5cc9ed4b9a7ac579362ccebac67f7a4cdb36de06 is the first bad commit
commit 5cc9ed4b9a7ac579362ccebac67f7a4cdb36de06
Author: Chris Wilson <email address hidden>
Date:   Fri May 16 14:22:37 2014 +0100
Commit:     Daniel Vetter <email address hidden>
CommitDate: Fri May 16 19:31:29 2014 +0200


    drm/i915: Introduce mapping of user pages into video memory (userptr) ioctl

    By exporting the ability to map user address and inserting PTEs
    representing their backing pages into the GTT, we can exploit UMA in order
    to utilize normal application data as a texture source or even as a
    render target (depending upon the capabilities of the chipset). This has
    a number of uses, with zero-copy downloads to the GPU and efficient
    readback making the intermixed streaming of CPU and GPU operations
    fairly efficient. This ability has many widespread implications from
    faster rendering of client-side software rasterisers (chromium),
    mitigation of stalls due to read back (firefox) and to faster pipelining
    of texture data (such as pixel buffer objects in GL or data blobs in CL).

    v2: Compile with CONFIG_MMU_NOTIFIER
    v3: We can sleep while performing invalidate-range, which we can utilise
    to drop our page references prior to the kernel manipulating the vma
    (for either discard or cloning) and so protect normal users.
    v4: Only run the invalidate notifier if the range intercepts the bo.
    v5: Prevent userspace from attempting to GTT mmap non-page aligned buffers
    v6: Recheck after reacquire mutex for lost mmu.
    v7: Fix implicit padding of ioctl struct by rounding to next 64bit boundary.
    v8: Fix rebasing error after forwarding porting the back port.
    v9: Limit the userptr to page aligned entries. We now expect userspace
        to handle all the offset-in-page adjustments itself.
    v10: Prevent vma from being copied across fork to avoid issues with cow.
    v11: Drop vma behaviour changes -- locking is nigh on impossible.
         Use a worker to load user pages to avoid lock inversions.
    v12: Use get_task_mm()/mmput() for correct refcounting of mm.
    v13: Use a worker to release the mmu_notifier to avoid lock inversion
    v14: Decouple mmu_notifier from struct_mutex using a custom mmu_notifer
         with its own locking and tree of objects for each mm/mmu_notifier.
    v15: Prevent overlapping userptr objects, and invalidate all objects
         within the mmu_notifier range
    v16: Fix a typo for iterating over multiple objects in the range and
         rearrange error path to destroy the mmu_notifier locklessly.
         Also close a race between invalidate_range and the get_pages_worker.
    v17: Close a race between get_pages_worker/invalidate_range and fresh
         allocations of the same userptr range - and notice that
         struct_mutex was presumed to be held when during creation it wasn't.
    v18: Sigh. Fix the refactor of st_set_pages() to allocate enough memory
         for the struct sg_table and to clear it before reporting an error.
    v19: Always error out on read-only userptr requests as we don't have the
         hardware infrastructure to support them at the moment.
    v20: Refuse to implement read-only support until we have the required
         infrastructure - but reserve the bit in flags for future use.
    v21: use_mm() is not required for get_user_pages(). It is only meant to
         be used to fix up the kernel thread's current->mm for use with
         copy_user().
    v22: Use sg_alloc_table_from_pages for that chunky feeling
    v23: Export a function for sanity checking dma-buf rather than encode
         userptr details elsewhere, and clean up comments based on
         suggestions by Bradley.

    Signed-off-by: Chris Wilson <email address hidden>
    Cc: Tvrtko Ursulin <email address hidden>
    Cc: "Gong, Zhipeng" <email address hidden>
    Cc: Akash Goel <email address hidden>
    Cc: "Volkin, Bradley D" <email address hidden>
    Reviewed-by: Tvrtko Ursulin <email address hidden>
    Reviewed-by: Brad Volkin <email address hidden>
    [danvet: Frob ioctl allocation to pick the next one - will cause a bit
    of fuss with create2 apparently, but such are the rules.]
    [danvet2: oops, forgot to git add after manual patch application]
    [danvet3: Appease sparse.]
    Signed-off-by: Daniel Vetter <email address hidden>