dll,fuse: allow dir buffer entry invalidation

The FUSE implementation of ReadDirectory issues readdir followed
by a slew of getattr. In the current implementation if a getattr fails
the whole readdir operation fails.

This commit adds the ability to invalidate individual entries in the
directory buffer. Entries for which getattr fails are now marked invalid
rather than fail the overall ReadDirectory operation.

See #292

src/dll/dirbuf.c

@@ -335,6 +335,18 @@ FSP_API VOID FspFileSystemReleaseDirectoryBuffer(PVOID *PDirBuffer)
 
     FSP_FILE_SYSTEM_DIRECTORY_BUFFER *DirBuffer = *PDirBuffer;
 
+    /* eliminate invalidated entries from the index */
+    PULONG Index = (PULONG)(DirBuffer->Buffer + DirBuffer->HiMark);
+    ULONG Count = (DirBuffer->Capacity - DirBuffer->HiMark) / sizeof(ULONG);
+    ULONG I, J;
+    for (I = Count - 1, J = Count; I < Count; I--)
+    {
+        if (FspFileSystemDirectoryBufferEntryInvalid == Index[I])
+            continue;
+        Index[--J] = Index[I];
+    }
+    DirBuffer->HiMark = (ULONG)((PUINT8)&Index[J] - DirBuffer->Buffer);
+
     FspFileSystemSortDirectoryBuffer(DirBuffer);
 
     ReleaseSRWLockExclusive(&DirBuffer->Lock);

src/dll/fuse/fuse_intf.c

@@ -1866,7 +1866,8 @@ static NTSTATUS fsp_fuse_intf_FixDirInfo(FSP_FILE_SYSTEM *FileSystem,
             Result = fsp_fuse_intf_GetFileInfoEx(FileSystem, PosixPath, 0,
                 &Uid, &Gid, &Mode, &DirInfo->FileInfo);
             if (!NT_SUCCESS(Result))
-                goto exit;
+                /* mark the directory buffer entry as invalid */
+                *Index = FspFileSystemDirectoryBufferEntryInvalid;
 
             if (0 != PosixPathEnd)
                 *PosixPathEnd = SavedPathChar;

src/dll/library.h

@@ -66,6 +66,7 @@ PSID FspWksidGet(WELL_KNOWN_SID_TYPE WellKnownSidType);
 
 PWSTR FspDiagIdent(VOID);
 
+#define FspFileSystemDirectoryBufferEntryInvalid ((ULONG)-1)
 VOID FspFileSystemPeekInDirectoryBuffer(PVOID *PDirBuffer,
     PUINT8 *PBuffer, PULONG *PIndex, PULONG PCount);
 

tst/winfsp-tests/dirbuf-test.c

@@ -145,7 +145,7 @@ static void dirbuf_dots_test(void)
     FspFileSystemDeleteDirectoryBuffer(&DirBuffer);
 }
 
-static void dirbuf_fill_dotest(unsigned seed, ULONG Count)
+static void dirbuf_fill_dotest(unsigned seed, ULONG Count, ULONG InvalidCount)
 {
     PVOID DirBuffer = 0;
     NTSTATUS Result;
@@ -202,6 +202,51 @@ static void dirbuf_fill_dotest(unsigned seed, ULONG Count)
         ASSERT(STATUS_SUCCESS == Result);
     }
 
+#if 1
+    {
+        ASSERT(Count > InvalidCount);
+
+#if !defined(FspFileSystemDirectoryBufferEntryInvalid)
+        const ULONG FspFileSystemDirectoryBufferEntryInvalid = ((ULONG)-1);
+#endif
+        typedef struct
+        {
+            SRWLOCK Lock;
+            ULONG Capacity, LoMark, HiMark;
+            PUINT8 Buffer;
+        } FSP_FILE_SYSTEM_DIRECTORY_BUFFER;
+        FSP_FILE_SYSTEM_DIRECTORY_BUFFER *PeekDirBuffer = DirBuffer;
+        PUINT8 PeekBuffer = PeekDirBuffer->Buffer;
+        PULONG PeekIndex = (PULONG)(PeekDirBuffer->Buffer + PeekDirBuffer->HiMark);
+        ULONG PeekCount = (PeekDirBuffer->Capacity - PeekDirBuffer->HiMark) / sizeof(ULONG);
+
+        ASSERT(Count == PeekCount);
+
+        for (ULONG I = 0; InvalidCount > I; I++)
+        {
+            for (;;)
+            {
+                N = rand() % PeekCount;
+                if (FspFileSystemDirectoryBufferEntryInvalid == PeekIndex[N])
+                    continue;
+
+                DirInfo = (PVOID)(PeekBuffer + PeekIndex[N]);
+                memcpy(CurrFileName, DirInfo->FileNameBuf, DirInfo->Size - sizeof *DirInfo);
+                CurrFileName[(DirInfo->Size - sizeof *DirInfo) / sizeof(WCHAR)] = L'\0';
+
+                /* do not invalidate dot entries as they are used in testing below */
+                if (0 == wcscmp(CurrFileName, L".") || 0 == wcscmp(CurrFileName, L".."))
+                    continue;
+
+                PeekIndex[N] = FspFileSystemDirectoryBufferEntryInvalid;
+                break;
+            }
+        }
+
+        Count -= InvalidCount;
+    }
+#endif
+
     FspFileSystemReleaseDirectoryBuffer(&DirBuffer);
 
     MarkerIndex = rand() % Count;
@@ -303,19 +348,32 @@ static void dirbuf_fill_test(void)
 {
     unsigned seed = (unsigned)time(0);
 
-    dirbuf_fill_dotest(1485473509, 10);
+    dirbuf_fill_dotest(1485473509, 10, 0);
+    dirbuf_fill_dotest(1485473509, 10, 3);
 
     for (ULONG I = 0; 10000 > I; I++)
-        dirbuf_fill_dotest(seed + I, 10);
+    {
+        dirbuf_fill_dotest(seed + I, 10, 0);
+        dirbuf_fill_dotest(seed + I, 10, 3);
+    }
 
     for (ULONG I = 0; 1000 > I; I++)
-        dirbuf_fill_dotest(seed + I, 100);
+    {
+        dirbuf_fill_dotest(seed + I, 100, 0);
+        dirbuf_fill_dotest(seed + I, 100, 30);
+    }
 
     for (ULONG I = 0; 100 > I; I++)
-        dirbuf_fill_dotest(seed + I, 1000);
+    {
+        dirbuf_fill_dotest(seed + I, 1000, 0);
+        dirbuf_fill_dotest(seed + I, 1000, 300);
+    }
 
     for (ULONG I = 0; 10 > I; I++)
-        dirbuf_fill_dotest(seed + I, 10000);
+    {
+        dirbuf_fill_dotest(seed + I, 10000, 0);
+        dirbuf_fill_dotest(seed + I, 10000, 3000);
+    }
 }
 
 void dirbuf_tests(void)