[ros-diffs] [reactos] 88/100: [NTOS:MM] Improve MmCanFileBeTruncated

[Jérôme Gardou]

https://git.reactos.org/?p=reactos.git;a=commitdiff;h=91a4e62376d1dbd5d7e155f2a86bb4b468649a24

commit 91a4e62376d1dbd5d7e155f2a86bb4b468649a24
Author:     Jérôme Gardou <jerome.gar...@reactos.org>
AuthorDate: Wed Jan 27 16:28:45 2021 +0100
Commit:     Jérôme Gardou <jerome.gar...@reactos.org>
CommitDate: Wed Feb 3 09:41:23 2021 +0100

    [NTOS:MM] Improve MmCanFileBeTruncated
---
 ntoskrnl/mm/section.c | 42 ++++++++++++------------------------------
 1 file changed, 12 insertions(+), 30 deletions(-)

diff --git a/ntoskrnl/mm/section.c b/ntoskrnl/mm/section.c
index 524b282f606..16767458bce 100644
--- a/ntoskrnl/mm/section.c
+++ b/ntoskrnl/mm/section.c
@@ -4077,54 +4077,36 @@ BOOLEAN NTAPI
 MmCanFileBeTruncated (IN PSECTION_OBJECT_POINTERS SectionObjectPointer,
                       IN PLARGE_INTEGER   NewFileSize)
 {
-    KIRQL OldIrql = MiAcquirePfnLock();
     BOOLEAN Ret;
     PMM_SECTION_SEGMENT Segment;
 
-CheckSectionPointer:
     /* Check whether an ImageSectionObject exists */
     if (SectionObjectPointer->ImageSectionObject != NULL)
     {
         DPRINT1("ERROR: File can't be truncated because it has an image 
section\n");
-        MiReleasePfnLock(OldIrql);
-
         return FALSE;
     }
 
-    Segment = (PMM_SECTION_SEGMENT)SectionObjectPointer->DataSectionObject;
-    /* Wait for it to be created/deleted properly */
-    while (Segment && (Segment->SegFlags & (MM_SEGMENT_INCREATE | 
MM_SEGMENT_INDELETE)))
+    Segment = MiGrabDataSection(SectionObjectPointer);
+    if (!Segment)
     {
-        LARGE_INTEGER ShortTime;
-
-        ShortTime.QuadPart = -10 * 100 * 1000;
-
-        /* Bad luck. Wait a bit for the operation to finish */
-        MiReleasePfnLock(OldIrql);
-        KeDelayExecutionThread(KernelMode, FALSE, &ShortTime);
-        OldIrql = MiAcquirePfnLock();
-        goto CheckSectionPointer;
+        /* There is no data section. It's fine to do anything. */
+        return TRUE;
     }
 
-    if (Segment)
+    MmLockSectionSegment(Segment);
+    if ((Segment->SectionCount == 1) && (SectionObjectPointer->SharedCacheMap 
!= NULL))
     {
-        if ((Segment->SectionCount == 1) && 
(SectionObjectPointer->SharedCacheMap != NULL))
-        {
-            /* If the cache is the only one holding a reference to the 
segment, then it's fine to resize */
-            Ret = TRUE;
-        }
-        else
-        {
-            /* We can't shrink, but we can extend */
-            Ret = NewFileSize->QuadPart >= Segment->RawLength.QuadPart;
-        }
+        /* If the cache is the only one holding a reference to the segment, 
then it's fine to resize */
+        Ret = TRUE;
     }
     else
     {
-        Ret = TRUE;
+        /* We can't shrink, but we can extend */
+        Ret = NewFileSize->QuadPart >= Segment->RawLength.QuadPart;
     }
-
-    MiReleasePfnLock(OldIrql);
+    MmUnlockSectionSegment(Segment);
+    MmDereferenceSegment(Segment);
 
     DPRINT("FIXME: didn't check for outstanding write probes\n");