Re: SMB2 DELETE vs UNLINK

[Ralph Boehme <slow@samba.org>]

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On 10/6/24 12:31 PM, Pali Rohár wrote:
> But starting with Windows 10, version 1709, there is support also
> for UNLINK operation, via class 64 (FileDispositionInformationEx)
> [1] where is FILE_DISPOSITION_POSIX_SEMANTICS flag [2] which does
> UNLINK after CLOSE and let file content usable for all other
> processes. Internally Windows NT kernel moves this file on NTFS from
> its directory into some hidden are. Which is de-facto same as what
> is POSIX unlink. There is also class 65 (FileRenameInformationEx)
> which is allows to issue POSIX rename (unlink the target if it
> exists).

interesting. Thanks for pointing these out!

> What do you think about using & implementing this functionality for
> the Linux unlink operation? As the class numbers are already
> reserved and documented, I think that it could make sense to use
> them also over SMB on POSIX systems.

for SMB3 POSIX this will be the behaviour on POSIX handles so we don't
need an on the wire change. This is part of what will become POSIX-FSA.

> Also there is another flag
> FILE_DISPOSITION_IGNORE_READONLY_ATTRIBUTE which can be useful for
> unlink. It allows to unlink also file which has read-only attribute
> set. So no need to do that racy (unset-readonly, set-delete-pending,
> set-read-only) compound on files with more file hardlinks.
> 
> I think that this is something which SMB3 POSIX extensions can use
> and do not have to invent new extensions for the same functionality.

same here (taking note to remember to add this to the POSIX-FSA and
check Samba behaviour).

-slow

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