Messages in this thread | | | Date | Tue, 22 May 2001 00:26:47 +0200 (CEST) | From | Mikulas Patocka <> | Subject | Re: question: permission checking for network filesystem |
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> Agree, but it will improve behavior. Or speed, rather. Otherwise open would > take 3(!) roundtrips (instead of two - now lookup can't be get rid of) - > lookup, permission and open. The protocol can do all three in one request. > The problem is I can't tell the 3 calls from VFS belong together.
You can write lookup so that it always succeeds and returns dummy inode without sending anything and do all the work in open & inode operations.
> > > Could anyone see a solution other than adding a flags to open mode (say > > > O_EXEC and O_EXEC_LIB), that would be added to the dentry_open in open_exec > > > and sys_uselib? I don't like the idea of pathing vfs for this. > > > > Send always 'open for read' and ignore 'open for execute'. > > Won't work for many reasons. Correct error code is one (could be removed by > pre-checking permission),
> exclusivity of write versus execute is the other > (can't be workaround).
MAP_DENYWRITE is used for this. If somebody is mapping file with MAP_DENYWRITE, lock it on server. Write locking does not depend on exec, and it is bad to expect that it may be used only in exec.
Mikulas
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