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Re: MVFS results


Corinna Vinschen <corinna-cygwin <at> cygwin.com> writes:

> > Basically, the NtOpenFile took over execution (I'm guessing that it 
triggered a 
> > fault handler, which interfered with single stepping?).  My next attempt:
> 
> Hmm.
> 
> STATUS_ACCESS_DENIED.  But why?
> 
> 
> Not exactly.  If I had MVFS here, I'd try various changes to the
> arguments to NtOpenFile which make sort of sense.
> 
> For instance, maybe it chokes on the sharing flags.  I'd try with
> FILE_SHARE_VALID_FLAGS instead of just FILE_SHARE_DELETE.
> 
> Btw., it's very helpful to observe what happens exactly using
> sysinternal's procmon.

What would you like to see?  Here's a few procman entries captured immediately 
before the breakpoint, and then for the failing NtOpenFile [*]:

7:39:53.9261746 AM	rm.exe	5912	QueryAttributeInformationVolume
	M:\u_fabt_eblake\FABT_Development\FABT_MPG_Process_BSP_SPCI\foo	SUCCESS
	FileSystemAttributes: Case Preserved, Case Sensitive, 
MaximumComponentNameLength: 255, FileSystemName: MVFS

7:39:53.9262013 AM	rm.exe	5912	QueryAllInformationFile
	G:\views\fabt_eblake.vws\.s\00049\800039b14a4a8b07foo	BUFFER OVERFLOW
	CreationTime: 7/15/2009 3:42:16 PM, LastAccessTime: 7/15/2009 3:42:16 
PM, LastWriteTime: 7/15/2009 3:42:16 PM, ChangeTime: 7/15/2009 3:42:16 PM, 
FileAttributes: RA, AllocationSize: 0, EndOfFile: 0, NumberOfLinks: 1, 
DeletePending: False, Directory: False, IndexNumber: 0x47283402d42464, EaSize: 
0, Access: None, Position: 0, Mode: , AlignmentRequirement: Byte

7:39:53.9275562 AM	rm.exe	5912	QueryAllInformationFile
	G:\views\fabt_eblake.vws\.s\00049\800039b14a4a8b07foo	BUFFER OVERFLOW
	CreationTime: 7/15/2009 3:42:16 PM, LastAccessTime: 7/15/2009 3:42:16 
PM, LastWriteTime: 7/15/2009 3:42:16 PM, ChangeTime: 7/15/2009 3:42:16 PM, 
FileAttributes: RA, AllocationSize: 0, EndOfFile: 0, NumberOfLinks: 1, 
DeletePending: False, Directory: False, IndexNumber: 0x47283402d42464, EaSize: 
0, Access: None, Position: 0, Mode: , AlignmentRequirement: Byte

7:39:53.9292306 AM	rm.exe	5912	QueryObjectIdInformationVolume
	M:\u_fabt_eblake\FABT_Development\FABT_MPG_Process_BSP_SPCI\foo	INVALID 
PARAMETER	

7:39:53.9292609 AM	rm.exe	5912	QueryAllInformationFile
	G:\views\fabt_eblake.vws\.s\00049\800039b14a4a8b07foo	BUFFER OVERFLOW
	CreationTime: 7/15/2009 3:42:16 PM, LastAccessTime: 7/15/2009 3:42:16 
PM, LastWriteTime: 7/15/2009 3:42:16 PM, ChangeTime: 7/15/2009 3:42:16 PM, 
FileAttributes: RA, AllocationSize: 0, EndOfFile: 0, NumberOfLinks: 1, 
DeletePending: False, Directory: False, IndexNumber: 0x47283402d42464, EaSize: 
0, Access: None, Position: 0, Mode: , AlignmentRequirement: Byte

7:39:53.9305921 AM	rm.exe	5912	QueryAllInformationFile
	G:\views\fabt_eblake.vws\.s\00049\800039b14a4a8b07foo	BUFFER OVERFLOW
	CreationTime: 7/15/2009 3:42:16 PM, LastAccessTime: 7/15/2009 3:42:16 
PM, LastWriteTime: 7/15/2009 3:42:16 PM, ChangeTime: 7/15/2009 3:42:16 PM, 
FileAttributes: RA, AllocationSize: 0, EndOfFile: 0, NumberOfLinks: 1, 
DeletePending: False, Directory: False, IndexNumber: 0x47283402d42464, EaSize: 
0, Access: None, Position: 0, Mode: , AlignmentRequirement: Byte

7:39:53.9321605 AM	rm.exe	5912	CloseFile
	M:\u_fabt_eblake\FABT_Development\FABT_MPG_Process_BSP_SPCI\foo	SUCCESS	

7:39:53.9321728 AM	rm.exe	5912	CloseFile
	G:\views\fabt_eblake.vws\.s\00049\800039b14a4a8b07foo	SUCCESS	

7:39:53.9322032 AM	rm.exe	5912	QueryAllInformationFile
	G:\views\fabt_eblake.vws\.s\00049\800039b14a4a8b07foo	BUFFER OVERFLOW
	CreationTime: 7/15/2009 3:42:16 PM, LastAccessTime: 7/15/2009 3:42:16 
PM, LastWriteTime: 7/15/2009 3:42:16 PM, ChangeTime: 7/15/2009 3:42:16 PM, 
FileAttributes: RA, AllocationSize: 0, EndOfFile: 0, NumberOfLinks: 1, 
DeletePending: False, Directory: False, IndexNumber: 0x47283402d42464, EaSize: 
0, Access: None, Position: 0, Mode: , AlignmentRequirement: Byte

7:40:37.3023584 AM	rm.exe	5912	CreateFile
	M:\u_fabt_eblake\FABT_Development\FABT_MPG_Process_BSP_SPCI\foo	ACCESS 
DENIED	Desired Access: Generic Write, Delete, Disposition: Open, Options: Open 
For Backup, Attributes: n/a, ShareMode: Delete, AllocationSize: n/a

7:40:37.3030100 AM	rm.exe	5912	RegCloseKey	<INVALID NAME>	INVALID 
HANDLE	

7:40:37.3031448 AM	rm.exe	5912	Thread Exit		SUCCESS	Thread 
ID: 276, User Time: 0.0000000, Kernel Time: 0.0000000


MVFS appears to be more of a forwarding file system - requests into MVFS (m:\, 
in my case) are interpreted by the driver and redirected to the backing store 
file system of the view directory.  In my case, foo is unversioned, so it is 
backed by my separate view directory (g:\views\fabt_eblake.vws).

$ df -T /cygdrive/[gm]
Filesystem    Type   1K-blocks      Used Available Use% Mounted on
G:           smbfs       20480     20480         0 100% /cygdrive/g
M:         unknown     1024000    512000    512000  50% /cygdrive/m

At any rate, it looks like all access to g:\ are due to the MVFS file system 
driver, and I'm hoping that the BUFFER OVERFLOW on QueryAllInformationFile is a 
benign effect within that driver (it certainly does not appear to be due to 
cygwin1.dll).

Next, I'll have to play with your advice to play with the various ShareMode 
flags.

[*] This was my first time using procmon - cool tool!

-- 
Eric Blake




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