• Shawn Bohrer's avatar
    IB: ib_umem_release() should decrement mm->pinned_vm from ib_umem_get · 87773dd5
    Shawn Bohrer authored
    In debugging an application that receives -ENOMEM from ib_reg_mr(), I
    found that ib_umem_get() can fail because the pinned_vm count has
    wrapped causing it to always be larger than the lock limit even with
    The wrapping of pinned_vm occurs because the process that calls
    ib_reg_mr() will have its mm->pinned_vm count incremented.  Later a
    different process with a different mm_struct than the one that
    allocated the ib_umem struct ends up releasing it which results in
    decrementing the new processes mm->pinned_vm count past zero and
    I'm not entirely sure what circumstances cause a different process to
    release the ib_umem than the one that allocated it but the kernel
    stack trace of the freeing process from my situation looks like the
        Call Trace:
         [<ffffffff814d64b1>] dump_stack+0x19/0x1b
         [<ffffffffa0b522a5>] ib_umem_release+0x1f5/0x200 [ib_core]
         [<ffffffffa0b90681>] mlx4_ib_destroy_qp+0x241/0x440 [mlx4_ib]
         [<ffffffffa0b4d93c>] ib_destroy_qp+0x12c/0x170 [ib_core]
         [<ffffffffa0cc7129>] ib_uverbs_close+0x259/0x4e0 [ib_uverbs]
         [<ffffffff81141cba>] __fput+0xba/0x240
         [<ffffffff81141e4e>] ____fput+0xe/0x10
         [<ffffffff81060894>] task_work_run+0xc4/0xe0
         [<ffffffff810029e5>] do_notify_resume+0x95/0xa0
         [<ffffffff814e3dd0>] int_signal+0x12/0x17
    The following patch fixes the issue by storing the pid struct of the
    process that calls ib_umem_get() so that ib_umem_release and/or
    ib_umem_account() can properly decrement the pinned_vm count of the
    correct mm_struct.
    Signed-off-by: default avatarShawn Bohrer <sbohrer@rgmadvisors.com>
    Reviewed-by: default avatarShachar Raindel <raindel@mellanox.com>
    Signed-off-by: default avatarRoland Dreier <roland@purestorage.com>
ib_umem.h 2.55 KB