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Re: [PATCH v2 15/30] xfs: Define usercopy region in xfs_inode slab cache

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On Tue, Aug 29, 2017 at 05:45:36AM -0700, Christoph Hellwig wrote:
> On Tue, Aug 29, 2017 at 10:31:26PM +1000, Dave Chinner wrote:
> > Probably should.  I've already been looking at killing the inline
> > extents array to simplify the management of the extent list (much
> > simpler to index by rbtree when we don't have direct/indirect
> > structures), so killing the inline data would get rid of the other
> > part of the union the inline data sits in.
> 
> That's exactly where I came form with my extent list work.  Although
> the rbtree performance was horrible due to the memory overhead and
> I've switched to a modified b+tree at the moment..

Right, I've looked at btrees, too, but it's more complex than just
using an rbtree. I originally looked at using Peter Z's old
RCU-aware btree code, but it doesn't hold data in the tree leaves.
So that needed significant modification to make work without a
memory alloc per extent and that didn't work with original aim of
RCU-safe extent lookups.  I also looked at that "generic" btree
stuff that came from logfs, and after a little while ran away
screaming. So if we are going to use a b+tree, it sounds like you
are probably going the right way.

As it is, I've been looking at using interval tree - I have kinda
working code - which basically leaves the page based extent arrays
intact but adds an rbnode/interval state header to the start of each
page to track the offsets within the node and propagate them back up
to the root for fast offset based extent lookups. With a lookaside
cache on the root, it should behave and perform almost identically
to the current indirect array and should have very little extra
overhead....

The sticking point, IMO, is the extent array index based lookups in
all the bmbt code.  I've been looking at converting all that to use
offset based lookups and a cursor w/ lookup/inc/dec/insert/delete
ioperations wrapping xfs_iext_lookup_ext() and friends. This means
the modifications are pretty much identical to the on-disk extent
btree, so they can be abstracted out into a single extent update
interface for both trees.  Have you planned/done any cleanup/changes
with this code?

> > OTOH, if we're going to have to dynamically allocate the memory for
> > the extent/inline data for the data fork, it may just be easier to
> > make the entire data fork a dynamic allocation (like the attr fork).
> 
> I though about this a bit, but it turned out that we basically
> always need the data anyway, so I don't think it's going to buy
> us much unless we shrink the inode enough so that they better fit
> into a page.

True. Keep it mind for when we've shrunk the inode by another
100 bytes...

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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[PATCH v2 00/30] Hardened usercopy whitelisting Kees Cook <keescook@chromium.org> - 2017-08-28 23:40 +0200
  [PATCH v2 07/30] ext4: Define usercopy region in ext4_inode_cache slab cache Kees Cook <keescook@chromium.org> - 2017-08-28 23:40 +0200
  [PATCH v2 09/30] jfs: Define usercopy region in jfs_ip slab cache Kees Cook <keescook@chromium.org> - 2017-08-28 23:40 +0200
  [PATCH v2 06/30] vfs: Copy struct mount.mnt_id to userspace using put_user() Kees Cook <keescook@chromium.org> - 2017-08-28 23:40 +0200
  [PATCH v2 05/30] vfs: Define usercopy region in names_cache slab caches Kees Cook <keescook@chromium.org> - 2017-08-28 23:40 +0200
  [PATCH v2 08/30] ext2: Define usercopy region in ext2_inode_cache slab cache Kees Cook <keescook@chromium.org> - 2017-08-28 23:40 +0200
    Re: [PATCH v2 08/30] ext2: Define usercopy region in  ext2_inode_cache slab cache Jan Kara <jack@suse.cz> - 2017-08-30 13:30 +0200
  [PATCH v2 13/30] ufs: Define usercopy region in ufs_inode_cache slab cache Kees Cook <keescook@chromium.org> - 2017-08-28 23:40 +0200
  [PATCH v2 16/30] cifs: Define usercopy region in cifs_request slab cache Kees Cook <keescook@chromium.org> - 2017-08-28 23:40 +0200
  [PATCH v2 02/30] usercopy: Enforce slab cache usercopy region boundaries Kees Cook <keescook@chromium.org> - 2017-08-28 23:40 +0200
  [PATCH v2 20/30] caif: Define usercopy region in caif proto slab cache Kees Cook <keescook@chromium.org> - 2017-08-28 23:40 +0200
  [PATCH v2 01/30] usercopy: Prepare for usercopy whitelisting Kees Cook <keescook@chromium.org> - 2017-08-28 23:40 +0200
  [PATCH v2 11/30] exofs: Define usercopy region in exofs_inode_cache slab cache Kees Cook <keescook@chromium.org> - 2017-08-28 23:40 +0200
  [PATCH v2 04/30] dcache: Define usercopy region in dentry_cache slab cache Kees Cook <keescook@chromium.org> - 2017-08-28 23:40 +0200
  [PATCH v2 15/30] xfs: Define usercopy region in xfs_inode slab cache Kees Cook <keescook@chromium.org> - 2017-08-28 23:40 +0200
    Re: [PATCH v2 15/30] xfs: Define usercopy region in xfs_inode slab cache Kees Cook <keescook@chromium.org> - 2017-08-29 00:00 +0200
      Re: [PATCH v2 15/30] xfs: Define usercopy region in xfs_inode slab  cache "Darrick J. Wong" <darrick.wong@oracle.com> - 2017-08-29 06:50 +0200
        Re: [PATCH v2 15/30] xfs: Define usercopy region in xfs_inode slab cache Kees Cook <keescook@chromium.org> - 2017-08-29 20:50 +0200
          Re: [PATCH v2 15/30] xfs: Define usercopy region in xfs_inode slab  cache "Darrick J. Wong" <darrick.wong@oracle.com> - 2017-08-29 21:10 +0200
          Re: [PATCH v2 15/30] xfs: Define usercopy region in xfs_inode slab  cache Dave Chinner <david@fromorbit.com> - 2017-08-30 00:20 +0200
            Re: [PATCH v2 15/30] xfs: Define usercopy region in xfs_inode slab cache Kees Cook <keescook@chromium.org> - 2017-08-30 00:30 +0200
    Re: [PATCH v2 15/30] xfs: Define usercopy region in xfs_inode slab  cache "Darrick J. Wong" <darrick.wong@oracle.com> - 2017-08-29 00:00 +0200
    Re: [PATCH v2 15/30] xfs: Define usercopy region in xfs_inode slab  cache Christoph Hellwig <hch@infradead.org> - 2017-08-29 10:20 +0200
      Re: [PATCH v2 15/30] xfs: Define usercopy region in xfs_inode slab  cache Dave Chinner <david@fromorbit.com> - 2017-08-29 14:40 +0200
        Re: [PATCH v2 15/30] xfs: Define usercopy region in xfs_inode slab  cache Christoph Hellwig <hch@infradead.org> - 2017-08-29 14:50 +0200
          Re: [PATCH v2 15/30] xfs: Define usercopy region in xfs_inode slab  cache Dave Chinner <david@fromorbit.com> - 2017-08-30 00:00 +0200
            Re: [PATCH v2 15/30] xfs: Define usercopy region in xfs_inode slab  cache Christoph Hellwig <hch@infradead.org> - 2017-08-30 09:20 +0200
              Re: [PATCH v2 15/30] xfs: Define usercopy region in xfs_inode slab  cache Dave Chinner <david@fromorbit.com> - 2017-08-30 10:10 +0200
                Re: [PATCH v2 15/30] xfs: Define usercopy region in xfs_inode slab  cache Christoph Hellwig <hch@infradead.org> - 2017-08-30 10:40 +0200
      Re: [PATCH v2 15/30] xfs: Define usercopy region in xfs_inode slab cache Kees Cook <keescook@chromium.org> - 2017-08-29 21:00 +0200
  [PATCH v2 10/30] befs: Define usercopy region in befs_inode_cache slab cache Kees Cook <keescook@chromium.org> - 2017-08-28 23:40 +0200
    Re: [PATCH v2 10/30] befs: Define usercopy region in befs_inode_cache  slab cache Luis de Bethencourt <luisbg@kernel.org> - 2017-08-29 12:20 +0200
      Re: [PATCH v2 10/30] befs: Define usercopy region in befs_inode_cache  slab cache Kees Cook <keescook@chromium.org> - 2017-08-29 17:40 +0200
        Re: [PATCH v2 10/30] befs: Define usercopy region in befs_inode_cache  slab cache Luis de Bethencourt <luisbg@kernel.org> - 2017-08-29 19:20 +0200
  [PATCH v2 25/30] fork: Define usercopy region in thread_stack slab caches Kees Cook <keescook@chromium.org> - 2017-08-28 23:50 +0200
    Re: [kernel-hardening] [PATCH v2 25/30] fork: Define usercopy  region in thread_stack slab caches Rik van Riel <riel@redhat.com> - 2017-08-30 21:00 +0200
  [PATCH v2 21/30] sctp: Define usercopy region in SCTP proto slab cache Kees Cook <keescook@chromium.org> - 2017-08-28 23:50 +0200
  [PATCH v2 19/30] ip: Define usercopy region in IP proto slab cache Kees Cook <keescook@chromium.org> - 2017-08-28 23:50 +0200
  [PATCH v2 22/30] sctp: Copy struct sctp_sock.autoclose to userspace using put_user() Kees Cook <keescook@chromium.org> - 2017-08-28 23:50 +0200
  [PATCH v2 29/30] arm: Implement thread_struct whitelist for hardened usercopy Kees Cook <keescook@chromium.org> - 2017-08-28 23:50 +0200
  [PATCH v2 30/30] usercopy: Restrict non-usercopy caches to size 0 Kees Cook <keescook@chromium.org> - 2017-08-28 23:50 +0200
  [PATCH v2 14/30] vxfs: Define usercopy region in vxfs_inode slab cache Kees Cook <keescook@chromium.org> - 2017-08-28 23:50 +0200
  [PATCH v2 24/30] fork: Define usercopy region in mm_struct slab caches Kees Cook <keescook@chromium.org> - 2017-08-28 23:50 +0200
    Re: [kernel-hardening] [PATCH v2 24/30] fork: Define usercopy  region in mm_struct slab caches Rik van Riel <riel@redhat.com> - 2017-08-30 21:30 +0200
  [PATCH v2 23/30] net: Restrict unwhitelisted proto caches to size 0 Kees Cook <keescook@chromium.org> - 2017-08-28 23:50 +0200
  [PATCH v2 26/30] fork: Provide usercopy whitelisting for task_struct Kees Cook <keescook@chromium.org> - 2017-08-28 23:50 +0200
    Re: [kernel-hardening] [PATCH v2 26/30] fork: Provide usercopy  whitelisting for task_struct Rik van Riel <riel@redhat.com> - 2017-08-30 21:00 +0200
  [PATCH v2 28/30] arm64: Implement thread_struct whitelist for hardened usercopy Kees Cook <keescook@chromium.org> - 2017-08-28 23:50 +0200
  [PATCH v2 27/30] x86: Implement thread_struct whitelist for hardened usercopy Kees Cook <keescook@chromium.org> - 2017-08-29 00:00 +0200
    Re: [kernel-hardening] [PATCH v2 27/30] x86: Implement  thread_struct whitelist for hardened usercopy Rik van Riel <riel@redhat.com> - 2017-08-30 21:00 +0200
  [PATCH v2 18/30] net: Define usercopy region in struct proto slab cache Kees Cook <keescook@chromium.org> - 2017-08-29 00:00 +0200

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