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Re: [PATCH v15 00/22] Richacls (Core and Ext4)

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On Tue, Nov 10, 2015 at 06:58:19PM +0100, Andreas Gruenbacher wrote:
> On Tue, Nov 10, 2015 at 6:07 PM, J. Bruce Fields <bfields@fieldses.org> wrote:
> > On Tue, Nov 10, 2015 at 10:43:46AM -0600, Steve French wrote:
> >> I don't have strong disagreement with using pseudo-xattrs to
> >> store/retrieve ACLs (we already do this) but retrieving/setting an ACL
> >> all at once can be awkward  when ACLs are quite large e.g. when it
> >> encodes to over 1MB
> >
> > At least in the NFS case, that's also a limitation of the protocol.
> 
> I couldn't find a limit in the NFSv4 specification, but the client and
> server implementations both define arbitrary ACL size limits. In
> addition, the xattr syscalls allow attributes to be up to 64k long.

I don't recall 4.0 specifying any limit, 4.1 does include negotiation of
maximum rpc calls and replies, and that effectively limits ACL sizes
since they have to fit in a single rpc.

> The bigger problem would be incrementally setting ACLs. To prevent
> processes from racing with each other, we would need a locking
> mechanism. In addition, the memory overhead would be prohibitive and
> access decisions would become extremely slow; we would have to come up
> with mechanisms to avoid those problems.

Right.  Anyway, not worth the trouble, I think.

(Though what might be worth thinking about at some point is just making
sure we fail in helpful ways.)

--b.
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[PATCH v15 00/22] Richacls (Core and Ext4) Andreas Gruenbacher <agruenba@redhat.com> - 2015-11-09 12:10 +0100
  [PATCH v15 02/22] vfs: Add MAY_CREATE_FILE and MAY_CREATE_DIR permission flags Andreas Gruenbacher <agruenba@redhat.com> - 2015-11-09 12:10 +0100
  [PATCH v15 21/22] ext4: Add richacl support Andreas Gruenbacher <agruenba@redhat.com> - 2015-11-09 12:20 +0100
  [PATCH v15 06/22] richacl: In-memory representation and helper functions Andreas Gruenbacher <agruenba@redhat.com> - 2015-11-09 12:20 +0100
  [PATCH v15 20/22] vfs: Add richacl permission checking Andreas Gruenbacher <agruenba@redhat.com> - 2015-11-09 12:20 +0100
  [PATCH v15 09/22] richacl: Permission check algorithm Andreas Gruenbacher <agruenba@redhat.com> - 2015-11-09 12:20 +0100
  [PATCH v15 14/22] richacl: Update the file masks in chmod() Andreas Gruenbacher <agruenba@redhat.com> - 2015-11-09 12:20 +0100
  [PATCH v15 19/22] richacl: Add richacl xattr handler Andreas Gruenbacher <agruenba@redhat.com> - 2015-11-09 12:20 +0100
    Re: [PATCH v15 19/22] richacl: Add richacl xattr handler Andreas Gruenbacher <agruenba@redhat.com> - 2015-11-11 02:20 +0100
  [PATCH v15 18/22] richacl: xattr mapping functions Andreas Gruenbacher <agruenba@redhat.com> - 2015-11-09 12:20 +0100
  [PATCH v15 22/22] ext4: Add richacl feature flag Andreas Gruenbacher <agruenba@redhat.com> - 2015-11-09 12:20 +0100
  [PATCH v15 08/22] richacl: Compute maximum file masks from an acl Andreas Gruenbacher <agruenba@redhat.com> - 2015-11-09 12:20 +0100
  [PATCH v15 13/22] vfs: Cache richacl in struct inode Andreas Gruenbacher <agruenba@redhat.com> - 2015-11-09 12:20 +0100
  [PATCH v15 17/22] richacl: Automatic Inheritance Andreas Gruenbacher <agruenba@redhat.com> - 2015-11-09 12:20 +0100
  [PATCH v15 12/22] vfs: Add get_richacl and set_richacl inode operations Andreas Gruenbacher <agruenba@redhat.com> - 2015-11-09 12:20 +0100
  [PATCH v15 15/22] richacl: Check if an acl is equivalent to a file mode Andreas Gruenbacher <agruenba@redhat.com> - 2015-11-09 12:20 +0100
  [PATCH v15 16/22] richacl: Create-time inheritance Andreas Gruenbacher <agruenba@redhat.com> - 2015-11-09 12:20 +0100
  [PATCH v15 10/22] posix_acl: Unexport acl_by_type and make it static Andreas Gruenbacher <agruenba@redhat.com> - 2015-11-09 12:20 +0100
  [PATCH v15 11/22] vfs: Cache base_acl objects in inodes Andreas Gruenbacher <agruenba@redhat.com> - 2015-11-09 12:30 +0100
  [PATCH v15 07/22] richacl: Permission mapping functions Andreas Gruenbacher <agruenba@redhat.com> - 2015-11-09 12:30 +0100
  [PATCH v15 01/22] vfs: Add IS_ACL() and IS_RICHACL() tests Andreas Gruenbacher <agruenba@redhat.com> - 2015-11-09 12:30 +0100
  Re: [PATCH v15 00/22] Richacls (Core and Ext4) Christoph Hellwig <hch@infradead.org> - 2015-11-10 12:30 +0100
    Re: [PATCH v15 00/22] Richacls (Core and Ext4) Andreas Gruenbacher <agruenba@redhat.com> - 2015-11-10 13:50 +0100
      Re: [PATCH v15 00/22] Richacls (Core and Ext4) Steve French <smfrench@gmail.com> - 2015-11-10 17:50 +0100
        Re: [PATCH v15 00/22] Richacls (Core and Ext4) "J. Bruce Fields" <bfields@fieldses.org> - 2015-11-10 18:10 +0100
          Re: [PATCH v15 00/22] Richacls (Core and Ext4) Andreas Gruenbacher <agruenba@redhat.com> - 2015-11-10 19:10 +0100
            Re: [PATCH v15 00/22] Richacls (Core and Ext4) "J. Bruce Fields" <bfields@fieldses.org> - 2015-11-10 20:20 +0100
      Re: [PATCH v15 00/22] Richacls (Core and Ext4) Christoph Hellwig <hch@infradead.org> - 2015-11-11 09:00 +0100
        Re: [PATCH v15 00/22] Richacls (Core and Ext4) Andreas Gruenbacher <agruenba@redhat.com> - 2015-11-11 15:00 +0100

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