Windows System Software -- Consulting, Training, Development -- Unique Expertise, Guaranteed Results
The free OSR Learning Library has more than 50 articles on a wide variety of topics about writing and debugging device drivers and Minifilters. From introductory level to advanced. All the articles have been recently reviewed and updated, and are written using the clear and definitive style you've come to expect from OSR over the years.
Check out The OSR Learning Library at: https://www.osr.com/osr-learning-library/
Hi,
Can someone shed light on how range tracking is done in NTFS UsnJournal? Is the information about modified ranges (the extents with offset and length) stored in some data structure, perhaps MFT?
The purpose of asking this question is to know if wrap around of UsnJournal can cause range tracking to get affected. For example, lets consider a file F1 whose size is above 1 MB and hence Is eligible for range tracking. Below are the operations on the file F1:
Open (creates a record in UsnJournal)
Write W1 (creates a record in UsnJournal)
Write W2 (does not create a record in UsnJournal as this operation is same as previous operation)
Write W3 (does not create a record in UsnJournal as this operation is same as previous operation)
...
Write Wn (does not create a record in UsnJournal as this operation is same as previous operation)
Close (creates a record in UsnJournal)
(Above example is based on UsnJournal documentation https://docs.microsoft.com/en-us/windows/win32/fileio/change-journal-records)
If the UsnJournal wraps around between lets say when write W3 happens and before Close of the file F1 is done, do we still get correct Extents as part of record written during Close operation? In other words, does journal wrap affect range tracking?
Also, can someone clarify if below is the right way detecting a wrap (T2 comes after T2)
At Time T1: fsutil usn queryJournal C: >> gives NextUsn = n1
At Time T2: fsutil usn queryJournal C: >> gives FirstUsn = f2
If f1 > n1, is it implied that between T1 and T2, the change journal wrapped over?
Thank you!
Upcoming OSR Seminars | ||
---|---|---|
OSR has suspended in-person seminars due to the Covid-19 outbreak. But, don't miss your training! Attend via the internet instead! | ||
Writing WDF Drivers | 12 September 2022 | Live, Online |
Internals & Software Drivers | 23 October 2022 | Live, Online |
Kernel Debugging | 14 November 2022 | Live, Online |
Developing Minifilters | 5 December 2022 | Live, Online |