ) ) ;
387+
388+ self . allocation . inodes . inc ( 1 ) ?;
389+ self . allocation . bytes . inc ( name. len ( ) as u64 ) ?;
390+ self . allocation
391+ . bytes
392+ . inc ( std:: mem:: size_of_val ( & child) as u64 ) ?;
393+
255394 match & mut node. write ( ) . unwrap ( ) . kind {
256395 VfsNodeKind :: File { .. } => {
257396 return Err ( std:: io:: Error :: new (
@@ -260,13 +399,7 @@ impl VfsState {
260399 ) ) ;
261400 }
262401 VfsNodeKind :: Directory { children } => {
263- children. insert (
264- name. to_owned ( ) ,
265- Arc :: new ( RwLock :: new ( VfsNode {
266- kind,
267- parent : Some ( Arc :: downgrade ( & node) ) ,
268- } ) ) ,
269- ) ;
402+ children. insert ( name. into ( ) , child) ;
270403 }
271404 }
272405 }
@@ -461,7 +594,7 @@ impl<'a> filesystem::types::HostDescriptor for VfsCtxView<'a> {
461594 } ;
462595
463596 DirectoryEntry {
464- name : name. clone ( ) ,
597+ name : name. as_ref ( ) . to_owned ( ) ,
465598 type_,
466599 }
467600 } )
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